Deserts and Wind Flashcards
On Exam 2 (Apr.1)
Desert
A barren land with little rainfall (does NOT have to be hot)
Covers 30% of Earth’s land surface
What is the Coriolis Effect? How does it affect deserts?
The Earth’s rotation causes apparent curvature in straight-line paths, creating 3 air circulation cells per hemisphere
The spaces between cells where air falls are where deserts occur
Faster spinning planets have more cells
Subtropical Desert
Caused by Hadley cells
As air moves towards the equator, it removes moisture from the land, creating deserts at about 30 degrees north and south and high rainfall at the equator (where the air rises and releases said moisture)
Rain-Shadow Deserts
As air rises above a mountain, it gradually releases moisture, so by the time it goes up, over, and down the other side, it’s dry
This causes heavy rainfall on one side (closer to the ocean) and a desert on the other (called the leeward side)
Coastal Deserts
Cold ocean currents blow cool, dry offshore air onto land, which absorbs the onshore moisture and causes deserts that are prone to wildfires (Californiaaa)
Continental Interior Deserts
Areas located so far from the coast that rain fails to reach them
The Sahara
Polar Deserts
Areas that are intensely cold and receive virtually no precipitation
Antarctica (the largest desert on Earth)
Why is desert weathering a slower process than streams?
The primary agent is wind, which is slower moving than water and can’t pick up as big of sediments
Weathering, then, is predominantly mechanical: smaller grains get picked up and will hit other rocks, slowing wearing them down in sharp, angular shapes
How does wind transport sediments?
Mainly via suspension (particles being held in the air)
Also has saltation (hops/skips) and creep (sliding/rolling)
How is transport different between wind and water?
Wind can only pick up smaller grains, so they don’t travel as far or for as long
It’s also less constant of a process than water
Abrasion
The wearing down of a rock by repeatedly impacting it with particles carried in the wind, leading to strange-shaped rocks and undercutting
Deflation
The lowering of the ground surface from the overall removal of loose material, leading to shallow depressions called blowouts
Can occur very quickly
Desert Pavement
Closely packed layers of coarse pebbles and cobbles that are too large to be moved by the wind
Dunes
Mound- or ridge-shaped deposits of windblown sand (look similar to asymmetrical ripple marks caused by rivers)
The shape and cross-bedding can tell us about the direction of the wind
Loess Deposits
Very tiny silt and clay carried great distances by wind
How do supercontinents affect deserts?
Deserts are mainly continental interior
