By size and population, Asia is the biggest continent in the world. With 44.5 million km2, including its adjacent islands, it covers 8,7% of the terrestrial surface of the earth and almost 30% of the emerged lands. Six of every ten inhabitants of the earth live in Asia.Asia borders, to the west, Ural Mountains, and Caspian and Black sea. To the east, with the Pacific Ocean. To the north, with the Glacial Arctic ocean and to the south with the Indian Ocean. The biggest country of Asia, and in the world, is Russia, with 17 millions of Km2. The smallest country are the Maldives islands.

• TO THE NORTH: ARCTIC OCEAN
• TO THE SOUTH: INDIAN OCEAN
• TO THE EAST: PACIFIC OCEAN
  TO THE WEST: CAUCASUS MOUNTAINS, CASPIAN AND BLACK SEA

Asia can be divided in five main physical regions: mountain systems, plateaus, plains, steppesand deserts; also important are freshwater ecosystems and saltwater ecosystems. The three main mountain systems are: Himalayas, Tien Shan and Urals.

1.The Himalayas:TheHimalaya mountainsextend for about 2,500 kilometers, separating theIndian subcontinentfrom the rest of Asia. The Indian subcontinent, once connected to Africa, collidedwith the Eurasian continent about 50 million to 55 millionyears ago, forming the Himalayas. The Indian subcontinent is still crashing northwardinto Asia, and the Himalayas are growing about 5 centimeters (2 inches) every year.The Himalayas cover more than 612,000 km2, a territory that covers the northern provinces of India and almost all of Nepal and Bhutan. The Himalayas are sovastthat they are composed of three different mountain belts. The northernmost belt, known as the Great Himalayas, has the highest averageelevationat 6,096 meters. The belt containsnine of the highest peaks in the world, which all reach more than 7,925 meters tall. This belt includes the highest mountainsummitin the world, Mount Everest, which stands at 8,850 meters.

2.Tien Shan:The Tien Shan mountain system stretches for about 2,400 kilometers, straddling the border between Kyrgyzstan and China. The name Tien Shan means “Celestial Mountains” in Chinese.Tien Shan also has more than 10,100 square kilometers of glaciers. The largestglacieris Engil'chek Glacier, which is about 60 kilometers long.

• Iranian plateaus:It covers more than 3.6 million km2 and embraces most of Iran, Afghanistan and Pakistan. It is not flat, but contains some high mountains and deep river basins. This plateau has two large deserts, the Dasht-e Kavir and Dasht-e Lut.
• The Deccan plateau:with an average height of 600m makes up most of southern India.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:It is considered the largest and highest area that ever existed in the history of the earth. The plateau covers an area of about half of the United States at an average height of 5,000 meters above sea level. It is known as the “Rooftop of the World”. The Tibetan Plateau is extremely important to the world’swater cyclebecause of itstremendousnumber of glaciers. These glaciers contain the largest volume of ice outside thepoles.The ice and snow from these glaciers feed

• The western plain of Siberia: 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 and from west to east about 1,900 kilometers.The plain contains some of the world’s largestswamps and flood plains.
• Central Asia is dominated by asteppelandscape, a large area of flat, unforested grassland.
  -The landscape of central Asia: It is dominated by steppes, large flat areas covered with grass without forests. Mongolia can be divided into different areas of steppe: the mountainous steppe with trees, the arid steppe and the desert steppe.
• The Rub'al Khali desert:It is considered the largest sand sea in the world, covers an area larger than France across Saudi Arabia, Oman, the United Arab Emirates, and Yemen.The desert is virtually inhospitable to humans except for Bedouin tribes that live on its edges.

• Baykal Lake:It is located south of Russia, is the deepest in the world (1,620 m). It contains 20% of the liquid fresh water in the world, which makes it the largest reservoir of water on Earth. It is also the oldest lake, it is 25 million years old.
• The Yangtze: It is the longest river in Asia and the third longest in the world (behind the Amazon of South America and the Nile of Africa). 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’seconomy.
• The Tigris and Euphratesrivers begin in the heights of Eastern Turkey and flow from 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 Sumerand the Akkadian Empire

• The Persian Gulf: It has an area of more than 234,000 km2. The seabed beneath the Persian Gulf contains an estimated 50 percent of the world’soil reserves.
• The Okhotsk Sea: It stretches for 1.5 million km2 between mainland Russia and the Kamchatka Peninsula.The sea is largely frozen between October and March. Largeice floes make winternavigationalmost impossible.
• The Bengal: It is the largest bay in the world, with an extension of almost 2.2 million km2.and bordering Bangladesh