EARTH AND LIFE SCIENCE - EXOGENIC AND ENDOGENIC PROCESSES.pptx

EARTH AND LIFE SCIENCE - EXOGENIC AND ENDOGENIC PROCESSES - GRADE 11

1. Exogenic Processes Exogenic processes   include geological phenomena and  processes  that originate externally to the Earth's surface. Exogenic processes are part of the rock cycle. They are responsible for transforming rock into sediments. They are genetically related to the atmosphere, hydrosphere and biosphere, and therefore to  processes  of weathering, erosion, mass wasting, sedimentation and transportation.

2. Exogenic Processes Exogenic processes   are influenced by human activities and are driven by solar energy and gravity. Exogenic processes may be degradation which include weathering, mass wasting, transportation and erosion or aggradation like deposition which is responsible as for erosion.

3. Weathering Weathering is the general term applied to the combined action of all physical and chemical processes that disintegrate and decompose rocks near Earth’s surface through the elements of weather. Weathering begins as soon as rocks are exposed to one or more elements of weather on the surface of Earth. It affects the rocks in place and no transport is involved .

4. Weathering a. Physical weathering happens whenever rocks are broken up without any change in their chemical composition. Sometimes called mechanical weathering , this type of weathering takes place in different ways, depending on the surface that acts on the rocks. These factors include pressure, warm temperature, water, and ice. Examples of physical weathering include block disintegration, exfoliation, and frost weathering. Block disintegration is caused by successive heating and cooling that causes the expansion and contraction of rocks. This repeated expansion and contraction creates stress along the joints, eventually breaking. Down the rock, block by block. Exfoliation is the stripping of the outer layers of rocks due to intense heating. Exfoliation peels off outer layers of rocks which are immediately affected by heat. Frost weathering refers to the alternate freezing and thawing of water inside the joints of the rocks, causing them to split into small particles or fragments.

5. b. Chemical weathering is the weakening or disintegration of rocks and the formation of new compounds or new substances caused by chemical reactions. Chemical processes include oxidation, hydrolysis, and carbonation. Oxidation is the process in which oxygen reacts with the rock and changes its mineral composition. The greatest impact of this process is observed on ferrous minerals, which contain iron. The oxygen in humid air reacts with iron in the rocks to form oxides of iron called rust . Hydrolysis is the chemical breakdown of substance when combined with water. Therefore hydrolysis is break down of rock due to reaction between rock and water. The most common example of hydrolysis is  feldspar  which can be found in granite changing to the  clay . When it rains water seep down into the ground and come into contact with granite rock. The  feldspar crystals within the  granite  reacts with the water and are chemically altered to form clay minerals which weaken the rock Carbonation  is the process of rock minerals reacting with  carbonic acid . Carbonic acid is formed when water combines with carbon dioxide. Carbonic acid dissolves or breaks down minerals in the rock.

6. c. Biotic weathering or biological weathering is the weathering or disintegration of rocks caused by living organisms. Plants contribute to both mechanical and chemical weathering. Plant roots can penetrate soil and break down rocks. Burrowing animals, such as earthworms, converts soil into smaller particles. Building houses can sometimes speed up weathering.

7. Mass Wasting Mass wasting refers to the downslope movement of rock, regolith , and soil because of gravity. Mass wasting is a natural process that occurs after weathering. Based on the type of motion, mass wasting could be generally classified as a fall, a slide, or a flow . The free-fall movement of detached individual pieces of rock is called fall. Slides occur when rock materials remain fairly coherent and move along a well-defined surface. Flow happens when rock materials are saturated with water and move downslope as a viscous fluid.

8. Erosion Erosion is the   removal of surface material from  Earth’s  crust, primarily  soil  and  rock debris, and the transportation of the eroded materials by natural agencies (such as  water  or  wind ) from the point of removal . It is the process of transporting weathered sediments by agents of erosions to different places.

9. Agents of Erosion Running water is the primary agent of erosion on Earth. M ost Running water is found in streams and rivers.

10. Types of water Erosion Splash erosion – raindrops cause tiny particles of soil to be detached and to move out. Valley erosion – continuous water flow alongside land and move downward, which deepens a valley. Bank erosion – continuous flow of water wears out stones along the bank of streams and rivers. Coastline erosion - Waves from ocean and seas crash against the shore, pounding the rocks into pebbles and reducing the pebbles to sand. Sand is also removed from the beaches, which changes the coastline. S easide cliff erosion – The battering of ocean waves erodes seaside cliffs, forming hales that create caves.

11. Types of water Erosion Sheet erosion is the removal of thin layers of soil because of surface runoff and rain. This type of erosion is common along the riverbeds and areas affected by floods. Rill erosion is the removal of soil by the action of concentrated running water. This process creates several centimetre-deep tiny channels called rills, which carry water during storms. Gully erosion is the removal of soil in water channels or drainage lines. The gullies gradually multiply and spread over a wide area. The land being dissected is called badlands or ravines.

12. Agents of Erosion Glacier is a thick large mass of ice formed hundreds or thousands of years mostly in remote areas like in the poles or in high mountains. They move very slowly. Wind Erosion happens when winds carry large amount of fine soil particles and sand away from a region, spreading it over adjoining cultivated land and destroying their fertility . It takes place in and around all desert regions of the world.

13. Transportation

14. Sedimentation or Deposition Sedimentation is the process of  deposition  of a solid material from a state of suspension or  solution  in a fluid (usually air or water). Broadly defined it also includes deposits from glacial ice and those materials collected under the  impetus  of gravity alone, as in talus deposits, or accumulations of  rock  debris at the base of cliffs.  The agents of erosion are also agents of deposition. Deposition is the aggradation or accumulation of weathered sediments to create different landforms.

15. Depositional Landforms Water and Landforms Whenever stream velocity decreases, it deposits the sediment it carries. The material deposit of a stream is called alluvium.

16. Water and Landforms Deltas are formed when river loses energy as it flows in to an area of slow-moving water , such as a lake or the sea. Alluvial fans are formed when a stream reaches a flat area or gently sloping plain. Flood plain is a flat wide expanse of alluvium covering flat areas prone to flooding. Levees are formed by successive floods over many years.

17. Glacier and Landforms In general, all unsorted deposits of rock formed directly by the ice are called glacial till . Moraines are layers or ridges of till. Esker is a winding ridge of sand and gravel deposited under a glacier by water melting from the ice. Drumlins are stream-lined asymmetrical hills composed of till. Kames are steep-sided hill composed of sand and gravel.

18. Wind and Landforms Accumulations of w indblown sediments are usually found in dry lands and along sandy coasts Two types: Loess is the accumulated blanket of silt carried by wind in suspension and deposited over broad areas. Sand dunes are deposits of coarse materials in the shape of hills or ridges.

19. Endogenic Processes Geologic processes that occur within or beneath the Earth’s surface. There are three main sources of heat on Earth: Heat from the accretion of Earth during its formation. Frictional heating, caused by the sinking or core materials to the center of the planet. Heat from the decay of radioactive elements.

20. Volcanism Volcanism  is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics and volcanic gases erupt through a break in the surface called a vent . Magma is generated when the right conditions are met. These conditions include the addition of heat, decrease in pressure, and change in composition of the mantle. The generation of magma is one of the processes in the rock cycle. The rock cycle shows the transformation of one rock type into another. Through metamorphism, the texture and mineral components of rocks change. Volcanic eruptions contribute to the recycling of rocks in the plane and the degree of metamorphism is reflected in the rock’s texture and mineral composition. A volcano is a vent in the surface of Earth where magma is expelled during volcanic eruption. It is sometimes referred to as igneous activity because the rock being formed is an igneous rock. Lava is the primary material extruded from a volcano in addition to volcanic rocks, ash, and dust during volcanic eruptions.

21. Tectonic Forces and Processes Deformation refers to any change in the shape or size of a rock as a response to the stress. The deformation may occur by either folding and faulting. Folding in rocks occur when they are subjected to tectonic forces from opposite sides . Compressional stress causes squeezing , tensional stress causes stretching , and shearing stress causes side-to-side movement . Folding in rocks often results in the appearance of physical folds called anticline and syncline

22. Faulting Faulting is the result of the fracture or displacement of rock layer or strata along a fault plane. A fault shows a displacement of the two sides of a nonvertical fault: the hanging wall and the footwall. There are different types of faults based on their relative movement of these sides. Dip-slip faults show vertical movement of the hanging wall and the footwall. Examples of dip-slip faults are the normal fault (caused by tension) and reverse fault (caused by compression). Strike-slip faults shows horizontal and parallel displacements of the fault planes. A transform fault, which is caused by shear strength, is an example of a strike-slip fault.

23. Plate Tectonics Today, the most accepted theory that explains the movement of plates are the continental drift theory and the theory of seafloor spreading. Continental drift is the gradual movement of the continents over time. The upper layer of the crust is broken down into large slabs called plates , which sit on a fluid level of molten rock. The movement of this lower molten layer, called plate tectonics , causes the plates to shift .

24. Alfred Wegener   He is most remembered as the originator of the theory of  continental drift  by hypothesizing in 1912 that the  continents  are slowly drifting around the Earth. He theorized that the continents once existed as a single landmass , which he called Pangaea. Wegener’s continental drift theory became generally accepted only after the concept of paleomagnetism was integrated. Paleomagnetism : As new oceanic crust cools, it acquires the magnetic orientation of Earth’s field, creating an alternating stripes of normal and reversed polarities.

25. Plate Tectonics and Plate Movements There are seven major plates and dozens of smaller plates that interact with one another in several ways . Seven major plate: African plate Antarctic plate Eurasian plate Indo-Australian plate North American plate Pacific plate South American plate Largest minor plate: Arabian plate Carribean plate Cocos plate Juan de Fuca plate Nazca plate Philippine plate Scotia plate

26. Types of Boundaries Divergent Boundary- occurs when two tectonic plates move away from each other. Convergent boundary- occurs when two plates come together. Transform boundary- occurs when two plates sliding past each other.

27. Seafloor Spreading Seafloor spreading  is a geologic process in which tectonic plates—large slabs of Earth's lithosphere— split apart from each other . Seafloor spreading and other tectonic activity processes are the result of mantle convection .  Mantle convection is the slow, churning motion of Earth’s mantle.  Convection currents carry heat from the lower mantle and core to the lithosphere. Convection currents also “recycle” lithospheric materials back to the mantle . Seafloor spreading occurs at divergent plate boundaries . As tectonic plates slowly move away from each other, heat from the mantle’s convection currents makes the crust more plastic and less dense. The less-dense material rises, often forming a mountain or elevated area of the sea floor. Eventually , the crust cracks. Hot magma fueled by mantle convection bubbles up to fill these fractures and spills onto the crust. This bubbled-up magma is cooled by frigid seawater to form igneous rock. This rock (basalt) becomes a new part of Earth’s crust .

28. Seafloor spreading disproves an early part of the theory of continental drift. Supporters of continental drift originally theorized that the continents moved (drifted) through unmoving oceans. Seafloor spreading proves that the ocean itself is a site of tectonic activity. Seafloor spreading is just one part of plate tectonics . Subduction is another. Subduction happens where tectonic plates crash into each other instead of spreading apart . At subduction zones, the edge of the denser plate  subducts , or slides, beneath the less-dense one. The denser lithospheric material then melts back into the Earth's mantle . Seafloor spreading creates new crust. Subduction destroys old crust. The two forces roughly balance each other, so the shape and diameter of the Earth remain constant.

29. Seafloor spreading creates new crust- the older crust moves away from the mid-Atlantic ridge replaced by new materials.