Desert LandscapesDominated by Wind
“We don’t survive the desert, we live here” - Pima Indian
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
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?
Deserts: where & whyWhat causes deserts?Global distribution of
◦ air pressure◦ wind
Relationship between◦ rainfall◦ evaporation
Deserts: where & whyLow-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 & whyMiddle-latitude deserts (ie. 45°N)
◦exist in rain shadows.
Deserts: where & whyMiddle-latitude deserts
The Great BasinBasin (valley)
and Range (mountains) topography◦ mountainous
desert landscape◦ Nevada, Arizona,
California, Utah◦ Death Valley,
Mojave Desert, Great Salt Lake
Great Salt Lake, Utah
Evaporation > PrecipitationPlaya: ephemeral (not existing all
year long) lake beds that consist of salt and mud flats
Spotted Lake, just outside of Osoyoos, BC
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?
Wind erosionDesert pavement
Wind erosionDeflation: the process of wind
removing silt and sand-sized particles
Wind erosion + depositionErgs: seas of dunes
Wind erosion + depositionHow sand dunes are formed…
Wind erosion + depositionSand dune formation
Singing Sand Dune Phenomenon
Fog in the Namib Desert???
Wind erosionVentifacts: rocks abraded, pitted,
polished by windblown sand
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
Water ErosionWadi: a dried up river bed that
only has water during rainy season
Town of Wadi Tiwi, Oman
Water ErosionFlash flood retaining basin in Las Vegas, NevadaWhy does the water runoff so quickly?
Water Erosion
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
Water ErosionFairy chimneys that people still live inside in Cappadocia, Turkey
Water ErosionAntelope Slot
Canyons, Page, AZ
Flash floods from localized thunderstorms carry sediments that abrade and polish the sandstone
Water Erosion
Mesa: a flat-topped “table” formed by differential erosion of softer rock underneath a layer of “cap” rock
Water ErosionButte: a smaller version of a mesa
Water ErosionPedestal rock:
softer rock erodes quicker than resistant “cap” rock
Water DepositionAlluvial Fan: deposition of sediments as rivers or flash floods leave mountain ranges and spread into the valley
Water DepositionBajada: several adjacent alluvial
fans that have merged together
Living in the Desert