3 - Hot Deserts

Where are hot deserts located?

15-30 degrees north and south of the equator mainly in dry continental interiors but a few are found in coastal locations such as the Atacama is South America

What are the temperatures like in hot deserts?

It can reach up to 50° in the daytime and drop as low as 0° at night

What is the difference between day and nighttime temperatures called?

Diurnal temperature range

How much rainfall does hot deserts receive?

Less than 250 mm per year

What is the largest hot desert called? Where is it? How much land does it cover?

The Sahara desert is found in North Africa covering 3.6 million square miles

What is the largest desert in the USA and what is the Australian desert known as?

The Great Basin and the Gibson/Outback

Explain why there is no cloud formation in a desert

Warm moist air rises at the equator and cools and condenses to form rain clouds. The air is circulated in the Hadley Cell and travels either north or south raining on the tropical rainforests. The air then sinks due to high-pressure around the desert because it is cool and dry as it has lost its moisture already so no clouds form because there isn't enough moisture in the air.

Why is there such a large range in temperature from day to night in a hot desert?

During the day temperature soar because deserts are closed the equator and receive a lot of sunlight however as there are no clouds to hold in the heat (acting as a blanket) temperatures plummet at night

What are desert soils like?

They are very infertile, sandy/rocky, shallow and coarse therefore they do not support much vegetation growth. Evaporation also draw salts to the surface leaving a white salty crust on the soil which makes it harder for plants to grow especially due to the lack of rainfall.

List an adaptation about roots of cacti in hot deserts

They have wide roots near the surface to catch as much water as possible when it rains or they have 'tap roots' which a long root 7 to 10 m deep to reach ancient underground water supplies

List an adaptation about the skin and dormant seeds of cacti in hot deserts

They have thick waxy skin to reduce water loss (transpiration) and the seeds only germinate when there is enough rainfall in order to live

List an adaptation about camels eyelashes, mouth, feet for a hot deserts environment

They have long eyelashes to keep out the sand and dust: their mouths are tough for eating thorny plants: they have large padded feet to stop them sinking in the sand:

List an adaptation about camels humps and skin for a hot desert environment

Based or fat in their humps for energy or to be broken down into water: they have light coloured skin to reflect the heat

Give a general adaptation of animals in hot desert environments - give 2 examples of animals

They are nocturnal to avoid high daytime temperatures such as Fennec Foxes and Jerboa mice

State two adaptations of lizards in hot desert environments

Lizards can withstand very high body temperatures and have waterproof skin to reduce water loss. They can also make their skin lighter to reflect the heat if they get too hot.

Why do plants and animals need to adapt in hot desert environment?

They have to adapt to the hot and dry conditions because plant growth is fast due to a lack of rainfall and infertile soil and animals need to avoid dehydration and cope with the heat still resisting predators

Where is the Thar desert located?

In the north west of India and parts of Pakistan

How big is the Thar desert and what is the population like?

200,000 km2 (about the size of the UK) with 83 people/km2

What are the main opportunities in the Thar desert?

Agriculture, Mining, Energy and Tourism

What is agriculture like in the Thar desert?

It is mostly subsistence farming however commercial agriculture is made possible due to the Indira Gandhi Canal which allows the irrigation. Cotton and wheat can therefore be grown and sold for profits.

What opportunities are there for mining in the Thar Desert?

There is a large coal reserve which provides jobs and income. Salt can also be harvested from Saline Lakes in the desert which is 9% of India salt production. Many minerals such as limestone and marble provide raw materials and allow for steel production as well as Feldspar, Kaolin and phosphorite.

How is energy produced in the Thar Desert?

It produces renewable energy such as solar power and has the Jaisalmer Wind Farm which is India's biggest producer of wind energy with 75 turbines generating 60MV. There are also large oilfield and cold deposits for non-renewable energy.

What are the opportunities for tourism like in the Thar Desert?

Jaisalmer is the 'Golden City' featuring the Jaisalmer Fort with Jain temples and traditional mansions (havelis). There are lots of national parks which provide camel rides and Safari parks such as the Desert National Park found in Rajasthan. The Gadisar Lake is a picturesque location.

List the three main challenges in hot deserts

Extreme temperatures, water supply, accessibility

Why is extreme temperatures a challenge in hot desert?

High temperatures lead to high rates of evaporation which cause water shortages the high diurnal temperature range causes uncomfortable living conditions and working outside in the heat is very hard especially for farmers and minor and can cause illness or death

Why is water supply a challenge in hot deserts? Where does the water come from?

Demand for water has increased due to population growth and drinking water is sparse. It is mainly stored in ponds - natural ones (tobas) or man-made ones (johads) or in rivers such as the River Luni however they are mainly intermittent and only flow after rainfall. Some water can be gained from ancient water supplies underground (aquifers) but the water can be salty and bad quality making it hard for farming and the people.

Why is accessibility a challenge in hot desert?

There are little road networks which make transportation of goods and communication difficult. The tarmac is melted in the Sun and roads become covered with sand due to winds so road maintenance is needed frequently and is expensive and hard. Most transport is by camel or overloaded buses which can be dangerous.

What is the Indira Gandhi Canal? What does it help and what are the issues?

It is a freshwater source that was constructed in 1958. It provides drinking water and is the main form of irrigation and allowing commercial agriculture however this is leading to salinisation (salty water).

What is desertification?

The process of land becoming dry and degraded as a result of climate change, human activities or both. The land is usually found on the edge of the desert due to a variety of physical and human causes.

List the six main causes of desertification

Climate change, population growth, removal of wood for fuel, overgrazing, overcultivation, soil erosion

Explain why climate change is a cause of desertification

There has been a long-term reduction in rainfall and changes in weather pattern so the land has become dry and temperatures have risen so rates of evaporation are higher causing desertification

Explain my population growth is a cause of desertification

There is a high demand for resource resources due to an increased birth rate and life expectancy (natural increase) as well as as factors such as migration. A demand for food has increased. The land is overgrazed and over cultivated causing the land to dry out and the soil to be eroded due to a lack of vegetation and water/minerals.

Explain why removal of wood for fuel is a cause of desertification

Air is a deforested for cooking heating and fuel in poor villages so the tree roots no longer buying the soil together leading to soil erosion

Explain why over grazing, over cultivation and soil erosion causes of deforestation

The vegetation is lost through over grieving so the roots don't buy the soil together and if the soil is no longer bonded it can easily blow away or will be lost by leaching. The intense farming in overcultivation exhaust soil fertility and aquifer have been drained making land dry.

What are the three main ways to reduce the risk of desertification?

Tree planting: Stone lines, planting pits and composting: Appropriate Technology

Explain how and why tree planting helps to reduce the risk of desertification. Give examples of where it is used and details.

Acacia trees are planted in order to restore the soils nutrients and bind it together as well as reduce CO2 in the atmosphere. They produce gum. For international markets to make profits and give food to animals. It is used in the Sahel in the edge of the Sahara desert. It led to the "Great Green Wall" project which is a wall of trees planted over 11 countries across Africa from Senegal to Djibouti in order to halt desertification.

Explain how and why stone lines, planting pits and composting reduces the risk of desertification

Stone lines placed along the contours trap water and sediment due to the semipermeable structure made up of stones. It is used in Burkina Faso, Mali and Niger because it is low cost and with skills that can be easily learnt by locals. Planting pits helped to hold water around crops and composting returns the nutrients from organic matter to the soil to improve yield for profit and food reducing soil erosion and exhausted land.

Explain how and why appropriate technology reduces the risk of desertification. Give specific examples.

In Malawi, they originally used three stone cookers which used a lot of wood causing deforestation and produce smoke which caused illnesses. The invention of Changu Changu Motor cook stones (meaning fast fast fire) use less wood reducing soil erosion and deforestation and produce less smoke. They were made of bricks and mud mixture which was reasonably cheap and easy to make and two pots could be used at one time on this new cooker for efficiency.