Areas that receive less than 10 inches (25.4 cm) of rain a year are generally classified as deserts. Dry (arid) regions are usually found in area of high pressure (subtropical highs, leeward sides of mountains, etc.) associated with descending divergent air masses that are common between 30 degrees N and 30 degrees S latitude.

As a consequence of low moisture, desert vegetation is sparse and specifically adapted to conserve water. Deserts are areas of high relief (e.g., mesas, buttes, etc). Desert regions typically feature well-sorted sands, often found in various dune formations shaped by sand type, moisture content, and eoilian processes.

In desert areas, change usually occurs by some form of physical weathering. The wide diurnal temperature can make the modest amounts of moisture present powerful weather factors through continual freezing and thawing cycles that can result in micro-fracturing of rock. Winds often allow high levels of...