Geology Unit 4

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Geology Unit 4
2013-02-24 23:13:31
eolian droughts sand dust

Questions on eolian, droughts, sand, dust
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  1. What effect can dust derived from the Sahara Desert have on the Americas and coral reefs within the Carribbean Sea?
    Responsible for deaths of some coral reefs in the Carribbean.
  2. Describe at least three environments from where large quantities of sand and dust can be eroded and transported by strong winds. 
    • 1.)Deserts & semi deserts
    • 2.)Beaches & shorelines
    • 3.)Construction sites
  3. Historically, what events are referred to as "black blizzards"?
    Dust storms were responsible for 850,000,000 tons of topsoil  in prime agricultural areas being blown away in 1935.
  4. Which decade was the "American Dust Bowl" a tragic phenomena?
  5. What defines a drought (time vs. rainfall)?
    Droughts are normal, recurring events of abnormally low precipitation that affects life.
  6. The continent with Earth's largest desert is ____ (because it has so little rainfall).
  7. Describe the extreme conditions of the Atacama Desert that make it unique.
    "No known rains" in 400 years.
  8. How much rain generally defines an area as a desert, as per our lecture?
    Less than 10 inches of rain a year.
  9. Is Texas a part of a large desert? if so, what is the name of this desert?
    Yes, Chihuahua Desert in West Texas.
  10. What is the average normal rainfall for Corpus Christi in inches and feet.
    Corpus Christi normally averages 34 inches rainfall per year which is almost 3 feet.
  11. What two major Earth features cause something called a "rain shadow" in western North America?
    A Pacific High Pressure zone and the high mountain ridges found along the Pacific coast.
  12. Water a more effective agent for erosion than wind because water has more___.
    Water has more mass than air.
  13. What effect can vegetation have on wind erosion?
    Vegetation tends to hold sediment in place.
  14. Describe a ventifact.
    Pebble or coble shaped and polished as a result of "sand blasting" abrasion.
  15. How is deflation different from abrasion?
    Abrasion impacts sand grains knock off tiny fragments of rocks. Deflation is caused by the lifting and removal of loose sand and dust particles from the Earth's surface.
  16. What effect does a large area of thick lag gravels have on continued deflation?
    The coarse material remains because the winds cannot remove it.
  17. What two methods of sand grain "movements" create deflation of an area?
    • Saltation
    • Creep
  18. Describe saltation of sand grains.
    • "jumping grains" a grain is lifted into the air and falls back down, colliding with another grain, which is lifted back into the air.
  19. You see long "thin trails" within a dried lake bed that leads to a large rock, and someone ask you if aliens were responsible for this. How would you explain the cause of those "trails" to this person?
    The trails are caused by Creep, where wind produced rock "creep" can produce strange-looking trails on dry lake beds.
  20. What must "underlie" a hoodoo for these strange rocks to be created?
    Hard rock masses resting on top of soft sedimentary rock, The piece of harder, less-eroded stone that protects the column of soft sedimentary rock or soil from rain erosion.
  21. Someone told you that they were driving through a dust storm but then suddenly they drove into a "mud storm" You would say-I believe you because you drove through a___.
  22. Describe the alignment of sand ripples to wind direction.
    Ripples are formed perpendicular to the wind direction.
  23. How is a dune different from a hill?
    Hills or ridges of sand deposited by wind.
  24. What is unique about the type of sands found at White Sands National Monument and a part of the Texas Guadalupe Peak National Park?
    The sands are composed of grains of pure gypsum. 
  25. Draw a typical sand dune showing it's slope according to a wind direction (show wind direction arrow)
    On page 5.
  26. raw a example of cross bedding within a dune, and show the wind direction (arrow) that would cause this slip face or cross bedding to occur.
    On page 5.
  27. Identify a type of sand dune from a picture on the exam. 
    On page 7.
  28. Draw and describe a coppice dune, also show wind direction.
    On page 7.
  29. At Padre Island, there is a fore-island dune ridge. What is the most common "type" of dune is found here?
    Most common type of dune found is the coppice dune.
  30. What causes a "blowout complex" that we can find on Padre Island.
    A depression in a sand field created by destroyed vegetation.
  31. Where have small clay dunes been found locally?
    Found along the west shore of Oso Bay, mostly covered by vegetation.
  32. Texas has a sand hill state park with dunes 70 feet tall. Where is this park located?
    Monahans Sand Hills State Park found in West Texas.
  33. Why are loess deposits of wind-blown sediments important to mankind?
    Forms soil.
  34. What are dust devils and what creates them?
    Localized heating and associated convection can develop into small scale vortices.The vortices are created from "rapidly rising bubbles" of hot air greatly resemble "tornades".
  35. Describe some of the eolian activity that has been observed on Mars.
    Mars has dunes and dust devils.
  36. Which state is the largest producer of wind generated electricity?
  37. What is a major problem for relying solely on wind generated electricity for any town or industry?
    Wind turbines do interfere with radar images, a problem for airports.
  38. What has happened to most of the older sand dunes that cover much of the western US.
    Stabilized by grass and shrubs.
  39. Near which local town do you find a large number of wind turbines for creating electricity?