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Geography > A Level Physical Geography (Hot Arid and Semi-Arid Environments) > Flashcards

A Level Physical Geography (Hot Arid and Semi-Arid Environments) Flashcards

Hot Arid and Semi-Arid Environments

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1
Q

What is Aridity?

A

The general dryness of an area due to intense moisture shortages or deficit attributed to little or no rainfall and high evapotranspiration.

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2
Q

What are Hyper-Arid areas?

A

areas that rarely exceed 100mm of annual precipitation e.g Sahara, Atacama, Arabian Deserts

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3
Q

Arid Areas

A

areas that rarely exceed 250mm of annual precipitation e.g Kalahari, Namib, The Great Australian, Gobi, Thar

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4
Q

Semi-Arid

A

These areas rarely exceed 500mm of annual precipitation e.g Sahel belt

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5
Q

Characteristics of Hot-Arid Environments

A

Found in the center of desert areas.
Rainfall is almost non-existent.
annual rainfall of less than 250mm per annum.
Rainfall is scarce due to the existence of sub-tropical high pressure and rain-shadow effect.
Limited cloud cover inducing high levels of insolation.
Day time temps are often over 40 degrees celsius.
High wind speeds.

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6
Q

Characteristics of Semi-Arid Climates

A

Occur on the margins of Arid areas.
Avg rainfall of 250-600mm per year.
Rainfall is unpredictable but still available for plant growth.
Rainfall is lost rapidly through high rates of evapotranspiration.
Rainfall is seasonal.
Temp is generally high throughout the year around 20-30 degrees celsius.

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7
Q

Factors influencing temperature in arid and semi-arid areas

A

Lack of Cloud Cover
Latitude
Distance from the sea.

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8
Q

How are Hot-Arid and Semi-Arid areas distributed?.

A

Located in the interior of continents.
Located on the Western sides or Margins of major continents.
Some are located on the rain-shadow areas or leeward side of mountain ranges.
Located in the sub-tropical high pressure belt around 30 degrees North and South of the equator.

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9
Q

Causes of Aridity

A

Continentality.
Cold ocean currents.
Rain shadow effect.
High pressure.

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10
Q

Water balance

A

the relationship that exists between inputs in the form of precipitation (P) and the losses arising from evaporation and transpiration (E)

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11
Q

What factors influence Rainfall effectiveness?

A

Rate of evaporation.
Seasonality.
Rainfall intensity.
Soil Type.

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12
Q

Why is PW dominant in Arid and Semi-Arid areas?.

A

Large diurnal temperature range.
Exposed Rock Surfaces.
Aridity or Lack of moisture.

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13
Q

CW can also occur in Arid and Semi-Arid environments. What facilitates this?

A

High Temperatures

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14
Q

Physical Weathering processes

A

Salt-crystal growth.
Pressure Release or Dilatation.
Freeze-thaw weathering.
Exfoliation.
Thermal fracturing.

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15
Q

Chemical Weathering processes

A

Carbonation in Limestone.
Oxidation in rocks with iron.
Hydrolises in crystaline rocks.
Solution in rocks that contain salts.

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15
Q

What is Exfoliation?

A

This is the “onion skin” effect were rocks peel parallel to the surface due to expansion and contraction from heating during the day and cooling during the night.

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16
Q

Landform produced from Exfoliation

A

Exfoliation domes.

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17
Q

What determines Wind Transport in Hot-Arid and Semi-Arid environments?

A

wind velocity, size of material and nature of the surface.

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18
Q

Suspension

A

loose, unconsolidated material of 0.5mm or less is picked up and transported while suspended above the ground.

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19
Q

Saltation

A

Larger and medium sized particles are transported in a hopping or bouncing manner.

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20
Q

Traction/Surface creep

A

Material above 2.5mm in diameter which resist uplift and are dragged on the surface.

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21
Q

What is Abrasion/Corrasion?

A

The sand blasting effect of the wind, as the wind picks up loose sand and hurls it against rock surfaces and the impact breaks away small segments.

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22
Q

Deflation

A

The removal of dry loose, unconsolidated material from the surface.

23
Q

Landforms formed from Corrasion/Abrasion.

A

Rock Pedestals.
Yardangs.
Zeugen.
Ventifact.

24
Q

What is a Rock Pedestal?.

A

A mushroom looking rock formed when the softer layer of the rock is weathered away faster than the harder layer, hence undercutting and forming that characteristic mushroom shape.

25
Q

What is a Yardang?

A

These are sharp keel-like ridges of rock separated from a parallel neighbour by a furrow. Formed where alternating hard and soft rocks are vertical.

26
Q

What is a Zeugen?

A

Where alternating hard and soft layers lie horizontally, this may lead to the formation of tabular undercut hills called Zeugen.

27
Q

What is a Ventifact?

A

When the facets/faces of pebbles and boulders in deserts have been worn or polished through abrasion.

28
Q

Landform formed from Deflation

A

Deflation Hollows.

29
Q

What are Deflation hollows?

A

Hollows carved out of weaker parts of the rock by the wind./ Major enclosed depressions that deepen below the surface due to wind eddy effect. An example being the Quattara Depression in Egypt.

30
Q

Sand Dunes are a major characteristic of Arid and Semi-Arid environments. What factors facilitate their formation?

A

Sand supply.
The strength and direction of the wind.
The amount of vegetation.
The shape of the ground surface.

31
Q

Types of Sand dunes

A

Barchans.
Seif/Longitudinal dunes.
Star dunes.
Parabolic dunes.

32
Q

The three types of rivers in arid areas:

A

Exogenous, Endorheic and Ephemeral.

33
Q

What are Exogenous Rivers?

A

Rivers which were formed in wet areas outside the desert but flow across it, e.g the River Nile

34
Q

What are Endorheic rivers?

A

Rivers that flow into inland lakes,
e.g the River Jordan flowing into the Dead Sea bordered by Jordan.

35
Q

What are Ephemeral rivers?

A

Rivers that only flow after rain.

36
Q

what is a Wadis?

A

an ephemeral river. The river channel has steep sides and is filled with alluvium.

37
Q

what is an Arroyo?

A

A stream bed which is usually dry except during flash floods.

38
Q

What is an Alluvial Fan?

A

Cones of debris found at the foot of mountains

39
Q

What is a Bajada?

A

A coalescence of a series of Alluvial Fans

40
Q

The 2 forms of running water in deserts?

A

Stream Flood and Sheet Flood

41
Q

What are stream floods?

A

channelised; disected uplands where water is channelised into streams.

42
Q

Sheet floods?

A

these are extensive flows of water over the desert surface.

43
Q

What is an Inselberg

A

An isolated upland.

44
Q

What is a Canyon

A

A deep; steep sided v-shaped gorge or chasm resulting from weathering and erosion.

45
Q

What is the Piedmont Zone?

A

the zone that includes the pediment, peri-pediment, bajada and alluvial fans.

46
Q

What is a pediment?

A

A pediment is a gently sloping rock platform, either bare or with a thin covering of rocks which stretches away from the foot of a mountain range.

47
Q

A Playa

A

A basin of inland drainage containing a shallow, fluctuating, saline lake.

48
Q

What are mesas and buttes?

A

They are types of inselbergs. (Flat-topped). Larger masses are Mesas and smaller ones are Buttes.

49
Q

How has vegetation adapted to survive in hot arid and semi-arid areas?

A

Mechanisms to reduce transpiration loss, to collect more water, to store water and use it effectively.

50
Q

What is Desertification?

A

The spreading of desert conditions.

51
Q

Natural Causes of Desertification

A

Climate Change
Global Warming

52
Q

Human causes of Desertification

A

Rapid Population Growth
Cultivation of marginal lands
Irrigation
Deforestation
Irrational use of water

53
Q

Environmental Impacts of Desertification

A

Loss of biodiversity
Expansion of area under sand dunes.

54
Q

Economic impacts of Desertification.

A

Reduced income from traditional economy.
Decreased availability of fuelwood.

Geography (2 decks)

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