Note_-_Chapter_17 - Dry Regions The Geology of Deserts Deserts Desert cover 25 of Earth\u2019s land surfaces Unique and lovely deserts are characterized by

Note_-_Chapter_17 - Dry Regions The Geology of Deserts...

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Dry Regions: The Geology of Deserts Deserts - Desert cover 25% of Earth’s land surfaces - Unique and lovely, deserts are characterized by: - Extreme dryness. They may be hot or cold - Specialized ecosystems and low human populations - Unique geologic processes What is a desert? - Land that is so extremely arid that: - No permanent streams flow, except those entering from temperate regions elsewhere - Vegetation covers less than 15% of its surface - Annual rainfall amounts to less than 10inches (25cm) - Desert exist in both hot and cold climates Hot versus Cold Deserts - Hot deserts: - Low latitudes - Low elevations - Far from oceans - Cold deserts: - High latitudes - High elevations - Near cold ocean currents Types of Deserts - Five types - with distinctive landscapes and biota: - Subtropical deserts (Sahara, Arabian, Kalahari) - Rain-shadow deserts (Eastern Oregon) - Coastal deserts (Atacama) - Continental interiors (Gobi) - Polar deserts (Antarctica) Subtropical Deserts - Subtropical deserts are Earth’s largest - Form due to patterns of atmospheric convection - Equator - 0 degree latitude - Solar energy evaporates water, which rises as hot, moist air. - Rising air cools and expands, dropping abundant rain on the equatorial rainforests - This air, stripped of moisture, flows to the north and south - Subtropics - 20 to 30 degrees North to South
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- Cool, sinking air wicks water from the surface - The air heats up and the landscape dries out - Occur at 20 to 30 degrees North and South latitude - African deserts bracket the equator: -
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  • Fall '09
  • Gobi Desert, Atacama Desert, interior Desert

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