Deserts and Winds

Practice exam questions written by Timothy H. Heaton,
Professor of Earth Sciences, University of South Dakota

Click the circle by an answer with the mouse, then click on the Submit button to get a response. You will be told if your answer is correct or not and will be given some comments.

  1. About what portion of the earth's land surface is arid or semiarid?
    1%.
    5%.
    10%.
    20%.
    30%.

  2. What atmospheric phenomenon leads to the formation of deserts?
    Coriolis effect.
    Falling air.
    Jet stream.
    Rising air.
    Strong winds.

  3. Near what latitude are most deserts found?
    10º north and south.
    30º north and south.
    50º north and south.
    70º north and south.
    90º north and south.

  4. On which side of mountains are deserts often found?
    Gently sloping side.
    Steep side.
    Downwind side.
    Upwind side.
    All equally likely.

  5. Why are valley deposits at mountain fronts usually fan shaped?
    Deposition of sediment constantly rechannelizes the stream.
    Sheet flow occurs over the whole area during storms.
    Slumping spreads sediment out evenly in all directions.
    The stream meanders across a broad floodplain.
    Wind reworks the stream deposits over a wide area.

  6. What name is given to evaporite desert lakes?
    Bajadas.
    Blowouts.
    Inselbergs.
    Playas.
    Ventifacts.

  7. What name is given to rocks sculptured by natural sandblasting?
    Bajadas.
    Blowouts.
    Inselbergs.
    Playas.
    Ventifacts.

  8. What name is given to wind eroded depressions?
    Bajadas.
    Blowouts.
    Inselbergs.
    Playas.
    Ventifacts.

  9. What name is given to coalesced alluvial fans?
    Bajadas.
    Blowouts.
    Inselbergs.
    Playas.
    Ventifacts.

  10. Why are playa lakes typically more salty than the ocean?
    All water entering them evaporates, leaving its salt behind.
    Extensive evaporite deposits are being eroded in desert regions.
    Playa lakes are areas that were previously part of the ocean.
    The wind blows fine salt particles into playa lakes.
    Meteoritic accumulates in great volumes in deserts.

  11. What is an ephemeral stream?
    A stream fed by groundwater.
    A stream that doesn't flow into a valley.
    A stream that flows continuously.
    A stream that only flows during and following storms.
    A stream that flows only in the Spring season.

  12. What are the largest particles that can generally be carried by the wind?
    Boulders.
    Dust.
    Pebbles.
    Sand.
    Silt.

  13. What process creates a desert pavement?
    Ablation.
    Aeration.
    Deflation.
    Inflation.
    Saltation.

  14. By what process is sand transported by wind?
    Ablation.
    Aeration.
    Deflation.
    Inflation.
    Saltation.

  15. Which material is a wind deposit derived from suspended load?
    Alluvium.
    Dune sand.
    Loess.
    Outwash.
    Till.

  16. How is the transportation of sediment by wind different from that of running water?
    Wind has a low density compared to water.
    Wind is not confined to channels.
    Wind can spread sediment over large areas.
    Wind is not capable of transporting coarse sediments.
    All of the above.

  17. What is the angle of repose for sand?
    28º.
    34º.
    38º.
    44º.
    48º.

  18. Which side of a sand dune is typically steepened to the angle of repose?
    Downwind.
    Upwind.

  19. Match each dune type with its description.
    Dune type Description
    Barchan.
    Longitudinal.
    Parabolic.
    Star.
    Transverse.
    Long, parallel to wind.
    Long, perpendicular to wind.
    Curved with center downwind.
    Curved with center upwind.
    Dunes with radiating ridges.

  20. Match each dune type with the wind and sand conditions that create it.
    Dune type Wind and sand supply
    Barchan.
    Barchanoid.
    Longitudinal.
    Parabolic.
    Star.
    Transverse.
    One wind direction, large sand supply.
    One wind direction, medium sand supply.
    One wind direction, small sand supply.
    Multiple similar wind directions.
    Multiple diverse wind directions.
    Sand anchored by vegetation.

Please report any problems or errors to Dr. Heaton.