14+deserts

14+deserts - Dry Regions: The Geology of Deserts Prepared...

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Dry Regions: The Geology of Deserts Prepared by Ronald Parker Earlham College Department of Geosciences Richmond, Indiana
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Chapter 21: Dry Regions: The Geology of Deserts Earth: Portrait of a Planet, 3 rd edition, by Stephen Marshak
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Chapter 21: Dry Regions: The Geology of Deserts Earth: Portrait of a Planet, 3 rd edition, by Stephen Marshak Deserts Deserts cover ~ 25% of land surfaces. The primary control on deserts? Plate tectonics! Unique and lovely, deserts are characterized by Extreme dryness. They may be hot or cold. Specialized ecosystems and low human populations. Unique geologic processes.
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Chapter 21: Dry Regions: The Geology of Deserts Earth: Portrait of a Planet, 3 rd edition, by Stephen Marshak What Is a Desert? Land that is so extremely arid, that Evaporation prevents permanent surface water. Vegetation covers less than 15% of its surface. Annual rainfall amounts to less than 10 z (25 cm). Desert types exist in both hot and cold climates.
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Chapter 21: Dry Regions: The Geology of Deserts Earth: Portrait of a Planet, 3 rd edition, by Stephen Marshak Hot vs. Cold Deserts Cold deserts. High latitudes. High elevations. Near cold ocean currents. Hot deserts. Low latitudes. Low elevations. Far from oceans.
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Chapter 21: Dry Regions: The Geology of Deserts Earth: Portrait of a Planet, 3 rd edition, by Stephen Marshak Desert Features Desert land surfaces often include Exposed bedrock. Accumulated clasts. Unweathered sediment. Precipitated salt. Windblown sand.
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Chapter 21: Dry Regions: The Geology of Deserts Earth: Portrait of a Planet, 3 rd edition, by Stephen Marshak Types of Deserts 5 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).
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Chapter 21: Dry Regions: The Geology of Deserts Earth: Portrait of a Planet, 3 rd edition, by Stephen Marshak Subtropical Deserts Due to patterns of atmospheric convection. Equator – 0 o latitude. Solar energy evaporates water, which rises as hot, moist air. Rising air cools and expands, forming abundant rain. This air, stripped of moisture, flows to the N and S. Subtropics – 20 o - 30 o N & S. Sinking dry air wicks water. Landscape below dries. Earth ` s largest deserts.
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Chapter 21: Dry Regions: The Geology of Deserts Earth: Portrait of a Planet, 3 rd edition, by Stephen Marshak Figure 19.3
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Chapter 21: Dry Regions: The Geology of Deserts Earth: Portrait of a Planet, 3 rd edition, by Stephen Marshak Found at 20 to 30 o N and S latitude across time. African deserts bracket the equator. Sahara & Arabian to the north.
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This note was uploaded on 02/22/2012 for the course CE 70 taught by Professor Johnson during the Fall '07 term at Berkeley.

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14+deserts - Dry Regions: The Geology of Deserts Prepared...

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