hot deserts Flashcards
what is a hot desert?
arid areas receiving less than 250 mm rain per year
where are hot deserts found
mostly in a belt between the tropics (30 north and south), with very little along the equator
how do hot deserts form
- sun heats ground at equator
- warm, moist air rises, leaving low air pressure
- air cools and condenses, forming clouds
- convectional rain occurs (trf formation)
- air moves north and south at high altitude
- dry air sinks near tropics, high pressure
- falling dry air warms and travels back to equator via trade winds, creating hot, dry conditions
why are deserts so hot?
sun relatively overhead in the tropics, energy is more intense as there is a smaller area and atmosphere to be heated.
little to no clouds also means there is no protection from sun in the day and no heat is retained in the night.
why are deserts so dry
prevailing winds have blow over large areas of land - no moisture.
define diurnal range, and what it is like in a desert
difference between max and min temperatures over 24 hours
high diurnal range in desert due to little to no clouds
how is a camel adapted to the desert
- tough, leathery mouth to eat thorny bush
- long, two layer eyelashes and closeable nostrils to stop sand
- broad, flat hooves to walk on hot sand
- hump stores fat, converts to energy when there is no food
how is a cactus adapted to the desert
- some horizontal roots to maximise rare rainfall collection
- taproots 7-10m deep for groundwater
- sharp spikes to avoid being eaten
- leaves waxy and small to reduce water loss
what do you call a plant in the desert that changes physical characteristics to survive
xerophytes
what do you call a plant in the desert that changes behavioural characteristics to survive
ephermerals
what are desert soils like
rocky and sandy, only 1m deep. lack of water and vegetation means there is little organic matter for fertile soil formation
what is the thar desert
most densely populated desert in the world, stretching across north west india and into pakistan. mostly within state of rajistan
what is climate like in the thar desert
little organic matter, soils not very fertile,
small clumps of vegetation e.g shrubs.
100-240mm annual rainfall
high summer temps, 53 degrees
what are the opportunities for development in the thar desert
mineral extraction
tourism
energy
farming
how is mineral extraction an opportunity for development in the thar desert
phosphorite - used in fertilisers
gypsum - plaster for construction, nearly all of india’s supply, improves its infrastructure
limestone - used extensively in india’s steel industry in furnaces
how is tourism an opportunity for development in the thar desert
- desert safaris on camels
- annual desert festival - locals can provide food and services e.g camel nurture
- tens of thousands annual tourists
how is energy an opportunity for development in the thar desert
- solar - sunny and cloudless climate, ideal conditions for solar power. 40km solar park being built, could power rajasthan
- wind- jaisalmer wind park, renewable (cheaper, no emissions)
- industry can develop (electricity), living conditions improve (cooking, lights)
how is farming and opportunity for development in the thar desert
- 1958 indira gandhi canal revolutionised farming - wheat and cotton now thrive, growth in commercial farming
- locals survive on their animals and crops
what is desertification
process by which fertile land becomes desert, usually as a result of drought, deforestation, or inappropriate farming methods
threats of desertification
not just lics - anywhere around fringes of existing deserts
loss of land
1 billion live in areas at risk
what are drylands / marginal land
semi arid areas at the fringe of deserts. home to 1 in 3 people. unreliable agriculture due to dryness
what are the causes of desertification
climate change
soil erosion
salinisation
population increase
overgrazing/overcultivation
deforestation
what is soil erosion
overgrazing, overcultivation, and deforestation leaves soil exposed. topsoil can be blown away, leaving infertile, barren wastelands
how does climate change cause desertification
hotter, drier conditions and unreliable rainfall
what is overgrazing
excessive grazing by too many cattle, damage to grassland and leads to soil erosion
what is overcultivation
excessive growing of crops, degrading quality and exhausting soil and making it vulnerable to soil erosion
what are the methods of tackling desertification
zai pits
magic stones
afforestation
water and soil management
national parks
what are zai pits and how do they tackle deforestation
growing crops in small holes with soil piled around edges to protect from wind. nutrients can also blow in and become trapped with the plant.
in the sahel, the holes are filled with manure and compost to provide nutrients. the manure also attracts termites, whose holes can help break up the soil. in the sahel, yield has improved by up to 500%
what are stone bunds and how do they tackle deforestation
rows of stone along contours of slopes, to prevent water and nutrients from flowing down the hillside and rather allowing them to soak into the soil. water can be used for irrigation or as local water supply.
- labour intensive, small scale
what is planting trees and how does it tackle desertification
reduces soil erosion as roots bind soil together. leaves provide shelter for crops and animals. some branches cut off so trees dont take too many nutrients compared to other crops, branches = local firewood
pros and cons of water soil management with example
the badhia desert, jordan.
used stone walls. water used for newly planted shrubs, which binds soil together. soil improves, plants grow, wildlife attrract.
- salinisation
what are the challenges of development in the thar
water supply
extreme temperatures
inaccessibility
how is water supply a challenge in the thar desert
population growth + development in farming industry means increasing water demand
high temps and low rainfall causes high evaporation rates, water is scarce.
- health affected
- farming affected
- tourism affected
however IGC…
what is the indira ghandi canal and what opportunities does it have
indias longest canal, over 650km, and main source of irrigation in thar.
- commercial farming, wheat and cotton
- drinking water for many in desert
- enables widespread tree planting/growing, stabilises sand, mitigates soil erosion and desertification
how are the extreme temps a challenge in thar desert
- presents health issues esp for those working outdoors. killed hundreds in 51 degree 2016 heatwave
- tourism becomes limited to cooler season
- low rain + high temps = water shortage
- dehydration of plants and animals, affecting farming and biodiversity
how is accessibility a challenge in thar desert
extreme weather + vast areas of wasteland means very limited road networks
- high temps melts tarmac
- strong winds blow sand over road
- though public transport offered, buses extremely cramped
