Almásy: "I'm going to have to walk to El Taj. Although, given all the traffic in the desert these days I'm bound to bump into one army or another."
The Sahara Desert is the western portion of the broad belt of arid land that extends from the Atlantic Ocean eastwards to the Red Sea. The entire desert is about 1,610 km deep and about 5,150 km wide from east to west. The total area of the Sahara is 9.1 million sq km, of which 207,200 sq km consist of partially fertile oases.
Geographically distinct are the western Sahara, which is sometimes called the Sahara proper; the central Ahaggar Mountains and the Tibesti Massif, a plateau region; and the Libyan Desert in the east.
The Libyan Desert is considered the most arid part of the Sahara. The land is characterized by sandy wastes and large sand dunes 122 m or more in height.
Deserts are barriers to travel because of the scarcity to water. People usually travel across the desert to trade. Usually they would travel in groups called caravans. Travelling together provided protection against raiders, and it was also safer in such severe weather conditions. Trade routes cross deserts from oasis to oasis where the travellers could replenish water supplies.
In the past, crossing the desert was a great challenge for adventurous explorers. From the fifteen century, most desert explorers were Europeans. They hired local guides for direction and survival.
Travelling now is far simpler, with roads across Sahara, and aeroplanes to reach remote places. Inventions such as air-conditioning, sun cream and light plastic water containers make journeys easier and more comfortable.
Although rainfall is rare or infrequent in the desert, there are other sources of ground water such as rivers and aquifers. An oasis is a place with sufficient water to allow plants to grow in an otherwise barren desert.
Some of the world's longest rivers flow through deserts. Many great civilizations in the past have developed along desert rivers. A perfect example of this is the Nile which supported the Egyptians. In order to use river water, humans have built dams across rivers and brought irrigation methods to farm in desert areas. But irrigation could cause desert soils which have a high salt content to damage it's soil.
Flowing through deserts are extraordinary underground channels called qanats or karez. People have tunneled them under deserts to bring water to nearby mountains to supply oases. Even though it travelled for many kilometres, the water still feel ice cold because it does not come into the contact with the desert surface.
Aquifers are underground reservoirs of water filled rock. It takes thousands of years for the water to accumulate. Some aquifiers are rechargable but some are not. The water tends to flow through aquifer rocks and surface naturally, sometimes in a basin or a fault in rock forces water upwards. People also drill wells or build pumps to extract the water. As long as the water is not too saltish or full of minerals, it can support life. However, the water is usually used up faster than it can recharge, therefore levels in underground water has dropped. It is also likely that the water would eventually run out.