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Deserts definitions Flashcards

(52 cards)

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1
Q

Abrasion

A

Material carried in the wind, sandblasts exposed rock surfaces and carves them into a variety of shapes

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2
Q

Arid

A

The climate of an area with less than 250mm of precipitation per year

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3
Q

Barchan

A

A crescent shaped type of sand dune

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4
Q

Block separation

A

Happens to well jointed rocks with prominent bedding planes. The rock separates along these lines of weakness

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5
Q

Crystal growth

A

Water and minerals react in a rock’s pores to form crystals, the expansion of the crystal forces open cracks in the rock

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6
Q

Deflation

A
  • Wind blows away fine sediments
  • Surface level drops
  • Larger sediments remain
  • Desert pavement is left
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7
Q

Deflation hollow

A
  • Underlying basin structure is hidden by large, homogeneous covering of sediment
  • Deflation lowers the surface only above the basin, this is a hollow created now
  • Eddies in the hollow further remove sand to show the basin shape
  • Weathering within the hollow is accelerated due to the lower, colder environment, allowing dew to form.
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8
Q

Desert varnish

A

Dark, polished looking coating or crust of rocks, usually iron or manganese oxides that forms when rocks are exposed to weathering in the desert

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9
Q

Desertification

A

Depletion of plant life, loss of topsoil at desert boundaries and in semi-arid regions, usually caused by a combination of drought and the over exploitation of vegetation by humans

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10
Q

Drought

A

An extended period of dry weather, especially one that is detrimental to crops

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11
Q

Dunes

A

The main resulting feature of sand deposition

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12
Q

Endorheic

A

Rivers that flow into an inland lake rather than to the sea.

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13
Q

Ephemeral

A

Water systems that flow intermittently after heavy rainfall

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14
Q

Erg

A

Large area of sand dunes

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15
Q

Evapotranspiration

A

Transferring moisture from biological and lithospheric stores to atmospheric stores by evaporation and transpiration

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16
Q

Exfoliation (onion skin weathering)

A

Daytime heat expands the outer layers of rocks, forming weaknesses. Night time cooling contracts outer layers. Repetition grows the weaknesses forming cracks which are parallel to the surface of the rock

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17
Q

Granular disintegration

A

When rocks have a granular structure like sandstone or grit. Weathering results in a much less regular disintegration than block separation

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18
Q

Halophyte

A

A plant that thrives in saline soil

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19
Q

Hydration

A

When rocks absorb water, they expand causing stresses in the rock. This makes the rock more vulnerable to other kinds of weathering

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20
Q

Irrigation

A

The artificial application of water to assist with agriculture

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21
Q

Inselberg

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A

Isolated mountain of rock which remains after softer rock has been weathered and eroded. A fluvial land form.

22
Q

Mesa

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A

A part of a plateau that has become detached due to weathering and erosion, leaving a large mound separated from the plateau. A fluvial land form.

23
Q

Butte

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A

When weaknesses in mesas or plateaus are weathered and eroded to leave a thin stack standing. A fluvial land form.

24
Q

Phreatophyte

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A

A long rooted plant that takes water from the water table or the soil just above it

25
Rock pedestal
Mushroom shaped rock formed when the lower parts of a rock are subject to abrasion. Aeolian land form
26
Zeugen
A land form of aeolian erosion when hard/soft rock is arranged in latitudinal layers. When joints in the rock bed are parallel to the direction of wind, they are eroded downwards to leave deep grooves.
27
Ventifact
A single rock that has had one or more sides that is flat due to abrasion. Aeolian land form
28
Yardang
Extensive parallel ridges of rock that are separated by grooves. Aeolian land form
29
Surface creep
Larger, coarser particles that are too heavy to be moved by saltation or suspension are rolled along the ground by the wind
30
Suspension
Fine sediments that are picked up and carried by the wind
31
Saltation
Sediments that are too heavy to be suspended are moved by the wind in a bouncing motion, being picked up and dropped repeatedly
32
Semi-arid
Very little annual rainfall, between 250 and 500 mm
33
Thermal fracturing
When a rock with a homogeneous structure breaks apart due to repeated expansion and contraction, usually in a clean shatter e.g. basalt
34
Solution/hydrolysis
Rain water, which is mildly acidic, dissolves rocks such as clays and minerals. A type of weathering
35
Trade winds
A wind with a regular course that in the past allowed trading along consistent routes
36
Xerophyte
Plant that is adapted for growth under very dry conditions
37
Oxidation
Minerals of iron in contact with oxygen and water are oxidised and weakened. A type of weathering
38
Weathering
The break down of rock in situ
39
Insolation
Incoming solar radiation
40
Potential evapotranspiration
The evapotranspiration that would occur if there was an unlimited supply of water
41
Erosion
The wearing down of surfaces by mechanical processes involving water, wind or ice
42
Deposition
When material is dropped due to the thing carrying it not having enough energy anymore
43
Open system
When energy and matter is transferred between boundaries of a system
44
Net primary productivity
Growth rate of vegetation in g/m^2/year
45
Aridosol
Soil that is: - high pH (7-8.5) - lacks water and organic content - thin - yellow/red/grey/brown - fertile when irrigated
46
Solonetz
Soil that is: - clay like - has enough water for some leaching but not enough to wash base away
47
Solonchaks
Soil with: - high evaporation rates - high concentration of mineral salts near the surface - thick crust - infertile
48
5 adaptations of succulents
Like catci, aloes, agaves - Spiky to prevent being eaten - Roots grow extensively sideways to ensure they catch the water when it rains - Stomata only open at night when it is more humid meaning less water escapes - Very few leaves so less surface area for water to transpire from - Waxy cuticle retains water well
49
Causes of aridity: cold current effect
When onshore winds holding moisture meet cold coastal currents, the moisture condenses and often rains before landfall. The cold temperatures effectively dry out the air before they reach the land.
50
Causes of aridity: contintentality
As weather fronts move across a continent, they lose moisture and don't tend to pick up much meaning at a point, there is very little moisture to precipitate. This is a reason as to why deserts tend to be on the western edges of continents, as weather front generally move from east - west meaning that by the time weather has reached the western edge, there is little moisture left.
51
Causes of aridity: rain shadow
When weather front move over mountain ranges, they are forced upwards meaning they cool and condense and then rain over the mountain ranges' windward side. This means the leeward side of the range subject to a lack of rainfall
52
Causes of aridity: GAC
Large band of high pressure is created at convergence of Ferrel and Hadley cell which means that precipitations cannot fall

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