Geography - Deserts

What is the geographical definition of desertification?

It is the process of semi-arid grassland becoming degraded and drier, eventually turning into desert.

The world's hot deserts are typically found between and degrees north and south of the Equator.

15 - 30

What is the maximum annual rainfall a region can receive to be classified as a hot desert?

Less than 250 ml per year.

The global atmospheric circulation pattern that causes dry, descending air at desert latitudes creates a persistent belt of what?

High pressure.

Describe the typical soil found in hot deserts.

The soil is sandy or stony, with little organic matter, and is therefore not very fertile.

The Western Desert in the USA is comprised of which three hot deserts?

The Mojave Desert, part of the Sonoran Desert, and part of the Chihuahuan Desert.

What is a major challenge related to infrastructure in sparsely populated areas of the Western Desert?

Inaccessibility, due to a lack of investment in surfaced roads and services like fuel stations.

How did traditional Native American communities in the Western Desert adapt their homes to the extreme heat?

They built homes with thick clay walls, which kept them cool during the day and warm at night.

In the Western Desert, what modern landscaping technique involves using drought-resistant plants in gardens?

Desert landscaping (or xeriscaping).

Name the economic opportunity that involves extracting copper from open-pit mines in the Sonoran Desert.

Mineral extraction.

How many people does the Morenci Mine, Arizona's largest copper producer, employ?

It employs 3,300 people.

The Albemarle Silver Peak Mine in Nevada primarily extracts which mineral, crucial for batteries?

Lithium.

What is the name of the large solar power facility located in the Mojave Desert, southwest of Las Vegas?

The Ivanpah Solar Electric Generating System.

The Ivanpah solar facility generates enough electricity to power how many homes?

Approximately 140,000 homes.

What is the name of the USA's largest wind farm, located in the Western Desert?

The Alta Wind Energy Center (also known as the Mojave Wind Farm).

What significant water source in the Western Desert was formed by the construction of the Hoover Dam?

Lake Mead.

What method allows for large-scale commercial agriculture in the Western Desert despite the lack of rain?

Irrigation, using water from aquifers and canals like the All-American Canal.

In the Coachella Valley, farming generates approximately how much revenue every year?

It produces around $575 million every year.

What is the most important economic activity in the Western Desert region, attracting over 37 million visitors annually to Las Vegas alone?

Tourism.

The Grand Canyon attracts approximately how many visitors each year?

Around 5 million visitors.

What is one of the main challenges for farmers in the Western Desert related to the climate?

Extreme temperatures, forcing them to alter their work patterns to avoid the midday heat.

The water level in _, which serves 18 million people in Arizona and Nevada, is now only about one-third full.

Lake Mead

Which major river, crucial for water supply in the Western Desert, has seen its water levels drop to historic lows?

The Colorado River.

What is the name of the strip of land south of the Sahara Desert that is at the highest risk of desertification?

The Sahel.

What are the two main reasons for population growth in semi-arid areas like the Sahel?

Natural increase (birth rate exceeding death rate) and migration (e.g., due to conflict).

How does armed conflict contribute to deforestation and desertification in regions like Darfur, Sudan?

It creates displaced people who need to cut down many trees to rebuild homes and fences.

How has climate change directly affected the Sahel's rainfall over the last 50 years?

The climate has become much drier with less rainfall.

In the Sahel, approximately what percentage of domestic energy comes from burning firewood, leading to deforestation?

Around 80%.

How does the removal of trees contribute to soil erosion?

Tree roots no longer bind the soil together, allowing the loose top layer to be blown or washed away.

What poor farming practice occurs when livestock are allowed to graze on one site for too long, stripping vegetation?

Overgrazing.

The farming practice of _, where more intensive use of land exhausts the soil of its nutrients, is a cause of desertification.

over-cultivation

What is monoculture, and how does it contribute to soil degradation?

It is planting just one crop, which leads to a lack of specific nutrients in the soil and results in infertility.

Poor irrigation systems can lead to a build-up of what substance on the soil surface after water evaporates?

Salt crusts.

The shrinking of which sea is a prime example of a water source drying up due to excessive water diversion for irrigation?

The Aral Sea.

One impact of desertification is , where the top layer of soil is blown or washed away due to a lack of vegetation cover.

soil erosion

How does desertification and subsequent crop failure impact food supply for local communities?

It leads to food insecurity, malnutrition, and in extreme cases, widespread famine.

Why might desertification lead to an increase in global food prices?

Crops become scarce in affected regions, reducing the global supply and driving up prices.

What is a major social impact of desertification, where people are forced to leave their land because it can no longer support them?

Migration.

How can desertification lead to an increase in diseases like malaria?

Water sources dry up and become stagnant, which encourages the breeding of mosquitoes.

Paradoxically, how can desertification increase the risk of localised flooding during heavy downpours?

The loss of vegetation reduces interception and the soil bakes hard, increasing surface runoff.

What is the name of the ambitious African-led project to plant an 8,000 km line of trees across the continent to combat desertification?

The Great Green Wall.

How does afforestation (planting trees) help reduce the risk of desertification?

Tree roots bind the soil, and leaves provide shade and leaf litter, which helps nutrient cycling.

What is a major challenge to the success of the Great Green Wall project?

Local people have used the newly planted trees for building materials and firewood.

In Burkina Faso, what appropriate technology involves building low lines of stones along contours to trap soil and water?

Stone bunds (or 'magic stones').

How have stone bunds in the Sahel helped to improve farming?

They have increased crop yields by up to 50% by preventing water and soil loss.

A _ is built across an ephemeral river, causing sand to deposit behind it, which then holds water for months.

sand dam

What is drip irrigation, and why is it effective in hot, arid regions?

It is a system where water drips slowly onto the ground from small holes in a hose, minimising water loss through evaporation.

How do fuel-efficient stoves help reduce desertification?

They use significantly less firewood, reducing the need to cut down trees for fuel.

Why are small-scale solutions using appropriate technology often successful in combating desertification?

They are cheap, easy to maintain, and ownership lies with the local community.

Term: Ephemeral River

Definition: A river that is most often dry but flows for brief periods after rainfall.

How have plant roots adapted to find water in hot deserts?

They are either extremely long to reach deep water supplies or spread out very wide near the surface to absorb moisture quickly.

Plants like cacti, which have large, fleshy stems for storing water, are known as what?

Succulents.

How do the small leaves or spines on desert plants help them survive?

They lower the surface area, which reduces water loss through transpiration.

Why are many desert animals nocturnal?

They stay cool by sleeping during the hottest part of the day and being active at night.

What adaptation allows the fennec fox to cool its body down?

It has huge ears which provide a large surface area to lose heat from.

How are camels' large, flat feet adapted for the desert?

They spread their weight on the sand, preventing them from sinking.

What two features help a camel keep sand out of its eyes and nose?

Slit-like nostrils and two rows of eyelashes.

How does the desert iguana regulate its body temperature using colour?

It is darkest in the morning to absorb heat and turns nearly pure white by the afternoon to reflect sunlight.

The population of the Sahel is projected to double every _ years.

20

In the Darfur region of Sudan, conflict has resulted in approximately how many people becoming homeless, increasing pressure on resources?

3 million people.

By 2050, what percentage of the Sahel's arable land could be unfit for agriculture due to desertification?

As much as 60%.

Over the past 50 years, Lake Chad has dried up by what percentage, largely due to lack of precipitation and poor irrigation?

95%.

What is the term for digging small pits in the ground to plant crops, which helps to trap water and nutrients?

Zai pits.

What type of erosion occurs when a thin layer of topsoil is removed by wind or water?

Sheet erosion.

What type of erosion carves deep channels into the land, making large areas of fertile ground unusable?

Gully erosion.

What is the name of the farming practice where farmers and their livestock move from one area to another to find grazing?

Nomadic farming (or pastoralism).

The world's highest ever recorded temperature of 56.7 degrees Celsius was in which part of the Western Desert?

Furnace Creek Ranch, Death Valley.

Which animal can reduce its heart rate and oxygen intake, allowing it to survive on just two insects per year?

The nocturnal Arabian death scorpion.

In Phoenix, Arizona, temperatures exceeded 38 degrees Celsius on how many days in one recorded year?

Over 144 days.

How much does the Alta Wind Energy Center contribute to the local economy?

$1 billion.

What are check dams designed to do in gullies to combat desertification?

They slow the water speed, allowing more water to be absorbed into the ground and trapping soil.

The discovery of what resource below ground has enabled large-scale open-cast mining in the Sonoran Desert?

Water supplies (aquifers).

Plans for uranium mining near the Grand Canyon were stopped due to concerns about contamination of drinking water and risks to what?

Endangered species of wildlife.

The Alta Wind Energy Center is projected to reduce carbon emissions by how much?

5.2 million metric tonnes.

How did early 20th-century settlers adapt their homes to the Western Desert's climate?

They built homes with flat roofs to collect rainwater and small windows to reduce sunlight entering.

What is a negative environmental impact associated with the construction of solar farms like Ivanpah?

Habitat loss, for example, affecting the desert tortoise.

In the state of Colorado, agriculture receives 80% of the available water but contributes only what percentage to the economy?

10%.

Approximately how many people across the globe are estimated to live in areas at risk from desertification?

One billion people.