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 global population.

Asia's Borders

Asia makes up the eastern portion of the Eurasian supercontinent; Europe occupies the western portion. Asia is bordered by the Arctic, Pacific and Indian oceans, and most geographers define Asia’s western border as an irregular line that follows the Ural Mountains, the Caucasus Mountains, the Caspian Sea and the Black Sea.

While the oceans provide a logical and undisputed border, the boundary between Asia and Europe is the subject of debate, due to both geographical and political factors. There is no clear geological barrier between the continents based on tectonic plates or natural formations. Furthermore, different populations have either emphasized or minimized the idea that Europe and Asia are divided. It is theorized that the names of the continents—Europe and Asia—come from the Mesopotamian words for “sunset” and “sunrise.” As Mesopotamia was located in between modern-day Europe and Asia, it would make sense that they would see the sun rise over Asia and set over Europe and characterize them as two different places.

The term and concept of Eurasia as a single entity became increasingly common after World War I, when Russians living in Eastern Europe used the term to emphasize the connection between the two continents and build camaraderie and a sense of a common culture among peoples of the far-flung land. Today, the concept of Eurasia as an interconnected supercontinent is important to political relationships among Russia, China, and countries that straddle Europe and Asia, such as Kazakhstan. While geographers have established a clearly defined border between Europe and Asia, it is perhaps best understood as a geopolitical concept with varying and sometimes contradictory interpretations.

Physical Regions

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) and separate the Indian subcontinent from the rest of Asia. The Indian subcontinent, once connected to Africa, collided with the Eurasian continent about 50 million to 55 million years ago, forming the Himalayas. The Indian subcontinent is still crashing northward into Asia, and the Himalayas are growing every year.

The Himalayas are important to the culture and spirituality of the communities living there. For instance, Mount Kailash is a significant holy site for both Tibetan Buddhists and Hindus. Historically, religious pilgrims have climbed the mountain as a step on the path to enlightenment.

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. Coined Mount Everest by British colonizers, the mountain soars to a height of approximately 8,850 meters (29,035 feet). Indigenous groups have various names for this giant: the Tibetan people call it Chomolungma, or “Goddess Mother of the Earth”; the Nepalese call it Sagarmatha, which is a word related to the sky; and the Chinese call it Qomolangma Feng, combining the Tibetan name with the Chinese word for "peak" or "summit."

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 at about 60 kilometers (37 miles) long. The Silk Road, which was a trade network that connected Europe with points farther east in Asia, went through the Tien Shan mountains, making the region important to cultural exchange and development among diverse peoples across the supercontinent.

The Ural Mountains run for approximately 2,500 kilometers (1,550 miles) in an indirect north-south line from Russia to Kazakhstan. The Urals are some of the world’s oldest mountains, dating back some 250 million to 300 million years. 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, which are areas of relatively level high ground. The Iranian plateau encompasses most of Iran, Afghanistan and Pakistan. The plateau is not uniformly flat, as it contains some high mountains and low river basins. The highest mountain peak is Damavand volcano. 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 Deccan Plateau is home to Hindu, Muslim and Jain communities. Many temples and mosques dedicated to the three religions are hundreds of years old.

The Tibetan Plateau is usually considered the largest and highest area ever to exist in Earth's history. 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 4,500 meters (14,764 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. The Tibetan Plateau is also a significant cultural region known for textiles and other traditional artisanal crafts. Thangkas, or scrolls with paintings depicting Buddhist teachings, were developed there, and their portable nature meant they were carried by traders to faraway lands, thereby facilitating the spread of Buddhism.

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. Nomadic communities in this area traditionally herded reindeer, and reindeer continue to provide livelihood for significant numbers of people there today.

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. The desert is known as the Empty Quarter because it is virtually inhospitable to humans except for Bedouin tribes that live on its edges. Scientists have found archaeological remains that date back to the prehistoric era, suggesting that there is still much to learn about the history of this desert.

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 fresh water, 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. It is also considered a major cultural hub of China, with 42 World Cultural Heritage sites along its banks, including 465 additional significant traditional sites and 91 museums.

The Tigris and Euphrates rivers begin in the highlands of eastern Turkey and flow through Syria and Iraq, converging in the city of Qurna, Iraq, before emptying into the Persian Gulf. The land between the two rivers, known as Mesopotamia, was the cradle of early civilizations, including Sumer and the Akkadian Empire. Today, the Tigris-Euphrates river system is under threat from increased agricultural and industrial use, including the construction of dams to produce hydroelectric power. These pressures have caused desertification and increased the level of salinity in the soil, severely damaging local watershed habitats and threatening local cultures that have developed along the rivers’ banks. For example, the local Kurdish community unsuccessfully fought the construction of Turkey’s Ilisu Dam, which contributed to flooding of culturally and historically important lands, including the ancient city of Hasankeyf.

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. Domestic and foreign interest in these reserves, particularly by oil-dependent countries, such as the United States and China, has contributed to war and political instability.

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. The Ganges River, which empties into the Bay of Bengal, is a sacred site for Hindus, who purify themselves spiritually by bathing in its waters.

Terrestrial Flora and Fauna

China has diverse landscapes, from the arid Gobi Desert to the tropical rain forests of Yunnan Province. From roses to peonies, many familiar flowers most likely originated in northern China, as did 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; their coats are sources of warm, hardy fiber, and yak milk is used for butter and cheese. Om Katel, a National Geographic Explorer, studies the intersection between traditional livestock care, the effects of climate change and other issues concerning animals in the Himalayas.

In the Mongolian steppe, the two-humped Bactrian camel is the traditional beast of burden. 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. Today, Bactrian camels are critically endangered in the wild.

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.