08 volcanism intrusive and extrusive features

1. As many adjectives as possible!As many adjectives as possible!

2. Your homework was to…Your homework was to…
Using internet research, create and example of a conservative
boundary. You will need to include the following from the
check list!
•Location (atlas!)
•Map onto your
tectonic plate map!
•Quick diagram
•Description of
processes
•Explanation of effects
•Future predictions
•Historic earthquakes
Useful websites!
http://www.geolsoc.org.uk/Plate-Tectonics/Chap3-
Plate-Margins/Conservative/San-Andreas-Fault
http://www.youtube.com/watch?v=roIEtkuXbvk
http://www.geolsoc.org.uk/Plate-Tectonics/Chap3-Plate-
Margins/Conservative/San-Andreas-Fault
http://pubs.usgs.gov/gip/earthq3/safaultgip.html
http://geology.com/articles/san-andreas-fault.shtml
http://www.sanandreasfault.org/Information.html

3. Learning Outcomes
Recap volcano basics
Describe intrusive features
Sort advantages and disadvantages of volcanoes
Differentiate between intrusive and extrusive features
VulcanicityVulcanicity
Learning Objective:Learning Objective: Understand major forms of extrusive Understand major forms of extrusive
volcanism and intrusive features.volcanism and intrusive features.

4. The Specification!The Specification!
Our next area of focus….Our next area of focus….
Remember, you should Remember, you should
highlight the specification as highlight the specification as
we complete each section!we complete each section!

5. Crater
Volcanic
bombs, ash
and gases
Main vent
Parasitic
cone
Magma
chamber
This 'cut through' is called a cross section. Make a sketch of the diagram
below then add the labels in the correct place.
Crater Volcanic Bombs Main Vent Parasitic Cone Magma Chamber

6. Is it sleeping?Is it sleeping?
There are three ways to classify a volcano:There are three ways to classify a volcano:
•ExtinctExtinct
•Dormant Dormant
•ActiveActive
Match up the definitions below with the Match up the definitions below with the
correct term and write them outcorrect term and write them out
If it has not erupted
for years, or even
centuries, but still
seeps gas sometimes.
If it has erupted
recently and is likely
to do so again.
If it has not erupted for
thousands of years and its
shape has been worn away by
the wind and rain.

7. Active volcano – If it has
erupted recently and is likely to
do so again. e.g. Mt Etna.
Dormant (sleeping) volcano – If
it has not erupted for years, or
even centuries, but still seeps
gas sometimes. For example, Mt
Pinatubo erupted in 1991 after
500 years of dormancy.
Extinct volcano – If it has not
erupted for thousands of years
and its shape has been worn
away by the wind and rain.e.g.
Edinburgh.
However, it is
often very
difficult to tell
whether a
volcano will
erupt again…El
Chichon,
Mexico erupted
in 1982 after
being dormant
for
approximately
1200 years!
Do all volcanoes erupt?

8. Volcancity; a beneficial hazard?!Volcancity; a beneficial hazard?!
Sort these statements into benefits and hazards associated with volcancity. Then
explain which you think are the most beneficial and which are the most
hazardous.
Submarine, coastal or island
eruptions may cause
Tsunamis.
Ash fall ruins crops and
machinery, pollutes the air,
and disrupts transport.
Dust emissions can seed
torrential rainstorms causing
dangerous wet ash and mud
lahars .
Flooding from laval flows
block and divert rivers.
Pyroclastic flows of superheated
gas, ash and pumice destroy life
and property.
Volcanic melting of
snow creates lahars.
Volcanic ash absorbs solar
energy so temperatures are
reduced.
Hot rocks can generate
geothermal power.
Igneous rocks contain
valuable minerals such as
gold, silver and diamonds.
Volcanic sulphur is used
pharmaceuticals and
agrochemistry industries.
Igneous rocks make great
building materials e.g
granite.
Extinct volcanoes make great
defensive sites e.g Edinburgh
Castle.
Lava and ash weather quickly
to create fertile soils.
Volcanoes make great tourist
attractions along with geysers,
fumeroles, hot springs and boiling
mud.
Lava creates new
land.

9. Volcancity; a beneficial hazard?!Volcancity; a beneficial hazard?!
Sort these statements into benefits and hazards associated with volcancity. Then
explain which you think are the most beneficial and which are the most
hazardous.
Submarine, coastal or island
eruptions may cause
Tsunamis.
Ash fall ruins crops and
machinery, pollutes the air,
and disrupts transport.
Dust emissions can seed
torrential rainstorms causing
dangerous wet ash and mud
lahars .
Flooding from laval flows
block and divert rivers.
Pyroclastic flows of superheated
gas, ash and pumice destroy life
and property.
Volcanic melting of
snow creates lahars.
Volcanic ash absorbs solar
energy so temperatures are
reduced.
Hot rocks can generate
geothermal power.
Igneous rocks contain
valuable minerals such as
gold, silver and diamonds.
Volcanic sulphur is used
pharmaceuticals and
agrochemistry industries.
Igneous rocks make great
building materials e.g
granite.
Extinct volcanoes make great
defensive sites e.g Edinburgh
Castle.
Lava and ash weather quickly
to create fertile soils.
Volcanoes make great tourist
attractions along with geysers,
fumeroles, hot springs and boiling
mud.
Lava creates new
land.

10. VolcanicityVolcanicity
The process through which gases and molten rock/ magma are either
extruded on the earth's surface or intruded into the earth's crust.
Intrusive- magma cools,
crystallises and solidifies into
igneous rocks below the earths
surface. Slow cooling results in
larger crystals e.g granite and
dolerite.
Extrusive- magma surfaces as lava
and cools, crystallises and solidifies
through contact with air (fast) or the
sea (rapid) into igneous rocks above
the earths surface. Quicker cooling
results in finer crystals e.g basalt.
Handle with
care and
describe the
specimens!

11. Intrusive features form below the earths surface, thus they only
become part of the landscape once erosional processes have removed
the overlying rocks. These are a common part of the UK landscape being
visible in Scotland, Northern Ireland and Northern England.
Intrusive Volcanic FeaturesIntrusive Volcanic Features
Dykes SillsLaccolithsBatholiths
Use the information sheets to describe and explain the formation of these
intrusive features and label them onto a diagram!
SillsLaccoliths

12. Intrusive Volcanic FeaturesIntrusive Volcanic Features
Remember- these only surface once the rock layers above have been eroded!
Over many years they solidify slowly within the earths surface.

13. Intrusive Volcanic FeaturesIntrusive Volcanic Features
Remember- these only surface once the rock layers above have been eroded!
Over many years they solidify slowly within the earths surface.

14. DykesDykes
These are vertical intrusions formed where magma solidifies in a
vertical crack/ fissure. They often form in groups called swarms. Dyke
material tends to be more resistant than the surrounding rock leaving
prominent wall like features on an eroded landscape. Erosion of less
resistant dyke material may leave ditch like features.
Isle of Mull,
Scotland.

15. SillsSills
These are horizontal intrusions formed where magma solidifies as sheets
in between layers of existing rock. When these are exposed at the surface
through erosion, they form steep sided cliffs along the landscape.
Great Whin Sill,
Northumberland.

16. LaccolithsLaccoliths
These are formed when thick viscous magma which is
resistant to flow bulges and forces the overlying rock strata to
arch into a dome.
Eildon Hills,
Scotland.

17. BatholithsBatholiths
These are on a much larger scale than Laccoliths. Usually, dykes, sills and
laccoliths will feed off the domed granite batholith before it solidifies. The
batholith is exposed to extreme heat and pressure which alters the
adjacent rock through metamorphism which forms a metamorphic
aureole.
Dartmoor,
England.

19. Outline the differences between the intrusive features
shown in Figure 2. (4 marks)

20. •Batholith- large, deep-seated mass of intrusive igneous rock, usually granite,
with a huge surface area of (more than 100 sq. km/40 sq mi.)
•Laccolith- intruded mass of igneous rock that forces apart strata and forms a
round dome shaped mass wider than thick. Can dome the surface above.
•Dyke- These are vertical intrusions form where magma solidifies in a vertical
crack/ fissure. They often form in groups called swarms. Dyke material tends
to be more resistant than the surrounding rock leaving prominent wall like
features on an eroded landscape. Erosion of less resistant dyke material may
leave ditch like features.
•Sill is igneous rock intruded horizontally between layers of rock formed
where magma solidifies as sheets in between layers of existing rock. When
these are exposed at the surface through erosion, they form steep sided cliffs
along the landscape.
Outline the differences between the intrusive features
shown in Figure 2. (4 marks)

21. Types of LavaTypes of Lava
Watch the clip and describe the types of lava you see.
Comment on the colour, thickness and quantity!

22. Major Extrusive Volcanic FeaturesMajor Extrusive Volcanic Features
Remember- these features which are eventually formed are dependent upon
the material ejected during eruption. This may be gaseous, solid or liquid.
Gaseous Emissions
•Dominated by steam
•Often superheated
•Includes carbon monoxide, hydrogen sulphide, sulphur
dioxide and chlorine.
Solids
•Ash, dust, glassy cinders
•Shattered blocks of material which previously plugged the
vent of the volcano
Liquids
•Lava bombs (tephra or pyroclasts) which
solidify mid-air as pumice
•Surface lavas which are acid or basic

23. Extrusive FeaturesExtrusive Features
Remember, these are the result magma rising to the surface and
erupting as lava. The features are dependent upon the types of lava
and whether the extrusion is gaseous, solid or liquid.

24. Types of LavaTypes of Lava
Basic or Basaltic Lava- dominated by iron manganese
and is low in silica. Gas bubbles have freedom to
expand as the magma rises to the surface.
Eruptions are fluid and free-flowing. Constructive
margins!

25. Types of LavaTypes of Lava
Andesitic Lava- medium in silica content. Acid lava is
medium in terms of viscosity. Temperature of
eruption 750-950°C. Destructive margins.

26. Types of LavaTypes of Lava
Acid or Rhyolitic Lava- rich in silica. Acid lava is so thick
and viscous the gas bubbles struggle to expand. This
builds up pressure to create violent eruptions.
Destructive margins.

27. Types of LavaTypes of Lava
Complete the following table to describe the chemical
compositions, viscosity and temperature of each
type of lava.
Basaltic Lava Andesitic Lava Rhyolitic Lava
Silica Content
Viscosity
Temperature of
Eruption
The thicker the lava, the more violent the eruption…
give reasons for this general rule!

28. Types of LavaTypes of Lava
Complete the following table to describe the chemical
compositions, viscosity and temperature of each
type of lava.
Basaltic Lava Andesitic Lava Rhyolitic Lava
Silica Content Medium
Viscosity Low (runny) High (thick)
Temperature of
Eruption
750-950°C Less that 750°C
The thicker the lava, the more violent the eruption…
give reasons for this general rule!

29. Types of LavaTypes of Lava
Complete the following table to describe the chemical
compositions, viscosity and temperature of each
type of lava.
Basaltic Lava Andesitic Lava Rhyolitic Lava
Silica Content Low Medium High
Viscosity Low (runny) Medium High (thick)
Temperature of
Eruption
1100-1200°C 750-950°C Less that 750°C
The thicker the lava, the more violent the eruption…
give reasons for this general rule!

30. Decipher the types of lava and justify your answer!Decipher the types of lava and justify your answer!
A
B

31. Decipher the types of lava and justify your answer!Decipher the types of lava and justify your answer!
A
•Basic/Basaltic
•Low Silica
•Low Viscosity
•High
Temperatures

32. Decipher the types of lava and justify your answer!Decipher the types of lava and justify your answer!
B
•Acid/ Rhyolitic
•High Silica
•High Viscosity
•Low
temperature

33. Extrusive Features in action!Extrusive Features in action!
Remember, these are the result magma rising to the surface and
erupting as lava. The features are dependent upon the types of lava
and whether the extrusion is gaseous, solid or liquid.
Aa forms when lava flows rapidly. Under
these circumstances, there is rapid heat
loss and a resulting increase in viscosity.
When the solid surface crust is torn by
differential flow, the underlying lava is
unable to move sufficiently rapidly to
heal the tear. Bits of the crust are then
tumbled in and coated by still liquid lava,
forming the chunks.
Pahoehoe forms when lava flows more
slowly. Under these circumstances, a
well-developed skin can form which
inhibits heat loss.

34. Fissures and VentsFissures and Vents
Lava can erupt from long cracks called fissures or localised vents. The
resultant landforms created are greatly determined by the nature of
the opening from which the magma emerged to form lava.
Fissure eruptions- basic lava
creates extensive lava plateaus.
Hollow areas of the landscape
are filled to create flat,
featureless basalt plans.
Vent eruptions- usually create
cone shaped landforms such as
the iconic volcano images
complete with a summit crater.

35. Classification of VolcanoesClassification of Volcanoes
Volcanoes are classified according to the violence of their eruption
which is determined by the pressure and quantity of gas in the
magma.
Join me on a journey of
discovery….lets go VOLCANO
SPOTTING! Just say what you
see to name the types of
volcano!

36. Classification of Volcanoes- Say what you see!Classification of Volcanoes- Say what you see!
Volcanoes are classified according to the violence of their eruption
which is determined by the pressure and quantity of gas in the
magma.
Fissure

37. Classification of Volcanoes- Say what you see!Classification of Volcanoes- Say what you see!
Volcanoes are classified according to the violence of their eruption
which is determined by the pressure and quantity of gas in the
magma.
Basic Shield Volcano
ic

38. Classification of Volcanoes- Say what you see!Classification of Volcanoes- Say what you see!
Volcanoes are classified according to the violence of their eruption
which is determined by the pressure and quantity of gas in the
magma.
Acid Dome Volcano

39. Classification of Volcanoes- Say what you see!Classification of Volcanoes- Say what you see!
Volcanoes are classified according to the violence of their eruption
which is determined by the pressure and quantity of gas in the
magma.
Caldera
a

40. Classification of Volcanoes- Say what you see!Classification of Volcanoes- Say what you see!
Volcanoes are classified according to the violence of their eruption
which is determined by the pressure and quantity of gas in the
magma.
Ash/ Cinder Cone

41. Classification of Volcanoes- Say what you see!Classification of Volcanoes- Say what you see!
Volcanoes are classified according to the violence of their eruption
which is determined by the pressure and quantity of gas in the
magma.
Composite Cone

42. Classification of VolcanoesClassification of Volcanoes
Volcanoes are classified according to the violence of their eruption
which is determined by the pressure and quantity of gas in the
magma.
Excellent job! Lets discover
more about each type!

43. Learning Outcomes
Recap volcano basics
Describe intrusive features
Sort advantages and disadvantages of volcanoes
Differentiate between intrusive and extrusive features
VulcanicityVulcanicity
Learning Objective:Learning Objective: Understand major forms of extrusive Understand major forms of extrusive
volcanism and intrusive features.volcanism and intrusive features.

44. Key Term Round Up!Key Term Round Up!
Watch the clip and trey to define the key terms in the time given!