1B - Hot environments Flashcards

Question

How does the Continentality Effect work and affect aridity?

Answer 1

Maritime places have higher rainfall than those inland. As air masses move over a continent, they will lose moisture - this causes the air to become very dry Central parts of the Sahara Desert are the parts of Africa that are furthest from the sea: 2000km away, and even further in central Australia

Answer 2

Prevailing winds across oceans gather moisture. As they reach land, the air is forced to rise over the mountains, leading to condensation and precipitation on the windward side. As the air descends on the leeward side, it warms and is high pressure

Answer 3

When winds blow towards shore their lower layers are cooled by contact with the water. This causes mist or fog to form offshore. This mist may roll inland, but it quickly evaporates again in contact with the warm surface. The air has lost some moisture and it becomes drier as it warms making rain even less likely

Answer 4

The difference between the amount of sediment that enters the system and the amount that leaves

Answer 5

Weathering of underlying rock, Fluvial (water) sources, Aeolian (wind) sources

Answer 6

Deposits, Landforms

Answer 7

Erosion (wind and water), Transportation (wind and water)

Answer 8

The breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters. Weathering occurs in situ, or "with no movement", and thus should not be confused with erosion, which involves the movement of rocks and minerals by agents such as water, ice, snow, wind and gravity. It occurs over a long period of time.

Answer 9

mechanical and chemical

Answer 10

Exfoliation, Granular disintegration, Shattering,

Answer 11

Heat doesn't penetrate easily into rock, so the surface is heated higher than the interior. This means that stresses are set up in the rock, leading to cracking that runs parallel to the surface, layering then peeling off.

Answer 12

Changes in temp can cause different minerals within a rock to expand and contract at different rates. This is common and granites and eventually leads to the breakdown of the rock.

Answer 13

Some rocks, such as basalt, which have a homogenous structure may shatter as a result of constant expansion and contraction

Answer 14

Crystal growth, oxidation, hydrolysis, hydration

Answer 15

Dissolved salts in water in cracks or joints form geometric shapes as the water evaporates. (Further heating causes the crystals to expand, resulting in rocks being prized apart, eventually falling off.)

Answer 16

Rocks containing iron are oxidised in air at the presence of salt and water, this causes them to turn a red/brown colour and they are weakened. (This colour is called desert varnish)

Answer 17

Certain rocks capable of absorbing water will become vulnerable to future breakdown as they swell and break

Answer 18

Rainwater is slightly acidic so when it falls on rocks containing clays and dissolvable salts, it can dissolve the rock

Answer 19

The creation of the high-pressure cell that generates strong winds blowing out of the desert The absence of vegetation and surface features to create friction and reduce wind speed, and provide shelter

Answer 20

the process by which wind removes surface materials (sand, soil etc.)

Answer 21

Desert Pavements, Deflation Hollows

Answer 22

Wind strips away fine grain particles from the surface of the desert floor. Large particles are too heavy to be transported by the wind and as such are left behind, creating a pebble strewn surface.

Answer 23

DEFLATION lowers the surface, creating a hollow, the best-known example is the Qattara Depression Cold air sinks into hollows at night forming dew Dew speeds up rock weathering making particles available for removal by the wind. This process repeats and the deflation hollow increases in size Depressions range from several metres to over 100m (Egypt). Oases have probably formed where deflation hollows reach the water table. Vegetation binds the sand and creates soil so preventing further erosion. Oases are settled and cultivated so the vegetation is no longer natural.

Answer 24

Sand carried in the wind, principally by saltation Sandblasts the rock, mostly close to the surface (up to about 1.5m) carving rocks with narrow bases, often sitting in hollows created as the sand is removed by winds swirling around the base (deflation).

Answer 25

``` Velocity of wind Frequency of wind Wind direction Rock lithology Size of loose particles on the desert floor ```

Answer 26

Sediment size is small Wind is strong (high-pressure gradient) and blows for a long period of time There is an absence of natural and man-made shelter e.g vegetation There is a lot of weathering and/or erosion to provide lose material that is dry and unconsolidated

Answer 27

Rock pedestals, Ventifacts, Yardangs, Zeugens

Answer 28

Caused by abrasion of the sand against the bottom of the rock

Answer 29

Fin-shaped rocks lying on the desert surface. Shaped by wind-driven sand (abrasion) They have a smooth, flat windward side, and sharp narrow edges

Answer 30

Formed when ridges of hard and soft rock run parallel to the direction of the prevailing wind. Wind erodes the softer rock (by abrasion) and leaves the ridges standing up as yardangs. May be broken down over time to become discontinuous features, but will still leave scars on the landscape A ridge and furrow landscape. Wind abrasion concentrates on weak strata; leaving harder material upstanding.

Answer 31

Zeugens are similar in appearance to yardang but formed on horizontal bedded structures rather than vertical beds. Often form where the surface has developed a duricrust (a brittle layer of mineral salts on the surface) If this surface gets broken, the softer rock beneath loses its protection so Aeolian erosion quickly strips away the underlying rock

Answer 32

Deposition occurs when wind velocity decreases such that sediment can no longer be transported

Answer 33

Sand dunes are large deposits of sand characteristic of many arid environments The formation depends mainly on wind direction and sand supply Some types of dune can be highly mobile, constantly moving and changing shape whereas others are stable and constant They can vary greatly in size from a few m’s high to several 00m high and many km’s long

Answer 34

Barchan, Seif

Answer 35

Contributes to weathering processes The action of rivers Flash floods and erosion

Answer 36

They are perennial (flow all year round) Have their source in mountains outside deserts and flow through them and out the other side Arid land contains some of the world’s largest rivers e.g Nile (Africa), Colorado (USA), Tigris and Euphrates (Middle East), Indus (Pakistan)

Answer 37

Flow into deserts but terminate within them, usually in an inland lake or sea such as the River Jordan that drains into the Dead Sea Many of them are incredibly saline because the heat causes the water to evaporate

Answer 38

Flow intermittently after periods of rain and are very short-lived

Answer 39

Exogenous rivers, Endoreic rivers, Ephemeral streams, Episodic flash floods

Answer 40

Infrequent events unleash huge amounts of water in a short period of time. Large rates of overland flow create sheet floods that spread over the surface, and channel floods if they are confined in river channels. They can result in huge amounts of sediment being transported and deposited in large alluvial fans.

Answer 41

``` Splash erosion Sheet erosion Rill erosion Gully erosion Bank erosion ```

Answer 42

The force of falling rainwater displacing soil particles

Answer 43

Water running as a sheet over impermeable surfaces or compacted soil washing away disturbed particles

Answer 44

Sheet wash wears down the soil to form a definite path to form rivulets in the soil, called rills

Answer 45

Over time, rills become wider and deeper to form gullies

Answer 46

Fast water flow wears away the streamsides, causing the banks to collapse and the channel to widen

Answer 47

``` Wadi Alluvial fan Bajada Pediment Playa Inselberg Mesa Butte ```

Answer 48

Features of erosion and deposition Arabic word for a dried up river bed Usually characterised by a steep sided ‘slot’ canyon with a flat bottom filled with sediment Sizes can vary considerably from few m’s wide and deep to several km’s long

Answer 49

Deposition from wadis usually creates alluvial fans as sediment is washed out of the canyon and spreads out in a characteristic fan shape as large amounts of sediment can block channels resulting in a complex network of braiding Alluvial fans show evidence of sorting and stratification: coarser sediment is concentrated closest to mountain and finer material is transported further away as it’s lighter

Answer 50

Where several alluvial fans join up

Answer 51

Gently sloping (1-7 degrees) aprons of bare rock at the foot of mountains – often partially or completely covered by sediment washed down by rivers Relic fluvial feature, not continuously eroded Periodic sheetwash removes material and leaves a smooth surface Commonly a distinct change in slope between start of pediment and foot of mountain Cliffs are weathered and eroded – steep scree slopes created Further debris is brought later washed down as alluvial fans and further sheet floods

Answer 52

Lowest part of the pediment – essentially an ephemeral lake fed by endoreic rivers (e.g. Dead Sea) Deposition of fine material creates flat landscape and then evaporation removes water and mineral salts are left behind Water flows over pediments and surface deposits carrying fine material onto the desert floor. Some water percolates to soil and be transferred underground to collect in hollows Evaporation and lack of new water will eventually cause this collection of water to dry up. Can create salt flats – evaporation leaves very flat saline surface

Answer 53

An isolated rounded hill An inselberg is a smooth-sided version of a butte. They are found in arid and semi-arid areas They are formed from crystalline rocks such as granite and are believed to have been subject to extensive chemical weathering which is more common in humid areas. They probably formed during wetter periods – pluvials – further evidence of climate change.

Answer 54

Mesas are plateau like features that are flat on top with steep edges The land has probably been uplifted and there has been extensive erosion. There will be scree slopes.

Answer 55

A butte is a version of a mesa which may be smaller (erosion) or separate. It is a bit like a sea stack.

Answer 56

Plateau – an elevated area of relative smooth terrain, frequently separated from adjacent areas by steep slopes Plateaus can be formed by a number of processes, including upwelling of volcanic magma, extrusion of lava, and erosion by water and glaciers. Magma rises from the mantle, causing the ground to swell upward; in this way, large, flat areas of rock are uplifted and this uplifted rock forms a plateau

Answer 57

Youthful - Following tectonic uplift, processes of weathering, mass movement and erosion (primarily water) result in the parallel retreat of mountain fronts, leaving behind a gently angled rock slope - the pediment. Mature - Over time, the uplifted landscape is gradually eroded away, leaving coalescing pediment surfaces and isolated remnants of the mountains - relic hills called inselbergs Old Age - Eventually these isolated hills crumble, leaving behind a largely flat surface known as a pediplain. With further uplift, the whole process will start again.

Answer 58

Last glacial maximum: • Widespread aridity • Far north deserts were cold deserts • Southern deserts in similar locations to today but more extensive Early Holocene: • Interglacial conditions – warmer and more humid • Aridity fell dramatically – widespread forests • Present day deserts were grassland 5000 years ago to present: • Aridity returned especially to Africa and Asia • 3000 years ago conditions similar to today • Potential vegetation – not including cleared forest

Answer 59

The persistent degradation of dryland ecosystems by variations in climate and human activities. It results in a reduction or loss of the biological or economic productivity of drylands.

Answer 60

It can take 500 years for 2.5cm of soil to form but not long to destroy it 1/3 of land is affected by desertification Land covering 12,000 hectares (size of Bulgaria) is lost every year to degradation

Answer 61

1. Many people in LEDCs are poor so have large families, this results in rapid population growth. 2. As the population grows, people plant more crops and so have to chop down more trees 3. The population also needs more wood for building fires, building homes and fences, and fodder for animals 4. The people move to another area of land and begin to clear some space for their homes and crops 5. The crops and animals rapidly use all nutrients in the soil. The lack of tree roots weakens the structure of the soil. 6. The land is not allowed to rest so loses its fertility and becomes exhausted 7. The soil loses its structure and is easily eroded, blown away by the wind 8. The soil becomes so infertile that crops will not grow and there is nothing for animals to eat 9. Desertification happens when land (usually on the edge of deserts) becomes too infertile to support people 10. The land becomes barren (infertile) and so the people have to move on to somewhere else

Answer 62

2.7 billion people. 90% of whom live in developing countries

Answer 63

Deforestation - soil not covered, and nutrients lost due to a lack of vegetation Overgrazing - constant removal of nutrients as livestock eat them Over cultivation of crops - nutrients taken up by the crops so when they are farmed, there are none left in the soil Inappropriate irrigation - fertilisers increase salt content and acidification

Answer 64

Climate change - the warming of ground = loss of water Erosion from wind or water - can remove nutrients from the soil

Answer 65

It is very complex and there is a lot of missing/unreliable information. There are also many different definitions Land degradation can’t be globally mapped by a single indicator

Answer 66

Loss of biodiversity Deforestation - global warming Growth in more invasive shrub species

Answer 67

Food insecurity due to infertile land Often need to skip meals Dust storms are bad for health People need to keep relocating

Answer 68

Loss of land means a significant loss in GDP People lose money in farming

Answer 69

Population growth will increase food demand and drive expansion and intensification of cultivated lands More globalisation could mean international laws might be passed in order to prevent it however the likelihood of these laws being passed is very slim

Answer 70

Desertification diminishes biodiversity which is needed for many services provided to humans by dryland ecosystems. As the land gets drier, more vegetation is lost, and vegetation is key for social conservation and regulation of surface water and local climate. Desertification also contributes to climate change as carbon stored in soils is released into the atmosphere. Increased global climate change also increases desertification as it heats up the soil and causes water to evaporate.

1B - Hot environments Flashcards

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