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Geography > Drylands > Flashcards

Drylands Flashcards

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1
Q

What is a Landscape?

A
  1. Landscape are an open system
  2. A landscape is an area that is spatially heterogenous in at least one factor of interests.
  3. Landscapes vary in structure
    and function due to natural and
    human factors
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2
Q

What are drylands?

A

Average annual evapotranspiration is significantly higher than precipitation

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3
Q

How are drylands classified?

A

Aridity

  • Hyper-arid <100mm per year
  • Arid 100-250mm per year
  • Semi-arid 250-500mm per year

Sediment type

  • Sand seas / ergs
  • Stony Desert / reg
  • Mid latitude / desert

Location
There are five major provinces of mid and low latitude deserts:

North Africa / Arabia / Central Asia - (Sahara, Arabian, Thar, Gobi)

Southern Africa (Kalahari, Namib)

North America (Mojave, Sonoran, Chihuahuan, Great Basin)

Southern America (Atacama, Patagonia)

Australian (Western, Simpson)

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4
Q

Different types of drylands

A

Polar drylands

Mid and Low latitude deserts

Semi-arid environments

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5
Q

Characteristics of polar drylands

A

Cold temperatures

Found in regions like the Arctic and Antarctica

Low precipitation

High winds

Seasonal variations ( 24 hour daylight in summer and complete darkness in the winter)

Permafrost

Active layer

Lack of vegetation

Limited biodiversity

Yardangs

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6
Q
A
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7
Q

Characteristics of a mid-low latitude deserts

A

15 - 30 degrees North and South of the Equator

Low precipitation

High temperatures

Seasonality

Trade winds

Rain shadows

Ephemeral streams

Ergs

Regs

Hamada

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8
Q

Characteristics of semi-arid environments

A

Moderate rainfall

Seasonal variability

Temperature extremes (Hot summers and cold winters)

High evaporation rates

Sparse but adapted vegetation

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9
Q

What is a system?

A

A set of interrelated elements comprising of stores and processes that are connected to form a working unit or a unified whole.

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10
Q

Why are drylands seen as open systems?

A

Inputs are received

Outputs are transferred

Across the boundary of a system

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11
Q

Dynamic equilibrium in drylands

A

When there is a state of balance between inputs and outputs.

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12
Q

Dryland stores

A

Depositional landforms/landscapes

Erosional landforms/landscapes

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13
Q

Dryland inputs

A

Climate change
Human activity
Precipitation
Solar radiation
Winds
Stream flow
Sediment

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14
Q

Dryland processes

A

Fluvial
Aeolian
Mass movement

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15
Q

Outputs

A

Long wave radiation
Streamflow
Evaporation
Sediment

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16
Q

The main components of a dryland?

A

Climate - Precipitation, cloud clover, temperature and wind

Water - Precipitation (and condensation) stores in rivers, lakes and aquifers.

Sediments - Boulders, screes, sand, silt and clay

Geology - Rocks, their lithology and structure.

17
Q

Sediment budget equation

A

O = I + CHANGE IN S

O = Output of sediment from a
system.
I = Input of sediment to a system

Change is S = Change in storage
within a system.

18
Q

Diurnal range

A

The only difference in temperature, between the highest and the lowest.

19
Q

Heat Surplus and Heat deficit

A

Heat surplus is being absorbed by the Earth’s surface than is being lost

Heat deficit is when more heat is being lost to space than is being received from the sun

20
Q

Rock lithology + examples

A

Refers to the physical and chemical composition of a rock

Clay - weak lithology - bonds that make it up are quite weak - impermeable and forms gentle landscapes

Basalt - very resistant - made of dense interlocking crystals

Chalk - largely composed of calcium carbonate - prone to chemical weathering as they are soluble in weak acids - porous.

21
Q

Consolidated sediments

A

Compacted and cemented rocks that have undergone lithification.

Firm and solid

Cohesion

E.G sandstone limestone, shale and conglomerates

22
Q

Unconsolidated sediments

A

Loose and Soft rocks that can be easily disturbed.

Lack of cohesion

Sand, Gravel, silt and clay

23
Q

Rock structure + types

A

Concerns the properties of individual rock types

Jointing - cracks (usually vertical) in rock caused by shrinkage or release of pressure as rocks above are eroded away

Bedding - layering formed in sedimentary rocks as the rate of sediment deposition varies. Layer boundaries are called bedding planes

Folding - bending of rock layers caused by compression of rocks, usually as part of the mountain -building when tectonic plates collide.

Faulting - deep crack caused by movement of rock during earthquakes. Different rock types are often seen on each side of a fault.

24
Q

What is a REG (Rocky or Stony)

A

This is where in some drylands sediments are scarce and the ground may be covered with tightly packed stones forming a desert pavement. This is known as a reg.

25
Q

What is an ERG (Sandy)

A

This generic term describes large expanses of sand desert. Large sediment supplies, often derived from earlier, wetter climatic phases, give rise to sand seas, which cover a large part of the Sahara desert.

26
Q

How does relief influence drylands?

A

Rainfall distribution - Elevated relief can block the movement of moist air masses, creating an orographic effect.

Water runoff

Vegetation Patterns

Soil formation

27
Q

How does aspect influence drylands?

A

Aspect is the direction that a slope faces. Some slopes may face the prevailing wind and be subjected to more erosion.
Ventifacts are rocks with one sided eroded by wind abrasion into a smooth flat face. Sometimes the wind blows over and can expose the other side to the abrasion of the wind.
Sun facing slopes (e.g. south-facing slopes in the Northern Hemisphere) receive more sunlight throughout the day. This increased exposure to solar radiation leads to higher temperatures, greater evaporation rates, and drier conditions.
Shaded slopes (e.g. north-facing slopes in the Northern Hemisphere) receive less direct sunlight, leading to cooler temperatures and reduced evaporation. These slopes are often slightly more humid and may retain moisture longer, even in drylands.

28
Q

Influence of latitude on drylands

A

Temperature increases as latitude decreases.
Places at the same latitude can have different climate due to other factors such as water relief of land and wind.

Geography (2 decks)

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