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Burkett, Virginia R., D. B. Zikoski, and D. A. Hart. "Sea-Level Rise and Subsidence: Implications for Flooding in New Orleans, Louisiana." In U.S. Geological Survey Subsidence Interest Group Conference, Proceedings for the Technical Meeting. Reston, Va.: U.S. Geological Survey. USGS Water Resources Division, Open File Report Series 03-308, 2003: 63-70.

Davis, R., and D. Fitzgerald. Beaches and Coasts. Maiden,

Mass.: Blackwell, 2004. Leatherman, Stephen P., ed. Barrier Islands, from the Gulf of St. Lawrence to the Gulf of Mexico. New York: Academic Press, 1979. National Research Council. Drawing Louisiana's New Map: Addressing Land Loss in Coastal Louisiana. Washington, D.C.: National Academies Press, 2005. Salvador, A., ed. The Gulf of Mexico Basin, Geology of North America. Boulder, Colo.: Geological Society of America, 1991. U.S. Geological Survey, Delta Subsidence in California. "The Sinking Heart of the State. U.S. Geological Survey Fact Sheet." Available online. URL: http:// ca.water.usgs.gov/archive/reports/fs00500/fs00500. pdf. Accessed October 10, 2008.

deserts The driest places on Earth, deserts by definition receive less than one inch (250 mm) of rain per year. Most deserts are so dry that more moisture is able to evaporate than falls as precipitation. At present about 30 percent of the global landmass is desert, and the United States has about 10 percent desert areas. With changing global climate patterns and shifting climate zones, much more of the planet is in danger of becoming desert.

Most deserts are also hot, with the highest recorded temperature on record being 136°F (58°C) in the Libyan Desert. With high temperatures the evaporation rate is high, and in most cases deserts evaporate more than the amount of precipitation that falls as rain. Many deserts evaporate 20 times the amount of rain that falls, and some places, like much of the northern Sahara, are capable of evaporating 200-300 times the amount of rain that falls in rare storms. Deserts are also famous for large variations in daily temperature, sometimes changing as much as 50-70°F (28-39°C) between day and night (called a diurnal cycle). These large temperature variations can be enough to shatter boulders. Deserts are also windy and are prone to sand and dust storms. The winds arise primarily because the heat of the day causes warm air to rise and expand, and other air must rush in to take its place. Airflow directions also shift frequently between day and night (in response to the large temperature difference between day and night), and between any nearby water bodies, which tend to remain at a constant temperature over a 24hour period.

There are many different types of deserts located in all different parts of the world. Some deserts are associated with patterns of global air circulation, and others form because they are in continental interiors far from any sources of moisture. Deserts can form on the "back," or leeward, side of mountain ranges,

World map showing location of deserts: Note how most deserts are concentrated between 15° and 30° latitude.

World map showing location of deserts: Note how most deserts are concentrated between 15° and 30° latitude.

where downwelling air is typically dry, or they can form along coasts where cold, upwelling ocean currents lower the air temperature and lower its ability to hold moisture. Deserts can also form in polar regions, where extremely dry and cold air can evaporate (or sublimate) much more moisture than falls as snow in any given year. Parts of Antarctica have not had any significant ice or snow cover for thousands of years.

Deserts have a distinctive set of landforms and hazards associated with these landforms. The most famous desert landform is a sand dune, a mobile accumulation of sand that shifts in response to wind. Deserts tend to be very windy, and some of the hazards in deserts are associated with sand and dust carried by the wind. Dust eroded from deserts can be carried around the world and is a significant factor in global climate and sedimentation. some sandstorms are so fierce that they can remove paint from cars or skin from an unprotected person. other desert hazards are associated with flash floods, debris flows, avalanches, extreme heat, and extreme temperature fluctuations.

Droughts are different from deserts—a drought is an extended lack of rainfall across a region that typically gets more rainfall. If a desert normally receives a small amount of rainfall and it still is getting little rainfall, then it is not experiencing a drought. In contrast, a different area that receives more rainfall than the desert may be experiencing a drought if it normally receives significantly more rainfall than it is at present. A drought-plagued area may become a desert if the drought is prolonged. Droughts can cause widespread famine, loss of vegetation, loss of life, and eventual death or mass migrations of entire populations.

Desertification is the conversion of previously productive lands to desert through a prolonged drought. Desertification may occur if the land is stressed before or during the drought, typically from poor agricultural practices, overuse of ground and surface water resources, and overpopulation. Global climate goes through several different variations that can cause belts of aridity to shift back and forth with time. The sahel region of northern

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The Basic Survival Guide

The Basic Survival Guide

Disasters: Why No ones Really 100 Safe. This is common knowledgethat disaster is everywhere. Its in the streets, its inside your campuses, and it can even be found inside your home. The question is not whether we are safe because no one is really THAT secure anymore but whether we can do something to lessen the odds of ever becoming a victim.

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