Lecture 15: Deserts Review

Vocabulary flashcards covering key concepts from Lecture 15 on deserts, including global distribution, weathering, erosion features, sand dune types, and causes of desertification.

Desert

A region defined by receiving less than 10 inches of precipitation annually (not by temperature), covering approximately 20% of Earth's land.

Hadley cells

Atmospheric circulation pattern where warm air rises near the equator, loses moisture, and sinks around 30° north and south latitude, creating dry desert conditions.

Rain-shadow region

A dry area formed where mountains block moisture, causing moist air to rise, cool, and drop precipitation on one side while leaving the other side with much less rain.

Chemical weathering (in deserts)

A weathering process limited by low moisture, though oxygen reacts with iron in rocks to produce iron oxides, giving desert rocks their reddish color.

Arroyo

A usually dry stream channel in a desert that can fill with water extremely quickly during heavy rainfall, presenting flash-flood hazards.

Deflation

The removal of loose, fine sediment such as sand and dust from the ground by wind, leaving larger rocks behind.

Desert pavement

A ground surface closely covered in rocks and pebbles left behind after wind deflation blows away finer sediment.

Alluvial fan

A fan-shaped pile of sediment deposited where water flows out of a narrow channel (such as an arroyo) onto flatter land.

Playa lake

A temporary desert lake formed when rainwater collects in a low area, disappearing due to high evaporation and leaving salts behind.

Inselberg

A large, isolated rock hill protruding above otherwise flat land, remaining after the surrounding less resistant material has eroded away.

Arch

A natural opening through rock created by localized weathering and erosion where weaker parts of the rock wear away faster.

Sand dune

A mound or ridge of sand deposited by wind that migrates as sand moves up one side and collapses down the steeper slip face.

Saltation

The process by which sand grains bounce or hop along the ground under the influence of wind, knocking other particles into motion.

Barchan dune

A crescent-shaped (C-shaped) sand dune whose horns point downwind in the direction the wind is blowing.

Transverse dune

A dune type formed from merged barchans under conditions with abundant sand, forming connected ridges that run perpendicular to the wind direction.

Linear dune

A long, straight ridge dune that runs parallel to the overall direction of sand transport, forming when wind direction varies somewhat.

Star dune

A sand dune featuring multiple arms extending in different directions, formed in areas where the wind changes direction frequently.

Parabolic dune

A U-shaped or V-shaped sand dune whose horns point upwind and are anchored by vegetation, commonly associated with beach environments.

Desertification

The process of land becoming more desert-like through degradation, driven by tectonic activity, climate change, and human activities.

Deforestation

The cutting down of trees, which removes vegetation that protects the soil and accelerates desertification.

Overgrazing

A human-related cause of desertification where excessive livestock consume vegetative cover, leaving the soil exposed to erosion.