{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

desert - 1 Deserts and Winds I Definition Originally the...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Deserts and Winds I- Definition : Originally, the word desert means a place that is deserted, or uninhabited because of its inability to sustain plant or animal life due to inadequate water supply. However, modern technological advances have allowed human beings to inhabit some deserts. Therefore, a desert is best defined as an area with very low rainfall or precipitation. Areas receiving < 25 cm/year of rainfall are considered "arid lands" and qualify for the definition of "desert", whereas areas receiving between 25 and 50 cm/year are "semi-arid", and may at times be considered "deserts". It should be noted that not all deserts are characterized by hot climates; some areas in polar regions are considered deserts as these areas also receive a limited amount of precipitation. Nevertheless, most deserts are characterized by temperatures in the range of ~30 to ~55°C (with the highest temperatures having been recorded in Death valley, California and the Libyan desert at ~ 57°C). II- Area and distribution of deserts: Arid lands constitute ~ 19% of total land area on earth, whereas semi-arid regions (also known as "Steppes") constitute another 13%. A quick look at a map of the world (Fig. 1) shows that most deserts occur within two belts; one between latitudes 20 and 30 N and another between latitudes 20 and 30 S. This distribution is a function of the global directions of wind flows; these two belts are always characterized by high atmospheric pressures, where subsiding air is warmed up as it sinks producing low humidity. However, not all deserts lie within these two belts (Fig. 1), which in turn leads us to identify different types of deserts. III- Types of deserts: (a) Subtropical deserts: These are the deserts located in belts of descending dry air between latitudes 20 and 30 N and S of the equator. Examples include the Sahara, the Arabian desert, the Great Australian desert and the Kalahari desert. (b) Continental deserts: These are deserts that occur in the continental interiors, far from sources of moisture. Examples include the Gobi desert in China. (c) Rain Shadow deserts: Are deserts located on the lee sides (sides protected from wind) of mountain chains, which act as barriers between such deserts and oceans. Moist air flowing inland therefore does not reach these areas as it is "blocked" by the mountain causing precipitation on the side of the mountain facing the ocean. Examples include deserts behind the Sierra Nevada and Cascade Mountains in the western U.S.A. Fig. 2 illustrates how a rain shadow desert forms. (d) Polar deserts: These form in polar regions where the cold air is extremely low in water vapour. Examples include the dry valley region of Southern Victoria Land in Antarctica.
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
2 IV- Agents of weathering, erosion and deposition in deserts: In order to understand the processes that take place in deserts and their geomorphological features, we must first identify the various agents of weathering, erosion and deposition in deserts. These include: (a) Winds : Wind is a turbulent stream of air that has the ability to erode, transport and deposit sediment in ways similar to the action of running water. However, unlike running
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern