Physical Geology
Erosional features in deserts
- sand grains carried along the ground by wind (saltation)
- deflation:
- removal of sand sized grains from the surface by wind, leaving only heavier rocks, produces desert pavement.
- Ventifacts:
- rocks polished on one side by abrasion from exposure to prevaling wind direction.
- Wind can erode away the base of plants and trees, leaving the root system exposed.
Depositional features in deserts:
- Sand dunes: Areas where the moving sand is deposited.
Several different types:
Barchan: sand supply limited, winds constant
Transverse: sand plentiful, winds constant
Longitudinal: sand limited, winds converge and are constant
Parabolic: where vegetation partially covers the sand, strong onshore winds, sand plentiful
Star dunes: sand plentiful, winds change direction variably
- Loess:
- deposits of windblown silt (dust) blanketing large areas
- covers 1/10th of the Earth
- common near areas recently glaciated, cuz glaciers powder rocks.
- Alluvial fans:
- streams traveling down canyons in the mountains drop their loads during high run-off times at the base of the mountain.
- form distinctive shapes, called alluvial fans.
- Fans can converge and meet one another to form a large deposit called a bajada.
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