Lecture 15

Deserts and Wind Action

Lecture Outline

I DesertsA) CharacteristicsB) DistributionC) Southwest United States

i. The Great Basinii. The Colorado Plateau

IIWind ActionA) ErosionB) TransportationC) Deposition

III Conclusions

Lecture 3ii

Characteristics of Deserts

< 25 cm rain per year

sparse rugged vegetation

two climatic typesarid deserts

semiarid steppes

Distribution of Deserts

Climate ControlsSolar Radiation and Heat Transfer

Climate ControlsAtmospheric Heat Transfer

Three Cell Model

Hadley Cell

Ferrell Cell

Polar Cell

Climate ControlsOceanic Heat Transfer

Climate ControlsOceanic Heat Transfer – Thermohaline Circulation

Distribution of DesertsControlling Climatic Factors

Atmospheric Circulation

Rain Shadow

Cold Ocean Currents

Continentality

Distribution of DesertsAtmospheric Circulation

Distribution of DesertsAtmospheric Circulation

Distribution of DesertsAtmospheric Circulation - The Sahara

Distribution of DesertsRain Shadow

Distribution of DesertsRain Shadow - The American Southwest

Distribution of DesertsCold Ocean Currents

Distribution of DesertsCold Ocean Currents - The Namib

Sea Surface Temperature (oC) - 03/17/02

Naval Research Laboratory, Stennis Space Centerhttp://www.ocean.nrlssc.navy.mil/global_ncom

Distribution of DesertsCold Ocean Currents - The Namib

Distribution of DesertsContinentality - The Gobi

Deserts of the American Southwest

The Great Basin (Basin and Range)

The Colorado Plateau

Deserts of the American SouthwestWater Bodies – Arroyos

Deserts of the American SouthwestThe Great Basin

rugged mountain ranges separated by flat valleysfault-controlled topography

Deserts of the American SouthwestThe Great Basin

Desert Landforms of the American SouthwestThe Great Basin

Desert Landforms of the American SouthwestGreat Basin Landforms - Alluvial Fan

alluvial fan - an outspread, gently sloping mass of alluvium deposited by a stream, particularly in an arid or semi-arid region where a stream issues from a narrow canyon onto a plain or valley floor.

Desert Landforms of the American SouthwestGreat Basin Landforms – Bajada

bajada - a broad, gently inclined detrital surface extending from the baseof a mountain range out into an inland basin, formed by the lateral build-up of a series of alluvial fans.

Desert Landforms of the American SouthwestGreat Basin Landforms - Playa

playa - a dry, barren area in the lowest part of an undrained desert basin. playa lake - a shallow, intermittent lake in an arid region.

Desert Landforms of the American SouthwestGreat Basin Landforms - Pediment

pediment - a broad gently sloping erosion surface or plain of low relief, typically developed by running water, in an arid or semiarid region at the base of an abrupt and receding mountain front.

Desert Landforms of the American SouthwestGreat Basin Landforms – Inselberg

Desert Landforms of the American SouthwestGreat Basin Landforms Evolution

Deserts of the American SouthwestThe Colorado Plateau

beds of flat-lying sedimentary rocks

>1500m above sea level due to uplift

marked by monoclines

Deserts of the American SouthwestColorado Plateau Landforms

plateau- a relatively elevated area of comparatively flat land bounded on at least one side by cliffsmesa - a broad flat-topped hillbutte - a narrow hill of resistant rock with a flat top and very steep sides

Desert Landforms of the American SouthwestThe Colorado Plateau – Monocline

monocline - a local steepening in an otherwise uniform gentle dip

Wind Action

Erosion

Transport

Deposition

Wind ActionErosion

Wind ActionErosion - Blowout

Wind ActionErosion - Deflation

Wind ActionErosion - Ventifacts

Wind ActionTransportation

Wind ActionTransportation - Dust Storms

Wind ActionDeposition – Dunes

Wind ActionDeposition – Dune Migration

Wind ActionDeposition – Dune Morphology

Wind ActionDeposition – Controlling Factors on Dune Morphology

Wind ActionDeposition - Barchan Dunes

Wind ActionDeposition – Transverse Dunes

Wind ActionDeposition – Barchanoid Ridge Dunes

Wind ActionDeposition – Star Dunes

Wind ActionDeposition – Parabolic Dunes

Wind ActionDeposition – Longitudinal Dunes