Aeolian (wind) Landscapes Mt Etna & the Aeolian Islands Aeolus, king of the Aeolian Islands, rules the winds in Greek Mythology

Wind Landscapes 1.Dust (Loess) 2.Dunes (sand) 3.Ventifacts (erosion)

1. Dust (loess) Dust collects on margins of deserts and glaciers

Breck P. Kent Deflation Hollow Deflation The process of removing all of the small (easily moved) particles by wind.

Deflation lowering surface Old Palm surface Medium Palm surface Young Palm surface

Dust Deflation 1500 m dust storm, 300 km/hr winds San Joaquin Valley, California, 1977 drought Dust storm across Red Sea Dust storm Kaho’olawe Island, Hawai’i

The Dustbowl, America, 1930’s Period of severe droughts Wind erosion of soil Organic matter, clay, and silt removed –carried great distances by wind –darkened sky on Atlantic coast Abandoned farms worsened problem

Classroom Resource Movie of dust blow era deflation

Loess Source: Negev Desert

Loess Accumulation: Wetter Margin of the Negev Desert

Loess Source: Peru Desert Loess Source: Atacama Desert

Loess Accumulation: Wetter Margin of the Atacama Desert

Loess Plateau, China

2. Dunes (sand) Tallest Dunes Found in Namibia (980 ft)

Dunes are less dominant than many think Deserts cover about 1/5 th of the land Only 10% of that is dune covered (1/50 th )

Transport of Wind-Borne Sediment

Classroom Resource Slowed down process of saltation (bouncing)

Ripples form on surface of Sand Dunes

Some dunes “anchored” Falling dunes, Sinai, Egypt (depend on mtn)

Coppice dunes, depending on vegetation

Beach Sand Dunes

Parabolic (blow-out) Dunes Horns pinned by plants

Parabolic (blow-out) Dune

True Dunes Migrate Stoss (backslope) Lee (slip) face Animation that will play in the powerpoint file, showing how older “slip faces” create the cross bedding

Ripples on Stoss Side Stoss (backslope)

Slip Face on Lee Side Steep side of dune Sand Surfing Dune Jumping

Cross Bedding characteristic of dunes Slip faces

Classroom Resources Crossbedding.swf – Animation of how crossbedding forms

Transverse Dunes

Slip face tells you the wind direction

Longitudinal (linear, seif) Dunes

Longitudinal (Linear or Seif) Dunes Elongate parallel to wind direction Slip faces change from one side to the other side, as wind changes directions

Longitudinal Dunes

Barchan Dunes

Barchan Dune Slip face tells you the wind direction

Transverse Dunes turn into Barchan when sand supply drops

Star Dunes

Erg (Sand Sea)

Largest Sand Seas Jurassic Today

Great Sand Dunes small erg

Great Sand Dunes Classroom Resource: Animation of how build up by wind reversing

Tremendous Variety Exists inside an Erg (Rub Al Khali, Arabia)

3. Ventifacts (wind erosion)

Look at surfaces: Polished Smooth (with grooves) by sand and dust abrasion If boulders, grooved

Wind flow

If small enough (pebbles,cobbles), rock is rotated so that polishing occurs on several sides

Ventifacts very common on Mars

How do you know it’s a true ventifact? Rub with your hand. If wind-abraded the surface is smooth Iceland Mojave Desert (Greeley et al., ASU)

NOT FROM Wind Abrasion No evidence of sand blasting. Only evidence of water erosion (rainsplash and rill)

NOT FROM Wind Abrasion No evidence of sand blasting. Only evidence of weathering, splitting apart the individual mineral grains – roughening surface No! Salt weathering

Not from wind abrasion! Wind can help blow out weathered products (clays, silt) from tafoni. But form is made by weathering (salt, chemical)

Erosion by the wind: Abrasion smooths surfaces Ventifacts

Erosion by wind polishes rental cars

Claims of Yardangs in Iran See mostly evidence of water flow, not wind

I am very skeptical about claims of hills eroded by wind – when you look carefully, you don’t see evidence of wind abrasion, only evidence of water erosion

Notch where saltating sand grains erode Yardangs, White Desert, Egypt Right scale & Good Evidence

Wrong Correct Weathering only

Online Animations Dunes: Process and Form Visualizations nes.html nes.html Visualizations for Soil Erosion (wind) erosion.html

Imagery seen in this presentation is courtesy of Ron Dorn and other ASU colleagues, students and colleagues in other academic departments, individual illustrations in scholarly journals such as Science and Nature, scholarly societies such as the Association of American Geographers, city,state governments, other countries government websites and U.S. government agencies such as NASA, USGS, NRCS, Library of Congress, U.S. Fish and Wildlife Service USAID and NOAA.c