The Living World: Hot deserts

Question 1

Where is the Thar desert and how big is it?

Answer 1

It is located in north-west India and stretches into Pakistan. It covers 200,000 square kilometres and is the most densely populated desert in the world. The desert forms a natural boundary between India and Pakistan.

Question 2

What is an opportunity in the Thar desert concerning mining resources ?

Answer 2

Many minerals are extracted from the ground in the Thar Desert
including limestone, marble, phosphorite, feldspar and gypsum. Oil discovered in Barmer.

Question 3

What is an opportunity in the Thar desert concerning tourism ?

Answer 3

Tourism in the Thar Desert has
increased recently, mainly from Pakistan. Desert safaris are popular as is ecotourism including camel treks to visit oases.

Question 4

What is an opportunity in the Thar desert concerning renewable energy ?

Answer 4

At Jaisalmer, 75 wind
turbines are generating 60MW of electricity. Solar energy is being used in Bhaleri to power water treatment works.

Question 5

What is an opportunity in the Thar desert concerning farming ?

Answer 5

Most farming is subsistence
including rearing animals, growing crops and foraging fruit and berries. Indira Gandhi canal =
irrigation of 3500km for commercial farming.

Question 6

What is a challenge of the Thar desert involving water?

Answer 6

Precipitation levels are in the Thar
Desert are very low, between 120-240mm, and evaporation rates are high. Water stored in tobas (natural ponds) in remote areas.

Question 7

What is a challenge of the Thar desert involving inaccessibility?

Answer 7

Covering 200,000km2,
The Thar Desert is vast. Despite having the highest desert population density in the
world, it has a limited road network.

Question 8

What is a challenge of the Thar desert involving temperature?

Answer 8

The average temperature
is 27°C. Temperatures can exceed 50°C in the Thar Desert which makes it very challenging
to for people, such as farmers, to work outside. High temperatures lead to rapid evaporation and a shortage of water.

Question 9

What are the characteristics of hot deserts?

Answer 9

• Deserts are any area that gets less than 250 mm of precipitation a year.
• Very hot in the daytime (50 C).
• Cooler at night (O C).
• Very few clouds.

Question 10

Describe the location of hot deserts.

Answer 10

Found near the Tropic of Cancer and The Tropic of Capricorn. Also between 15-30 degrees north and south of the equator.

Question 11

Where is the Sahara desert?

Answer 11

It is the largest hot desert, found in Africa. it spreads across the whole width of the continent at the furthest north. It also borders the Atlantic Ocean.

Question 12

Why are deserts located around the Tropics?

Answer 12

The location of hot deserts can be explained by the global atmospheric circulation. At these latitudes air that has risen at the Equator descends forming a persistent belt of high pressure. This explains the lack of clouds and rain and the very high daytime temperatures. It also explains why, with the lack of cloud cover, temperatures can plummet to below freezing at night as heat is quickly lost from the ground.

Question 13

Why are hot deserts have high temperatures? (1)
HINT: Talk about the sun’s rays and the equator.

Answer 13

Because they are close to the equator where the sun’s rays are more concentrated into a smaller area causing intense heating of the air at the surface. The sun’s rays also have to pass through less atmosphere at the equator than in other areas, which means they retain more heat than in other parts of the world such as the poles.

Question 14

Why do deserts have high temperatures? (2)
HINT: Talk about the pressure of the tropics

Answer 14

Hot deserts are located around the Tropics of Cancer and Capricorn which are areas of high pressure (this means that air is sinking and pushing down). This means there is little condensation because their is no moisture in the air and condensation only happens when air is rising and cooling. Because there is no condensation there are no clouds which means all the sun’s heat energy reaches the surface and is used to cause very high temperatures.

Question 15

Why do deserts have low rainfall? (1)
HINT: Talk about dry winds.

Answer 15

Some deserts, like the Sahara are caused by dry winds. The air is so dry because the prevailing wind blows over land towards the sea, so it is very dry as it hasn’t has the opportunity to pick up any moisture, this creates very low rainfall totals.

Question 16

Why do deserts have low winds? (2)
HINT: Talk about cold ocean currents.

Answer 16

A number of deserts are found on the western side of continents near cold ocean currents. Any winds which blow over this cold water create cold air, which is particularly bad at holding moisture. When the cold air reaches land it is condensed to form sea fog near the coast. As the winds continue inland they are now dry and this helps deserts like the Atacama and Kalahari remain dry.

Question 17

Why do deserts have low winds? (3)
HINT: Talk about rainshadow areas.

Answer 17

Some deserts are inland like the Australian desert. This is because they are sheltered by a ridge of mountains. As winds are blown up and over these, the air coold and condensation causes rain in the mountains. By the time the winds have blown inland they are all rained out and become increasingly dry. The area of land beyond the mountain is called a ‘rainshadow’ area where deserts can be found due to the dry nature of the air.

Question 18

What are desert soils like?

Answer 18

• Hardly any leaf litter so not very fertile.
• Little rain and plant material so very dry.
• Rocky, sandy, thin and grey in colour.
• Contain lots of salt due to evaporation.
• Usually very shallow with coarse gravely texture.

Question 19

What are the characteristics of the nutrient cycle in the hot desert?

Answer 19

The low amount of rain means that decomposition only works very slowly. The desert biomass store is small because of the lack of water and low supply of nutrients. The climate is also very challenging for plants so only a few species can survive here. The soil is the largest store. This is because there are few plants taking up nutrients.

Question 20

Why do plants and animals need to adapt in the desert?

Answer 20

• The desert has a diurnal range, meaning it’s very hot in the day but very cold at night.
• There is very little precipitation, meaning dehydration is prominent and also the landscape is very dry.
• The temperature is very hot during the day, so the plants and anumals would have to be able to keep themselves cool / at a safe temperature.

Question 21

What is the name given to plants with adaptations that allow them to live in hot and dry conditions?

Answer 21

Xerophytic.

Question 22

Describe three adaptations of a camel and what they mean for it.

Answer 22

• They can drink up to 46 litres of water in 1 drinking session and go a week or more without water, meaning that when rainfall is non-existent, camels can survive long enough until the next one.
• They have large flat feet which are very thick, allowing them to walk on the sand without it sinking into it and burning their feet.
• Camels have thick lips, meaning they can eat the prickly plants that other animals avoid.

Question 23

Describe three adaptations of a cactus and what they mean for it.

Answer 23

• Cacti are covered with a thick waxy cuticle, which helps conserve water.
• The stem of the cactus can swell and expand, which allows them to take up as much water as it can to survive without water for long periods of time.
• They have long deep roots, which anchor the plant as the soil is very shallow with a coarse texture. This also allows the plant to reach nutrients that are stored deep underground as the soil is very dry.

Question 24

What are opportunities that exist in deserts?

Answer 24

Farming = money.
Wind turbines = power.
Quarry / mining = Trading + money
Camel rides = tourism = money.
Solar panels = energy / power.
Food and crops = money.

Question 25

What is desertification?

Answer 25

The desgradationnof land so it becomes more desert like. It becomes drier, damaged and less productive.

Question 26

What are the main causes of desertification?

Answer 26

Over-cultivation.
Removal of fuel wood.
Overgrazing.

Question 27

How can water management reduce the risk of desertifiction?

Answer 27

• Growing crops that don’t need much water.
• Using drip irrigation on crops instead of surface irrigation means that the soil isn’t eroded by lots of water added all at once.
• It is needed to stop the process of salinisation which leaves a salty layer on the surface, restricting plant growth.

Question 28

How can soil management reduce the risk of desertification.

Answer 28

• Leaving areas of land to rest in between grazing or planting crops can allow the land to recover.
• Rotating crops that use different nutrients from the soil means that the same nutrients don’t keep being removed.
• Compost can be used to replace nutrients in the soil.

Question 29

How can planting trees reduce the risk of desertification?

Answer 29

• Trees can be used to act as windbreaks to protect the soil from wind erosion.
• Can be used to stabilise land.
• Growing trees amongst crops protects the crops by providing shade, which reduces temperatures and evaporation rates.

Question 30

How an appropriate technology reduce the risk of desertification?

Answer 30

• Involves using cheap, sustainable and easily available materials that are easy for local people to maintain.
• E.g solar cookers can help reduce the rate of deforestation for fuel wood.
• E.g sand or stone fences can be constructed to help stabilise the soil and reduce erosion.