Central Asia includes Mongolia and central and eastern Russia. This part of Asia is mostly cold and inhospitable. While only 5% of the country is mountainous, Mongolia has an average elevation of 5,184 ft (1,580 m). Most of the country consists of plateaus. The temperature variation is extreme, ranging from -40 to 104°F ( -40 to 40°C). The Gobi Desert takes up about 17% of Mongolia's land mass, and an additional 28% is desert steppe. The remainder of the country is forest steppe and rolling plains.
North of China and Mongolia lies Russian Siberia. This region is almost half as large as the African continent,
and is usually divided into the eastern and western regions. About the top third of Siberia lies within the Arctic Circle, and the climate is very harsh. The most extreme temperatures occur in eastern Siberia, where it falls as low as -94°F ( -70°C), and there are only 100 days a year when it climbs above 50°F (10°C). Most of the region along the east coast is mountainous, but in the west lies the vast West Siberian Plain.
The most important lake in this area, and one of the most important lakes in the world, is called Lake Baikal. Its surface area is about the size of Belgium, but it is a mile deep and contains about a fifth of the world's fresh water supply. The diversity of aquatic life found here is unparalleled; it is the only habitat of 600 kinds of plants and 1,200 kinds of animals, making it the home of twothirds of the freshwater species on earth.