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