Aeolian processes

pertain to the activity of the winds and more specifically, to the winds' ability to shape the surface of the Earth and other planets

Wind-carved alcove in the Navajo Sandstone near Moab, Utah.

Wind erosion

Transport

Deposition

Wind erosion

Wind erodes the Earth's surface by deflation (the removal of loose, fine-grained particles), by the turbulent eddy action of the wind and by abrasion (the wearing down of surfaces by the grinding action and sandblasting of windborne particles).

deflation zonesRegions which experience intense and sustained erosion. Composed of desert pavement, a sheet-like surface of rock fragments that remains after wind and water have removed the fine particles

Rock carved by drifting sand below Fortification Rock in Arizona (Photo by

Timothy H. O'Sullivan, USGS, 1871)

A rock sculpted by wind erosion in the Altiplano region of Bolivia

Sand blowing off a crest in the Kelso Dunes of the Mojave Desert, California

Transport

SUSPENSIONSUSPENSI

ONSUSPENS

IONSALTATION

SUSPENSIONCREEP

SUSPENSION

Small particles may be held in the atmosphere in suspension.

Upward currents of air support the weight of suspended particles and hold them indefinitely in the

surrounding air.

downwind movement of particles in a

series of jumps or skips. Saltation

normally lifts sand-size

particles no more than one

centimeter above the ground

Surface creep accounts for as much as 25 percent of grain

movement in a desert.

A massive sand storm cloud is close to enveloping a military camp as it rolls over Al Asad, Iraq, just before nightfall on April

27, 2005.

Dust storm approaching Spearman, Texas April 14, 1935.

Dust storm in Amarillo, Texas. FSA photo by Arthur Rothstein (1936)

Deposition

Wind-deposited materials hold clues to past as well as to present wind directions and intensities.

These features help us understand the present climate and the forces that molded it. Wind-deposited sand bodies occur as sand sheets, ripples, and dunes. 

SAND SHEETS

Sand sheets are flat, gently undulating sandy plots of sand surfaced by grains that may be

too large for saltation. They form approximately 40 percent

of aeolian depositional surfaces.

Ripples

In ripples, the coarsest materials collect at the crests causing inverse grading.

This distinguishes small ripples from dunes, where the coarsest materials are generally in the troughs.

Dunes Dunes have gentle

upwind slopes on the wind-facing side.

The downwind portion of the dune, the lee slope, is commonly a steep avalanche slope referred to as a slipface.

Dunes may have more than one slipface. The minimum height of a slipface is about 30 centimeters.

Crossbedding of sandstone near Mt. Carmel road, Zion Canyon, indicating wind action and sand dune formation prior to formation of rock (NPS photo

by George A. Grant, 1929)

Mesquite Flat Dunes in Death Valley looking toward the Cottonwood Mountains from the north west arm of Star

Dune (2003)

Holocene eolianite deposit on Long Island, The Bahamas. This unit is formed of wind-blown carbonate grains. (2007)

The EndThank You!!

Mwuah.