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Desert landscapes dominated by wind
 

Desert landscapes dominated by wind

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    Desert landscapes dominated by wind Desert landscapes dominated by wind Presentation Transcript

    • Desert LandscapesDominated by Wind
    • “We don’t survive the desert, we live here” - Pima Indian
    • Deserts: where & why Earth’s dry regions: 30% of all land 2 climate types of dry regions: ◦ desert (arid) ◦ steppe (semi-arid, surrounds deserts) Question:How much rain do deserts get every year? ◦ Sahara Desert receives as little as 2mm and as much as 100mm of precipitation per year
    • Climate Graphs – Semi-arid and AridWhat do you notice about the minimum and maximum temperatures?What do you notice about the amount of precipitation?
    • Deserts: where & why What causes deserts? Global distribution of ◦ air pressure ◦ wind Relationship between ◦ rainfall ◦ evaporation
    • Deserts: where & why Low-latitude deserts ◦ Tropic of Cancer ◦ Tropic of Capricorn In contrast…. ◦ Equator:  hot air  rises to 15-20 km  low pressure belt
    • Deserts: where & why
    • Deserts: where & why
    • Deserts: where & why
    • Deserts: where & why
    • Deserts: where & why Middle-latitude deserts (ie. 45°N) ◦ exist in rain shadows.
    • Deserts: where & whyMiddle-latitude deserts
    • The Great Basin Basin (valley) and Range (mountains) topography ◦ mountainous desert landscape ◦ Nevada, Arizona, California, Utah ◦ Death Valley, Mojave Desert, Great Salt Lake
    • Great Salt Lake, Utah
    • Evaporation > Precipitation Playa: ephemeral (not existing all year long) lake beds that consist of salt and mud flats Spotted Lake, just outside of Osoyoos, BC
    • Wind erosion + deposition Wind erosion: Important in arid environments Example…Sand dune shape depends on: ◦ Flat or hilly? ◦ How much sand? ◦ Winds steady or intermittent? ◦ Wind direction constant? ◦ Vegetation present?
    • Wind erosion Desert pavement
    • Wind erosion Deflation: the process of wind removing silt and sand-sized particles
    • Wind erosion + deposition Ergs: seas of dunes
    • Wind erosion + deposition Sand dune formation
    • Wind erosion Ventifacts: rocks abraded, pitted, polished by windblown sand
    • Wind Deposition Loess from Aeolian (or Eolian) transportation: ◦ Deposit of wind- blown silt and clay in angular grains and weakly cemented by calcite ◦ Develop rich, fertile soils
    • Water Erosion Wadi: a dried up river bed that only has water during rainy season Town of WadiTiwi, Oman
    • Water Erosion  Hoodoos (or fairy chimneys): column of soft sedimentary rock often with resistant layer of “cap” rock on top  Water flows through badlands causing further erosion to theBryce Canyon National Park, Utah spires
    • Water ErosionFairy chimneys that people still live inside in Cappadocia,Turkey
    • Water Erosion  Antelope Slot Canyons, Page, AZ  Flash floods from localized thunderstorms carry sediments that abrade and polish the sandstone
    • Water ErosionMesa: a flat-topped “table” formed bydifferential erosion of softer rockunderneath a layer of “cap” rock
    • Water Erosion Butte: a smaller version of a mesa
    • Water Erosion  Pedestal rock: softer rock erodes quicker than resistant “cap” rock
    • Water DepositionAlluvial Fan: deposition of sediments as rivers or flashfloods leave mountain ranges and spread into thevalley
    • Water Deposition Bajada: several adjacent alluvial fans that have merged together