18.1: What Is a Desert?
What Is a Desert?
About 30% of the land surface of the world is arid Links to an external site. or semi-arid Links to an external site.. This includes much of the polar regions, where little precipitation occurs and so are considered polar deserts Links to an external site.. 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.
Figure 18.1: The Panamint Valley located in the northeastern reach of the Mojave Desert. (Public Domain; Jesse Pluim/BLM Links to an external site.)
A person who studies the deserts and desert processes may have many titles including geomorphologist, sedimentologist or climate scientist. Like many other geoscientists, working with other disciplines is common, with a heavy influence from both math and technology. Many are employed by universities where they teach and/or do research, and state and federal agencies, including geological surveys, like the California Geological Survey Links to an external site. or United State Geological Survey (USGS) Links to an external site.. 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 Links to an external site., CA State Parks Links to an external site., 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 Links to an external site., Natural History Museum of Los Angeles County Links to an external site., Santa Barbara Museum of Natural History Links to an external site., and Kimball Natural History Museum Links to an external site.. Many colleges and universities also have their own collections/museums.