Hot Desert Systems and Landscapes

Question 1

Desert

Answer 1

A place receiving less than 250 mm of rainfall per year

Question 2

Different stages of Aridity

Answer 2

Arid- less than 250mm per year
Semi arid- 250-500mm per year
Hyper arid- very dry, not enough water to support life

Question 3

What is an open system?

Answer 3

Matter and material is free to move out of the system into the surroundings

Question 4

Dynamic equilibrium

Answer 4

When there is a balance between inputs an outputs so the stores stay the same

Question 5

Positive feedback

Answer 5

When one element changes and the other stay the same and assistant a change of state

Question 6

Negative feedback

Answer 6

When a system returns to what it used to be

Question 7

Global distribution of deserts

Answer 7

No deserts on the equator to air currents
Almost all deserts lie on the Tropic of Cancer and Capricorn
Cancer- Sahara desert, Syrian desert
Capricorn- Atacama desert, Namib desert

Question 8

Four characteristics that define deserts

Answer 8

Climate
Soils
Vegetation
Animals

Question 9

Desert climate

Answer 9

0-55 degrees
Day is hot- no cloud coverage, short wave radiation
Night is cold- no clouds to retain long wave radiation
Therefore deserts have a large diurnal radiation

Very little precipitation, rapid surface run-off and low infiltration
Negative water balance EVAPOTRANSPIRATION>PRECIPITATION

Question 10

Desert soil

Answer 10

Poor quality and lacks organic content
Thin- lacks ‘horizons’
Highlight saline
Majority is aridisol which has a high pH (7-8.5)

Question 11

Types of vegetation and their adaptations

Answer 11

Xerophytes- cactus-stores moistures in body
Phreatophytes- creosote bush- deep roots
Halophytes- salt bush- can tolerate high levels of saline soil
Ephemerals- Boerhavia- has a short life cycle

Question 12

Four causes of aridity in deserts

Answer 12

Formation of subtropical high-pressure cells
Continentality affect
Rainshadow affect
Cold current affect

Question 13

Subtropical high-pressure cells- Hadley cells

Answer 13

Net air at the equator heats up and rises- water vapour condenses and causes severe rainfall
Air moves poleward and begins to cool and fall
Sinking air causes high-pressure and therefore winds
This is where deserts form as the air quickly warms up and remains without water

Question 14

The continentality affect

Answer 14

Maritime places have a high rainfall than those inland

Air moving over content masses lose water as they go inland- this is where most deserts lie

Question 15

The rainshadow affect

Answer 15

Air from the sea contains moisture as it is forced inland it rises over areas of high topography
It loses all its water through precipitations and sinks down the leeward much more dry

Question 16

Cold current affect

Answer 16

Called current move towards the equator from the poles and a soon as it comes in contact with heartland it condenses and falls as precipitation

Question 17

Three sources of energy in the desert

Answer 17

Insolation
Winds
Run off

Question 18

Sediment sources, cells and budgets

Answer 18

Inputs-
Rivers, wind, rain

Stores
Landforms, deposits

Outputs-
Erosion, transportation

Area dominated by erosion- net sediment loss
Area dominated by deposition- net sediment gain

Question 19

Five geomorphological processes

Answer 19

Weathering 
mass movement 
erosion 
transportation 
deposition

Question 20

What is weathering

Answer 20

The breaking down of rocks, soils and minerals as well as artificial materials to contact with the earths atmosphere biota and water. Weathering occurs in situ so it’s not the same as erosion

Question 21

Mechanical weathering

Answer 21

Rocks are physically broken down
Forms of mechanical weathering include exfoliation, differential expansion, shattering/thermal fracture
LEARN EACH PROCESS

Question 22

Chemical weathering

Answer 22

Amico process is reacting with minerals in the rocks causing them to break up
Forms of chemical weathering include crystal growth, oxidation, hydration and hydrolysis
LEARN PROCESSES

Question 23

Mass movement

Answer 23

Mass movement is the movement of material downhill under the influence of gravity but may also be assisted by rainfall
Due to minimal rainfall and vegetation mass movement in deserts is dominated by rockfalls and rockslides

Question 24

What is a erosion?

Answer 24

The process that wear away the land surface through mechanical action, erosion is a different form of weathering as it removes material by processes of wind and water

Question 25

What is transportation?

Answer 25

The process that moves materials from the site where erosion took place to the site of deposition This is done through traction, saltation, suspension and solution

Question 26

Deposition in deserts

Answer 26

Water and when deposit material when they experience reduction in capacity- causes a loss of energy

Question 27

Role of wind in erosion in the desert

Answer 27

Causes abrasion and deflation

Question 28

Role of the wind in transportation in the deserted

Answer 28

Suspension- when particles very fine and easily picked up by the wind Saltation- wind speeds exceed the threshold velocity and lifted vertically before falling back down, creating a bouncing motion Surface creep

Question 29

What is wind deposition?

Answer 29

Because when the velocity of the wind increases until it can no longer transport the grains is Currin

Question 30

Four main sources of water in the desert

Answer 30

Exogenous rivers - permant rivers flowing through deserts e.g. The Nile Endogenous rivers- water bodies with the source within the desert, have a severed flow to the ocean Ephemeral streams- flow intermittently or seasonally after rainfall, generate high levels of discharge and surface run off Episodic flash floods- three types (sheet flood, overland flow and channel flash flooding)

Question 31

Name all of the fluvial landforms in a desert

Answer 31

``` Wadi Alluvial fan Bajada Pediment Playas Mesa Buttes Inselbergs READ DESCRIPTION ```

Question 32

Name all of the Aeolian landscapes in the desert

Answer 32

``` Venitfacts Yardangs Zuegen Deflation hollows Desert pavements ```

Question 33

Name the two types of Sand dune

Answer 33

Sief dunes | Barchan dunes

Question 34

Brachan dunes

Answer 34

Crescent shaped mounds backs face 90 degrees to the wind Up to 30m tall and hundreds of meters long Two faces Gentle back slope and steep slip face Forms when a prevailing wind in a constant direction blows with a limited sand supply It moves when sand is added to the crest and the leeward face collapses and therefore causes a forward movement E.g brachan dunes in southern Peru

Question 35

Seif dunes

Answer 35

Sinuous longitudinal dunes 200m tall Form in areas of bi- directional wind regimes and limited sand supply Stretch hundreds of meters Has two faces Form parallel to the wind direction , Wind approaches the dune obliquely and flows parallel through the troughs moving the sand down and in the elongating the Dune Minimal movement, well-established and stable E.g. Seif dunes in Morocco

Question 36

How are desert landscapes characterised

Answer 36

The lack of vegetation causing exposure and making geomorphical features clearly visible Speed and nature of weathering dependent on diurnal temperature changes and rapid heating and cooling The presence of moisture

Question 37

What is desertification?

Answer 37

The persistent degradation of dryland ecosystems by variation in climate and human activities. It results in a reduction or loss of the biological or economic production of drylands. It is a a process by which fertile land is becoming infertile.

Question 38

Causes of desertification

Answer 38

Climate change- loss in rainfall and higher temps Desert population growth due to natural increase and migration as populations flee environmental/human problems in neighbouring areas Change in farming

Question 39

Reasons for why population growth cause desertification

Answer 39

Intensification of agriculture to feed large populations | Over-cultivation, overgrazing and deforestation- means vegetation cannot be established and causes of soil erosion

Question 40

Areas at risk of desertification

Answer 40

1 billion people and 100 countries are at risk of desertification 12,000,000 ha of land been lost to the desertification

Question 41

Impacts of desertification

Answer 41

Species lost Reduction habitats Increased competition between species Extinction risks Drought and famine Forced migration Loss of land Loss of culture Increase salinity of soils Increased numbers of sandstorms Vegetation and damaged by sandblasting from desert winds

Question 42

Alternative futures the local populations

Answer 42

Global Orchestration- increase in globalised world but ecosystem management is reactive to current issues and development initiatives are top down TechnoGarden- Technology is shared to allow populations affected by future desertification to be proactive in prevention by using green technologies Order from strength- Community is on power to react to environmental problems as the development focus is more bottom up to concentrate on security and economic growth Adapting Mosaic- bottom up proactive scenario where the emphasis is on empowering the development of local adaptations and learning