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.
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
15. The Great Basin
Basin (valley) and
Range (mountains)
topography
◦ mountainous desert
landscape
◦ Nevada, Arizona,
California, Utah
◦ Death Valley,
Mojave Desert,
Great Salt Lake
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
18.
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?
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
30.
31.
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
