16.1: What is a desert?

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About 30% of the land surface of the world is classified as arid or semi-arid. This includes much of the polar regions, where little precipitation occurs, and are considered polar deserts. Deserts are typically classified by the amount of precipitation that falls (fewer than 10 inches), by the temperature that prevails, or by geographical location. While temperature extremes are often associated with deserts, they do not define them. Deserts exhibit extreme temperatures because of the lack of moisture in the atmosphere, including the low humidity and scarce cloud cover. Without cloud cover, the Earth’s surface absorbs more of the Sun’s energy during the day and emits more heat at night.

A person who studies the deserts and desert processes may have many titles including geomorphologist, sedimentologist, or climate scientist. Many of these scientists are employed by universities, where they teach and/or do research, or state and federal agencies, including geological surveys like the California Geological Survey or United States Geological Survey (USGS). Additional career pathways include environmental policy and legislation and consulting, via the private sector or state and federal agencies. Many of these career options require a college degree and postgraduate work. If this pathway is of interest to you, talk to your geology instructor for advice. We recommend completing as many math and science courses as possible. Also, visit National Parks, CA State Parks, museums, gem & mineral shows, or join a local rock and mineral club. Typically, natural history museums will have wonderful displays of rocks, including those from your local region. Here in California, there are a number of large collections, including the San Diego Natural History Museum, Natural History Museum of Los Angeles County, Santa Barbara Museum of Natural History, and Kimball Natural History Museum. Many colleges and universities also have their own collections/museums.