Key Terms: Arid Landscape Development (AQA A Level Geography): Revision Note

Hot desert landforms - key terms

Alluvial fan – A cone-shaped deposit of sediment formed where a river loses energy as it exits a mountain range, commonly after flash floods.

Bajada – A broad slope of alluvial material formed by the merging of multiple alluvial fans along the base of desert mountains.

Barchan dune – A crescent-shaped sand dune with horns pointing downwind, formed in areas with limited sand and a dominant wind direction.

Canyon – A deep valley with steep sides, formed over millions of years by vertical river erosion (e.g. the Grand Canyon).

Deflation hollow – A shallow depression formed when wind removes loose, fine sediment from the desert surface.

Desert pavement – A surface layer of closely packed gravel and stones left behind after finer particles have been removed by wind.

Inselberg – An isolated hill or mountain rising abruptly from a plain, often formed from granite or sandstone through prolonged erosion.

Mesa – A flat-topped landform with steep sides, wider than it is tall, formed from erosion of sedimentary plateaus.

Pedestal rock – Also known as a mushroom rock, formed by wind abrasion eroding softer rock near the base faster than the upper harder rock.

Pediment – A gently sloping rock surface at the base of a mountain, formed by sheetwash and erosion.

Playas – Flat, dry lake beds found in desert basins where water temporarily collects after rain; often saline and covered with mud cracks or salt.

Rock pedestal – See Pedestal rock.

Salt pan – A flat expanse of ground covered with salt and minerals left behind after evaporation of water from a playa or seawater pool.

Sand dune – A mound or ridge of sand formed by wind deposition, with a windward slope and a leeward slip face.

Sand ripple – Small ridges formed on the surface of sand by wind, with crests and troughs that develop at right angles to wind direction.

Sand sea – A vast region of wind-blown sand dunes, often found in the heart of major deserts.

Sand sheet – A flat area of desert sand where the grains are too large to be moved by saltation; covers a large proportion of desert surfaces.

Seif dune – A long, narrow sand dune formed by winds blowing from two directions at different times of year; aligned parallel to prevailing wind.

Slot canyon – A very narrow canyon, deeper than it is wide, typically formed by flash flooding in arid areas with soft rock (e.g. sandstone).

Ventifact – A rock that has been abraded and shaped by wind-blown sand, often forming sharp edges and polished faces.

Wadi – A dry stream channel that temporarily fills with water during flash floods; can vary in shape and may show signs of past fluvial activity.

Yardang – A wind-eroded ridge of resistant rock, streamlined in the direction of prevailing wind, with adjacent troughs eroded from less resistant rock.

Zeugen – Similar to yardangs, but formed in horizontal layers; wind abrasion undercuts softer rock below a protective hard cap rock.

Past and present desert landforms - key terms

Basin and range – A landscape formed by tectonic extension, featuring alternating mountain ranges and sunken basins, often found in western USA.

Pleistocene pluvial – A wetter climatic phase during the Pleistocene epoch, which led to the formation of many desert landforms seen today.

Relict feature – A landform that formed under previous climatic conditions and no longer actively develops in the current environment.

Vertical deformation - Displacement which takes place along the fault lines.