30 terms



Terms in this set (...)

dry or lacking rainfall; also a climate or climate zone that is hot and dry all year with very little rain
an isolated spot in a desert where water is found
The Sahel
semiarid grassland that is located along the Sahara's southern edge
-Arabic word sahel, which means "border" or "shore."
africa: language/desert names derived from
climate Sahara
-136 highest day, freezing at night, less than 5 in of rain a year
-when it does rain it can cause flashfloods
Sahara thousands of years ago
region had a much wetter climate. Rivers and lakes were filled with fish, and elephants and other animals roamed through grasslands and forests. People settled throughout the region and survived by hunting and fishing. About 6,000 years ago, the climate of North Africa began to change, as year by year less rain fell. Eventually the Saharan region began its transformation into a desert. Ever since then, the desert has gradually been expanding.
Trade winds
-steady winds in tropical latitudes that blow toward the equator from the north and south
-As trade winds pass over the Sahara, they pick up any moisture from the ground below, leaving so little moisture that few clouds form over the Sahara. With no clouds to provide shade, the sun beats down on the land, making it even drier.
Most of the plants and animals that live in the Sahara are found....
...near oasis's
Sahel climate/agraculture
-receives more precipitation than the Sahara, but it often suffers from long periods of drought.
-Most of the Sahel is marginal land, or land that is not well suited for farming. People who farm marginal land may harvest barely enough food for their families to survive.
pastoral nomads
-groups of herders who move with their animals from place to place in search of pasture and water
-have adapted to life on the Sahel's marginal lands. Pastoral nomads are herders who wander endlessly in search of water and grazing land for their animals. Once their herds have grazed an area, the nomads move on. This gives marginal grazing land a chance to recover.
-the process by which land becomes more and more dry until it turns into desert. This may be caused by climate change, human activities, or both.
-happening to the sahel
-In areas with little rain, few plants grew. Without vegetation to anchor the dry soil in place, desert winds picked up the soil and carried it away. When this happened, marginal lands were transformed into desert.
-great seas of sand with tall sand dunes that can reach heights of over 400 feet.
gravel-covered desert plain
a high, rock-covered flatland in the Sahara, some of which are so tall that maps indicate their locations as mountains
Only two rivers flow through the Sahara:
Nile and the Niger, with the water in both rivers coming from mountains beyond the desert.
the usually dry bed of a river or stream in a desert or semiarid area
Plants are able to adapt to these changing conditions in several ways...
Some plants sprout rapidly after a rain and then set seed and die. The seeds then lie in wait—sometimes for years—until the next rain. Other plants send roots deep into the ground to find water. Deep roots anchor these plants in place during sandstorms and flash floods. Most desert trees and shrubs have small, waxy leaves that lose little moisture. During long periods of drought, they may shed their leaves, further reducing water loss.
-raise camels, goats, cattle, or sheep. When the pasture in one area has been exhausted, or used up, the Tuareg move their animals to a fresh grazing area.
-also called the blue men of the desert because of their flowing blue robes. Their long, loose clothing protects them from the scorching sun.
-live in family groups of fewer than 100 people
-when reach an oasis, they trade meat, cheese, or milk for grain, vegetables, fruit, and water.
Modern technology has improved life for many desert dwellers...
- Pastoral nomads have found many uses for lightweight plastic and metal containers. Meanwhile, some desert traders can afford satellite phones to keep in touch with their customers.
- Trucks and planes have improved desert transportation. Trucks are replacing camels for hauling heavy loads, and small planes are used to fly people and goods between oases.
how are oasises formed?
-Some oases are formed by natural processes. Many are created by springs that bubble up to the surface from streams that flow beneath the ground. Other oases appear in low spots, where the land dips down to meet an underground stream.
-Humans have also created some oases. In the past, people constructed oases by digging wells by hand. As you read earlier, drilling machines are now being used to dig deep into the ground to locate hidden water.
Many species of plants and animals can be found at a desert oasis. Acacia and baobab trees mix with smaller shrubs. Gazelles and other animals drink in the pools, while butterflies, crickets, and other insects flit through oasis gardens. Date palms are by far the most important and common oasis plant. Every part of the date palm is useful. Its fruit, the date, is eaten fresh or dried. Its trunk and leaves are used as building materials, and the fiber from its bark is twisted together to make rope
Trading and farming are the major economic activities at an oasis.
Most people are subsistence farmers, but others grow cash crops such as dates, wheat, barley, and vegetables.
Most homes within an oasis town are constructed from mud bricks; in order to keep out the heat, the homes have few windows.
Little work is done during the hottest part of the day. In the cool of the evening, people gather to discuss the day's news.
-use windbreaks to shelter from the sand
-Oasis settlements come in a variety of sizes. Most are small villages, but a few settlements are growing into towns and cities.
As an oasis settlement expands, its water problems increase as well...
-how to transport water to people as the town expands. New housing areas and camps that are established to shelter refugees often lack wells or piped water. If the residents of these settlements cannot walk to water sources, water may have to be brought to them by truck.
-Water shortages are the second problem facing oasis towns. In some oases, palm groves have been expanded into the surrounding desert. The new palm trees are kept alive with water that is pumped out of the ground. However, if too much water is pumped out, the underground streams that create an oasis could run dry.
Sahel agraculture
The land here is marginal for farming because the soil is not fertile and water is scarce most of the year. The natural vegetation of the Sahel is a mixture of grasslands, acacia trees, baobab trees, and small bushes. Farther south, where rain is more plentiful, there is a greater variety of vegetation.
Most people in the Sahel are farmers or herders. In the past, these people have adapted to the challenge of farming and herding on marginal land in many ways.
One adaptation was to plant crops such as millet and sorghum, which are grains that will flourish in dry places. Another adaptation was to use a farming system known as shifting agriculture. In this method, a farmer first cleared a field and planted it with crops for a year or two. Then the farmer moved on to a new field. Herders used a similar system to feed their animals, moving their herds from one grazing area to another throughout the year. Both of these systems provided worn-out fields with an opportunity to rest.
shifting agriculture
the practice of clearing one area for farming for a few years and then moving on to another area when the first has lost its fertilit
Human Causes of Desertification
-Some farmers, for example, have begun to raise cash crops, like peanuts, which often wear out the soil faster than traditional crops. After the soil has been depleted, or worn out, it may blow away before it can recover its fertility.
-increased the size of their herds, Loss of vegetation from overgrazing may also contribute to desertification.
Most people in the Sahel rely on wood as their fuel for cooking. In their search for firewood, the people cut down trees. When the trees are gone, soil erosion increases, which is why the government of Niger has been promoting coal as a cooking fuel. "I think that with coal, our sparse forests could be saved," says a forestry expert in Niger.
ways to counter react desertation
-Cooking with coal
-farmers are testing new agricultural methods that can conserve water and reduce soil erosion. Many farmers are working to keep desert sand from burying their fields by building windbreaks of trees and brush.