Drylands

Question 1

What is a Landscape?

Answer 1

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

Question 2

What are drylands?

Answer 2

Average annual evapotranspiration is significantly higher than precipitation

Question 3

How are drylands classified?

Answer 3

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)

Question 4

Different types of drylands

Answer 4

Polar drylands

Mid and Low latitude deserts

Semi-arid environments

Question 5

Characteristics of polar drylands

Answer 5

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

Question 7

Characteristics of a mid-low latitude deserts

Answer 7

15 - 30 degrees North and South of the Equator

Low precipitation

High temperatures

Seasonality

Trade winds

Rain shadows

Ephemeral streams

Ergs

Regs

Hamada

Question 8

Characteristics of semi-arid environments

Answer 8

Moderate rainfall

Seasonal variability

Temperature extremes (Hot summers and cold winters)

High evaporation rates

Sparse but adapted vegetation

Question 9

What is a system?

Answer 9

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

Question 10

Why are drylands seen as open systems?

Answer 10

Inputs are received

Outputs are transferred

Across the boundary of a system

Question 11

Dynamic equilibrium in drylands

Answer 11

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

Question 12

Dryland stores

Answer 12

Depositional landforms/landscapes

Erosional landforms/landscapes

Question 13

Dryland inputs

Answer 13

Climate change
Human activity
Precipitation
Solar radiation
Winds
Stream flow
Sediment

Question 14

Dryland processes

Answer 14

Fluvial
Aeolian
Mass movement

Question 15

Outputs

Answer 15

Long wave radiation
Streamflow
Evaporation
Sediment

Question 16

The main components of a dryland?

Answer 16

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.

Question 17

Sediment budget equation

Answer 17

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.

Question 18

Diurnal range

Answer 18

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

Question 19

Heat Surplus and Heat deficit

Answer 19

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

Question 20

Rock lithology + examples

Answer 20

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.

Question 21

Consolidated sediments

Answer 21

Compacted and cemented rocks that have undergone lithification.

Firm and solid

Cohesion

E.G sandstone limestone, shale and conglomerates

Question 22

Unconsolidated sediments

Answer 22

Loose and Soft rocks that can be easily disturbed.

Lack of cohesion

Sand, Gravel, silt and clay

Question 23

Rock structure + types

Answer 23

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.

Question 24

What is a REG (Rocky or Stony)

Answer 24

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.

Question 25

What is an ERG (Sandy)

Answer 25

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.

Question 26

How does relief influence drylands?

Answer 26

Rainfall distribution - Elevated relief can block the movement of moist air masses, creating an orographic effect. Water runoff Vegetation Patterns Soil formation

Question 27

How does aspect influence drylands?

Answer 27

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.

Question 28

Influence of latitude on drylands

Answer 28

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.