rOCKS AND wEATHERING notes.pdf for free notes
chaubanda128
28 views
140 slides
Mar 02, 2025
Slide 1 of 140
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
About This Presentation
rocks and weathering notes for AS level and A level students cie 9696
Slide Content
Rocks and
Weathering
Weathering
Elementary Plate Tectonics
•The theory of plate tectonics states that the Earth is made of a number of layers
1.The Crust: Thin outer layer which holds tectonic plates.
2.The Mantle: Thickest layer making up 82% of Earths volume. Made up of
magma, with diameter of approximately 2900KM
3.The Outer Core: Hot layer surrounding inner core. Liquid layer made up of iron
and nickel, with temperatures of approximately 5000degrees.
4.The Inner Core: Dense, solid core made of iron and nickel with temperatures
exceeding 5500degrees Celsius.
•There are two types of crust:
1.Oceanic: Dense, thinner plate made up of Basaltic rock, approximately 16km
thick.
2.Continental: Much thicker plate made up of granite, silica and aluminium, less
dense than oceanic plate.
•The upper mantle and crust make up a layer called the Lithospherewhich is broken
into a number of plates. These move over the Asthenosphere, which is a plastic
layer in the mantle, which drives plate movement.
•The theory of plate tectonics states that the Earth is made of a number of layers
1.The Crust: Thin outer layer which holds tectonic plates.
2.The Mantle: Thickest layer making up 82% of Earths volume. Made up of
magma, with diameter of approximately 2900KM
3.The Outer Core: Hot layer surrounding inner core. Liquid layer made up of iron
and nickel, with temperatures of approximately 5000degrees.
4.The Inner Core: Dense, solid core made of iron and nickel with temperatures
exceeding 5500degrees Celsius.
•There are two types of crust:
1.Oceanic: Dense, thinner plate made up of Basaltic rock, approximately 16km
thick.
2.Continental: Much thicker plate made up of granite, silica and aluminium, less
dense than oceanic plate.
•The upper mantle and crust make up a layer called the Lithospherewhich is broken
into a number of plates. These move over the Asthenosphere, which is a plastic
layer in the mantle, which drives plate movement.
Earths Structure
Alfred Wegener's theory for continental
drift
•Wegener in 1912 proposed his hypothesis on continental drift, using several lines of evidence
to support his ideas that the continents were once joined together in one super continent
called Pangaea (which means “entire earth” in Greek) These included…
1.The apparent fit of the continents like a jigsaw puzzle
2.The correlation of multiple fossils such as the mesosaurus, found in only South America
and Africa. As a creation who could only live in shallow water, couldn’t swim well or fly,
how could it have travelled over an entire ocean? Solution: The continents were once
connected.
3.Matching rock formations and mountain chains found in South America and Africa,
consisting of the same rock and same age.
4.Glacial striationsfound in tropical rainforests suggests that countries were always in their
current climatic regions.
•However whilst Wegener had some very valid points and a good argument, he had no driving
mechanism to make this happen. He believes that somehow continents were pushing ocean
plates along –however critics commented that continental plates lacked momentum to
achieve this and thus his theory fell through.
drift
•Wegener in 1912 proposed his hypothesis on continental drift, using several lines of evidence
to support his ideas that the continents were once joined together in one super continent
called Pangaea (which means “entire earth” in Greek) These included…
1.The apparent fit of the continents like a jigsaw puzzle
2.The correlation of multiple fossils such as the mesosaurus, found in only South America
and Africa. As a creation who could only live in shallow water, couldn’t swim well or fly,
how could it have travelled over an entire ocean? Solution: The continents were once
connected.
3.Matching rock formations and mountain chains found in South America and Africa,
consisting of the same rock and same age.
4.Glacial striationsfound in tropical rainforests suggests that countries were always in their
current climatic regions.
•However whilst Wegener had some very valid points and a good argument, he had no driving
mechanism to make this happen. He believes that somehow continents were pushing ocean
plates along –however critics commented that continental plates lacked momentum to
achieve this and thus his theory fell through.
Harry Hess’s hypothesis of Sea floor
spreading 1960s
•Harry Hess in the 1960ssuggested that convection currents within the mantle could be
forcing magma to rise and crack the crust above it forcing it apart.
•He believes that as it welled up and cooled on the ocean floor at divergent zones, new
oceanic crust was forming at mid ocean ridges, pushing older, colder and more dense crust
towards deep sea trenches, where it is subducted, recycled back into the mantle or creates
volcanism.
•However when there is no trench for old crust to subject under (such as the coast of Africa),
then in pushes the continent along with it as crust accumulates.
•As there are few trenches in the Atlantic Ocean it is expanding
•As there are many trenches in the Pacific Ocean it is shrinking
•How did Hess support his theory? Rock Magnetism. Hess looked at the polarity on either
sides of the ridge, a correlation of identical bonds between the two sides supported his
theory.
•Magnetic grains in the rock align with the Earth’s magnetic field at the time of cooling
(known as paleomagnetism)
spreading 1960s
•Harry Hess in the 1960ssuggested that convection currents within the mantle could be
forcing magma to rise and crack the crust above it forcing it apart.
•He believes that as it welled up and cooled on the ocean floor at divergent zones, new
oceanic crust was forming at mid ocean ridges, pushing older, colder and more dense crust
towards deep sea trenches, where it is subducted, recycled back into the mantle or creates
volcanism.
•However when there is no trench for old crust to subject under (such as the coast of Africa),
then in pushes the continent along with it as crust accumulates.
•As there are few trenches in the Atlantic Ocean it is expanding
•As there are many trenches in the Pacific Ocean it is shrinking
•How did Hess support his theory? Rock Magnetism. Hess looked at the polarity on either
sides of the ridge, a correlation of identical bonds between the two sides supported his
theory.
•Magnetic grains in the rock align with the Earth’s magnetic field at the time of cooling
(known as paleomagnetism)
Sea floor spreading
J Wilson 1965
•In 1965 J Wilson linked together ideas of continental drift and sea floor spreading,
developing the concept of plate tectonics.
•Wilson said that Earth’s crust, or lithosphere, was divided into large, rigid pieces
called plates. These plates “float” atop an underlying rock layer called the
asthenosphere. In the asthenosphere, rocks are under such tremendous heat and
pressure that they behave like a viscous liquid (like very thick honey). The term
“continental drift” was no longer fully accurate, because the plates are made up of
continental and oceanic crust, which both “drift” over Earth’s face.
TuzoWilson predicted three types of boundaries between plates: mid-ocean ridges
(where ocean crust is created), trenches (where the ocean plates are subducted) and
large fractures in the seafloor called transform faults, where the plates slip by each
other.
•In 1965 J Wilson linked together ideas of continental drift and sea floor spreading,
developing the concept of plate tectonics.
•Wilson said that Earth’s crust, or lithosphere, was divided into large, rigid pieces
called plates. These plates “float” atop an underlying rock layer called the
asthenosphere. In the asthenosphere, rocks are under such tremendous heat and
pressure that they behave like a viscous liquid (like very thick honey). The term
“continental drift” was no longer fully accurate, because the plates are made up of
continental and oceanic crust, which both “drift” over Earth’s face.
TuzoWilson predicted three types of boundaries between plates: mid-ocean ridges
(where ocean crust is created), trenches (where the ocean plates are subducted) and
large fractures in the seafloor called transform faults, where the plates slip by each
other.
Types of Plate boundaries
•Divergent/Constructive: These plates are moving away from each other.
They are usually found in the middle of the oceans and mid ocean
ridges are found here.
•Convergent/Destructive: These plates are moving towards each other
causing earthquakes, volcanoes, deep ocean trenches and fold
mountains.
•Transform/conservative: These plates are sliding past each other. At
these zones land is not being created nor destroyed , however frequent
earthquakes are common. An example is San Andrea Fault in California
•Divergent/Constructive: These plates are moving away from each other.
They are usually found in the middle of the oceans and mid ocean
ridges are found here.
•Convergent/Destructive: These plates are moving towards each other
causing earthquakes, volcanoes, deep ocean trenches and fold
mountains.
•Transform/conservative: These plates are sliding past each other. At
these zones land is not being created nor destroyed , however frequent
earthquakes are common. An example is San Andrea Fault in California
How do the plates move?
•There are three main theories explaining plate movement…
1.Convection currents: This states that huge convection currents occur in the earths
interior causing hot magma to rise to the surface and then spread out at mid ocean
ridges, whilst the cooler magma gets denser and sinks back deep into the mantle where
it is reheated.
2.Dragging Theory: Plates are dragged or subducted by their oldest edge when they
become cold and dense. Plates are hot at mid ocean ridges, but cool as they are pushed
further away. As the cold plates descend at the trenches, pressure causes the rocks to
become heavier and therefore they are subducted.
3.Hotspot: Hotspots are plumes of molten rock which rise underneath a plate penetrating
weaknesses in the crust and resulting in volcanic activity. As plates are moving and
hotspots stay still, these therefore led to chains of land creation such as Hawaii.
•There are three main theories explaining plate movement…
1.Convection currents: This states that huge convection currents occur in the earths
interior causing hot magma to rise to the surface and then spread out at mid ocean
ridges, whilst the cooler magma gets denser and sinks back deep into the mantle where
it is reheated.
2.Dragging Theory: Plates are dragged or subducted by their oldest edge when they
become cold and dense. Plates are hot at mid ocean ridges, but cool as they are pushed
further away. As the cold plates descend at the trenches, pressure causes the rocks to
become heavier and therefore they are subducted.
3.Hotspot: Hotspots are plumes of molten rock which rise underneath a plate penetrating
weaknesses in the crust and resulting in volcanic activity. As plates are moving and
hotspots stay still, these therefore led to chains of land creation such as Hawaii.
Convection
Currents
Hot Spots Dragging Theory
Currents
Hot Spots Dragging Theory
Subduction Zones
•Subduction occurs when an oceanic lithospheric plate collides with another plate. As
the density of the ocean plate Is similar to that of the asthenosphere it can easily be
subducted. Subduction zones dip mainly at 30-70 degree angles.
•If a continental and oceanic plate meet, the oceanic plate will be subducted beneath
the continental as it is more dense.
•Evidence of subduction:
•The existence of certain landforms such as deep sea trenches and folded sediments
(usually arc shaped and containing volcanoes)
•Benioffzone –a deep active seismic area dipping away from the deep sea trench.
•Earthquake focal mechanisms (ring of fire)
•Subduction occurs when an oceanic lithospheric plate collides with another plate. As
the density of the ocean plate Is similar to that of the asthenosphere it can easily be
subducted. Subduction zones dip mainly at 30-70 degree angles.
•If a continental and oceanic plate meet, the oceanic plate will be subducted beneath
the continental as it is more dense.
•Evidence of subduction:
•The existence of certain landforms such as deep sea trenches and folded sediments
(usually arc shaped and containing volcanoes)
•Benioffzone –a deep active seismic area dipping away from the deep sea trench.
•Earthquake focal mechanisms (ring of fire)
Island Arcs
•Island arcs are features of
oceanic/continental
convergence. They are
chains of volcanoes which
are aligned in an arc shape
and sit close to the boundary
where two plates meet.
During subduction hot re-
melted material from the
subducting slab rises and
leaks into the crust forming a
series of volcanoes. These
volcanoes can make a chain
of islands called Island arcs.
Many are found in the Pacific
and Western Atlantic.
•Island arcs are features of
oceanic/continental
convergence. They are
chains of volcanoes which
are aligned in an arc shape
and sit close to the boundary
where two plates meet.
During subduction hot re-
melted material from the
subducting slab rises and
leaks into the crust forming a
series of volcanoes. These
volcanoes can make a chain
of islands called Island arcs.
Many are found in the Pacific
and Western Atlantic.
Mountain Building
•Plate tectonics are associated with mountain building. Where oceanic plates meet
continental, the light less dense plate may be bulked and folded up creating fold
mountains, such as the Andes.
•Where two continental plates meet, both may be folded and buckled, forming
mountains such as the Himalayas formed by the collision of the Eurasian and Indian
plates.
•The Indian subcontinent moved rapidly north during the last 70 million years,
eventually colliding with the main body of Asia. The huge ocean Tethys has been
entirely lost between these masses in the collision zone and the crust has thickened
because Asia overrides India, resulting in crust thickening causing the uplift of the
Himalayas.
•Plate tectonics are associated with mountain building. Where oceanic plates meet
continental, the light less dense plate may be bulked and folded up creating fold
mountains, such as the Andes.
•Where two continental plates meet, both may be folded and buckled, forming
mountains such as the Himalayas formed by the collision of the Eurasian and Indian
plates.
•The Indian subcontinent moved rapidly north during the last 70 million years,
eventually colliding with the main body of Asia. The huge ocean Tethys has been
entirely lost between these masses in the collision zone and the crust has thickened
because Asia overrides India, resulting in crust thickening causing the uplift of the
Himalayas.
Plate landforms
Four features at a convergent boundary you need to know about
and how they form
1.Subduction zones
2.Ocean trenches
3.Benioff Zones
4.Island Arcs
Subduction zones
•Subduction zone is the name given to the area where one plate moves
underneath another plate
•The denser plate is pushed underneath (oceanic or oldest oceanic
plate)
•The oceanic crust remains cooler and therefore denser than the
surrounding mantle for millions of years , so subduction continuesand
the crust is destroyed.
•As the earth has not grown any bigger, the amount of subduction
balances against the new crust created at divergent boundaries.
•The plate subducting tends to dip at an angle of between 30 and 70
degrees
•The older the crust, the steeper it dips.
and how they form
1.Subduction zones
2.Ocean trenches
3.Benioff Zones
4.Island Arcs
Subduction zones
•Subduction zone is the name given to the area where one plate moves
underneath another plate
•The denser plate is pushed underneath (oceanic or oldest oceanic
plate)
•The oceanic crust remains cooler and therefore denser than the
surrounding mantle for millions of years , so subduction continuesand
the crust is destroyed.
•As the earth has not grown any bigger, the amount of subduction
balances against the new crust created at divergent boundaries.
•The plate subducting tends to dip at an angle of between 30 and 70
degrees
•The older the crust, the steeper it dips.
Oceanic trenches
•Ocean trenches are formed at subduction zones.
•They are long, narrow depressions in the ocean floor with depths from 6000m to
11000m
•Most numerous in the Pacific Ocean
•Trenches are usually symmetric with the steepest side towards a landmass
•Ocean trenches are formed at subduction zones.
•They are long, narrow depressions in the ocean floor with depths from 6000m to
11000m
•Most numerous in the Pacific Ocean
•Trenches are usually symmetric with the steepest side towards a landmass
Benioff zone is a narrow zone of deep earthquake foci at a subduction zone.
The zone extends from the surface of the ocean trench down to a depth of 680km.
Discovered by Hugo Benioff
The deeper earthquakes occur further from the subduction zone
The zone extends from the surface of the ocean trench down to a depth of 680km.
Discovered by Hugo Benioff
The deeper earthquakes occur further from the subduction zone
Island Arcs
Island arcs are chains of volcanic islands on the continental side of an ocean trench. They are associated
with subduction zones.
Island Arcs are normally formed when oceanic crust subducts below ocean crust
Most are located in the Pacific ocean also in Western Atlantic in the Caribbean.
Island arcs are chains of volcanic islands on the continental side of an ocean trench. They are associated
with subduction zones.
Island Arcs are normally formed when oceanic crust subducts below ocean crust
Most are located in the Pacific ocean also in Western Atlantic in the Caribbean.
Formation of Island Arcs
The descending plate starts to heat up and at a depth of about 75 miles, the rocks are melted to form
magma and rise toward the surface.
Eventually this magma makes it way up into the overriding plate, where they add material to the crust
and build volcanoes above it.
If the upper plate is oceanic, the volcanoes pile up until they poke through the surface of the ocean and
form an elegant arc.
The descending plate starts to heat up and at a depth of about 75 miles, the rocks are melted to form
magma and rise toward the surface.
Eventually this magma makes it way up into the overriding plate, where they add material to the crust
and build volcanoes above it.
If the upper plate is oceanic, the volcanoes pile up until they poke through the surface of the ocean and
form an elegant arc.
Some famous island arcs
Most mountain ranges have been formed at convergent boundaries where two plates move towards
each other
each other
The Andes were formed when the Nazca oceanic plate moved towards and subducted under continental
crust on the west coast of South America
As the subduction occurred, rocks from the continental margin of south America were folded
Additionally pieces of the subducting plate were scraped off and became part of an accretionary wedge
adding to the mountain range
This subduction also resulted in partial melting of the subducting plate producing volcanoes in this
mountain range
crust on the west coast of South America
As the subduction occurred, rocks from the continental margin of south America were folded
Additionally pieces of the subducting plate were scraped off and became part of an accretionary wedge
adding to the mountain range
This subduction also resulted in partial melting of the subducting plate producing volcanoes in this
mountain range
The Himalayas were formed when two continental plates collided as Indian plate moved towards the
rest of Asia during the last 70 million years
The leading edge of the Indian plate have been thrust beneath the edge of the Asian continent
In the collision zone the Asia overrides India and is therefore uplifted and folded to form mountains
As no magma escapes to the surface in the Himalaya region there is little volcanic activity
rest of Asia during the last 70 million years
The leading edge of the Indian plate have been thrust beneath the edge of the Asian continent
In the collision zone the Asia overrides India and is therefore uplifted and folded to form mountains
As no magma escapes to the surface in the Himalaya region there is little volcanic activity
•(a) (i) Define sea floor spreading and ocean ridge. [4]
•Sea floor spreading is the extension of ocean floors laterally, as oceanic plates
•move apart (1) and magma is added to the ocean floor (1).
•An ocean ridge is a (large scale) mid-ocean elevation/mountain range, (1) typically
•with a rift along the spine/central ridge/where magma escapes (1).
•(ii) Describe an island arc. [3]
•A chain of islands/archipelago (1), generally in a curved line (1), usually volcanic
•close to or parallel to a destructive plate margin/convergent oceanic plates (1).
•(b) Draw a labelled diagram showing the convergence of an oceanic plate and a
•continental plate. Explain the processes occurring and the types of landforms
•produced. [8]
•The diagram should show an oceanic plate being subducted beneath a continental
•plate with attendant volcanic, ocean trench and fold mountains. Explanation should
•involve the role of convection currents, crustal melting in the Benioff zone and the
•upwelling of magma through fissures and faults in the continental plate and folding of
•marine sediments/continental plate to form fold mountains. The ocean trench
•represents the dragging downward of crust at the subduction zone.
•If no diagram: max 5 marks.
•A higher band response could be characterisedby a well labelled diagram and will link
•processes to a variety of specific landforms.
•Use three bands of marks: 1–3, 4–6 and 7–8.
•Sea floor spreading is the extension of ocean floors laterally, as oceanic plates
•move apart (1) and magma is added to the ocean floor (1).
•An ocean ridge is a (large scale) mid-ocean elevation/mountain range, (1) typically
•with a rift along the spine/central ridge/where magma escapes (1).
•(ii) Describe an island arc. [3]
•A chain of islands/archipelago (1), generally in a curved line (1), usually volcanic
•close to or parallel to a destructive plate margin/convergent oceanic plates (1).
•(b) Draw a labelled diagram showing the convergence of an oceanic plate and a
•continental plate. Explain the processes occurring and the types of landforms
•produced. [8]
•The diagram should show an oceanic plate being subducted beneath a continental
•plate with attendant volcanic, ocean trench and fold mountains. Explanation should
•involve the role of convection currents, crustal melting in the Benioff zone and the
•upwelling of magma through fissures and faults in the continental plate and folding of
•marine sediments/continental plate to form fold mountains. The ocean trench
•represents the dragging downward of crust at the subduction zone.
•If no diagram: max 5 marks.
•A higher band response could be characterisedby a well labelled diagram and will link
•processes to a variety of specific landforms.
•Use three bands of marks: 1–3, 4–6 and 7–8.
Explain the formation of mountain ranges and island arcs. [6]
•A well labelled diagram can gain credit, but it needs to be of the convergent plate boundary
•At convergent plate margins, plates are moving towards one another. Convergent margins
•behave differently depending on whether the plates are oceanic, continental or one of each.
•The question states 2 landforms and so it is necessary to make referenceto both. This may
•be done through case study examples or perhaps more generically. The key points are that
•subduction of the plate into the mantle, where oceanic plates are involved, causes partial
•melting, which produces magma, which rises to the surface as volcanoes. Volcanoes form in
•a curved linear pattern known as island arcs where two oceanic plates converge.
•Where subduction occurs at the convergences of an oceanic and continental plate, sediment
•from the sea floor can be scraped off and deformed, and it forms a thickening of the crust
•forming mountain ranges. Mountains ranges can also be formed by the collision of two
•continental plates.
•A well labelled diagram can gain credit, but it needs to be of the convergent plate boundary
•At convergent plate margins, plates are moving towards one another. Convergent margins
•behave differently depending on whether the plates are oceanic, continental or one of each.
•The question states 2 landforms and so it is necessary to make referenceto both. This may
•be done through case study examples or perhaps more generically. The key points are that
•subduction of the plate into the mantle, where oceanic plates are involved, causes partial
•melting, which produces magma, which rises to the surface as volcanoes. Volcanoes form in
•a curved linear pattern known as island arcs where two oceanic plates converge.
•Where subduction occurs at the convergences of an oceanic and continental plate, sediment
•from the sea floor can be scraped off and deformed, and it forms a thickening of the crust
•forming mountain ranges. Mountains ranges can also be formed by the collision of two
•continental plates.
Explain how fold mountains are formed [4]
•The focus here is on the explanation. The formation of mountain chains on continents is from
•the movement of the tectonic plates. The movement of the plates leads to the folding of
•sediments trapped between the plates and subsequent uplift. The result is mountain chains.
•The term orogeny can be used. Annotated diagrams can be credited as they can be used to
•enhance the explanation. Give some credit for collision margins e.g.Himalayas
Explain why the process of sea floor spreading only occurs at some
tectonic plate boundaries.4
•The main points are:
•• Sea floor spreading is present under the ocean, on margins which
•are diverging (1).
•• This process occurs as the plates are drawn away from each other
•through the convection currents, forming new oceanic crust.
•Thereforeit is the presence of two diverging oceanic plates which
•develops this process (1).
•• Plate margins which draw plates together (convergent) (1) or
•allowing them to run side by side (conservative, such as the San
•Andreasfault) (1) will not have the process, as in convergent
•margins, for example, there is no separation or divergence of the
•plates to allow the molten material to be released in this way.
•The focus here is on the explanation. The formation of mountain chains on continents is from
•the movement of the tectonic plates. The movement of the plates leads to the folding of
•sediments trapped between the plates and subsequent uplift. The result is mountain chains.
•The term orogeny can be used. Annotated diagrams can be credited as they can be used to
•enhance the explanation. Give some credit for collision margins e.g.Himalayas
Explain why the process of sea floor spreading only occurs at some
tectonic plate boundaries.4
•The main points are:
•• Sea floor spreading is present under the ocean, on margins which
•are diverging (1).
•• This process occurs as the plates are drawn away from each other
•through the convection currents, forming new oceanic crust.
•Thereforeit is the presence of two diverging oceanic plates which
•develops this process (1).
•• Plate margins which draw plates together (convergent) (1) or
•allowing them to run side by side (conservative, such as the San
•Andreasfault) (1) will not have the process, as in convergent
•margins, for example, there is no separation or divergence of the
•plates to allow the molten material to be released in this way.
WEATHERING
Decomposition and Disintegration
Decomposition and Disintegration
Weathering
•Describes the processes that break up rocks. There are three types of weathering…
1.Chemical Weathering (Decomposition): Processes that break down rocks atom by
atom through chemical reactions. Water plays a key role here.
2.Mechanical Weathering (Disintegration): The tearing apart and breaking of rocks
through physically destroying them
3.Biological Weathering: When animals and vegetation (root wedging) break up
rocks.
•Hotwet climates enhance chemical weathering
•Coldwet climates enhance mechanical weathering.
•Describes the processes that break up rocks. There are three types of weathering…
1.Chemical Weathering (Decomposition): Processes that break down rocks atom by
atom through chemical reactions. Water plays a key role here.
2.Mechanical Weathering (Disintegration): The tearing apart and breaking of rocks
through physically destroying them
3.Biological Weathering: When animals and vegetation (root wedging) break up
rocks.
•Hotwet climates enhance chemical weathering
•Coldwet climates enhance mechanical weathering.
Mechanical/Physical Weathering
Processes
•Freeze Thaw: Water becomes trappedin the cracks and joints in a rock and freezesin
cold conditions. As this happens the water puts pressure on the rock as it expands by 9%.
When temperaturesrise the ice will meltand the pressure will be released, but the rock
weakened. After many repetitive cycles this eventually breaks up rocks and causes them
to fragment.
•Salt Crystallisation: This causes decomposition of rock by solution of salts. When
temperatures fluctuate around 26-28 degrees sodium sulphate and sodium carbonate in
rocks expand by 300%creating pressure on joints forcing them to crack. Also when rocks
are near salt water, the water evaporates leaving behind salt crystals. Similarly as
temperatures rise further these crystals expand and exert pressure on the rock causing it
to slowly break apart.
•Exfoliation/Disintegration: This process is found in hot desert areas where there are
large diurnal temperature ranges. Rocks heat up during the day and expand, then cool
and contract at night. As a rock is a poor conductor of heat, stresses occur only in the
outer layers, causing peeling or exfoliation to occur. Griggs 1936 showed that moisture is
essential for this to happen and that temperature change alone did not cause rock
breakdown. Exfoliation is most common in granite.
•Pressure release/fracturing/ dilatation: This is the process whereby overlying rocks are
removed by erosion, causing underlying rocks to expand and fracture parallel to the
surface due to loss of pressure(referred to unloading). The unloading of pressure by
removal of underlying rocks causes cracks or joints to form at right angles to the
unloading surface. The cracks are lines of weakness in the rocks.
Processes
•Freeze Thaw: Water becomes trappedin the cracks and joints in a rock and freezesin
cold conditions. As this happens the water puts pressure on the rock as it expands by 9%.
When temperaturesrise the ice will meltand the pressure will be released, but the rock
weakened. After many repetitive cycles this eventually breaks up rocks and causes them
to fragment.
•Salt Crystallisation: This causes decomposition of rock by solution of salts. When
temperatures fluctuate around 26-28 degrees sodium sulphate and sodium carbonate in
rocks expand by 300%creating pressure on joints forcing them to crack. Also when rocks
are near salt water, the water evaporates leaving behind salt crystals. Similarly as
temperatures rise further these crystals expand and exert pressure on the rock causing it
to slowly break apart.
•Exfoliation/Disintegration: This process is found in hot desert areas where there are
large diurnal temperature ranges. Rocks heat up during the day and expand, then cool
and contract at night. As a rock is a poor conductor of heat, stresses occur only in the
outer layers, causing peeling or exfoliation to occur. Griggs 1936 showed that moisture is
essential for this to happen and that temperature change alone did not cause rock
breakdown. Exfoliation is most common in granite.
•Pressure release/fracturing/ dilatation: This is the process whereby overlying rocks are
removed by erosion, causing underlying rocks to expand and fracture parallel to the
surface due to loss of pressure(referred to unloading). The unloading of pressure by
removal of underlying rocks causes cracks or joints to form at right angles to the
unloading surface. The cracks are lines of weakness in the rocks.
. As a rock is a poor conductor of heat, stresses occur only in the outer
layers, causing peeling or exfoliation to occur. Griggs 1936 showed that
moisture is essential for this to happen and that temperature change alone
did not cause rock breakdown. Exfoliation is most common in granite
/Disintegration
layers, causing peeling or exfoliation to occur. Griggs 1936 showed that
moisture is essential for this to happen and that temperature change alone
did not cause rock breakdown. Exfoliation is most common in granite
/Disintegration
Pressure release/fracturing/
dilatation:
dilatation:
Freeze Thaw
Exfoliation
Salt Crystallisation
Pressure Release
Exfoliation
Salt Crystallisation
Pressure Release
Chemical Weathering
•Carbonation: Occurs on rocks with calcium carbonate such as chalk and limestone.
Rainfall combines with dissolved CO2 to form a weak carbonic acid. When the
carbonic acid and calcium carbonate in rocks react they form a calcium bicarbonate
which is soluble. This is then carried away in percolating water, removing particles
holding the rock together and slowly breaking it apart.
•Hydrolysis: Occurs on rocks containing feldspar –notably granite. Feldspar reacts
with acid water to form kaolin, which is a soft clay mineral which weakens the rock.
It is described as the chemical breakdown due to a reaction with water.
•Hydration: is the process whereby certain minerals absorb water, expand and
change.
•Oxidation: Is the reaction of a substance with oxygen. Especially with iron
compounds leading to rusting.
•Carbonation: Occurs on rocks with calcium carbonate such as chalk and limestone.
Rainfall combines with dissolved CO2 to form a weak carbonic acid. When the
carbonic acid and calcium carbonate in rocks react they form a calcium bicarbonate
which is soluble. This is then carried away in percolating water, removing particles
holding the rock together and slowly breaking it apart.
•Hydrolysis: Occurs on rocks containing feldspar –notably granite. Feldspar reacts
with acid water to form kaolin, which is a soft clay mineral which weakens the rock.
It is described as the chemical breakdown due to a reaction with water.
•Hydration: is the process whereby certain minerals absorb water, expand and
change.
•Oxidation: Is the reaction of a substance with oxygen. Especially with iron
compounds leading to rusting.
Carbonation ^
Hydrolysis v
Hydration ^
Carbonation
Chemical
Weathering
Hydrolysis v
Hydration ^
Carbonation
Chemical
Weathering
How does climate affect weathering?
It appears that thewetter and more humid the climate, the deeper and more
intense the weathering becomes.
It appears that thewetter and more humid the climate, the deeper and more
intense the weathering becomes.
How does Climateaffect weathering
•The type and rate of weathering
varies with climate.
•Pelletier's diagram (1950) shows
how weathering is related to
moisture availability and average
annual temperatures in an area.
•Cold temperatures for instance,
would increase the number of
freeze thaw cycles.
•Whereas in warm moist regions
chemical weathering increases.
•Van Hoff's law states that the rate
of chemical weathering increases 2-
3 times for everything increase in
temperature of 10 degrees
•The type and rate of weathering
varies with climate.
•Pelletier's diagram (1950) shows
how weathering is related to
moisture availability and average
annual temperatures in an area.
•Cold temperatures for instance,
would increase the number of
freeze thaw cycles.
•Whereas in warm moist regions
chemical weathering increases.
•Van Hoff's law states that the rate
of chemical weathering increases 2-
3 times for everything increase in
temperature of 10 degrees
Describe the relationship shown on the graph between annual rainfall and chemical
weathering (1m)
Why do you think strong chemical weathering is placed on the graph where it is? (2m)
Describe the temperature and rainfall characteristics of the zone labeled‘Very Slight
weathering’. Try to explain why it is placed here. (4m)
Where would you place ‘freeze-thaw’ on the graph, and why?(2m)
Use the graph to explain the type of weathering that would mostly occur in Sabah (2m)
weathering (1m)
Why do you think strong chemical weathering is placed on the graph where it is? (2m)
Describe the temperature and rainfall characteristics of the zone labeled‘Very Slight
weathering’. Try to explain why it is placed here. (4m)
Where would you place ‘freeze-thaw’ on the graph, and why?(2m)
Use the graph to explain the type of weathering that would mostly occur in Sabah (2m)
•Answers
•1) As annual rainfall increases chemical weathering gets stronger
•2) Because there is more chemical weathering when there is higher rainfall and higher temperatures (For
example Carbonation)
3) Very slight weathering exists where mean annual rainfall is from 0-1000mm a year
•And when mean annual temperature s are from -15 0c to + 30 0c
•It is placed here as much weathering occurs with high rainfall and this area of the graph has low rainfall
•Thereforethere is only slight weathering
•4) Freeze-thaw should be placed on the graph where temperatures vary between -10 and +10 0Cand rainfall
is moderate
•This is so that water could freeze and thaw in cycles.
•5) Sabah is a wet tropical climate
•It would therefore experience strong chemical weathering
•1) As annual rainfall increases chemical weathering gets stronger
•2) Because there is more chemical weathering when there is higher rainfall and higher temperatures (For
example Carbonation)
3) Very slight weathering exists where mean annual rainfall is from 0-1000mm a year
•And when mean annual temperature s are from -15 0c to + 30 0c
•It is placed here as much weathering occurs with high rainfall and this area of the graph has low rainfall
•Thereforethere is only slight weathering
•4) Freeze-thaw should be placed on the graph where temperatures vary between -10 and +10 0Cand rainfall
is moderate
•This is so that water could freeze and thaw in cycles.
•5) Sabah is a wet tropical climate
•It would therefore experience strong chemical weathering
How does Geology affect weathering
•Rock type and structure also influence the rate and type of weathering due to…
•Chemical composition
•Nature of cements in sedimentary rocks
•Faults/Joints and bedding planes
•Rock type: Determines that resistanceof the rock to the weathering processes that
operate in a particular environment. Each rock type consists of different minerals
which are joined together by crystallisation, chemical bonding or cementing for
example –limestone consists of calcium carbonate and is therefore susceptible to
carbonation, whereas granite contains feldspar and is therefore susceptible to
hydrolysis.
•Rock structure: is also important as rocks consisting of many joints or faults have
lines of weakness along which penetrating weathering agents can attack, whereas
rocks without these are more resistant to weathering.
•Grain size: influences the speed at which rocks weather. Coarse grained rocks
weather quickly due to a large void space and high permeability, whereas fine
grainedrocks offer a greater surface area and are therefore more resistant. The
importance of individual materials was stressed by Goldish(1938). Rocks formed of
resistant minerals such as quartz and feldspar in granite will resist weathering, by
contrast to those consisting of weaker
•Rock type and structure also influence the rate and type of weathering due to…
•Chemical composition
•Nature of cements in sedimentary rocks
•Faults/Joints and bedding planes
•Rock type: Determines that resistanceof the rock to the weathering processes that
operate in a particular environment. Each rock type consists of different minerals
which are joined together by crystallisation, chemical bonding or cementing for
example –limestone consists of calcium carbonate and is therefore susceptible to
carbonation, whereas granite contains feldspar and is therefore susceptible to
hydrolysis.
•Rock structure: is also important as rocks consisting of many joints or faults have
lines of weakness along which penetrating weathering agents can attack, whereas
rocks without these are more resistant to weathering.
•Grain size: influences the speed at which rocks weather. Coarse grained rocks
weather quickly due to a large void space and high permeability, whereas fine
grainedrocks offer a greater surface area and are therefore more resistant. The
importance of individual materials was stressed by Goldish(1938). Rocks formed of
resistant minerals such as quartz and feldspar in granite will resist weathering, by
contrast to those consisting of weaker
How does rock type affect weathering?
How does rock structure affect weathering?
Limestone scenery
•Limestone pavement is a habitat with a high geological interest. Forms of limestone
pavement can be found in many places in the world, especially in Alpine and
Mediterranean areas, but these lack the distinctive surface patterning seen on British
pavements.
•Limestone pavement is a habitat with a high geological interest. Forms of limestone
pavement can be found in many places in the world, especially in Alpine and
Mediterranean areas, but these lack the distinctive surface patterning seen on British
pavements.
The two main types of weathering to affect Limestone are:
Carbonation a form of chemical weathering
Freeze thaw a form of mechanical weathering
Carbonation a form of chemical weathering
Freeze thaw a form of mechanical weathering
How does limestone scenery form?
1.Limestone is a hard sedimentary rock consisting of calcium carbonate, formed by the
deposition of plant and animal remains on the sea floor and is thus known as a
calcareous rock.
2.As limestone is a sedimentary rock, it is laid down in layers or ‘beds’ separated by
‘bedding planes’ which are caused by changes in deposition rates or content of
material deposited. Limestone pavements in England, Wales and Ireland are mainly
formed on deep beds of Carboniferous limestoneswhich were deposited about 350
million years ago.
3.The formation of limestone pavements in the UK and Ireland began with the scouring
of the limestone by kilometre thick glaciers during the last ice age. The weight of the
ice removed the soil that lay over the limestone, and also fractured the limestone
along bedding planes. Fractured rocks were stripped away leaving level platforms of
limestone
4.From the flat limestone surfaces, the characteristic features of limestone pavement
have been formed by water in the glacially deposited soil exploiting cracks and fissures
in the rock such as bedding planes and joints (lines of weakness in the rock generally
running at 90o to bedding planes).These faults allow water to percolate into the rock
and dissolve it via carbonation solution, forming caverns and other features.
5.Limestone pavement is a type of karst landform. Karst is the word for an area of
soluble rock in which the landforms are of a solutional nature where drainage is usually
underground through rock fissures rather than in surface streams.
1.Limestone is a hard sedimentary rock consisting of calcium carbonate, formed by the
deposition of plant and animal remains on the sea floor and is thus known as a
calcareous rock.
2.As limestone is a sedimentary rock, it is laid down in layers or ‘beds’ separated by
‘bedding planes’ which are caused by changes in deposition rates or content of
material deposited. Limestone pavements in England, Wales and Ireland are mainly
formed on deep beds of Carboniferous limestoneswhich were deposited about 350
million years ago.
3.The formation of limestone pavements in the UK and Ireland began with the scouring
of the limestone by kilometre thick glaciers during the last ice age. The weight of the
ice removed the soil that lay over the limestone, and also fractured the limestone
along bedding planes. Fractured rocks were stripped away leaving level platforms of
limestone
4.From the flat limestone surfaces, the characteristic features of limestone pavement
have been formed by water in the glacially deposited soil exploiting cracks and fissures
in the rock such as bedding planes and joints (lines of weakness in the rock generally
running at 90o to bedding planes).These faults allow water to percolate into the rock
and dissolve it via carbonation solution, forming caverns and other features.
5.Limestone pavement is a type of karst landform. Karst is the word for an area of
soluble rock in which the landforms are of a solutional nature where drainage is usually
underground through rock fissures rather than in surface streams.
Characteristics of limestone scenery
Features of limestone scenery
•Due to the solubility of limestone, limestone pavements are associated with some very
curious and unusual landforms. The most characteristic surface feature of limestone
pavements is their division into blocks, called clints,bounded by deep vertical fissures known
as grikes.Clintsand grikesform under relatively deep cover of soil where water, carrying
carbonic acid which is formed from dissolved carbon dioxide as well as organic acids from
decaying vegetation, picks out vertical lines of weakness (joints) in the rock. These fissures
widen over the years as the acidic water preferentially attacks the lines of weakness. As the
carbonic acid dissolved the lime stone a swallow hole usually is formed where water
percolates through bedding planes and jointsin the limestone due to gravity. As it moves in
faults in the limestone, it continues to chemically weather the rock (carbonation solution)
creating a cavern. As calcium bicarbonate drips off the ceiling of the cavern, wheather
evaporates leaving behind a calcite deposit which forms stalactites and stalagmites. As these
grow bigger they sometimes form, creating a pillar, therefore reversing the erosional process.
Sometimes however the cavern becomes very large and collapses under gravity, leaving
behind a gorge.
•Due to the solubility of limestone, limestone pavements are associated with some very
curious and unusual landforms. The most characteristic surface feature of limestone
pavements is their division into blocks, called clints,bounded by deep vertical fissures known
as grikes.Clintsand grikesform under relatively deep cover of soil where water, carrying
carbonic acid which is formed from dissolved carbon dioxide as well as organic acids from
decaying vegetation, picks out vertical lines of weakness (joints) in the rock. These fissures
widen over the years as the acidic water preferentially attacks the lines of weakness. As the
carbonic acid dissolved the lime stone a swallow hole usually is formed where water
percolates through bedding planes and jointsin the limestone due to gravity. As it moves in
faults in the limestone, it continues to chemically weather the rock (carbonation solution)
creating a cavern. As calcium bicarbonate drips off the ceiling of the cavern, wheather
evaporates leaving behind a calcite deposit which forms stalactites and stalagmites. As these
grow bigger they sometimes form, creating a pillar, therefore reversing the erosional process.
Sometimes however the cavern becomes very large and collapses under gravity, leaving
behind a gorge.
Factors controlling the amount and rate of
limestone solution
1.The amount of carbon dioxide in the atmosphere, groundwater and soil
2.The amount of water in contact with the limestone
3.Water temperature (limestone is more soluble with lower temperatures)
4.The turbulence of water
5.The presence of lead, iron, sulphides, sodium or potassium in the water.
6.Limestone weathers more quickly under soil cover than bare surfaces.
limestone solution
1.The amount of carbon dioxide in the atmosphere, groundwater and soil
2.The amount of water in contact with the limestone
3.Water temperature (limestone is more soluble with lower temperatures)
4.The turbulence of water
5.The presence of lead, iron, sulphides, sodium or potassium in the water.
6.Limestone weathers more quickly under soil cover than bare surfaces.
Granite Tors
•Granite is an igneous rock made up of 3
very resistant minerals to weathering
1.Quartz
2.Mica
3.Feldspar
Granite tors: are isolated blocks of granite which have weathered slower than the
granite around them.
Linton in 1955 advocated deep chemical weathering as the exponent, suggesting
that where joints in the rock were closer together the rock would be more deeply
weathered and so easily removed by later erosion. He saw a prolonged chemical
weathering under tropical conditions as the main factor in tor genesis.
A second theory favoured by arctic workers suggests mechanical weathering during
the ice age was responsible. King believed them to be nothing more than the
residual remains of sub aerial erosion surfaces.
•Granite is an igneous rock made up of 3
very resistant minerals to weathering
1.Quartz
2.Mica
3.Feldspar
Granite tors: are isolated blocks of granite which have weathered slower than the
granite around them.
Linton in 1955 advocated deep chemical weathering as the exponent, suggesting
that where joints in the rock were closer together the rock would be more deeply
weathered and so easily removed by later erosion. He saw a prolonged chemical
weathering under tropical conditions as the main factor in tor genesis.
A second theory favoured by arctic workers suggests mechanical weathering during
the ice age was responsible. King believed them to be nothing more than the
residual remains of sub aerial erosion surfaces.
Linton – 1955– Chemical weathering theory
Linton believed chemical weathering (Hydrolysis) created Tors
He argued that deep sub-surface chemical weathering of the batholith occurred with acidic ground
water travelling through the joints of the granite rock
He believes this occurred during humid conditions in the warm, wet periods in the Tertiary era (before
the ice age)
Decomposition was most rapid along joint planes where the water could trickle
This led to the formation of core stones (large rounded boulders of rock) under the ground
Denudation ( removal of the weathered material) then occurred during the ice age in glacial conditions
taking the growan (granite broken into pieces) away.
Linton believed chemical weathering (Hydrolysis) created Tors
He argued that deep sub-surface chemical weathering of the batholith occurred with acidic ground
water travelling through the joints of the granite rock
He believes this occurred during humid conditions in the warm, wet periods in the Tertiary era (before
the ice age)
Decomposition was most rapid along joint planes where the water could trickle
This led to the formation of core stones (large rounded boulders of rock) under the ground
Denudation ( removal of the weathered material) then occurred during the ice age in glacial conditions
taking the growan (granite broken into pieces) away.
Palmer and Nielson- 1962– Mechanical weathering Theory
They believed mechanical (freeze thaw) weathering was the dominant process in creating tors)
They believed freeze-thaw activity broke up the rock during the ice age
Solifluction ( the gradual movement of material down a slope) then removes the debris left from frost
shattering.
Clitter (a collection of rocks, pebbles lying on the ground) is sometimes left at the base of the hill below
the tor.
Their evidence to suggest that Linton is wrong, is that little Kaolin has been found in the joint, which
should be left behind after hydrolysis has occurred
They believed mechanical (freeze thaw) weathering was the dominant process in creating tors)
They believed freeze-thaw activity broke up the rock during the ice age
Solifluction ( the gradual movement of material down a slope) then removes the debris left from frost
shattering.
Clitter (a collection of rocks, pebbles lying on the ground) is sometimes left at the base of the hill below
the tor.
Their evidence to suggest that Linton is wrong, is that little Kaolin has been found in the joint, which
should be left behind after hydrolysis has occurred
Briefly explain how organic action can weather rocks. [3]
•Expect reference here to either chemical or physical weathering.
•Chemical weathering: through chelation with humicacids from decomposing vegetation
•enabling decomposition. The term chelation is not necessary as there is debate over its
•action but the mention of humicacids is.
•Physical weathering: by the action of roots in joints and cracks.
Explain the influence of rock type on the nature and rate of weathering. [8]
•A clear explanation of the way rock type affects weathering is needed. Reference to actual
•rock types and the way it influences the rate of the weathering because of its structure and
•mineralogy is needed: for example, the blocky, jointed nature of limestone and its
•susceptibility to carbonation means a faster rate of weathering. The mineralogy of granite
•would be a good example for chemical weathering of feldspar by hydrolysis. For high marks
•both nature and rate must be analysed.
•Maximum 6 if no link to rate.
Briefly describe how temperature influences rates of weathering.[4]
•• Increased temperatures speed up chemical reactions and thus
•increase the chemical weathering.
•• Variations of temperature around 0 °C means that water freezes
•and expands by around 9% of its volume. This means that
•temperature fluctuations also may increase the rate and extent of
•physical weathering processes such as freeze-thaw.
•• Expansion and contraction of the rock through fluctuations of
•temperature also affects rates of physical weathering such as
•exfoliation or granular disintegration.
•• High temperatures increase evaporation and encourage salt
•crystallisation.
•Expect reference here to either chemical or physical weathering.
•Chemical weathering: through chelation with humicacids from decomposing vegetation
•enabling decomposition. The term chelation is not necessary as there is debate over its
•action but the mention of humicacids is.
•Physical weathering: by the action of roots in joints and cracks.
Explain the influence of rock type on the nature and rate of weathering. [8]
•A clear explanation of the way rock type affects weathering is needed. Reference to actual
•rock types and the way it influences the rate of the weathering because of its structure and
•mineralogy is needed: for example, the blocky, jointed nature of limestone and its
•susceptibility to carbonation means a faster rate of weathering. The mineralogy of granite
•would be a good example for chemical weathering of feldspar by hydrolysis. For high marks
•both nature and rate must be analysed.
•Maximum 6 if no link to rate.
Briefly describe how temperature influences rates of weathering.[4]
•• Increased temperatures speed up chemical reactions and thus
•increase the chemical weathering.
•• Variations of temperature around 0 °C means that water freezes
•and expands by around 9% of its volume. This means that
•temperature fluctuations also may increase the rate and extent of
•physical weathering processes such as freeze-thaw.
•• Expansion and contraction of the rock through fluctuations of
•temperature also affects rates of physical weathering such as
•exfoliation or granular disintegration.
•• High temperatures increase evaporation and encourage salt
•crystallisation.
Explain the extent to which temperature affects the weathering of granite.[10]
•A discussion of how important temperature is in both physical and chemical weathering is
necessary. Howevertemperature is not the only factorand the candidate needs to make
reference to the other factors which also play a role, such as the nature of granite (jointing,
mineralogy). The availability of water, aspect and gradient of slope, as well as the amount
and nature of vegetation all play a part. Expect freeze-thaw, granular disintegration and
hydrolysis.
With the aid of diagrams, explain how rock type and structure may influence the
development of slopes. [8]
•A series of diagrams would be appropriate here, showing how the angle of the bedding
planes or joints affects the development of a slope. Reference to specific rock types, namely
granite or limestone, would enhance the answer when discussing how rock type affects the
development of a slope. The better answers would be specific with detail and examples.
•Weaker answers would be vague about which type of rock or the specific structures.
•Maximum of 5 marks with no diagram.
•A discussion of how important temperature is in both physical and chemical weathering is
necessary. Howevertemperature is not the only factorand the candidate needs to make
reference to the other factors which also play a role, such as the nature of granite (jointing,
mineralogy). The availability of water, aspect and gradient of slope, as well as the amount
and nature of vegetation all play a part. Expect freeze-thaw, granular disintegration and
hydrolysis.
With the aid of diagrams, explain how rock type and structure may influence the
development of slopes. [8]
•A series of diagrams would be appropriate here, showing how the angle of the bedding
planes or joints affects the development of a slope. Reference to specific rock types, namely
granite or limestone, would enhance the answer when discussing how rock type affects the
development of a slope. The better answers would be specific with detail and examples.
•Weaker answers would be vague about which type of rock or the specific structures.
•Maximum of 5 marks with no diagram.
Explain how rainfall affects the type and rate of weathering. [8]
•Candidates should explain how rainfall supplies the moisture needed for
•certain chemical reactions to take place in the case of chemical weathering.
•Carbonation with limestone is one example with the rainfall being acidulated
•as a result of absorption of carbon dioxide. A lack of rainfall results in only
•very slight weathering. This may underpin discussion of rate. As mean annual
•rainfall increases, the rate of weathering increases. This is most notable with
•chemical weathering. Physical weathering such as freeze-thaw and salt
•crystallisationmay be explained. Biological weathering, a result of the relation
•between rainfall and vegetation, may also be explained. Secondary impacts
•may be explained such as vegetation protecting land surfaces and erosion by
•water leading to the exposure of rock leading to pressure release and
•renewed weathering at the rock surface.
Explain the influence of climate on the weathering of rocks. [8]
•The answers should cover both physical and chemical weathering but there is no necessity
•for there to be an equal coverage. Candidates may answer generically or with reference to
•granite or limestone.
•The relationship between climate and weathering is more straightforward and many may
•refer to the Peltier diagram. The emphasis should be on explanation rather than just a
•description.
•Candidates should explain how rainfall supplies the moisture needed for
•certain chemical reactions to take place in the case of chemical weathering.
•Carbonation with limestone is one example with the rainfall being acidulated
•as a result of absorption of carbon dioxide. A lack of rainfall results in only
•very slight weathering. This may underpin discussion of rate. As mean annual
•rainfall increases, the rate of weathering increases. This is most notable with
•chemical weathering. Physical weathering such as freeze-thaw and salt
•crystallisationmay be explained. Biological weathering, a result of the relation
•between rainfall and vegetation, may also be explained. Secondary impacts
•may be explained such as vegetation protecting land surfaces and erosion by
•water leading to the exposure of rock leading to pressure release and
•renewed weathering at the rock surface.
Explain the influence of climate on the weathering of rocks. [8]
•The answers should cover both physical and chemical weathering but there is no necessity
•for there to be an equal coverage. Candidates may answer generically or with reference to
•granite or limestone.
•The relationship between climate and weathering is more straightforward and many may
•refer to the Peltier diagram. The emphasis should be on explanation rather than just a
•description.
•Briefly describe how rock type affects the rate of physical weathering.
•Reference to:
• the different rates of permeability (e.g.typically igneous rocks are less
•permeable than sedimentary rocks) (1)
• different rates of porosity (1)
• the blocky nature (jointing) such as limestone (1) or bedding planes
•such as a sandstone (1) strata etc. in some (1)
• different mineralogy affecting insolation weathering (1)
• types of physical weathering (freeze-thaw, heating/cooling, salt crystal
•growth, pressure release (dilatation)), and vegetation root action (1)
Explain how vegetation and relief affect the type of weathering. [8]
•Explanation might include:vegetation producing humic(organic) acids which may increase the rate
of weathering. The presence of microbes, such as fungi also affects the rate of weathering. Physical
weathering can be increased by the presence of roots from vegetation exerting pressure on the
rocks.
•Relief will have a potential effect such as a steeper angle of the slope may decrease the rate of
chemical weathering by removing moisture quicker from soils. Shallow slopes will aid infiltration
and chemical weathering of the bedrock. The aspect of the slope may determine the dominant
temperature regime, which may result in processes such as freeze-thaw
Rainfall is the most important factor in the weathering of rocks.’ With the aid of examples, how far
do you agree? [15]
•There may be detailed consideration of a case study/one or more examples, or a broadly conceived
response, drawing on several examples to illustrate the factors involved.
•Answers will need to be based on an understanding of the weathering of rocks and how rainfall
affects this weathering. Discussions could include
•Freeze/Thaw, Salt Crystal growth, Chemical Weathering, Biological
•Weathering, etc. Evaluation needs to be in terms of the role of other factors
•such as rock structure and composition, temperature, vegetation, relief, and
•human activity.
•Reference to:
• the different rates of permeability (e.g.typically igneous rocks are less
•permeable than sedimentary rocks) (1)
• different rates of porosity (1)
• the blocky nature (jointing) such as limestone (1) or bedding planes
•such as a sandstone (1) strata etc. in some (1)
• different mineralogy affecting insolation weathering (1)
• types of physical weathering (freeze-thaw, heating/cooling, salt crystal
•growth, pressure release (dilatation)), and vegetation root action (1)
Explain how vegetation and relief affect the type of weathering. [8]
•Explanation might include:vegetation producing humic(organic) acids which may increase the rate
of weathering. The presence of microbes, such as fungi also affects the rate of weathering. Physical
weathering can be increased by the presence of roots from vegetation exerting pressure on the
rocks.
•Relief will have a potential effect such as a steeper angle of the slope may decrease the rate of
chemical weathering by removing moisture quicker from soils. Shallow slopes will aid infiltration
and chemical weathering of the bedrock. The aspect of the slope may determine the dominant
temperature regime, which may result in processes such as freeze-thaw
Rainfall is the most important factor in the weathering of rocks.’ With the aid of examples, how far
do you agree? [15]
•There may be detailed consideration of a case study/one or more examples, or a broadly conceived
response, drawing on several examples to illustrate the factors involved.
•Answers will need to be based on an understanding of the weathering of rocks and how rainfall
affects this weathering. Discussions could include
•Freeze/Thaw, Salt Crystal growth, Chemical Weathering, Biological
•Weathering, etc. Evaluation needs to be in terms of the role of other factors
•such as rock structure and composition, temperature, vegetation, relief, and
•human activity.
questions
1. Briefly explain how organic action can weather rocks. [3]
2. Briefly describe how temperature influences rates of weathering.[4]
3. Explain the extent to which temperature affects the weathering
of granite.[10]
5. Explain how rainfall affects the type and rate of
weathering. [8]
6. Explain how vegetation and relief affect the type of weathering. [8]
7. Rainfall is the most important factor in the weathering of rocks.’
With the aid of examples, how far do you agree? [15]
1. Briefly explain how organic action can weather rocks. [3]
2. Briefly describe how temperature influences rates of weathering.[4]
3. Explain the extent to which temperature affects the weathering
of granite.[10]
5. Explain how rainfall affects the type and rate of
weathering. [8]
6. Explain how vegetation and relief affect the type of weathering. [8]
7. Rainfall is the most important factor in the weathering of rocks.’
With the aid of examples, how far do you agree? [15]
SLOPE PROCESSES AND DEVELOPMENT
Slopes
•A slope is described as an inclined surface or angle of inclination and can be…
1.sub aerial (exposed)
2.sub-marine (underwater)
3.Aggradational (depositional)
4.Degradational (erosional)
5.Transportational
6.Or a mixture
•Given the large scale of the definition geographers generally study the hill slope (the
area between the water shed and the base)
•Slope form = the shape of the slopes cross section
•Slope processes = activities acting on the slope
•Slope evaluation = development of slopes over time
•A slope is described as an inclined surface or angle of inclination and can be…
1.sub aerial (exposed)
2.sub-marine (underwater)
3.Aggradational (depositional)
4.Degradational (erosional)
5.Transportational
6.Or a mixture
•Given the large scale of the definition geographers generally study the hill slope (the
area between the water shed and the base)
•Slope form = the shape of the slopes cross section
•Slope processes = activities acting on the slope
•Slope evaluation = development of slopes over time
•Slope processes are the activities acting on the slopes
The slope system
•Slopes can be thought of as an open system (inputs and outputs)
•Inputs to the system = Energy from the sun, mass (water and sediment)
•Outputs from the system = Energy (re-radiated heat), and mass (water and
regolith). Regolithis the name for the unconsolidated material on top of rock
(soil etc)
The slope system
•Slopes can be thought of as an open system (inputs and outputs)
•Inputs to the system = Energy from the sun, mass (water and sediment)
•Outputs from the system = Energy (re-radiated heat), and mass (water and
regolith). Regolithis the name for the unconsolidated material on top of rock
(soil etc)
The diagram below shows a slope system and all the factors affecting it.
Some factors occur on the outside of the slope (exogenetic)
Some factors occur on the inside of the slope (endogenetic)
Some factors occur on the outside of the slope (exogenetic)
Some factors occur on the inside of the slope (endogenetic)
How does climate affect slopes
•Many slopes vary with climate…
•In humid areas slopes are generally rounder due to chemical weathering, soil creep and
fluvial transport.
•By contrast, in arid areas, slopes are jaggeredor straight owing to mechanical weathering.
•Climatic geomorphology studies how different processes operate in different climatic
zones. Climate affects the type and rate of processes that operate in the region. For
example in humid tropics, accelerated chemical weathering occurs due to hot wet
conditions and the availability of organic acids. Deep clays are produced favouring low
angle slopes.
•Many slopes vary with climate…
•In humid areas slopes are generally rounder due to chemical weathering, soil creep and
fluvial transport.
•By contrast, in arid areas, slopes are jaggeredor straight owing to mechanical weathering.
•Climatic geomorphology studies how different processes operate in different climatic
zones. Climate affects the type and rate of processes that operate in the region. For
example in humid tropics, accelerated chemical weathering occurs due to hot wet
conditions and the availability of organic acids. Deep clays are produced favouring low
angle slopes.
How does Geological Structures
affect slopes
•Faults, angles of dip and vulcanicity
influence the strength of rocks and
create potential weaknesses within it.
•Rock types and character affect the
vulnerability to weathering and the
degree of resistance to downslope
movement.
•Faulting may produce steep valley
sides and foldingcan produce steep or
gentle slopes.
•Geological structure can influence the
occurrence of land slides –slopes
consisting of multiple rock types are
more vulnerable to landslides due to
differential erosion.
•Regular jointing in rocks may also
increase the risk of movement as well
as increase the amount of water that
enters the rock.
affect slopes
•Faults, angles of dip and vulcanicity
influence the strength of rocks and
create potential weaknesses within it.
•Rock types and character affect the
vulnerability to weathering and the
degree of resistance to downslope
movement.
•Faulting may produce steep valley
sides and foldingcan produce steep or
gentle slopes.
•Geological structure can influence the
occurrence of land slides –slopes
consisting of multiple rock types are
more vulnerable to landslides due to
differential erosion.
•Regular jointing in rocks may also
increase the risk of movement as well
as increase the amount of water that
enters the rock.
How does Regolithaffect slopes
•Regolith is the layer of
unconsolidated material (lose) at
the earths surface covering bed
rock. It includes…
•Soil
•Scree
•Weathered bedrock and
•Deposited material.
•Its un-consolidated nature makes it prone to down slope movement.
Clay rich regolith are particularly unstable because of there ability to retain water.
•By contrast, where the regolith has a high pressure of sand particles, slope failure is
reduced.
•Soil can be considered apart of regolith. Its structure and texture will greatly influence
how much water it can hold. Clay soils hold more than sand soils. A deep clay on a
slope with removed vegetation would therefore have little resistance to mass
movement.
•Regolith is the layer of
unconsolidated material (lose) at
the earths surface covering bed
rock. It includes…
•Soil
•Scree
•Weathered bedrock and
•Deposited material.
•Its un-consolidated nature makes it prone to down slope movement.
Clay rich regolith are particularly unstable because of there ability to retain water.
•By contrast, where the regolith has a high pressure of sand particles, slope failure is
reduced.
•Soil can be considered apart of regolith. Its structure and texture will greatly influence
how much water it can hold. Clay soils hold more than sand soils. A deep clay on a
slope with removed vegetation would therefore have little resistance to mass
movement.
Slope Controls -Aspect
•Aspect relates to the direction in which a slope is facing. Aspect only really affects
local climate, not global ones. In the Northern Hemisphere, south facing slopes
receive far more sunlight than north facing ones. These are therefore much better
for agriculture and often settlement will locate there due to the better aspect.
•Aspect relates to the direction in which a slope is facing. Aspect only really affects
local climate, not global ones. In the Northern Hemisphere, south facing slopes
receive far more sunlight than north facing ones. These are therefore much better
for agriculture and often settlement will locate there due to the better aspect.
How does vegetation affect how
slopes look and act
•Vegetation can decrease overland runoff through interception and storage of
moisture.
•Deforested slopes are frequently exposed to intense erosion and gullying.
•Vegetation can also increase the chance of major landslides. Dense forests reduce
surface wash, causing a build-up of soil between trees, thus depending the regolith
and increasing the potential for failure.
slopes look and act
•Vegetation can decrease overland runoff through interception and storage of
moisture.
•Deforested slopes are frequently exposed to intense erosion and gullying.
•Vegetation can also increase the chance of major landslides. Dense forests reduce
surface wash, causing a build-up of soil between trees, thus depending the regolith
and increasing the potential for failure.
Rain splash erosion
•soilerosion caused from the impactof raindrops
•The impact of rain droplets on the soil surface often detaches
individual grains of soil moving them some distance from their
source
•On flat surfaces, the effect of rain drop impact is to
redistribute the material without any net transport in any
particular direction
•However, on a slope the influence of gravity and slope
encourage more material to be redistributed downslope
rather than upslope
•When slopes become 25 degrees or greater, almost all the
redistribution occurs in a downslope direction.
•soilerosion caused from the impactof raindrops
•The impact of rain droplets on the soil surface often detaches
individual grains of soil moving them some distance from their
source
•On flat surfaces, the effect of rain drop impact is to
redistribute the material without any net transport in any
particular direction
•However, on a slope the influence of gravity and slope
encourage more material to be redistributed downslope
rather than upslope
•When slopes become 25 degrees or greater, almost all the
redistribution occurs in a downslope direction.
Classification by type of movement
Different parts of a slope can be named differently
several controls , or things which affect how a slope
looks and acts. iea summary of the slope controls.
looks and acts. iea summary of the slope controls.
Mass movement
•Mass movement, is the downward movement by gravity of rock, regolith
(loose, weathered rock) and/or soil on the sloped top layers of the Earth’s
surface. It is a significant part of the process of erosion because it moves
material from high elevations to lower elevations. It can be triggeredby
natural events like earthquakes, volcanic eruptions and floodsbut gravity is
its driving force. Wateroften acts as alubricant in mass movement.
•Mass movement, is the downward movement by gravity of rock, regolith
(loose, weathered rock) and/or soil on the sloped top layers of the Earth’s
surface. It is a significant part of the process of erosion because it moves
material from high elevations to lower elevations. It can be triggeredby
natural events like earthquakes, volcanic eruptions and floodsbut gravity is
its driving force. Wateroften acts as alubricant in mass movement.
Slow movement
•Soil Creep: Very slow continuous process that occurs on very
gentle slopes because of the way soil particles repeatedly
expand and contract in wet and dry periods. When wet, soil
particles increase in size and weight, and expand at right
angles. When the soil dries out, it contracts vertically. As a
result, the soil slowly moves downslope.
Cycles of freeze thaw heave particles up on freezing and allow
them to fall further down slope when the ice melts. Alternating
hydration and dehydration have the same effect.
•Soil Creep: Very slow continuous process that occurs on very
gentle slopes because of the way soil particles repeatedly
expand and contract in wet and dry periods. When wet, soil
particles increase in size and weight, and expand at right
angles. When the soil dries out, it contracts vertically. As a
result, the soil slowly moves downslope.
Cycles of freeze thaw heave particles up on freezing and allow
them to fall further down slope when the ice melts. Alternating
hydration and dehydration have the same effect.
Soil creep/ heave
-Very slow and small scaleprocess.
-Occurs mainly in winter
-Individual soil particles are pushed to the surface by wetting, heating or freezing of
water
-Rates of 1-3mm per year in the UK
-Up to 10mm in tropical rainforest
-Very slow and small scaleprocess.
-Occurs mainly in winter
-Individual soil particles are pushed to the surface by wetting, heating or freezing of
water
-Rates of 1-3mm per year in the UK
-Up to 10mm in tropical rainforest
mass movement change from fast to slow and dry to wet.
So the wettest fastest mass movement is a mudflow
The slowest driest movement is a soil creep
So the wettest fastest mass movement is a mudflow
The slowest driest movement is a soil creep
There are two categories of mass
movement.
1.Slow movement: gravity is main factor, but
water also plays important role > Soil creep,
Rock Creep, Solidification
2.Fast movement: Water is main factor >
Landslide, earth flow, mud flow sheet wash
movement.
1.Slow movement: gravity is main factor, but
water also plays important role > Soil creep,
Rock Creep, Solidification
2.Fast movement: Water is main factor >
Landslide, earth flow, mud flow sheet wash
Talus creep
This is the slow movements of fragments on a scree slope
This is the slow movements of fragments on a scree slope
Evidence of soil creep
Slow movement
•Solifluction:flowage of saturated soil
down a steep slope.
Becausepermafrostis impermeable
to water, soil overlying it may
become oversaturated and slide
downslope under the pull of gravity.
Soil that has been opened and
weakened by frost action is most
susceptible. Movement is at a
maximum rate of a few inches per
day, eventually producing smooth,
gentle, concave slopes. Original
stratifications of the soil become
contorted if not completely
destroyed.
•Solifluction:flowage of saturated soil
down a steep slope.
Becausepermafrostis impermeable
to water, soil overlying it may
become oversaturated and slide
downslope under the pull of gravity.
Soil that has been opened and
weakened by frost action is most
susceptible. Movement is at a
maximum rate of a few inches per
day, eventually producing smooth,
gentle, concave slopes. Original
stratifications of the soil become
contorted if not completely
destroyed.
Fast movements
•Mudflowsare movement of materials such as sand, silt and
clay-sized particles, downhill due to prolonged or heavy
rainfall. When water saturates the ground e.g. heavy or
prolonged rainfall -it causes a thick, liquid downhill flow of
Earth in a lobe. The saturated soils and debris form a stream.
Some broad mudflows are rather viscous and therefore slow;
others begin very quickly and continue like an avalanche. They
usually occur on slopes of more than 10 degrees.
•Mudflowsare movement of materials such as sand, silt and
clay-sized particles, downhill due to prolonged or heavy
rainfall. When water saturates the ground e.g. heavy or
prolonged rainfall -it causes a thick, liquid downhill flow of
Earth in a lobe. The saturated soils and debris form a stream.
Some broad mudflows are rather viscous and therefore slow;
others begin very quickly and continue like an avalanche. They
usually occur on slopes of more than 10 degrees.
Fast movements
•Earth flow: Occurs on slopes between 5 and 15 degrees, often after
the regolith has become saturated, and flow then results. It
represents the intermediate stage between creep and mudflow.
Earthflows usually begin in a large basin on the upper part of a slope
where debris and weathered material accumulate; the movement,
usually set off by heavy rainfall, may be relatively slow or very fast,
depending on the amount of water present, the angle of the slope,
and other aspects of the terrain.Vegetation can be destroyed and
speeds range from 1 to 15km per year.
•Earth flow: Occurs on slopes between 5 and 15 degrees, often after
the regolith has become saturated, and flow then results. It
represents the intermediate stage between creep and mudflow.
Earthflows usually begin in a large basin on the upper part of a slope
where debris and weathered material accumulate; the movement,
usually set off by heavy rainfall, may be relatively slow or very fast,
depending on the amount of water present, the angle of the slope,
and other aspects of the terrain.Vegetation can be destroyed and
speeds range from 1 to 15km per year.
Rapid movements –Rock fall
•Rock fall: is a rapid free-fall of rock from a steep cliff face, usually where little or no
vegetation is found. The rock face is usually exposed and suffers from weathering on
a regular basis causing well jointed rocks to be detached from the cliff face and fall
quickly due to gravity –gathering as scree.
•Triggers are usually earthquakes, heavy rain or eruptions as well as undercutting and
traffic vibrations.
•Rock fall: is a rapid free-fall of rock from a steep cliff face, usually where little or no
vegetation is found. The rock face is usually exposed and suffers from weathering on
a regular basis causing well jointed rocks to be detached from the cliff face and fall
quickly due to gravity –gathering as scree.
•Triggers are usually earthquakes, heavy rain or eruptions as well as undercutting and
traffic vibrations.
-Falls occur on steep slopes (greater than 700)
–On bare rock faces where joints are exposedthey are more common
-Normally caused by weathering, and once the rocks are detachedthey fall under the
influence of gravity.
-If the fall is shortit produces straight scree, if it is longit forms a concave slope
–On bare rock faces where joints are exposedthey are more common
-Normally caused by weathering, and once the rocks are detachedthey fall under the
influence of gravity.
-If the fall is shortit produces straight scree, if it is longit forms a concave slope
Rapid movements
•Slides: occur when an entire mass of material move across a slip plane. This includes
rockslides, landslides and rotational slides, which are weakened by weathering.
•Slip planes occur for a variety of reasons
1.At the junction of two layers
2.At a fault line
3.Where there's a joint
4.Along a bedding plane
5.At a point beneath the surface where shear stress > shear strength
•Weak rocks such as clay have little shear strength and are particularly vulnerable to
the development of slip planes.
•Slides: occur when an entire mass of material move across a slip plane. This includes
rockslides, landslides and rotational slides, which are weakened by weathering.
•Slip planes occur for a variety of reasons
1.At the junction of two layers
2.At a fault line
3.Where there's a joint
4.Along a bedding plane
5.At a point beneath the surface where shear stress > shear strength
•Weak rocks such as clay have little shear strength and are particularly vulnerable to
the development of slip planes.
slides
-Slides occur when an entire mass of material moves along a slip plane
-They occur where there is a combination of weak rocks, and steep slope and
undercutting
-As the slide moves along the slip plane, it tends to retain its shape and structure
until it hits the bottom of the slope
-Slip planes occur at fault lines, along a bedding plane and at the junction of two
layers
-Rock slides are when a huge volume of rock moves together like in Madison River
Valley in 1959 (80 million tonnes of rock moved in less than a minute)
-Landslides include rock, stones and soil
-Slides occur when an entire mass of material moves along a slip plane
-They occur where there is a combination of weak rocks, and steep slope and
undercutting
-As the slide moves along the slip plane, it tends to retain its shape and structure
until it hits the bottom of the slope
-Slip planes occur at fault lines, along a bedding plane and at the junction of two
layers
-Rock slides are when a huge volume of rock moves together like in Madison River
Valley in 1959 (80 million tonnes of rock moved in less than a minute)
-Landslides include rock, stones and soil
Rapid movements -slides
•Landslides: Is the down slope movement of large blocks of material that moves as a
coherent mass –it retains its internal structure until hitting the base of the slope and
fracturing into smaller pieces.
•It is more common over wet periods and on steep slopes, often coastlines.
•Landslides are very sensitive to water content
•Landslides: Is the down slope movement of large blocks of material that moves as a
coherent mass –it retains its internal structure until hitting the base of the slope and
fracturing into smaller pieces.
•It is more common over wet periods and on steep slopes, often coastlines.
•Landslides are very sensitive to water content
Slumps & Flows
-Slumps occur on weaker rocks , especially clay.
-This is often rotational along a curved slip plane
-Clay absorbs water and becomes saturated and exceeds its
liquid limit
-It then flows along a slip plane.
-This can be due to the undercutting at the base of a cliff
-Flows are more continuous and less jerky
-Slumps occur on weaker rocks , especially clay.
-This is often rotational along a curved slip plane
-Clay absorbs water and becomes saturated and exceeds its
liquid limit
-It then flows along a slip plane.
-This can be due to the undercutting at the base of a cliff
-Flows are more continuous and less jerky
Rotational slumping
•Slumps:Occur for a number of reasons usually where softer material overlies
resistant rocks, especially clay that becomes saturated and heavy. They can also
develop due to undercutting of cliffs by wave action as well as human activity
increasing pressure on rocks, as shown in Scarborough in 1993, where the Holbeck
Hall Hotel slumped into the sea.
•Slumps:Occur for a number of reasons usually where softer material overlies
resistant rocks, especially clay that becomes saturated and heavy. They can also
develop due to undercutting of cliffs by wave action as well as human activity
increasing pressure on rocks, as shown in Scarborough in 1993, where the Holbeck
Hall Hotel slumped into the sea.
Rapid movement -Avalanche
•rapid movement of snow, ice rock and earth downslope
•Can reach up to 400km / hr. especially fast if air gets trapped between rock
fragments as it acts rather like a hovercraft cushion
•Common in mountainous areas, on slopes of over 22º and on North facing slopes
where a lack of sun limits snow stability
•In winter new snow falling on old triggers dry avalanches
•In spring partially melted snow makes the slope unstable and skiers often trigger
movement
•rapid movement of snow, ice rock and earth downslope
•Can reach up to 400km / hr. especially fast if air gets trapped between rock
fragments as it acts rather like a hovercraft cushion
•Common in mountainous areas, on slopes of over 22º and on North facing slopes
where a lack of sun limits snow stability
•In winter new snow falling on old triggers dry avalanches
•In spring partially melted snow makes the slope unstable and skiers often trigger
movement
Avalanches
-Avalanches are rapid movements of snow down a slope
-They are common in mountainous areas
-New snow can fall of older snow ( a dry avalanche)
-Or partially melted snow moves ( a wet avalanche)
-They occur most frequently on slopes over 22o
-They also occur on north facing slopes where the lack of snow limits snow
stability (doesn’t have time to cohesewith partial melting)
-Avalanches are rapid movements of snow down a slope
-They are common in mountainous areas
-New snow can fall of older snow ( a dry avalanche)
-Or partially melted snow moves ( a wet avalanche)
-They occur most frequently on slopes over 22o
-They also occur on north facing slopes where the lack of snow limits snow
stability (doesn’t have time to cohesewith partial melting)
Landslides (6m)
•Landslides are the result of sudden and massive slope failure. This occurs along a
slideplanewhere shear stress overcomes shear strength. This could be due to a
geological unconformity or to the percolation of water. Human agency can play a
part in producing instability in slopes and hence land slides through increases in
weight (buildings reservoirs etc), undercutting and diversions of water flows. The
result is to produce a shallower slope where the angle of rest has been reduced and
the length of the slope increased.
•Landslides are the result of sudden and massive slope failure. This occurs along a
slideplanewhere shear stress overcomes shear strength. This could be due to a
geological unconformity or to the percolation of water. Human agency can play a
part in producing instability in slopes and hence land slides through increases in
weight (buildings reservoirs etc), undercutting and diversions of water flows. The
result is to produce a shallower slope where the angle of rest has been reduced and
the length of the slope increased.
Causes of mass movement
-Why do mass movements occur?
•Safety Factor (relative strength or resistance of a slope) Rock particles on slopes are held on the slope
by friction in a state of dynamic equilibrium. Their steady state (not moving) represents a balance
between the internal (within/ between the particles known as internal or shear strength) and external
forces (known as external/shear stress). When shear strength = shear stress = no movement. If one is
greater than the other = movement.
•Volcanic activity many times causes huge mudflows when the icy cover of a volcano melts and mixes
with the soil to form mud as the magma in the volcano stirs preceding an eruption.
•Human modification of the land orweathering and erosionhelp loosen large chunks of earth and start
them sliding downhill.
•Vibrations from machinery, traffic, weight loading from accumulation of snow; stockpiling of rock or
ore; from waste piles and from buildings and other structures.
•Gravitational pull of the earth on soil, rocks, and mud.
•Wateris a very important factor in influencing slope stability. Particles in the soil stick together if it
rains, the rain infiltrates via the pores and lubricates the weathered material therefore reduces
friction and makes the weathered material easier to move down the slopes. Water may also increase
external stress because it adds weight to the slope (because of an increase in pore pressure)
•If an area has decreased vegetation, it will be more prone to mass wasting. Vegetation stabilizes soil
particles on the surface and anchors soil under the surface through its root system. This is much like
comparing two sand dunes on a beach. If one sand dune has grasses growing on it, it will resist the
erosion of water and wind better than a sand dune without vegetation.
•Another factor that plays a role in mass wasting is earthquakes. The violent shakingthat occurs in a
region where an earthquake takes place has the ability to break off sectionsof mountains or hills,
causing them to slide down the slope.
-Why do mass movements occur?
•Safety Factor (relative strength or resistance of a slope) Rock particles on slopes are held on the slope
by friction in a state of dynamic equilibrium. Their steady state (not moving) represents a balance
between the internal (within/ between the particles known as internal or shear strength) and external
forces (known as external/shear stress). When shear strength = shear stress = no movement. If one is
greater than the other = movement.
•Volcanic activity many times causes huge mudflows when the icy cover of a volcano melts and mixes
with the soil to form mud as the magma in the volcano stirs preceding an eruption.
•Human modification of the land orweathering and erosionhelp loosen large chunks of earth and start
them sliding downhill.
•Vibrations from machinery, traffic, weight loading from accumulation of snow; stockpiling of rock or
ore; from waste piles and from buildings and other structures.
•Gravitational pull of the earth on soil, rocks, and mud.
•Wateris a very important factor in influencing slope stability. Particles in the soil stick together if it
rains, the rain infiltrates via the pores and lubricates the weathered material therefore reduces
friction and makes the weathered material easier to move down the slopes. Water may also increase
external stress because it adds weight to the slope (because of an increase in pore pressure)
•If an area has decreased vegetation, it will be more prone to mass wasting. Vegetation stabilizes soil
particles on the surface and anchors soil under the surface through its root system. This is much like
comparing two sand dunes on a beach. If one sand dune has grasses growing on it, it will resist the
erosion of water and wind better than a sand dune without vegetation.
•Another factor that plays a role in mass wasting is earthquakes. The violent shakingthat occurs in a
region where an earthquake takes place has the ability to break off sectionsof mountains or hills,
causing them to slide down the slope.
slope failure to occur there needs to be a one of the following situations
or a combination of the two
•1)A reduction in shear strength/resistance
•(The internal resistance of the slope itself)
•2)An increase in shear stress
•(The forces that attempt to pull a mass down slope)
or a combination of the two
•1)A reduction in shear strength/resistance
•(The internal resistance of the slope itself)
•2)An increase in shear stress
•(The forces that attempt to pull a mass down slope)
Shear Strength and Resistance
•Slope failure is caused by two factors…
1.A reductionin the internal resistance or shear strength of a slope (ability to overcome
gravity)
2.An increase in shear stress (forces trying to pull a mass downslope)
3.When the shear strength and shear stress are in equillibriumthere is no mass
movement –when shear stress exceeds a slopes shear strength mass movement will
occur.
•Downward movement can be opposed by…
•Friction: can be overcome on gentle slope angles if water is present.
•Cohesive forces: bind particles to the slope. Clay may have high cohesion, but this may
reduce as water contents get too high.
•Vegetation: binds the soil and therefore stabilises slopes
•Slope failure is caused by two factors…
1.A reductionin the internal resistance or shear strength of a slope (ability to overcome
gravity)
2.An increase in shear stress (forces trying to pull a mass downslope)
3.When the shear strength and shear stress are in equillibriumthere is no mass
movement –when shear stress exceeds a slopes shear strength mass movement will
occur.
•Downward movement can be opposed by…
•Friction: can be overcome on gentle slope angles if water is present.
•Cohesive forces: bind particles to the slope. Clay may have high cohesion, but this may
reduce as water contents get too high.
•Vegetation: binds the soil and therefore stabilises slopes
Factors that contribute to shear stress
•Removal of lateral support through undercutting or slope steepening –Erosion by
rivers, glaciers, wave action, faulting, previous rock falls or slides.
•Removal of underlying support –Undercutting by rivers, waves, sub-surface solution,
loss of strength by extrusion of underlying sediments.
•Loading of slope –Weight of water, vegetation, and accumulation of debris.
•Lateral pressure –Water in cracks, freezing in cracks, swelling and pressure release.
•Transient stresses –Earthquakes and movement of trees in the wind.
•Removal of lateral support through undercutting or slope steepening –Erosion by
rivers, glaciers, wave action, faulting, previous rock falls or slides.
•Removal of underlying support –Undercutting by rivers, waves, sub-surface solution,
loss of strength by extrusion of underlying sediments.
•Loading of slope –Weight of water, vegetation, and accumulation of debris.
•Lateral pressure –Water in cracks, freezing in cracks, swelling and pressure release.
•Transient stresses –Earthquakes and movement of trees in the wind.
Factors that contribute to reduced shear
strength:
•Weathering effects –Disintegration of granular rocks, hydration of clay materials,
dissolution of cementing minerals in rock or soil.
•Changes in pore water pressure –Saturation or softening of material
•Changes in structure –Creation of fissures in shale's and clays, remoulding of sand
and sensitive clay.
•Organic effects –Burrowing of animals and decaying tree root
strength:
•Weathering effects –Disintegration of granular rocks, hydration of clay materials,
dissolution of cementing minerals in rock or soil.
•Changes in pore water pressure –Saturation or softening of material
•Changes in structure –Creation of fissures in shale's and clays, remoulding of sand
and sensitive clay.
•Organic effects –Burrowing of animals and decaying tree root
VajontDam Debris/Rock SlideCase
Study: Causes and Effects (Impacts)
Study: Causes and Effects (Impacts)
•Completed in 1960, the VaiontDam was the world’s highest thin arch dam.
•It reached 265 metresabove the floor of the valley below.
•It was built to supply hydroelectric power to the rapidly growing large cities of
northern Italy
•
•In October 1963a massive landslide occurred on the slopes surrounding the
reservoir behind the dam
•260 million cubic metresof debris (rock, mud and vegetation) slid into the reservoir
at 30 metresper second.
•This displaced 50 million cubic metresof water with waves at 250 metreshigh which
overflowed the dam.
•It reached 265 metresabove the floor of the valley below.
•It was built to supply hydroelectric power to the rapidly growing large cities of
northern Italy
•
•In October 1963a massive landslide occurred on the slopes surrounding the
reservoir behind the dam
•260 million cubic metresof debris (rock, mud and vegetation) slid into the reservoir
at 30 metresper second.
•This displaced 50 million cubic metresof water with waves at 250 metreshigh which
overflowed the dam.
The wave of water destroyed the villages of Langarone, Casso, Piaroso, Rivalta and Fae
killing between 1900 and 2500 people.
killing between 1900 and 2500 people.
•Events leading up to the landslide
•In March 1960 –during first filling of the reservoir, a small landslide occurred,
the area was monitored but filling continued.
•November 1960-during more filling, large landslide where 700,000 cubic
metres material slid into reservoir in 10 minutes. Reaction to this event was
to lower the reservoir level of water. (engineers decided there was no way to
stabilise the left bank so lowering the water was the only viable option)
•Continued to keep filling the reservoirs. Numerous small landslides occurred,
and each time the reservoir level was lowered to combat this.
•In March 1960 –during first filling of the reservoir, a small landslide occurred,
the area was monitored but filling continued.
•November 1960-during more filling, large landslide where 700,000 cubic
metres material slid into reservoir in 10 minutes. Reaction to this event was
to lower the reservoir level of water. (engineers decided there was no way to
stabilise the left bank so lowering the water was the only viable option)
•Continued to keep filling the reservoirs. Numerous small landslides occurred,
and each time the reservoir level was lowered to combat this.
What were the causes and impacts of this disaster? Any cause highlighted in yellow
increased shear stress Any cause highlighted in green reduced shear strength
increased shear stress Any cause highlighted in green reduced shear strength
HUMAN IMPACT
What influences mass movement?
•The actual movement itself can be influenced by both human and physical factors;
•Amount and type of vegetation–Less vegetation means the land is prone to damage. More
vegetation, such as trees and bushes means that they can intercept and help prevent the land
from damage. Also, roots from the vegetation make the soil stronger as they bind the soil.
•Degree of weathering and erosion–Higher amounts of weathering and erosion leads to the
actual movement more likely to happen-there is more material available to move. Processes
such as frost shattering, wetting & drying and heating & cooling loosen the soil. Removal of
material from the base of the slope by marine or fluvial erosion destabilises the slope.
•Amount of moisture present–If the land is heavily saturated, the material is loosened and
therefore more likely to collapse.
•Human activity–Recreational/leisure activities (walking, golf courses etc) and farming all
damage the slope and weaken it. Road, railway and housing construction.
•Type and structure of rock–Weaker rocks are more liable to collapse, whereas harder rocks
retain their structure. Porous rocks allow water into the rock therefore weakening it, whereas
impermeable rocks do not.
•Slope angle–Higher slopes mean quicker/more rapid movement.
•Climate–More rain leads to heavier saturation, more weathering/erosion equals quicker rates
of mass movement. Slopes will become weaker quicker.
•The actual movement itself can be influenced by both human and physical factors;
•Amount and type of vegetation–Less vegetation means the land is prone to damage. More
vegetation, such as trees and bushes means that they can intercept and help prevent the land
from damage. Also, roots from the vegetation make the soil stronger as they bind the soil.
•Degree of weathering and erosion–Higher amounts of weathering and erosion leads to the
actual movement more likely to happen-there is more material available to move. Processes
such as frost shattering, wetting & drying and heating & cooling loosen the soil. Removal of
material from the base of the slope by marine or fluvial erosion destabilises the slope.
•Amount of moisture present–If the land is heavily saturated, the material is loosened and
therefore more likely to collapse.
•Human activity–Recreational/leisure activities (walking, golf courses etc) and farming all
damage the slope and weaken it. Road, railway and housing construction.
•Type and structure of rock–Weaker rocks are more liable to collapse, whereas harder rocks
retain their structure. Porous rocks allow water into the rock therefore weakening it, whereas
impermeable rocks do not.
•Slope angle–Higher slopes mean quicker/more rapid movement.
•Climate–More rain leads to heavier saturation, more weathering/erosion equals quicker rates
of mass movement. Slopes will become weaker quicker.
Physical causes
•Natural hazards such as volcanic eruptions and earthquakes exceed the strength of the
rock, making it difficult for the slope to retain its structure. Slopes can fail during
earthquakes and cause major damage to structures and facilities as well as people.
•An example of this is the Huascaran Avalanche triggered by the Peru earthquake in 1970.
An offshore earthquake in the Pacific Ocean (7.7 on the Richter scale) triggered rock and
snow avalanches on NevadoHuascaran. The movement began as a rock fall, but soon
transformed into a debris avalanche and then a debris flow, about 100 million cubic
metres of material. The overall vertical drop was approximately 4000 metres and
travelled 16km laterally. The debris buried the town of Yungay, killing 18,000 people.
•Other physical factors, such as heavy rainfall, can also lead to slope instability and thus
failure. If there is a prolonged period or heavy rainfall, the slope becomes heavily
saturated. The water infiltrates and percolates into the slope, making it weaker. Snow
melt works in the same way.
•Normal everyday processes such as gravitycan also lead to slope failure. Gravity has two
effects; it acts to move the material down slope (slide component) and it acts to stick the
particle to the slope (stick component). The down slope movement is proportional to
the weight of the particle and the slope angle. Water lubricated particles, and, in some
cases, fills the spaces between the particles. This forces them apart under pressure. Pore
pressure will greatly increase the ability of the material to move. This factor is
particularly important in movements of wet material on low angleslopes
•Natural hazards such as volcanic eruptions and earthquakes exceed the strength of the
rock, making it difficult for the slope to retain its structure. Slopes can fail during
earthquakes and cause major damage to structures and facilities as well as people.
•An example of this is the Huascaran Avalanche triggered by the Peru earthquake in 1970.
An offshore earthquake in the Pacific Ocean (7.7 on the Richter scale) triggered rock and
snow avalanches on NevadoHuascaran. The movement began as a rock fall, but soon
transformed into a debris avalanche and then a debris flow, about 100 million cubic
metres of material. The overall vertical drop was approximately 4000 metres and
travelled 16km laterally. The debris buried the town of Yungay, killing 18,000 people.
•Other physical factors, such as heavy rainfall, can also lead to slope instability and thus
failure. If there is a prolonged period or heavy rainfall, the slope becomes heavily
saturated. The water infiltrates and percolates into the slope, making it weaker. Snow
melt works in the same way.
•Normal everyday processes such as gravitycan also lead to slope failure. Gravity has two
effects; it acts to move the material down slope (slide component) and it acts to stick the
particle to the slope (stick component). The down slope movement is proportional to
the weight of the particle and the slope angle. Water lubricated particles, and, in some
cases, fills the spaces between the particles. This forces them apart under pressure. Pore
pressure will greatly increase the ability of the material to move. This factor is
particularly important in movements of wet material on low angleslopes
Human impact -Weathering
•Weathering processes can be intensified by local climate. Changes in
the nature and rate of weathering are closely linked to air quality.
•Increased emissions of sulphur dioxide (from burning fossil fuels)
has led to high levels of sulphuric acid. Chemical reactions with
sulphuric acid can create salts such as calcium sulphate and
magnesium sulphate, which can weather rocks.
•Similarly, as atmospheric levels of carbon dioxide increase, the
potential for carbonation increases. Thus as carbon dioxide levels
rise, so does the potential for increased weathering in rocks such as
chalks and limestone containing calcium carbonate.
•Human activity has many impacts on the nature and rate of
limestone denudation…
1.Burning of fossil fuels and deforestationare increasing carbon
dioxide levels.
2.Agriculture and forestry are affecting soil acidity
3.Increased lighting in caves allows plants to grow and biological
weathering has increased in some cases due to increased levels of
organic acids.
•Weathering processes can be intensified by local climate. Changes in
the nature and rate of weathering are closely linked to air quality.
•Increased emissions of sulphur dioxide (from burning fossil fuels)
has led to high levels of sulphuric acid. Chemical reactions with
sulphuric acid can create salts such as calcium sulphate and
magnesium sulphate, which can weather rocks.
•Similarly, as atmospheric levels of carbon dioxide increase, the
potential for carbonation increases. Thus as carbon dioxide levels
rise, so does the potential for increased weathering in rocks such as
chalks and limestone containing calcium carbonate.
•Human activity has many impacts on the nature and rate of
limestone denudation…
1.Burning of fossil fuels and deforestationare increasing carbon
dioxide levels.
2.Agriculture and forestry are affecting soil acidity
3.Increased lighting in caves allows plants to grow and biological
weathering has increased in some cases due to increased levels of
organic acids.
Mass movement –Human impact
•Mass movement is the movement of matter on a slope due to gravity. This varies with the nature of the
material, topography, climate and vegetation. Mass movement can be increased and triggered by human
activities such as…
1.Building, excavation, drainage or agriculture.
2.Destabilising of slopes
3.Footpath trampling in recreational areas (increases erosion)
4.Piling up of soils and rocks into unstable accumulations
5.Undercutting and overloading.
6.Urbanisationcan completely destroy the slope’s structure. In LEDC cities such as Rio de Janeiro, Brazil, the
city often has little room to accommodate the population. The city and its population begins to spread out,
and the low income residents are forced to build on the only available land, usually on steep slopes.
7.Miningcan also have a severe effect on the internal structure of the slope. Continuous mining can
eventually destabilise the slope and force it to collapse. This is also similar when extracting resources.
8.Deforestation, which means there are no roots to bind the soil/earth together, However vegetation can
also increase the chance of landslips. In dense forests, surface runoff is reduced causing a build up of soil
between trees. This extra weight of this regolith increases the potential for failure.
•Mass movement is the movement of matter on a slope due to gravity. This varies with the nature of the
material, topography, climate and vegetation. Mass movement can be increased and triggered by human
activities such as…
1.Building, excavation, drainage or agriculture.
2.Destabilising of slopes
3.Footpath trampling in recreational areas (increases erosion)
4.Piling up of soils and rocks into unstable accumulations
5.Undercutting and overloading.
6.Urbanisationcan completely destroy the slope’s structure. In LEDC cities such as Rio de Janeiro, Brazil, the
city often has little room to accommodate the population. The city and its population begins to spread out,
and the low income residents are forced to build on the only available land, usually on steep slopes.
7.Miningcan also have a severe effect on the internal structure of the slope. Continuous mining can
eventually destabilise the slope and force it to collapse. This is also similar when extracting resources.
8.Deforestation, which means there are no roots to bind the soil/earth together, However vegetation can
also increase the chance of landslips. In dense forests, surface runoff is reduced causing a build up of soil
between trees. This extra weight of this regolith increases the potential for failure.
How to reduce impacts of mass
movement
•the replanting of trees, or afforestation, can stabilise the
slope. The roots from the trees will bind the soil, making it
harder to collapse.
•Avoid building structures on the slopes (but some may deter
this advice and continue to build)
•Improve slope drainage (reduce the impact of the water)
•Attach the slope material to the bedrock with physical
restraints –this can include things such as chicken wire
movement
•the replanting of trees, or afforestation, can stabilise the
slope. The roots from the trees will bind the soil, making it
harder to collapse.
•Avoid building structures on the slopes (but some may deter
this advice and continue to build)
•Improve slope drainage (reduce the impact of the water)
•Attach the slope material to the bedrock with physical
restraints –this can include things such as chicken wire
impact of human activities on rocks,
weathering and slopes
•quarrying
•mining
•pollution
•acid rain
•dumping material on the Earth’s surface
weathering and slopes
•quarrying
•mining
•pollution
•acid rain
•dumping material on the Earth’s surface
•Human’s impact on the shape and form of slopes
•How and to what extent can human activities affect the shape and
form of slopes? [10]
•Explain how human activities may influence the form and
development of slopes. [10]
•Human’s impact on the stability of a slope
•
•To what extent can human activities affect slope stability? [10]
•To what extent can human activities affect the stability and shape of
slopes? [10]
•How and to what extent can human activities affect the shape and
form of slopes? [10]
•Explain how human activities may influence the form and
development of slopes. [10]
•Human’s impact on the stability of a slope
•
•To what extent can human activities affect slope stability? [10]
•To what extent can human activities affect the stability and shape of
slopes? [10]
Human’s impact on the rate and
type of weathering
Explain how acid rain may affect the weathering of rocks[5]
Explain the extent to which human activities can affect the weathering of rocks [10]
Explain how human activities may affect the nature and intensity of weathering. [8]
type of weathering
Explain how acid rain may affect the weathering of rocks[5]
Explain the extent to which human activities can affect the weathering of rocks [10]
Explain how human activities may affect the nature and intensity of weathering. [8]
Acidification causes and impacts: added to the websitebyMaxime Porcheron, Wellington Wong (Year 12 2015)
What is Acidification?
What is Acidification?
•Sulphur Dioxide (SO2) and Nitrogen Oxides (NO3) are emitted from industrial
complexes, vehicles and urban areas.
•Some of these oxides fall directly to the ground as dry deposition close to the
source in the form of gases, particles and aerosols.
•These oxides can be carried thousands of kilometersaway from the source.
The longer the oxides remain in the air, the greater the chance they will be
oxidized, forming Sulphuric acid (H2SO4) and Nitric Acid (HNO3).
•These acids then dissolve in cloud droplets (rain, snow, mist, hail) and reach
the ground as wet deposition.
complexes, vehicles and urban areas.
•Some of these oxides fall directly to the ground as dry deposition close to the
source in the form of gases, particles and aerosols.
•These oxides can be carried thousands of kilometersaway from the source.
The longer the oxides remain in the air, the greater the chance they will be
oxidized, forming Sulphuric acid (H2SO4) and Nitric Acid (HNO3).
•These acids then dissolve in cloud droplets (rain, snow, mist, hail) and reach
the ground as wet deposition.
The impacts of acidification
•Acid rain and the dry deposition of acidic particles contribute to the
corrosion of metals such as bronze, the deterioration of paint and stone
such as marble and limestone. These effects significantly reduce the
societal value of buildings, bridges, cultural objects such as statues and
monuments.
•Dry deposition of acidic compounds can also dirty buildings and other
structures, leading to increased maintenance costs. To reduce damage to
automotive paint caused by acid rain and acidic dry deposition, some
manufacturers use acid-resistant paints, at an average cost of $5 for each
new vehicle or a total of $61 million per year for all new cars and trucks
sold in the U.S
•Over 18,000 lakes in Sweden are acidified, 4000 of them or seriously
affected. Fish stocks in about 9000 Swedish lakes, mostly in the south and
the centreof the country are also very badly affected. Sweden aluminum
levels of up to 1.7mg/l compared to the safe limit of 0.2mg/l. High metal
mercury in fish can cause serious health problems when eaten by people.
•Trees and forests are severely affected by acid rain. Sulphuricdioxide
interferes with the process of photo synthesis.
•The removal of a whole tree, branch included can be equivalent to the
accumulation of 60 years of acid rain.
•Acid rain and the dry deposition of acidic particles contribute to the
corrosion of metals such as bronze, the deterioration of paint and stone
such as marble and limestone. These effects significantly reduce the
societal value of buildings, bridges, cultural objects such as statues and
monuments.
•Dry deposition of acidic compounds can also dirty buildings and other
structures, leading to increased maintenance costs. To reduce damage to
automotive paint caused by acid rain and acidic dry deposition, some
manufacturers use acid-resistant paints, at an average cost of $5 for each
new vehicle or a total of $61 million per year for all new cars and trucks
sold in the U.S
•Over 18,000 lakes in Sweden are acidified, 4000 of them or seriously
affected. Fish stocks in about 9000 Swedish lakes, mostly in the south and
the centreof the country are also very badly affected. Sweden aluminum
levels of up to 1.7mg/l compared to the safe limit of 0.2mg/l. High metal
mercury in fish can cause serious health problems when eaten by people.
•Trees and forests are severely affected by acid rain. Sulphuricdioxide
interferes with the process of photo synthesis.
•The removal of a whole tree, branch included can be equivalent to the
accumulation of 60 years of acid rain.
Mining impacts:
•Habitat destruction
•Open cast mining (also known as strip mining) is a form of extensive excavation in which the
overlying material (overburden) is removed by machinery, revealing seams or deposit below. This
destroys the homes of animalsand it completely removes the habitat
•Disposal of waste rocks and ‘tailings’ (impurities left behind after mineral has been extracted by
ore) may destroy the ecosystem
•Smelting (melting metal) causes widespread deforestation. The Grande Carajasproject in Brazil
removes up to 50000 hectares of tropical forest each year
•Pollution
•Copper mining is polluting: to produce 9 million tons of copper = creating 990million tons of waste
rock
•Results from extraction, transport and processing of the raw materials and affects air, soil and
water. Water affected by heavy metal pollution, acid mine drainage, eutrophication (lots of
nutrients in lake because of runoff from land leading to dense growth of water plants) and
deoxygenation.
•The use of mercury to separate fine gold particles from other minerals in riverbed sediments leads
to contamination in rivers. Mercury is highly toxic
•Habitat destruction
•Open cast mining (also known as strip mining) is a form of extensive excavation in which the
overlying material (overburden) is removed by machinery, revealing seams or deposit below. This
destroys the homes of animalsand it completely removes the habitat
•Disposal of waste rocks and ‘tailings’ (impurities left behind after mineral has been extracted by
ore) may destroy the ecosystem
•Smelting (melting metal) causes widespread deforestation. The Grande Carajasproject in Brazil
removes up to 50000 hectares of tropical forest each year
•Pollution
•Copper mining is polluting: to produce 9 million tons of copper = creating 990million tons of waste
rock
•Results from extraction, transport and processing of the raw materials and affects air, soil and
water. Water affected by heavy metal pollution, acid mine drainage, eutrophication (lots of
nutrients in lake because of runoff from land leading to dense growth of water plants) and
deoxygenation.
•The use of mercury to separate fine gold particles from other minerals in riverbed sediments leads
to contamination in rivers. Mercury is highly toxic
THE IMPACTS OF MINING (ON SLOPE STABILITY, SHAPE AND WEATHERING
•STABILITY:
•SATURATED GROUND-Mining requires a more extensive road network. Hence, all the
vegetation on the surface of the land, where mining occurs, would be removed. This causes
an increase in surface runoff which saturates the ground, subsequently decreasing stability.
•FLOODING-Water resources (used for mining) are based on underground caves and tunnels
which result in reduced flow and water. This means that underground streams are prone to
damage through in-filling, siltation and accumulation of solid waste. Hence, mining could
lead to flooding of previously safe areas.
•DIGGING-Underground mining requires digging tunnels and shafts. Layer of support is
removed and hence decreases the internal resistance of the slope and hence, increases
instability.
•SHAPE:
•OPEN CAST MINING-This requires creating an open-pit which changes the shape of the
slope.
•WEATHERING:
•GREENHOUSE GAS EMISSION-Deforestation for mining increases the concentration of
greenhouse gases. Increase in Carbon Dioxide concentration leads.
•SATURATED GROUND-Mining requires a more extensive road network. Hence, all the
vegetation on the surface of the land, where mining occurs, would be removed. This causes
an increase in surface runoff which saturates the ground, subsequently decreasing stability.
•FLOODING-Water resources (used for mining) are based on underground caves and tunnels
which result in reduced flow and water. This means that underground streams are prone to
damage through in-filling, siltation and accumulation of solid waste. Hence, mining could
lead to flooding of previously safe areas.
•DIGGING-Underground mining requires digging tunnels and shafts. Layer of support is
removed and hence decreases the internal resistance of the slope and hence, increases
instability.
•SHAPE:
•OPEN CAST MINING-This requires creating an open-pit which changes the shape of the
slope.
•WEATHERING:
•GREENHOUSE GAS EMISSION-Deforestation for mining increases the concentration of
greenhouse gases. Increase in Carbon Dioxide concentration leads.
CASE STUDY: Opencast mining in West Virginia, USA
What is opencast mining?
Opencast mining is a type of surface mining in which mineral resources are excavated from the earth through large holes or
pits dug into the surface
What is opencast mining?
Opencast mining is a type of surface mining in which mineral resources are excavated from the earth through large holes or
pits dug into the surface
•Opencast mining in West Virginia
•America’s second largest coal producer, Arch Coal, has been blasting away mountaintops and
dumping the debris in the valleys below. This has been occurring at PigeonroostHollow, West
Virginia. Most families in Pigeonroostsold their homes and left the town instead of enduring the
dynamiting, noise and dust as the company prepared the land to start a strip-mining operation,
known as opencast mining or mountaintop removal.
•Mountain top removal mining (MTR) is a form of surface mining which involves the mining of the
summit of the mountain. Once trees are cut and the topsoil removed, the rock above the coal
seams are blasted away. The debris is then moved by trucks and draglines. Many coal companies
claim that MTR is the least destructive and most efficient way to extract a vital resource.
•In West Virginia, the coal is prized as it is low-sulphurcoal, which burns efficiently and produces
less pollution than other coal. Arch coal wants to remove several mountaintops, extract coal, and
dump all the debris into five valley fills. If the work begins in earnest, PigeonroostHollow will
become part of a 12.55 km² strip-mine. It is predicted that by 2020, half of the peaks in West
Virginia will disappear.
•Studies show that mountaintop mining has serious environmental impacts, including loss of
biodiversity, and many human health impacts which result from contact with affected streams r
exposure to airborne toxins and dusts.
•America’s second largest coal producer, Arch Coal, has been blasting away mountaintops and
dumping the debris in the valleys below. This has been occurring at PigeonroostHollow, West
Virginia. Most families in Pigeonroostsold their homes and left the town instead of enduring the
dynamiting, noise and dust as the company prepared the land to start a strip-mining operation,
known as opencast mining or mountaintop removal.
•Mountain top removal mining (MTR) is a form of surface mining which involves the mining of the
summit of the mountain. Once trees are cut and the topsoil removed, the rock above the coal
seams are blasted away. The debris is then moved by trucks and draglines. Many coal companies
claim that MTR is the least destructive and most efficient way to extract a vital resource.
•In West Virginia, the coal is prized as it is low-sulphurcoal, which burns efficiently and produces
less pollution than other coal. Arch coal wants to remove several mountaintops, extract coal, and
dump all the debris into five valley fills. If the work begins in earnest, PigeonroostHollow will
become part of a 12.55 km² strip-mine. It is predicted that by 2020, half of the peaks in West
Virginia will disappear.
•Studies show that mountaintop mining has serious environmental impacts, including loss of
biodiversity, and many human health impacts which result from contact with affected streams r
exposure to airborne toxins and dusts.
Tags
Categories
GeneralDownload
Download Slideshow Get the original presentation fileQuick Actions
Statistics
- Views 28
- Slides 140
- Age 280 days
Related Slideshows
22
Pray For The Peace Of Jerusalem and You Will Prosper
RodolfoMoralesMarcuc
34 views
26
Don_t_Waste_Your_Life_God.....powerpoint
chalobrido8
37 views
31
VILLASUR_FACTORS_TO_CONSIDER_IN_PLATING_SALAD_10-13.pdf
JaiJai148317
34 views
14
Fertility awareness methods for women in the society
Isaiah47
31 views
35
Chapter 5 Arithmetic Functions Computer Organisation and Architecture
RitikSharma297999
30 views
5
syakira bhasa inggris (1) (1).pptx.......
ourcommunity56
31 views