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Hot arid and semi arid
What processes and factors give hot arid and semi arid environments their
distinctive characteristics?

Defining hot arid and semi arid environments

Characterised by high temperatures, low and unreliable precipitation and sparse vegetation. Hot arid has
less then 250 mm anual precipiation, semi has between…

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advection fog (created when warm air contactswith cold surface)- fog carried inland and eventually
dissipiates . Fog is frequent as it is trapped under an inversion layer(where air temp rises rather
than falls with height), by sinking air in a tropical high pressure cell- when fog condenses it adds to…

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ALVEOLES -(small hollows 5-50cm , occuring in clusters with thin pairtrons) & TAFONI (hollows a few metres
across developed along lines of weaknesses) responsible by crystal growth , wetting and drying and
hydration , wind scouring & case hardening (a hard layer of salt encrusted rock formed where salts have…

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Sand dunes can be fixed anchor dunes formed around obstacles such as a rock or free dunes where
no obstacles are present, further sub-divided into tranverse dunes where sand movement is normal
to wind direction or linear dunes where sand movement is parallel to the wind

CASE STUDY - Features…

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and pan are can be used for the same purpose. Sabahka refers to a type of salt pan fringing coastal aread
such as the Arabian Penisula.

Why are hot arid and semi arid environments considered to be fragile

Plant adaptations

Ephemerals - escape drought by remaining as seeds until rain…

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collect as much water as possible. The leaves have a type of varnish on them so that they can seal
in moisture. The smell and taste of the plant puts off any animal from trying to eat it. Plant spacing
is controlled by water availability, that is creosote bushes grow…

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Generates forein currency earnings - benefits countries with few other resources (egypt 45% from
creates direct (waiter) employment and indirect (fishermen) employment -multiplier effect
encourage local people to learn new skills (Tunisia hotel training schools)
tourists spendings help to preserve and revialise tradional crafts. Money used to restore tombs…

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controlled and popular tombs such as Tutankhamen have a higher entry fee. A new visitor centre opened in
2007 which should help spread visitor flow. Paths have been widened between tombs to prevent
overcrowding. Movin car parks and replacing tarmac roads with those of sand and gravel so they are…

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Loss of plant cover has exposed soils to wind erosion - heavy trampling (waterholes) has compacted the soil ,
limiting seed development , damaging plant roots and encouraging runoff. Loss of native tree Khejari
deprives soil of valuable nitrate fertiliser

Population pressure causes trees and shrubs to be removed and…

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3000 in central Australia in 2005. The company owning the mine has contributed $45 million to the South
Australian Government which has benefitted the area. There have been improvments in local service and
has had the multiplier effect- however local housing prices have therfore increased and people cannot afford


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