An oasis is an area made fertile by a source of freshwater in an otherwise dry and arid region. Oases (more than one oasis) are irrigated by natural springs or other underground water sources. They vary in size from a cluster of date palms around a well or a spring to a city and its irrigated cropland. Dates, cotton, olives, figs, citrus fruits, wheat and corn (maize) are common oasis crops.
Underground water sources called aquifers supply most oases. In some cases, a natural spring brings the underground water to the surface. At other oases, manmade wells tap the aquifer. In some oasis settlements, these wells might be centuries old and might have been diligently maintained for generations to preserve access to their life-giving water.
Sands blown by desert winds threaten wells as well as agricultural areas in oases. Sand can destroy crops and pollute water. Communities have traditionally planted strong trees, such as palms, around the perimeter of oases to keep the desert sands from their delicate crops and water.
Some of the world's largest supplies of underground water exist beneath the Sahara Desert, supporting about 90 major oases there. The Sahara is the largest desert on Earth—about the size of the continental United States. Though there are many oases there, traveling between them can take days because the desert is so vast.
For this reason, oases in the Sahara and throughout the world have become important stops along trade routes. Merchants and traders who travel along these routes must stop at oases to replenish food and water supplies. This means that whoever controls an oasis also controls the trade along the route—making oases desirable to political, economic, and military leaders.
Al-Hasa, Saudi Arabia, has been an important farming area for the Arabian Peninsula for thousands of years. Today, it continues to be a leading agricultural region, producing dates, rice, corn, sheep, cattle, and eggs. The al-Hasa region also lies above one of the richest oil fields in the world, making the oasis an important center of international trade.
Rivers that flow through some deserts provide permanent sources of water for large, elongated oases. The fertile Nile River valley and delta in Egypt, supplied with water from the Nile River, is an example of this type of large oasis. At 22,000 square kilometers, it might be the largest oasis in the world.
Meadow in the Mojave
The Las Vegas Valley, in the U.S. state of Nevada, is a popular tourist destination known for gaming and entertainment. Before the arrival of casinos, however, Las Vegas was the site of a natural oasis in the Mojave Desert. Springs brought water from the regions aquifer to the surface, ultimately flowing into the Colorado River. Las Vegas means the meadows in Spanish, and was named when the oasis was discovered by Mexican merchants in 1829.
The Las Vegas oasis has dried up. Development drained the springs. The areas empty aquifers are now used to store water from Lake Mead, an artificial lake created by the Hoover Dam on the Colorado River. Water is a major environmental and political issue in Las Vegas and throughout the U.S. Southwest.
Term Part of Speech Definition Encyclopedic Entry aquifer Noun
an underground layer of rock or earth which holds groundwater.
Encyclopedic Entry: aquifer arid Adjective
building filled with equipment and games for gambling.
type of fruit tree, including lemon and orange.
group of organisms or objects that share at least one characteristic.
Colorado River Noun
(2,335 kilometers/1,450 miles) river in the western U.S. and Mexico, draining into the Gulf of California.
continental United States Noun
U.S. land continuously stretching from the Atlantic to Pacific oceans (not including the states of Alaska and Hawaii.)
Encyclopedic Entry: crop date palm Noun
type of fruit tree.
fragile or easily damaged.
the flat, low-lying plain that sometimes forms at the mouth of a river from deposits of sediments.
Encyclopedic Entry: delta desert Noun
area of land that receives no more than 25 centimeters (10 inches) of precipitation a year.
Encyclopedic Entry: desert development Noun
construction or preparation of land for housing, industry, or agriculture.
hardworking and consistent.
having to do with money.
able to produce crops or sustain agriculture.
water that is not salty.
industry surrounding games of luck and skill in which players use their own money or goods to have a chance to win more. Also called gambling.
group in a species made up of members that are roughly the same age.
Hoover Dam Noun
dam on the Colorado River between the U.S. states of Arizona and Nevada. Also called the Boulder Dam.
having to do with more than one country.
Lake Mead Noun
(588 square kilometers/227 square miles) lake formed by the Hoover Dam in the U.S. states of Arizona and Nevada.
person who sells goods and services.
Mojave Desert Noun
arid landscape in the U.S. states of California, Arizona, Nevada, and Utah.
Nile River Noun
(5,592 kilometers/3,473 miles) river in East Africa.
area made fertile by a source of fresh water in an otherwise arid region.
Encyclopedic Entry: oasis oil field Noun
region with a large number of oil wells or other extractive technologies.
outline or border.
constant or lasting forever.
to introduce harmful materials into a natural environment.
amount of precipitation that falls in a specific area during a specific time.
to supply or refill.
large stream of flowing fresh water.
Encyclopedic Entry: river Sahara Desert Noun
world's largest desert, in north Africa.
small, loose grains of disintegrated rocks.
small flow of water flowing naturally from an underground water source.
buying, selling, or exchanging of goods and services.
trade route Noun
path followed by merchants or explorers to exchange goods and services.
huge and spread out.
a hole drilled in the Earth to obtain a liquid or gaseous substance.
movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun.