Asia is the world's largest continent, encompassing an area of 17,177,000 sq mi (44,500,000 sq km), 29.8% of the world's land area. The Himalaya Mountains, which are the highest and youngest mountain range in the world, stretch across the continent from Afghanistan to Burma. The highest of the Himalayan peaks, Mount Everest, reaches an altitude of 29,028 ft (8,848 m). There are many famous deserts in Asia, including the Gobi Desert, the Thar Desert, and Ar-Rubʾal-Khali ("the Empty Quarter"). The continent has a wide range of climatic zones, from the tropical jungles of the south to the Arctic wastelands of the north in Siberia.

The continent of Asia encompasses such an enormous area and contains so many countries and islands that its exact borders remain unclear. In the broadest sense, it includes central and eastern Russia, the countries of the Arabian Peninsula, the Far Eastern countries, the Indian subcontinent, and numerous island chains. It is convenient to divide this huge region into five categories: the Middle East, South Asia, Central Asia, the Far East, and Southeast Asia.

The Middle Eastern countries lie on the Arabian Peninsula, southwest of Russia and northeast of Africa, separated from the African continent by the Red Sea and from Europe in the northwest by the Mediterranean Sea. This area stretches from Turkey in the northwest to Yemen in the south, which is bordered by the Arabian Sea. In general, the climate is extremely dry, and much of the area is still a desert wilderness. Precipitation is low, so the fertile regions of the Middle East lie around the rivers or in valleys that drain the mountains. Much of the coastal areas are arid, and the vegetation is mostly desert scrub.

Saudi Arabia is the largest of the Middle Eastern countries. In the west it is bordered by the Red Sea, which lies between Saudi Arabia and the African continent. The Hijaz Mountains run parallel to this coast in the northwest, rising sharply from the sea to elevations ranging from 3,000 to 9,000 ft (910 to 2,740 m). In the south is another mountainous region called the Asir, stretching along the coast for about 230 mi (370 km) and inland about 180–200 mi (290–320 km). Between the two ranges lies a narrow coastal plain called the Tihamat ash-Sham. East of the Hijaz Mountains are two great plateaus called the Najd, which slopes gradually downward over a range of about 3,000 ft (910 m) from west to east, and the Hasa, which is only about 800 ft (240 m) above sea level. Between these two plateaus is a desert region called the Dahna.

About one third of Saudi Arabia is estimated to be desert. The largest of these is the Ar-Rub'al-Khali, which lies in the south and covers an area of about 250,000 sq mi (647,500 sq km). In the north is another desert, called the An-Nafud. The climate in Saudi Arabia is generally very dry; there are no lakes and only seasonally flowing rivers. Saudi Arabia, like most of the Middle Eastern countries, has large oil reserves; also found here are rich gold and silver mines which are thought to date from the time of King Solomon.

Israel contains three main regions. Along the Mediterranean Sea lies a coastal plain. Inland is a hilly area that includes the hills of Galilee in the north and Samaria and Judea in the center. In the south of Israel lies the Negev Desert, which covers about half of Israel's land area. The two bodies of water in Israel are the Sea of Galilee and the Dead Sea. The latter, which takes its name from its heavy salinity, lies 1,290 ft (393 m) below sea level, and is the lowest point on the earth's landmasses. It is also a great resource for potassium chloride, magnesium bromide, and many other salts. Jordan borders on Israel in the east near the Dead Sea. To the east of the Jordan River, which feeds the Dead Sea, is a plateau region. The low hills gradually slope downward to a large desert, which occupies most of the eastern part of the country.

Lebanon borders Israel in the north and is divided up by its steep mountain ranges. These have been carved by erosion into intricate clefts and valleys, lending the landscape an unusual rugged beauty. On the western border, which lies along the Mediterranean Sea, is the Mount Lebanon area. These mountains rise from sea level to a height of 6,600–9,800 ft (2,000–3,000 m) in less than 25 mi (40 km). On the eastern border is the Anti-Lebanon mountain range, which separates Lebanon from Syria. Between the mountains lies Bekaa Valley, Lebanon's main fertile region.

Syria has three major mountain ranges. In the southwest, the Anti-Lebanon mountain range separates the country geographically from Lebanon. In the southeast is the Jabal Ad-Duruz range, and in the northwest, running parallel to the Mediterranean coast, are the Ansariyah Mountains. Between these and the sea is a thin stretch of coastal plains. The most fertile area is in the central part of the country east of the Anti-Lebanon and Ansariyah mountains; the east and northeastern part of Syria is made up of steppe and desert region.

Turkey, at the extreme north of the Arabian Peninsula, borders on the Aegean, the Mediterranean, and the Black Seas. Much of the country is cut up by mountain ranges, and the highest peak, called Mount Ararat, reaches an altitude of 16,854 ft (5,137 m). In the northwest is the Sea of Marmara, which connects the Black Sea with the Aegean Sea. Most of this area, called Turkish Thrace, is fertile and has a temperate climate. In the south, along the Mediterranean, there are two fertile plains called the Adana and the Antalya, which are separated by the Taurus Mountains.

The two largest lakes in Turkey are called Lake Van, which is close to the border with Iraq, and Lake Tuz, which lies in the center of the country. Lake Tuz has such a high level of salinity that it is actually used as a source of salt. Turkey is a country of seismic activity, and earthquakes are frequent.

Most of the Far Eastern countries are rugged and mountainous, but rainfall is more plentiful than in the Middle East, so there are many forested regions. Volcanic activity and plate tectonics have formed many island chains in this region of the world, and nearly all the countries on the coast include some of these among their territories.

China, with a land area of 3,646,448 sq mi (9,444,292 sq km), is an enormous territory. The northeastern part of the country is an area of mountains and rich forestland, and its mineral resources include iron, coal, gold, oil, lead, copper, and magnesium. In the north, most of the land is made up of fertile plains. It is here that the Yellow (Huang) River is found, which has been called "China's sorrow" because of its great flooding. The northwest of China is a region of mountains and highlands, including the cold and arid steppes of Inner Mongolia. It is here that the Gobi Desert, the fifth largest desert in the world, is found. The Gobi was named by the Mongolians, and its name means "waterless place." It encompasses an area of 500,000 sq mi (1,295,000 sq km), and averages 2–4 in (5–10 cm) of rainfall a year. In contrast, central China is a region of fertile land and temperate climate. Many rivers, including the great Chang (Yangtze) River, flow through this region, and there are several freshwater lakes. The largest of these, and the largest in China, is called the Poyang Hu. In the south of China the climate becomes tropical, and the land is very fertile; the Pearl (Zhu or Chu) River delta, which lies in this region, has some of the richest agricultural land in China. In the southwestern region, the land becomes mountainous in parts, and coal, iron, phosphorous, manganese, aluminum, tin, natural gas, copper, and gold are all found here. In the west, before the line of the Himalayas which divides China from India, lies Tibet, which is about twice as large as Texas and makes up about a quarter of China's land area. This is a high plateau region, and the climate is cold and arid. A little to the north and east of Tibet lies a region of mountains and grasslands where the Yangtze and Yellow Rivers arise.

Japan consists of a group of four large islands, called Honshu, Hokkaido, Kyushu, and Shikoku, and more than 3,000 smaller islands. It is a country of intense volcanic activity, with more than 60 active volcanoes, and frequent earthquakes. The terrain is rugged and mountainous, with lowlands making up only about 29% of the country. The highest of the mountain peaks is an extinct volcano found on Honshu called Mount Fuji. It reaches an altitude of 12,388 ft (3,776 m). Although the climate is generally mild, tropical cyclones usually strike in the fall, and can cause severe damage.

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 two-thirds of the freshwater species on Earth.

Southeast Asia includes a number of island chains as well as the countries east of India and south of China on the mainland. The area is quite tropical, and tends to be very humid. Much of the mountainous regions are extremely rugged and inaccessible; they are taken up by forest and jungle and have been left largely untouched; as a result, they provide habitat for much unusual wildlife.

Thailand, which is a country almost twice the size of Colorado, has a hot and humid tropical climate. In the north, northeast, west, and southeast are highlands that surround a central lowland plain. This plain is drained by the river Chao Phraya, and is rich and fertile land. The highlands are mostly covered with forests, which include tropical rainforests, deciduous forests, and coniferous pine forests. Thailand also has two coastal regions; the largest borders on the Gulf of Thailand in the east and southeast, and on the west is the shore of the Andaman Sea.

South of the mainland countries lie the island chains of Malaysia, Indonesia, and the Philippines. The latter two are both sites of much volcanic activity; Indonesia is estimated to have 100 active volcanoes. These islands, in particular Malaysia, are extremely fertile and have large regions of tropical rain forests with an enormous diversity in the native plant and wildlife.

South Asia includes three main regions: the Himalayan mountains, the Ganges Plains, and the Indian Peninsula.

The Himalayas stretch about 1,860 mi (3,000 km) across Asia, from Afghanistan to Burma, and range from 150 to 210 mi (250 to 350 km) wide. They are the highest mountains in the world, and are still being pushed upward at a rate of about 2.3 in (6 cm) a year. This great mountain range originated when the Indian subcontinent collided with Asia, which occurred due to the subduction of the Indian plate beneath the Asian continent. The Himalayas are the youngest mountains in the world, which accounts in part for their great height. At present they are still growing as India continues to push into the Asian continent at the rate of about 2.3 in (6 cm) annually. The Indian subcontinent is believed to have penetrated at least 1,240 mi (2,000 km) into Asia thus far. The range begins in Afghanistan, which is a land of harsh climate and rugged environment.

Bordered by China, several former Russian breakaway republics, Pakistan, and Iran, Afghanistan is completely land-locked. High, barren mountains separate the northern plains of Turan from the southwestern desert region, which covers most of Afghanistan's land area. This desert is subject to violent sandstorms during the winter months. The mountains of Afghanistan, which include a spur of the Himalayas called the Hindu Kush, reach an elevation of more than 20,000 ft (6,100m), and some are snow-covered year-round and contain glaciers. The rivers of the country flow outward from the mountain range in the center of the country; the largest of these are the Kabul, the Helmand, the Hari Rud, and the Kunduz. Except for the Kabul, all of these dry up soon after flowing onto the dry plains.

To the east of Afghanistan and separated from it by the Hindu Kush, lies Pakistan. In the north of the country are the mountain ranges of the Himalayas and the Karakoram, the highest mountains in the world. Most of the peaks are over 15,000 ft (4,580 m) and almost 70 are higher than 22,000 ft (6,700 m). By comparison, the highest mountain in the United States, Mount McKinley in Alaska, is only 20,321 ft (6,194m). Not surprisingly, many of the mountains in this range are covered with glaciers.

In the west of the country, bordering on Afghanistan, is the Baluchistan Plateau, which reaches an altitude of about 3,000–4,000 ft (900–1,200 m). Further south, the mountains disappear, replaced by a stony and sandy desert. The major rivers of Pakistan are the Kabul, the Jhelum, the Chenab, the Ravi, and the Sutlej; all of these drain into the Indus River, which flows into the Arabian Sea in the south of Pakistan.

Also found in the Himalaya Mountains are Nepal and the kingdom of Bhutan. Both of these countries border on the fertile Ganges Plains, so that in the south they are densely forested with tropical jungles; but most of both territories consist of high mountains. It is in Nepal that the highest peak in the world, called Mount Everest, is found; it is 29,028 ft (8,848 m) high.

South of the Himalaya Mountains, India is divided into two major regions. In the north are the Ganges Plains, which stretch from the Indus to the Ganges River delta. This part of India is almost completely flat and immensely fertile; it is thought to have alluvium reaching a depth of 9,842 ft (3,000m). It is fed by the snow and ice from the high peaks, and streams and rivers from the mountains have carved up the northern edge of the plains into rough gullies and crevices. Bangladesh, a country to the north and east of India, lies within the Ganges Plains. The Ganges and the Brahmaputra flow into Bangladesh from India, and they are fed by many tributaries, so the country is one of the most well-watered and fertile regions of Asia. However, it is also close to sea level, and plagued by frequent flooding.