3. Characteristics of Deserts Besides being dry > few plants > consist of nearly continuous rock and/or sand exposures  little soil development Weathering, erosion, & deposition still operate. > in a balance with the local climate Besides being dry > few plants > consist of nearly continuous rock and/or sand exposures  little soil development Weathering, erosion, & deposition still operate, but more slowly. > In a balance with the local climate

4. The Distribution of Deserts Deserts form in two regions > areas of persistent high pressure - latitude effects related to Hadley Cell circulation > Areas on the lee side of Topographic barriers - rainshadow effect > other things influence too - cold water ocean currents - extremely cold temperatures Deserts form in two regions > areas of persistent high pressure - latitude effects related to Hadley Cell circulation > Areas on the lee side of Topographic Barriers (lee= downwind side) - rainshadow effect > other things influence too - cold water ocean currents - extremely cold temperatures

5. Area of persistent arid conditions (sub- tropical desert)

6. Distribution of Arid and Semiarid Regions Subtropical deserts occur at 20-30° N-S latitude. Gobi Arabian Sahara Australian Mojave Sonoran Chihuahuan Atacama Kalahari Namib Thar Patagonian Antarctica

7. Rainshadow Deserts Air that must cross coastal mountains loses much of its moisture, thus when it arrives over the inland areas it is drier.

8. Distribution of Arid and Semiarid Regions Rainshadow deserts occur in places down wind of major mountain chains like the Himalayas, Sierra Nevadas, and Andes.

9. Weathering and Soils Mechanical weathering dominates desert regions. Chemical weathering is not effective > Rock varnish is a thin coating of iron and/or manganese oxides on many surface rocks in deserts.

10. Agents of Change Water > scarce > when it rains, it really rains hard! > erodes and deposits distinct landforms - no plants to slow erosion down Wind > common > lack of plants facilitates effectiveness as an agent of change. > erodes and deposits distinct landforms Water > scarce > when it rains, it really rains hard! > erodes and deposits distinct landforms - no plants to slow erosion down Wind > common > lack of plants facilitates effectiveness as an agent of change. > erodes and deposits distinct landforms

11. Exotic & Local Streams. Arroyos usually exhibit braided channels > coarse-grained sediments > prone to severe flash floods! Exotic Streams > Perennial rivers that begin outside the desert - Nile River, Egypt. - Colorado River, Southwest US. > Can be either Meandering or Braided Local braided streams in deserts flow infrequently- known as Arroyos. Arroyos usually exhibit braided channels > coarse-grained sediments > prone to severe flash floods! Exotic Streams > Perennial rivers that begin outside the desert - Nile River, Egypt. - Colorado River, Southwest US. > Can be either Meandering or Braided

12. Arroyo- a dry, often braided stream channel in the desert

13. Nile River: An exotic stream

15. Playa lakes

16. Alluvial Fan

17. Inselbergs are isolated mountains composed of more resistant rock types. Location: Ayers Rock in central Australia.

19. New Mexico Mesa Buttes

20. Wind is a common agent of erosion and deposition in deserts The dust storm shown below transports sand, silt and clay across the Sahara desert in North Tunisia

23. Desert pavement with Inselberg

26. QTVR of dune crest

27. Barchan Dunes Barchan

28. Transverse Dunes Transverse

29. Parabolic Dunes Parabolic (Blowout)

30. Longitudinal Dunes Longitudinal

31. Star Dunes Star