arid landforms

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Arid Landforms : 

Arid Landforms

Basic Concepts : 

Basic Concepts I. Most deserts exhibit highly angular landscapes. mechanical weathering dominates angular particles of weathered rock; bedrock outcrops little soil or vegetation to soften landscape II. Softer, more rounded landscapes appear where deposition is predominant. dunes III. Desert rainfall is infrequent, intense, and unreliable. intense flash flooding, intense erosion ephemeral streams

Slide 5: 

Death Valley, July 15, 1999

Slide 6: 

Las Vegas Flash Flood

Types of Deserts : 

Types of Deserts Erg - sea of sand largest are in Sahara and Arabian Deserts, sand covers about 20% of world’s deserts vegetation rare sand probably formed during more humid climate

Slide 8: 

Death Valley, California

Types of Deserts : 

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

Slide 10: 

A gibber plain in Australia Desert pavement

Slide 11: 

Hamada - bedrock predominates

Slide 12: 

Desert varnish - oxidation of iron and manganese, useful for dating desert surfaces

DESERT FLUVIAL PROCESSES/LANDFORMS : 

DESERT FLUVIAL PROCESSES/LANDFORMS Fluvial Erosion - rare, intense flash floods. steep slopes; steep-walled canyons; washes, wadis, arroyos, canyons. fluvial systems decrease in discharge downstream Fluvial Transportation - large amounts of rock and sand moved short distances. Fluvial Deposition – where water slows on flat playas material is deposited and sorted by size. alluvial fans rock debris in piedmont region

Slide 14: 

Arroyo

Slide 15: 

Virga

Slide 16: 

Joshua Tree N.P.

Slide 17: 

Slot Canyon

Slide 18: 

The Narrows, Zion N.P., Utah

AEOLIAN (WIND) PROCESSES/LANDFORMS : 

AEOLIAN (WIND) PROCESSES/LANDFORMS Aeolian Erosion - much less effective than fluvial deflation - the movement of small particles abrasion - polishes and etches exposed surfaces Aeolian Transportation - moves nothing bigger than sand dust storms - can extend thousands of feet up sand storms - only very near the surface Aeolian Deposition - dunes form and shift where winds and terrain combine to slow the winds or block the movement of dunes.

Slide 21: 

Dust Storm, Senegal Sand Storm

AEOLIAN (WIND) PROCESSES/LANDFORMS : 

AEOLIAN (WIND) PROCESSES/LANDFORMS

Types of Dunes : 

Types of Dunes BARCHAN TRANSVERSE DUNES SEIFS

Types of Dunes : 

Types of Dunes Barchans - migrating crescent dune with horns pointing downwind; form where strong winds blow in a consistent direction. Move fast. Common in central Asia and Sahara. Can reach hundreds of feet in height.

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Transverse Dunes - parallel waves of crescent dunes perpendicular to wind direction; migrate downwind. Found in areas with large supply of sand.

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Seifs - multiple very long narrow, parallel dunes. May be caused in areas with at least two dominant wind directions. Can be tens of miles long. Common outside of U.S.

Slide 27: 

Namib Desert Star Dunes

BASIN AND RANGE TOPOGRAPHY : 

BASIN AND RANGE TOPOGRAPHY

Slide 29: 

Piedmont - gently sloping land that extends out from base of mountains. Pediment - sloping bedrock at base that develops.

Slide 30: 

Badwater, Death Valley, CA

Slide 32: 

Playas

Mesa and Scarp Topography : 

Mesa and Scarp Topography

Slide 34: 

Differential Erosion

Slide 38: 

Uluru (Ayer’s Rock), Australia

Slide 39: 

Inselberg - “island mountains” rise abruptly out of desert landscapes Bornhardt - highly resistant rock landform; a type of inselberg. Kata Tjuta (The Olgas), Australia

Slide 40: 

Bornhardt, Arches National Park, Utah

Slide 41: 

Delicate Arch, Arches National Park, Utah

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