Chapter 16: Deserts and Wind

Desert

An arid region where evaporation exceeds precipitation.

Steppe

A semi-arid region located on the margins of deserts.

Subtropical Desert

Deserts located around 30 degrees North and South of the equator, caused by high-pressure atmospheric zones.

Rain Shadow Desert

A dry area on the leeward (downwind) side of a mountain range.

Ephemeral Stream

A temporary stream that only carries water in response to specific episodes of rainfall.

Interior Drainage

A drainage system in arid regions where streams do not reach the ocean.

Alluvial Fan

A cone-shaped deposit of sediment formed where a high-gradient stream leaves a narrow mountain canyon.

Bajada

A broad apron of sediment along a mountain front created by the merging of multiple alluvial fans.

Playa Lake

A temporary, shallow lake formed in the lowest part of a desert basin during wet periods.

Playa

The dry, flat, and often salty lake bed left behind after a playa lake evaporates.

Inselberg

An isolated, erosional remnant of a mountain (a "bedrock island") standing above a desert plain.

Bed Load

Sand and gravel transported by bouncing, rolling, or sliding along the ground surface.

Saltation

The skipping and bouncing motion of sand grains being transported by wind or water.

Suspended Load

Fine dust and silt carried high in the air by the wind.

Deflation

The lifting and removal of loose, fine-grained material by wind.

Blowout

A shallow depression excavated by wind erosion (deflation).

Desert Pavement

A tightly packed surface layer of coarse pebbles and cobbles left behind after wind removes the finer sand and dust.

Loess

Extensive, unstratified blankets of windblown silt.

Sand Dune

A mound or ridge of wind-deposited sand, typically formed where an obstruction slows the wind.

Crossbeds

Inclined, internal layers within a dune formed as sand is deposited on the slip face.

Slip Face

The steep, leeward slope of a dune where sand cascades down.

Angle of Repose

The steepest angle at which loose material remains stationary (approximately 34° for loose dry sand).

Barchan Dune

A solitary, crescent-shaped dune with tips pointing downwind, formed where sand is limited and vegetation is absent.

Transverse Dune

Long, linear ridges of sand oriented perpendicular (at a right angle) to the prevailing wind direction.

Barchanoid Dune

A scalloped dune ridge that forms a transition between barchan and transverse dunes.

Longitudinal Dune

Long ridges of sand oriented parallel to the prevailing wind direction.

Parabolic Dune

A crescent-shaped dune with tips pointing upwind, typically forming along coasts where vegetation partially anchors the sand.

Star Dune

An isolated hill of sand featuring 3 or 4 sharp crests, formed in areas where wind directions are highly variable.