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Flashcards in Final Study Guide 12 Deck (41):
1

What is desertification?

- The process by which fertile land becomes desert, typically as a result of drought, deforestation, or inappropriate agriculture. Such as sand dunes moving often and desert taking over. Increase in temperature and change in wind pattern drive desertification.
- Desertification is the expansion of desert areas (deserts: Deserts are, according to some climatologist, a “dry” region, i.e one in which yearly rainfall is less than the potential evaporation rate in that region).
- Process governed by:
> how close to certain temp range likely for turning land into a desert
> type of vegetation→ taking away vegetation in which roots normally stabilize ground. No stabilization = deflation (easier to erode the ground material)

2

What determines the geographic location of deserts?

Mainly things such as rain fall amount, wind/atmospheric circulation, temperature, climate, and orographics (rain shadow effect)

3

What are the possible impacts of sandstorms, locally and globally?

- Sand storms interrupt air/ground traffic, create big wind/season climate variations, destroy vegetation, low visibility and diseases.
- Carry sand to different places locally and even across oceans to help enrich soils and sustain beaches.
- The sand from these storms stays in the atmosphere and is dangerous because it settles at the deepest part of your lungs
- Seasonal climate variation
- Drastic changes in weather and climate due to changes in albedo
- Air pollution is enhanced by sandstorms
> Beijing and Gobi Desert

4

Desert

- “dry” regions in which yearly rainfall is less than the potential evaporation rate in that region
> features: topography, latitude, away from oceans, human impact
> Develop because of: atmospheric circulation, location within continental interiors, or orographic (rain shadow) deserts.

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Sandy desert

Ex: Great Sandy Desert, Australia

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Rocky desert

- Ex: Mojave in CA
- Cacti

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Devil’s racetrack

huge boulders that leave a track on the surface of a dried lake bed

8

Sandstorms

- Jets of sand being transported by wind
- Seasonal
- Interrupt air traffic
- Enhance air pollution

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Particulate smog

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Precipitation

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Evaporation

The change of state from a liquid to a gas form. This typically happens with liquids that come in contact with energy or heat and rise into the air as vapor

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Low Latitude Desert

- closer to the equator where the sun is hotter and heats sand more
- Hot sand heats air→air rises→prevents cool, moisture filled air from lowering and prevents precipitation

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Orographic desert

- Desert caused by a rain shadow
- Receive little moisture due to rain shadow

14

Rain Shadow

- dry area on the side of a mountain away from the wind
- Mountains block the passage of rain-producing weather systems and cast a dry shadow

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Kalahari

Large, semi-arid, sandy desert in southern Africa

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Sahara

- World’s hottest desert and third largest
- Huge sand dunes

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Gobi

- a type of desert, the advance of Gobi Desert Dunes in China
- Rock floor desert plain

18

Trade winds

- Prevailing pattern of easterly surface winds found in the tropics (near the equation), within the lower portion of earth’s atmosphere
- Blow from northeast in the northern hemisphere and from the southeast in the southern hemisphere
- East→West

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Westerlies

- Prevailing pattern of winds in middle latitude between 30-60 degrees
- Blows West→East
- Affects ocean currents

20

Taklamakan

- Desert in China
- Shifting sand desert with lots of dunes
- Lies in rain shadow of Himalayas→cold desert climate

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Sierra Nevada

- Snowy mountain range in CA and NV
- Casts a rain shadow into the Great Basin

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Vulnerability

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Desertification

The process by which fertile land becomes desert

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Wind erosion

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Settling velocity

the faster settling velocity = thicker particles

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Turbulence

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Wind shadow

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Dune formation

- Dunes can form in different ways, but often from saltation
- Saltation: particle transport by wind or water

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Vortex

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Stream lines

direction of wind movement

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Slip face

Also known as “Lee face” , side of mountain that does not get wind

32

Deposition

the laying down of sediment carried by wind, water, or ice. Sediment can be transported as pebbles, sand & mud, or as salts dissolved in water. Salts may later be deposited by organic activity (e.g. as sea-shells) or by evaporation

33

Critical angle

34 degrees

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Sand stone

- clastic sedimentary rock composed mainly of sand-sized minerals or rock grains
- Rock formations of sandstone are porous enough to store large quantities of liquids--good aquifers as they also filter out pollutants

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Barchan

Crescent shaped dunes with horns pointing downwind

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Transverse dune

Linear dune that moves perpendicular to the wind

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Longitudinal Dune

Linear dune that moves parallel to the wind

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Avalanche

rapid flow of snow down a sloping surface

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Desert Pavement

- packed surface coating of rocks, usually above a layer of windblown dust
- Two proposed ways:
> Deflation→remove finer particle→desert pavement established→deflation ends
> Weathered pebbles on bedrock→wind-blown silt accumulated and sifts downward through coarse particles→silt continues to accumulate→makes desert pavement

40

Desert varnish

- A layer of minerals formed over long times, by means of chemical interactions between the rock and the little humidity you find in deserts
- Very slow process; 1mm can take up to 1,000 years

41

Deflation

- Wind or water picks up and carries small particles
- Three types:
> Surface Creep: larger, heavier particles, slide or roll across the ground
> Saltation: particles are lifted a short height into the air, bounce, and transported
> Suspension: very small & light particles are lifted in the air and carried a long way by the wind