Formation

Sand sheets are formed by the deposition of windblown particles, creating a layered structure of sand and fine sediments

Characteristics

Structure

Sand sheets have a layered structure of coarse silt and fine to medium sand, interspersed with thin layers of coarser sand and pea-sized gravel

Wind Patterns

Wind speeds exceeding 24 kilometers per hour can generate small, temporary ripples on the sand sheets, which are aligned perpendicular to the wind direction and change with variations in wind patterns

Desert Pavement

The larger particles in sand sheets can lead to the formation of desert pavement, where stones are compacted on the surface

Formation and Migration

Sand dunes are dynamic landforms created by the wind's ability to transport and deposit sand, often forming mounds or ridges downwind from sources of loose sand

Structure

Windward and Leeward Sides

The windward side of a dune typically has a gentler slope, while the leeward side is steeper, at the angle of repose for dry sand

Dune Fields

Dune fields, or ergs, consist of numerous dunes, and their shapes are determined by prevailing wind conditions and the availability of sand

Formation

Unique gypsum dune fields, like those in White Sands National Park, New Mexico, are formed from the evaporation of mineral-rich water in closed basins, leaving behind gypsum crystals

Desert Pavement

Desert pavement is formed when wind erosion removes smaller particles, leaving a layer of larger rocks, resulting in a stable surface that is resistant to further erosion

Adaptation to Aridity

Desert and semi-desert ecosystems are adapted to the extreme conditions of arid and semi-arid climates, with vegetation and animal populations that have adapted to the scarcity of water

Plant Adaptations

Water Conservation

Desert plants have evolved a variety of adaptations, such as crassulacean acid metabolism, to conserve water in arid environments

Heat Avoidance

Some desert plants have reduced or absent leaves to minimize transpiration and protect against extreme temperatures

Water Storage

Other desert plants, like cacti, have adapted to store water in their trunks and have specialized cellular structures to support this function

Animal Adaptations

Water Conservation

Desert animals have adapted to conserve water through behaviors such as burrowing or nocturnal activity

Heat Avoidance

Some desert animals have physical adaptations, such as light-colored fur, to reflect heat and stay cool in hot environments

Opportunistic Breeding

Desert animals may breed opportunistically following rainfall events, taking advantage of temporary water sources in arid environments