Asia is the largest of the world’s continents, covering approximately 30 percent of the Earth’s land area. It is also the world’s most populous
continent
, with roughly 60 percent of the total population.
Asia makes up the eastern portion of the Eurasian supercontinent; Europe occupies the western portion. The border between the two
continents
is debated. However, most geographers define Asia’s western
border
as an indirect line that follows the Ural Mountains, the Caucasus Mountains, and the Caspian and Black Seas. Asia is
bordered
by the Arctic, Pacific, and Indian Oceans.
Asia’s physical geography, environment and resources, and human geography can be considered separately.
Asia can be divided into five major physical regions: mountain systems; plateaus; plains, steppes, and deserts; freshwater environments; and saltwater environments.
Mountain Systems
The Himalaya mountains extend for about 2,500 kilometers (1,550 miles), separating the Indian subcontinent from the rest of Asia. The
Indian sub
continent
, once connected to Africa, collided with the Eurasian
continent
about 50 million to 55 million years ago, forming the Himalayas. The
Indian sub
continent
is still crashing northward into Asia, and the Himalayas are growing about 5 centimeters (2 inches) every year.
The Himalayas cover more than 612,000 square kilometers (236,000 square miles), passing through the northern states of India and making up most of the terrain of Nepal and Bhutan. The Himalayas are so vast that they are composed of three different mountain belts. The northernmost belt, known as the Great Himalayas, has the highest average elevation at 6,096 meters (20,000 feet). The belt contains nine of the highest peaks in the world, which all reach more than 7,925 meters (26,000 feet) tall. This belt includes the highest mountain summit in the world, Mount Everest, which stands at 8,849 meters (29,032 feet).
The Tien Shan mountain system stretches for about 2,400 kilometers (1,500 miles), straddling the
border
between Kyrgyzstan and China. The name Tien Shan means “Celestial Mountains” in Chinese. The two highest peaks in the Tien Shan are Victory Peak, which stands at 7,439 meters (24,406 feet), and Khan Tängiri Peak, which stands at 6,995 meters (22,949 feet). Tien Shan also has more than 10,100 square kilometers (3,900 square miles) of glaciers. The largest
glacier
is Engil'chek
Glacier
, which is about 60 kilometers (37 miles) long.
The Ural Mountains run for approximately 2,500 kilometers (1,550 miles) in an indirect north-south line from Russia to Kazakhstan. The Ural Mountains are some of the world’s oldest, at 250 million to 300 million years old. Millions of years of erosion have lowered the mountains significantly, and today their average
elevation
is between 914 and 1,220 meters (3,000 to 4,000 feet). The highest peak is Mount Narodnaya at 1,895 meters (6,217 feet).
Plateaus
Asia is home to many
plateaus
, areas of relatively level high ground. The Iranian
plateau
covers more than 3.6 million square kilometers (1.4 million square miles), encompassing most of Iran, Afghanistan, and Pakistan. The
plateau
is not uniformly flat, but contains some high mountains and low river basins. The highest mountain peak is Damavand, at 5,610 meters (18,410 feet). The
plateau
also has two large
deserts
, the Dasht-e Kavir and Dasht-e Lut.
The Deccan
Plateau
makes up most of the southern part of India. The
plateau
’s average
elevation
is about 600 meters (2,000 feet). It is
bordered
by three mountain ranges: the Satpura Range in the north, and the Eastern and Western Ghats on either side. The
plateau
and its main waterways—the Godavari and Krishna
rivers
—gently slope toward the Eastern Ghats and the Bay of Bengal.
The Tibetan
Plateau
is usually considered the largest and highest area ever to exist in the history of Earth. Known as the “Rooftop of the World,” the
plateau
covers an area about half the size of the contiguous United States and averages more than 5,000 meters (16,400 feet) above sea level. The Tibetan
Plateau
is extremely important to the world’s water cycle because of its tremendous number of
glaciers
. These
glaciers
contain the largest volume of ice outside the poles. The ice and snow from these
glaciers
feed Asia’s largest
rivers
. Approximately 2 billion people depend on the
rivers
fed by the
plateau
’s
glaciers
.
Plains, Steppes, and Deserts
The West Siberian Plain, located in central Russia, is considered one of the world’s largest areas of continuous flatland. It extends from north to south about 2,400 kilometers (1,500 miles) and from west to east about 1,900 kilometers (1,200 miles). With more than 50 percent of its area at less than 100 meters (330 feet) above sea level, the plain contains some of the world’s largest swamps and flood plains.
Central Asia is dominated by a
steppe
landscape, a large area of flat, unforested grassland. Mongolia can be divided into different
steppe
zones: the mountain forest
steppe
, the arid
steppe
, and the
desert
steppe
. These zones transition from the country’s mountainous region in the north to the Gobi
Desert
on the southern
border
with China.
The Rub’ al Khali
desert
, considered the world’s largest sand sea, covers an area larger than France across Saudi Arabia, Oman, the United Arab Emirates, and Yemen. It holds roughly half as much sand as Africa’s Sahara
desert
, even though it is 15 times smaller in size. The
desert
is known as the Empty Quarter because it is virtually inhospitable to humans except for Bedouin tribes that live on its edges.
Freshwater
Lake Baikal, located in southern Russia, is the deepest
lake
in the world, reaching a depth of 1,620 meters (5,315 feet). The
lake
contains 20 percent of the world’s unfrozen
freshwater
, making it the largest reservoir on Earth. It is also the world’s oldest
lake
, at 25 million years old.
The Yangtze is the longest
river
in Asia and the third longest in the world (behind the Amazon of South America and the Nile of Africa). Reaching 6,300 kilometers (3,915 miles) in length, the Yangtze moves east from the
glaciers
of the Tibetan
Plateau
to the
river
’s mouth on the East China Sea. The Yangtze is considered the lifeblood of China. It drains one-fifth of the country’s land area, is home to one-third of its population, and contributes greatly to China’s economy.
The Tigris and Euphrates
Rivers
begin in the highlands of eastern Turkey and flow through Syria and Iraq, joining in the city of Qurna, Iraq, before emptying into the Persian Gulf. The land between the two
rivers
, known as Mesopotamia, was the center of the earliest civilizations, including Sumer and the Akkadian Empire. Today, the Tigris-Euphrates
river
system is under threat from increased agricultural and industrial use. These pressures have caused desertification and increased salts in the soil, severely damaging local watershed habitats.
Saltwater
The Persian
Gulf
has an area of more than 234,000 square kilometers (90,000 square miles). It
borders
Iran, Oman, United Arab Emirates, Saudi Arabia, Qatar, Bahrain, Kuwait, and Iraq. The
gulf
is subject to high rates of evaporation, making it shallow and extremely salty. The seabed beneath the Persian
Gulf
contains an estimated 50 percent of the world’s oil reserves. The countries that
border
the
gulf
have engaged in a number of disputes over this rich resource.
The Sea of Okhotsk covers 1.5 million square kilometers (611,000 square miles) between the Russian mainland and the Kamchatka Peninsula. The sea is largely frozen between October and March. Large ice floes make winter navigation almost impossible.
The
Bay
of Bengal is the largest
bay
in the world, covering almost 2.2 million square kilometers (839,000 square miles) and
bordering
Bangladesh, India, Sri Lanka, and Burma. Many large
rivers
, including the Ganges and Brahmaputra, empty into the
bay
. The briny wetlands formed by the Ganges-Brahmaputra on the
Bay
of Bengal is the largest delta in the world.
Terrestrial Flora and Fauna
Botanists nickname China the “Mother of Gardens.” It has more flowering plant species than North and South America combined. Because China has such diverse
landscapes
, from the
arid
Gobi
Desert
to the tropical rain forests of Yunnan Province, many
flowers
can adapt to climates all over the world. From roses to peonies, many familiar
flowers
most likely originated in northern China. China is the likely origin of such fruit trees as peaches and oranges. China is also home to the dawn redwood, the only redwood tree found outside North America.
Asia’s diverse physical and cultural
landscape
has dictated the way animals have been domesticated. In the Himalayas, communities use yaks as beasts of burden.
Yaks
are large animals related to cattle, but with a thick fiber coat and the ability to survive in the oxygen-poor high altitude of the mountains.
Yaks
are not only used for transportation and for pulling plows, but their coats are sources of warm, hardy
fiber
.
Yak
milk is used for butter and cheese.
In the Mongolian
steppe
, the two-humped Bactrian camel is the traditional beast of burden. Bactrian camels are critically endangered in the wild. The camel’s humps store nutrient-rich fat, which the animal can use in times of drought, heat, or frost. Its size and ability to
adapt
to hardship make it an ideal pack animal. Bactrians can actually outrun horses over long distances. These camels were the traditional animals used in caravans on the Silk Road, the legendary trade route linking eastern Asia with India and the Middle East.
Aquatic Flora and Fauna
The
freshwater
and marine
habitats
of Asia offer incredible biodiversity.
Lake
Baikal’s age and isolation make it a unique biological site.
Aquatic
life has been able to evolve for millions of years relatively undisturbed, producing a rich variety of flora and
fauna
. The
lake
is known as the “Galápagos of Russia” because of its importance to the study of evolutionary science. It has 1,340 species of animals and 570 species of plants.
Hundreds of
Lake
Baikal’s species are endemic, meaning they are found nowhere else on Earth. The Baikal seal, for instance, is one of the few
freshwater
seal species in the world. The Baikal seal feeds primarily on the Baikal oil fish and the omul. Both fishes are similar to salmon, and provide fisheries for the communities on the
lake
.
The
Bay
of Bengal, on the Indian Ocean, is one of the world’s largest
tropical
marine ecosystems. The
bay
is home to dozens of marine mammals, including the bottlenose dolphin, spinner dolphin, spotted dolphin, and Bryde’s whale. The
bay
also supports healthy tuna, jack, and marlin fisheries.
Some of the
bay
’s most diverse array of organisms exist along its coasts and wetlands. Many wildlife reserves in and around the
bay
aim to protect its biological diversity.
The Sundarbans is a wetland area that forms at the
delta
of the Ganges and Brahamaputra
rivers
. The Sundarbans is a huge mangrove forest.
Mangroves
are hardy trees that are able to withstand the powerful, salty tides of the
Bay
of Bengal as well as the
freshwater
flows from the Ganges and Brahamaputra. In addition to
mangroves
, the Sundarbans is forested by palm trees and
swamp
grasses.
The
swampy
jungle of the Sundarbans supports a rich animal community. Hundreds of species of fish, shrimp, crabs, and snails live in the exposed root system of the
mangrove
trees. The Sundarbans supports more than 200 species of
aquatic
and wading birds. These small animals are part of a food web that includes wild boar, macaque monkeys, monitor lizards, and a healthy population of Bengal tigers.
