Deserts and Winds Lecture Notes

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.