desert landscapes dominated by wind
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Desert LandscapesDominated by Wind
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“We don’t survive the desert, we live here” - Pima Indian
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Deserts: where & whyEarth’s dry regions: 30% of all land2 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
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Climate Graphs – Semi-arid and Arid
What do you notice about the minimum and maximum temperatures?What do you notice about the amount of precipitation?
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Deserts: where & whyWhat causes deserts?Global distribution of
◦ air pressure◦ wind
Relationship between◦ rainfall◦ evaporation
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Deserts: where & whyLow-latitude deserts
◦Tropic of Cancer◦Tropic of Capricorn
In contrast….◦ Equator:
hot air rises to 15-20 km low pressure belt
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Deserts: where & why
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Deserts: where & why
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Deserts: where & why
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Deserts: where & why
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Deserts: where & whyMiddle-latitude deserts (ie. 45°N)
◦exist in rain shadows.
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Deserts: where & whyMiddle-latitude deserts
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The Great BasinBasin (valley)
and Range (mountains) topography◦ mountainous
desert landscape◦ Nevada, Arizona,
California, Utah◦ Death Valley,
Mojave Desert, Great Salt Lake
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Great Salt Lake, Utah
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Evaporation > PrecipitationPlaya: ephemeral (not existing all
year long) lake beds that consist of salt and mud flats
Spotted Lake, just outside of Osoyoos, BC
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Wind erosion + depositionWind erosion: Important in arid
environmentsExample…Sand dune shape
depends on:◦Flat or hilly?◦How much sand?◦Winds steady or intermittent?◦Wind direction constant?◦Vegetation present?
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Wind erosionDesert pavement
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Wind erosionDeflation: the process of wind
removing silt and sand-sized particles
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Wind erosion + depositionErgs: seas of dunes
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Wind erosion + depositionHow sand dunes are formed…
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Wind erosion + depositionSand dune formation
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Singing Sand Dune Phenomenon
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Fog in the Namib Desert???
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Wind erosionVentifacts: rocks abraded, pitted,
polished by windblown sand
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Wind DepositionLoess from
Aeolian (or Eolian) transportation: ◦ Deposit of wind-
blown silt and clay in angular grains and weakly cemented by calcite
◦ Develop rich, fertile soils
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Water ErosionWadi: a dried up river bed that
only has water during rainy season
Town of Wadi Tiwi, Oman
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Water ErosionFlash flood retaining basin in Las Vegas, NevadaWhy does the water runoff so quickly?
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Water Erosion
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Water ErosionHoodoos (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 the spires
Bryce Canyon National Park, Utah
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Water ErosionFairy chimneys that people still live inside in Cappadocia, Turkey
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Water ErosionAntelope Slot
Canyons, Page, AZ
Flash floods from localized thunderstorms carry sediments that abrade and polish the sandstone
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Water Erosion
Mesa: a flat-topped “table” formed by differential erosion of softer rock underneath a layer of “cap” rock
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Water ErosionButte: a smaller version of a mesa
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Water ErosionPedestal rock:
softer rock erodes quicker than resistant “cap” rock
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Water DepositionAlluvial Fan: deposition of sediments as rivers or flash floods leave mountain ranges and spread into the valley
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Water DepositionBajada: several adjacent alluvial
fans that have merged together
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Living in the Desert