Chapter 8- erosional forces


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Chapter 8- erosional forces

  1. 1. Erosional Forces Chapter 8
  2. 2. Erosion & Deposition Sec 8-1 H.W. pg. 214 ques. 1-4 <ul><li>Erosion- the removal or movement of surface material from one place to another. </li></ul><ul><li>Gravity plays a big part in erosion. It is the force of attraction that pulls all objects toward Earth’s center. We call gravity an erosional agent, along with wind, water and glaciers. </li></ul><ul><li>As these erosional agents lose energy they drop or deposit the sediments that they are carrying. This is called deposition. </li></ul>
  3. 3. <ul><li>The greater an objects mass, the greater its gravitational pull is. And rock and other sediment, especially ones that sit on top of steep slopes are pulled toward the center of the Earth by gravity. </li></ul><ul><li>Mass movement is any type of erosion that occurs as gravity moves materials down slope. </li></ul><ul><li>These can occur quickly or so slowly that you cant even see it. </li></ul><ul><li>Ex: Landslide, Slump, Creep, Rock fall, Rock Slide & mud flows. </li></ul>
  4. 4. Slump & Creep <ul><li>Slump is when a mass of material slips down along a curved surface. It occurs when the supporting rock cannot hold the rock and sediment above it, and it collapses and slides down the side of the slope. </li></ul><ul><li>Sometimes the accumulation of water at the base of a slipping mass can cause weakening and slipping of a mass. </li></ul><ul><li>Creep is the slow shift of sediments downhill, like on the side of a highway. </li></ul>
  5. 5. Rock falls & Rock slides <ul><li>A rock fall is when large pieces of rock break loose from a steep slope and tumble down a slope. </li></ul><ul><li>These rocks usually crash into other rocks on the way down and cause more rock falls and cause serious damage to things at the bottom of the slope. </li></ul><ul><li>Rock slides are when layers of rock slip down hill suddenly. </li></ul><ul><li>Both happen quickly and cause a lot of destruction. They usually occur in areas of steep cliffs and happen often after heavy rains or during earthquakes. </li></ul>
  6. 6. Mudflow <ul><li>A mudflow os a thick mixture of sediments and water flowing downhill. </li></ul><ul><li>They occur in areas that have a lot of loose sediment and often occur after vegetation is removed and heavey rain fall mixes with the sediment and allows gravity to pull this mass down a slope. </li></ul><ul><li>When these reach the bottom the spread out in a fan shape and deposit whatever sediment they held. </li></ul>
  7. 8. <ul><li>Rock falls, slides, slumps, and creeps all have things in common: </li></ul><ul><li>They occur more often after rain. </li></ul><ul><li>They all occur on steep slopes. </li></ul><ul><li>They all depend on gravity for them to occur. </li></ul>
  8. 9. Making slopes safe <ul><li>The best way to prevent erosion and slumps, slides, etc… is by planting on a slope. </li></ul><ul><li>The roots of plants will allow the soil to be stronger because the roots allow the soil to bind and become thicker. </li></ul><ul><li>Also, inserting drainage pipes into slopes will not allow excess water to build up in an area. </li></ul><ul><li>Building walls around the slope will also help by holding back the above sediment. </li></ul>
  9. 10. Glaciers Sec 8-2 H.W. pg 220 ques 1-4 <ul><li>A glacier is a large mass of snow and ice that moves on land under its own wieght. </li></ul><ul><li>Glaciers form from the build up of snow layers. The newly added snow will cause the bottom layers to compress and become ice. </li></ul><ul><li>When the weight of the glacier becomes to heavy it will start to slide away from its origin. </li></ul>
  10. 11. 2 types <ul><li>There exists two types of glaciers: Valley Glaciers and Continental Glaciers .  </li></ul><ul><li>Valley Glaciers form in mountainous regions and are sometimes called alpine glaciers.  They flow downhill following mountain valleys.  The other type is called a Continental Glacier.  </li></ul><ul><li>Continental glaciers are usually much larger and more slowly moving than valley glaciers.  These glaciers can cover most of a continent.  </li></ul><ul><li>Two very large continental glaciers are the Greenland and Antarctica glaciers (sometimes called ice sheets). </li></ul>
  11. 12. <ul><li>A glacier is another agent of erosion. When they pass over land they erode it and change the surface features. </li></ul><ul><li>They than carry the eroded material along and deposit it somewhere else. </li></ul><ul><li>The sheer size and weight of a glacier has the ability to move extremely large rocks, boulders and sediments. </li></ul>
  12. 13. Plucking <ul><li>Glaciers weather and erode solid rocks when glacial ice melts and re freezes inside of rock and cause them to crack. </li></ul><ul><li>These rock pieces can then be carried awy by the glacier one it starts to move, and can be deposited else where. </li></ul><ul><li>This is called plucking. </li></ul><ul><li>This results in boulders, sand and gravel being deposited on the sides of glaciers. </li></ul>
  13. 14. Plucking
  14. 15. Scouring <ul><li>When the plucked rock is moved along by the glacier it scours and scrapes the land and soil below it. ( Like sandpaper) </li></ul><ul><li>Deep, long, parallel scars on rocks are called grooves. </li></ul><ul><li>Shallow marks on rocks are called striations. </li></ul><ul><li>Both of these marks indicate the direction the glacier was moving. </li></ul>
  15. 17. Glacial sediment <ul><li>When glaciers begin to melt they can not carry as much sediment so it becomes deposited on the land. </li></ul><ul><li>This melting of a glacier is called retreat, and the sediments that are left behind are called till deposits, and they can cover huge areas of land. </li></ul><ul><li>Till deposits are very fertile responsible for a lot of farm land in Iowa and Montana, Ohio, and Indiana. </li></ul>
  16. 18. Moraines and Outwashes & Eskers <ul><li>A moraine is a large pile of deposited sediments that has built up at the front of a glacier. Picture a big pile of dirt that has been moved by a bulldozer. </li></ul><ul><li>Outwash is the material deposited by the melt water of a glacier. Usually beyond the end of the glacier. </li></ul><ul><li>An esker is a type of outwash. It is a winding ridge of sand and gravel left behind by a glacier. Form around bodies of meltwater. </li></ul>
  17. 19. Moraine, Esker
  18. 20. Esker
  19. 21. Evidence of Valley glaciers <ul><li>In mountains they cause bowl shaped basins, called cirques. </li></ul><ul><li>An arete is formed when 2 valley glaciers erode a mountain along a ridge. </li></ul><ul><li>A horn, or a sharp peak of a mountain is formed when a glacier erodes a mountain in several different directions. </li></ul>