Desert Formation and Characteristics Quiz

Study Notes

Desert Formation and Characteristics

Deserts comprise approximately 30% of Earth's land surface, defined by low precipitation.
Extreme temperatures are a consequence of low atmospheric moisture (humidity and cloud cover), not a defining characteristic.
Deserts at latitudes 15° to 30° are formed by sinking, dry air currents, creating trade winds.
Rain shadow deserts occur downwind of mountain ranges where winds lose moisture as they ascend and cool.

Atmospheric Circulation in Desert Formation

Earth's uneven heating due to latitude and angle of incidence drives atmospheric circulation.
Three atmospheric cells (Hadley, Ferrel, and Polar) circulate air between the equator and poles.
The Hadley cell, near the equator, heats and rises air, releasing moisture. This rising dried air travels poleward.
Near 30° N and S, the dry air sinks, creating high-pressure zones (horse latitudes) and arid conditions.
Trade winds form near the equator from these sinking air currents, and westerlies form in the mid-latitudes.
The Coriolis effect (due to Earth's rotation) deflects air masses to the right in the Northern Hemisphere and left in the Southern Hemisphere, affecting wind patterns.
Polar cells create polar deserts by sinking, cold, dry air at the poles, which is unable to hold much moisture.

Desert Weathering and Erosion

Weathering in deserts is slower due to less water.
Water is the dominant agent of erosion, yet also wind plays a major role.
"Desert varnish" (a dark layer on rocks) is a distinctive desert weathering product.
Wind erosion, including dust storms (haboobs) and loess (wind-blown dust), is common.
Saltation (sand grains bouncing along the ground) is a significant erosive process creating well-rounded, frosted grains.
The Coriolis effect affects wind patterns affecting landscapes.
"Yardangs" are bedrock outcrops sculpted by wind-blown sand and "Ventifacts" are wind-worn rocks.
Playas form in enclosed desert basins where water evaporates, leaving a dry lake bed.
Alluvial fans and bajadas are fan-shaped and apron-like deposits of sediments at mountain fronts.
Inselbergs are leftover, eroded mountain remnants.
Flash floods occur from intense storms, posing a risk to desert travellers.

Desert Landforms and Sand

Ergs (sand seas), are vast areas covered with wind-blown sand, forming dunes.
Dunes have a characteristic cross-bedding structure where sand accumulates on the windward side, slips down the leeward side, creating layered structures.
Dune types (barchan, longitudinal, parabolic, and star dunes) reflect variations in wind direction and sand supply.
Examples of ancient sand dune environments (Navajo Sandstone) found in regions such as Zion and Arches national parks demonstrate cross-bedding features.
Sand is recycled over time through various erosion and deposits, showing how these environments are constantly evolving.

The Great Basin and Basin and Range

The Great Basin is a large interior drainage basin in North America, without an outlet to the ocean.
The Basin and Range is a subregion within the Great Basin, with a series of alternating horsts (uplifted blocks) and grabens (down-dropped blocks) created by crustal extension.
Dramatic shifts in elevation are characteristic of this region along with dramatic changes in precipitation patterns.
Pluvial lakes, like Lake Bonneville, were prominent during past ice ages, and remnants like the Great Salt Lake still exist today.
Desertification arises from environmental changes that make once arable land progressively less productive, with a positive feedback loop that accelerates drying conditions.

Desertification

Desertification is the transformation of arable land into desert.
Human activities (unsustainable farming, overgrazing, groundwater overuse) and global climate change can cause desertification.
Desertification is a significant worldwide problem affecting many areas globally, including some areas in the United States.

Description

Test your knowledge on desert formation and atmospheric circulation. This quiz explores the characteristics of deserts, their climatic influences, and the role of atmospheric cells in shaping arid environments. Perfect for students studying geography or environmental science!