Arid and Semi-Arid Arid and Semi-Arid Landscapes ( Aeolian Landscapes ( Aeolian

LandformLandform

World's DesertsWorld's Deserts about 1/5th of land

Types: subtropical, rain-shadow,coastal, interior, polar

Arid and Semi-aridArid and Semi-arid

EgyptLibya

Tunisia

Algeria

Morocco

Wind-Borne Sediment causes Wind-Borne Sediment causes deflation and abrasiondeflation and abrasion

Sahara to CaribbeanEffect on Hurricanes

Surface creep

InselbergInselberg

UluruUluru (Ayers Rock) (Ayers Rock)

Pediment

MushroomMushroom

Types of DesertsTypes of DesertsErg - sea of sand• vegetation rare• sand probably formed during more humid climate

Death Valley, California

Types of DesertsTypes of DesertsReg - desert “pavement” of pebbles and stones• all small materials and sand removed by wind• may be very thin coating of stones

Desert pavement

Hamada - bedrock predominates

Erosional Landform - Deflation HollowErosional Landform - Deflation Hollow

Anecdote – How fast does this occur?

Abrasion Origin of VentifactsAbrasion Origin of Ventifacts

Erosional Landforms - Erosional Landforms - VentifactsVentifactsWind eroded (sand blasted) surfaces

Erosional Landform – Erosional Landform – Yardangs and Yardangs and Zeugen Zeugen

Sphinx?

White Desert, EgyptWhite Desert, Egypt

Dune MigrationDune Migration

Just like ripples in a stream

Windward slopeerosion and transport

Slip face (deposition)

Star DunesStar Dunes

Copyright © Frank Eckardt 2002

Star DunesStar Dunes

Variable Wind DirectionVariable Wind Direction

Longitudinal DunesLongitudinal Dunes

Constant wind direction, no vegetation

Longitudinal DunesLongitudinal Dunes

Constant wind direction, no vegetation

Transverse Dunes Transverse Dunes

Massive volumes of sand, low consistent winds

Transverse Dunes Transverse Dunes

Massive volumes of sand, low consistent windsMassive volumes of sand, low consistent winds

Barchan DunesBarchan Dunes

Isolated Dunes, low sand supply, migrating across rock

Barchan DunesBarchan Dunes• Isolated – low sand supply; migrating across rock

Parabolic DunesParabolic Dunes

Horns pinned by plantsTypical of coasts

Fig. 15-12a, p. 354

Parabolic DunesParabolic Dunes

• Stabilized “horns" point upwind

A Playa in Death Valley, CaliforniaA Playa in Death Valley, California

Evaporite Pan of dried-up PlayaEvaporite Pan of dried-up Playa

Playas

Differential Erosion

Desert LandformsDesert Landforms• plateaus: a broad, flat-topped area elevated

above the surrounding land and bounded, at least in part, by cliffs

• mesa: a broad, flat-topped hill bounded by cliffs and capped with a resistant rock layer

• butte: a narrow hill of resistant rock with a flat top and very steep sides

Inselberg or Bornhardt - highly resistant rock landform; a type of monadnock.

Bornhardt, Arches National Park, Utah