Desert Erosion
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Transcript Desert Erosion
How do you think this formed?
What are the main agents of
erosion in deserts?
Wind
Water
Contrary to what we might believe, water is actually
thought to be the most significant agent of erosion at
work in desert environments
Weathering
What is the difference between chemical and physical
weathering? Write a definition for each.
Which is most important in a desert? (see p 290 PG)
Why is weathering in deserts so slow?
Insolation Weathering
Insolation weathering
Also known as exfoliation or onion skin weathering.
Why?
Large diurnal temp range (alternate heating & cooling)
Occurs when there is a sudden temperature change (eg
cool rainfall)
In deserts rock temperatures of up to 80 degrees have
been recorded. Rocks may be 20 degrees hotter than
the surrounding air.
Salt Crystallisation
Most efficient underground, where there is more
moisture
Salt crystallisation is where rocks are broken down by
salt crystals growing in the cracks
Salts in the soil and rock are dissolved and penetrate
porous rocks eg sandstone
As they recrystallise they exert pressure and force the
rocks to break apart
Sand Blasting
Entrained particles (those picked up by the wind) are
carried by the wind, and act like sandpaper on the
bottom of rocks where most sand particles are carried.
(abrasion)
Helps to form mushroom rocks (but chemical
weathering is important too)
Solution weathering
A form of chemical weathering, where rainwater
dissolves soluble particles in the rock.
Relic Features
Many desert features are actually relic features from
times when there was much more water present in the
environment.
What is badland topography?
See p 292 PG
What is the impact of the slow rate of weathering in
arid environments on the development of landforms?
What is the difference between weathering and
erosion?
How does the rate of weathering affect desert erosion?
Desert Landforms
Weathering and erosion combine to form some
significant desert landforms.
Water and wind both play an important role in their
formation
Water and landform development
in arid environments
Make notes from p292-294 on:
The role of water
Rainsplash
Exotic rivers
Internal drainage
Playas
Evaporites
Wadis/arroyos/dry creeks
Alluvial fan
Piedmont
Bajada
Box canyon
Anabranches
Reticulate drainage
Inselbergs (see p 192 landform systems)
Why is water more effective than wind at shaping
landforms in arid environments?
Wind and landform development
in arid environments.
Make notes from p295-296 on
Aeolian action
Ergs
Deflation & deflation hollows
Saltation
Sand sheets
Barchans
Parabolic dunes
Longitudinal or seif dunes
lunettes
Pics from
http://www.egyptoffroad.com/trips.html
http://farm4.static.flickr.com/3017
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