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Reshaping Earth’s Crust, Part 2: Erosion

Reshaping Earth’s Crust, Part 2: Erosion. http://www.muenchphotography.com/dstockthm5.html. Erosion . Is the removal of rock, soil or sediment by moving water , wind , ice or gravity 3 basic components: the picking up of rock material ( erosion )

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Reshaping Earth’s Crust, Part 2: Erosion

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  1. Reshaping Earth’s Crust, Part 2: Erosion http://www.muenchphotography.com/dstockthm5.html

  2. Erosion • Is the removal of rock, soil or sediment by moving water, wind, ice or gravity • 3 basic components: • the picking up of rock material (erosion) • the actual movement (transportation) • the ultimate “laying to rest” (deposition) EARTHSCIENCE@Phuhs.schrock

  3. Geologic agents: rivers groundwater ocean waves and currents glaciers wind gravity (oh...man, too!) the LANDFORMS we see are shaped by the erosional and depositional work of one or more of these agents Erosion, cont. EARTHSCIENCE@Phuhs.schrock

  4. Rivers...most dominate agent http://www.geo.cornell.edu/geology/classes/Geo101/101images.html EARTHSCIENCE@Phuhs.schrock

  5. Rivers • Rivers erode because • have the ability to pick up rock fragments • and transport them to a new location • Size of the fragments transported depends on velocity of the stream http://www.edu-source.com/GCpages/CVOpage4.html EARTHSCIENCE@Phuhs.schrock

  6. Sediment Load • They carry sediments in 3 ways • Solution (dissolved load) • Suspension (carried within the water) • Bed load (pushed along the bottom) • As velocity decreases, the water is unable to carry as much sediment, so deposition occurs EARTHSCIENCE@Phuhs.schrock

  7. What are meanders? • A sharp bend, loop or turn in a stream's course EARTHSCIENCE@Phuhs.schrock

  8. How do oxbow lakes form? • A meander becomes so curved that is cuts across the narrow neck of land, making a separate “meander” or lake http://www.tulane.edu/~sanelson/geol111/streams.htm EARTHSCIENCE@Phuhs.schrock

  9. Young River • V-shaped valley with steep sides • Waterfalls • rapids http://www.serve.com/wizjd/parks/yellowstone/yellowstone.html EARTHSCIENCE@Phuhs.schrock

  10. Old River • Broad, shallow plain (flood plain) • Many meanders and oxbow lakes • Delta at the mouth (where it flows into ocean) • This is the lower Mississippi http://earth.jsc.nasa.gov/photoinfo.cgi?PHOTO=STS062-086-107 EARTHSCIENCE@Phuhs.schrock

  11. Delta: fan shaped deposit of sediments at the mouth of a river http://epod.usra.edu/archive/epodviewer.php3?oid=54592 EARTHSCIENCE@Phuhs.schrock

  12. Ground Water • Ground water • water stored beneath earth’s surface in openings in soil and rock • Aquifer • body of rock that can store much water (porosity) • and from which water flows freely (permeability) EARTHSCIENCE@Phuhs.schrock

  13. Porosity • The amount of open spaces in a rock or sediment http://agcwww.bio.ns.ca/schools/EarthNet/english/glossary/p/porosity.html EARTHSCIENCE@Phuhs.schrock

  14. Permeability • The ease with which water flows through open spaces in a rock or sediment • dependent upon how well the pore spaces are connected http://agcwww.bio.ns.ca/schools/EarthNet/english/glossary/p/permeability.html EARTHSCIENCE@Phuhs.schrock

  15. Regions of Ground Water Zone of Aeration is the zone below the surface in which openings in soil and rock contain air and some moisture Water Table is the boundary between these two zones Zone of Saturation is below the zone of aeration where all the pore spaces are completely filled with water. EARTHSCIENCE@Phuhs.schrock

  16. Ground Water Erosion • As ground water (weak carbonic acid) passes through permeable rock (especially limestone), • Chemical weathering takes place • Limestone is dissolved, forming large cavities underground • Features • Caves or caverns • Stalagmites , Stalactites • Sink holes http://www.luraycaverns.com/ EARTHSCIENCE@Phuhs.schrock

  17. Sinkhole • Circular depression formed when the roof of a cavern collapses • This one occurred in Winter Park, FL http://www.dc.peachnet.edu/~janderso/physical/grdh2o.htm EARTHSCIENCE@Phuhs.schrock

  18. Sink Hole (with Porches in it) EARTHSCIENCE@Phuhs.schrock

  19. Karst Topography • Land where the effects of chemical weathering due to ground water are clearly visible (sinkholes & caverns) • Common in Florida EARTHSCIENCE@Phuhs.schrock

  20. Karst Topography http://geollab.jmu.edu/vageol/outreach/fieldtrips/rockingham/caves.html EARTHSCIENCE@Phuhs.schrock

  21. Karst Topography Satellite photo of karst topography in Florida. (NASA) EARTHSCIENCE@Phuhs.schrock

  22. Glaciers • Continental glaciers (ice sheets) • 96% of all glaciers • Found in Antarctica and Greenland • Covered most of Canada and northern USA during the last ice age (up until about 18,000 years ago) • Mountain or Valley glaciers • Found in the valleys of some mountains • Rivers of ice EARTHSCIENCE@Phuhs.schrock

  23. Antarctic Ice Sheet

  24. Mountain glaciers in Alaska viewed from the space shuttle, 300 km above surface Future U-shape valleys Mountain Glaciers http://earth.jsc.nasa.gov/photoinfo.cgi?PHOTO=STS028-097-085

  25. Mountain Glacier: Rivers of Ice http://www.usd.edu/esci/figures/GeologyToday.html EARTHSCIENCE@Phuhs.schrock

  26. River Valley to Glacial Valley Visit this site http://www.nps.gov/olym/uv.htm EARTHSCIENCE@Phuhs.schrock

  27. V-shaped to U-shaped Valleys Glaciers scour river valleys down when they move to give the valley a U-shaped profile http://darkwing.uoregon.edu/~millerm/Ushapes.html EARTHSCIENCE@Phuhs.schrock

  28. Glacial Deposits • Moraines • large accumulations of rock debris piled up by glaciers • Cape Cod is a moraine http://www.geo.duke.edu/geo41/gla.htm http://tvl1.geo.uc.edu/ice/Image/misc/exitdouble.html EARTHSCIENCE@Phuhs.schrock

  29. Gravity • Mass wastingis the downslope movement of rock and soil, under the influence ofgravity. Also called “mass movement.” • Examples: • Rock falls • Landslides • Creep http://www.geog.ouc.bc.ca/physgeog/contents/11h.html EARTHSCIENCE@Phuhs.schrock

  30. Wind • Soil erosion • One of the best examples in history of severe wind erosion is the Dust Bowl of the 1930s • Sand dunes http://www.geo.lsa.umich.edu/~crlb/COURSES/117/Lec28/lec28.html EARTHSCIENCE@Phuhs.schrock

  31. Man as an Agent of Erosion Erosion Copper Mine in Arizona http://www.mc.maricopa.edu/academic/phy_sci/Geology/copper/ EARTHSCIENCE@Phuhs.schrock

  32. Man as an Agent of Erosion Glen Canyon Dam EARTHSCIENCE@Phuhs.schrock

  33. Retard reforestation strip farming terracing Rates of Soil Erosion • Accelerate • deforestation • overgrazing • plowing EARTHSCIENCE@Phuhs.schrock

  34. Alluvial Fan To the left is the Panamint Mountain Range. To the right is Death Valley http://www.geog.ouc.bc.ca/physgeog/contents/11g.html EARTHSCIENCE@Phuhs.schrock

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