GEO 102 Final -- Unit 47
Where is loess found on earth?
Central United States, all over Europe, south South America
Where are sandy regions located in the world?
Northern Africa mostly also in eastern Austalia and southern Russia
What factors help shape arid environments?
a. Weathering b. Little soil and vegetation: therefore, bedrock is exposed c. Rainfall intense but infrequent d. Wind is common
Are alluvial fans created by fluvial or aeolian processes?
fluvial (water); alluvial fans are water-deposited debris at the end of canyons
aeolian landforms
landforms created or caused by wind erosion
Describe how material is carried by the wind during saltation
like in water, the particles are too heavy to be carried all the time so they bounce along
longitudinal dunes (look at pics)
looks like a fence strong angled winds -- 2 directions, limited sand
Star dunes
looks like a star... multidirectional winds, large amounts of sand
arid landforms
most are created or caused by water erosion
How is water a dominant agent of erosion in an arid region?
most arid landforms are actually made by water (clay and mud structures), therefore severe erosion occurs when they receive their intense but infrequent precipitation
deflation
removal of loose particles by the wind
What is an important feature of loess?
tends to maintain vertical walls when exposed
abrasion
the bombardment of rock and other surfaces by particles carried in the airflow
What is the distribution of sediment size on an alluvial fan?
the size of the sediment on the fan decreases the further away from the canyon it is
Describe how material is carried by the wind during suspension
the smallest particles are carried in the air
How is desert pavement formed?
they form through the gradual removal of sand, dust and other fine-grained material by the wind and intermittent rain, leaving the larger fragments behind.
Describe how material is carried by the wind during a surface creep
too heavy to be picked up, so they are pushed/rolled by the wind
Alluvial fans
water-deposited debris at the end of canyon. Size of sediment on fan decreases away from canyon
transverse dunes (look at pics)
wave-shaped strong winds in the same direction with large amounts of sand
Bajadas
when two or more alluvial fans overlap
Butte
width < height
Pinnacle
width < height
plateau
width > height
Mesa
width ≈ height
What factors are necessary for dunes to form?
wind direction sand supply vegetation
What is loess?
Aeolian-deposited Silt (smaller sand) Primary source regions for the silt comprising loess deposits - Deserts - Glacial Outwash Plains - River Floodplains
What factors are necessary for wind to be a dominant erosional agent in arid landscapes?
Small particle size • Wind • Dry surface conditions - Wet sand doesn't blow • Little surface vegetation - Grass, trees, and roots stabilize small particles
What does desert pavement look like?
Surfaces deflated of fine-grained sediments, leaving a cover of gravel-size or coarser sediments
barchan dunes (look at pics)
U-shaped with the opening in the same direction as the wind moderate sand supply
parabolic dunes (look at pics)
U-shaped with the wind going in hitting the curve of the U moderate sand supply, vegetation present, generally associated with beaches
