The document discusses desert landscapes and the climatic and geological processes that shape them. Deserts cover 30% of the Earth's land and experience little rainfall each year, typically less than 100mm. They are located in subtropical regions near the 30 degree latitudes, where global wind patterns limit rainfall. Deserts form due to low rainfall and high evaporation. Wind erosion shapes deserts by removing sand and depositing it in dunes and loess deposits. Water erosion forms features like hoodoos, slot canyons, mesas and buttes through processes like deflation and abrasion. Water deposition builds up alluvial fans and bajadas at the edges of deserts.

1. Desert Landscapes
Dominated by Wind

2. “We don’t survive the desert,
we live here”
- Pima Indian

5. Deserts: where & why
 Earth’s dry regions: 30% of all land
 2 climate types of dry regions:
◦ desert (arid)
◦ steppe (semi-arid, surrounds deserts)
 Question:How much rain do deserts get
every year?
◦ Sahara Desert receives as little as 2mm and as
much as 100mm of precipitation per year

6. Climate Graphs – Semi-arid and Arid
What do you notice about the minimum and maximum temperatures?
What do you notice about the amount of precipitation?

7. Deserts: where & why
 What causes deserts?
 Global distribution of
◦ air pressure
◦ wind
 Relationship between
◦ rainfall
◦ evaporation

8. Deserts: where & why
 Low-latitude deserts
◦ Tropic of Cancer
◦ Tropic of Capricorn
 In contrast….
◦ Equator:
 hot air
 rises to 15-20 km
 low pressure belt

9. Deserts: where & why

10. Deserts: where & why

11. Deserts: where & why

12. Deserts: where & why

13. Deserts: where & why
 Middle-latitude deserts (ie. 45°N)
◦ exist in rain shadows.

14. Deserts: where & why
Middle-latitude deserts

15. The Great Basin
 Basin (valley) and
Range (mountains)
topography
◦ mountainous desert
landscape
◦ Nevada, Arizona,
California, Utah
◦ Death Valley,
Mojave Desert,
Great Salt Lake

16. Great Salt Lake, Utah

17. Evaporation > Precipitation
 Playa: ephemeral (not existing all year
long) lake beds that consist of salt and
mud flats
Spotted Lake, just outside of Osoyoos, BC

19. Wind erosion + deposition
 Wind erosion: Important in arid
environments
 Example…Sand dune shape depends
on:
◦ Flat or hilly?
◦ How much sand?
◦ Winds steady or intermittent?
◦ Wind direction constant?
◦ Vegetation present?

20. Wind erosion
 Desert pavement

21. Wind erosion
 Deflation: the process of wind
removing silt and sand-sized particles

22. Wind erosion + deposition
 Ergs: seas of dunes

24. Wind erosion + deposition
 Sand dune formation

27. Wind erosion
 Ventifacts: rocks abraded, pitted,
polished by windblown sand

28. Wind Deposition
 Loess from Aeolian
(or Eolian)
transportation:
◦ Deposit of wind-
blown silt and clay in
angular grains and
weakly cemented by
calcite
◦ Develop rich, fertile
soils

29. Water Erosion
 Wadi: a dried up river bed that only
has water during rainy season
Town of WadiTiwi,
Oman

32. Water Erosion
 Hoodoos (or fairy
chimneys): column
of soft sedimentary
rock often with
resistant layer of
“cap” rock on top
 Water flows
through badlands
causing further
erosion to the
Bryce Canyon National Park, Utah
spires

33. Water Erosion
Fairy chimneys that people still live inside in Cappadocia,
Turkey

34. Water Erosion
 Antelope Slot
Canyons, Page,
AZ
 Flash floods from
localized
thunderstorms
carry sediments
that abrade and
polish the
sandstone

35. Water Erosion
Mesa: a flat-topped “table” formed by
differential erosion of softer rock
underneath a layer of “cap” rock

36. Water Erosion
Butte: a smaller version of a mesa

37. Water Erosion
 Pedestal rock:
softer rock erodes
quicker than
resistant “cap” rock

38. Water Deposition
Alluvial Fan: deposition of sediments as rivers or flash
floods leave mountain ranges and spread into the
valley

39. Water Deposition
 Bajada: several adjacent alluvial fans
that have merged together