• Section A: Wednesday, Dec. 15^th, 2010, 9:30am-11:10pm in 108 Tomanek Hall
• Section B: Monday, Dec. 13^th, 2010, 10:30am-12:10pm in 108 Tomanek Hall

Themes of the Day:

• Global Air Circulation and Deserts
• Wind as an Agent of Erosion
• Wind as an Agent of Deposition
• More Desert Landforms

Global Air Circulation and Deserts

• Variable Heating of the Earth's Surface
• The Coriolis Effect
• Global Wind Patterns
• Deserts - defined by average precipitation < 25cm/year of water
• Global Distribution of Deserts
  • Hot Deserts at 30^o N,S of equator - example: Sahara Desert
  • Cold Deserts in Polar Regions
  • Rain Shadow Deserts - Coastal mountains suck moisture out of air - example: Western USA, Mexico
  • Other Deserts

Wind as an Agent of Erosion

• Wind speed vs. rate of sand movement
• Wind must move faster than an equivalent volume of water to do the same work
• Most windblown sediment is sand size or smaller
• Effects of Wind Erosion
  • Deflation
  • Desert Pavement - causes
• Ventifacts - Ventifact Ridge, Death Valley
• Yardangs

Wind as an Agent of Deposition

• sand ripples
• sand dunes - migration - slip face on leeward side is at angle of repose - preserved as cross-beds
  • barchan
  • transverse
  • blowout
  • linear(longitudinal)
  • star
• festoon cross-beds - petrified dunes
• Loess - e.g., California, China, Kansas

More Desert Landforms

• Landforms related to lack of water:
  • desert varnish - oxidation
  • arroyos (dry washes) - flash floods
  • playas (dry lakes) - salt pans
  • alluvial fans and bajadas
  • pediments
  • mesas - Monument Valley