Asia

Categoria: Referat Engleza

Descriere:

According to the theory of plate tectonics, the crust of the Earth’s surface is made up of vast continental and oceanic plates. These are in constant motion, rubbing and pushing against one another, moving only small amounts each year. The Eurasian continental plate is the largest. It is composed of some of the most ancient rocks on Earth, originating in Precambrian time from 4.65 billion to 570 million years ago. These ancient materials can today be found in eastern Siberia, throughout the Arabian Peninsula, and in India south of the Indus and Ganges rivers...

Asia

I

INTRODUCTION

Asia, largest of the Earth’s seven continents, lying almost entirely in the Northern Hemisphere. With outlying islands, it covers an estimated 44,391,000 sq km (17,139,000 sq mi), or about 30 percent of the world’s total land area. Its peoples account for three-fifths of the world’s population; in 2005 Asia had an estimated 3.91 billion inhabitants.

Most geographers regard Asia as bounded on the north by the Arctic Ocean, on the east by the Bering Strait and the Pacific Ocean, on the south by the Indian Ocean, and on the southwest by the Red Sea and Mediterranean Sea. On the west, the conventional boundary between Europe and Asia is drawn at the Ural Mountains, continuing south along the Ural River to the Caspian Sea, then west along the Caucasus Mountains to the Black Sea. Some geographers include Europe and Asia together in a larger Eurasian region, noting that western Asian countries, such as Turkey, merge almost imperceptibly into Europe.

The continental mainland stretches from the southern end of the Malay Peninsula to Cape Chelyuskin in Siberia. Its westernmost point is Cape Baba in northwestern Turkey, and its easternmost point is Cape Dezhnyov in northeastern Siberia. The continent’s greatest width from east to west is 8,500 km (5,300 mi). The lowest and highest points on the Earth’s surface are in Asia, namely, the shore of the Dead Sea (408 m/1,340 ft below sea level in 1996) and Mount Everest (8,850 m/29,035 ft above sea level).

South of the mainland in the Indian Ocean are Sri Lanka and smaller island groups, such as the Maldives and the Andaman and Nicobar islands. To the southeast is an array of archipelagoes and islands that extend east to the Oceanic and Australian realms. Among these islands are those of Indonesia, including Java, Sumatra, Sulawesi, and Borneo. The western end of the island of New Guinea is within Indonesia and for that reason geographers occasionally consider it part of Asia. In this encyclopedia, however, it is treated as a part of the Pacific Islands. The Philippine Islands, which include Luzon and Mindanao, are also among the Southeast Asian islands. To their north lie Taiwan, the Chinese island of Hainan, the islands of Japan, and the Russian island of Sakhalin.

Because of its vast size and diverse character, Asia is divided into five major realms: East Asia, including China, Mongolia, North Korea, South Korea, and Japan; Southeast Asia, including Myanmar (formerly known as Burma), Thailand, Cambodia, Laos, Vietnam, Malaysia, Singapore, Indonesia, Brunei, and the Philippines; South Asia, including India, Bangladesh, Pakistan, Sri Lanka, Maldives, Nepal, and Bhutan; and Southwest Asia, including Afghanistan, Iran, Iraq, Turkey, Cyprus, Armenia, Azerbaijan, Georgia, Syria, Lebanon, Israel, Jordan, Saudi Arabia, Yemen, Oman, United Arab Emirates, Qatar, Bahrain, and Kuwait. Most of the countries of Southwest Asia are also considered part of the Middle East, a loosely defined region that includes Egypt. Afghanistan and Myanmar are sometimes considered part of South Asia, but most geographers place Afghanistan in Southwest Asia and Myanmar in Southeast Asia. The fifth realm consists of the area of Russia that lies east of the Ural Mountains (Russian Asia) and the states of Central Asia that were formerly part of the Union of Soviet Socialist Republics (USSR). These states are Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, Uzbekistan.

The continent may also be divided into two broad cultural realms: that which is predominantly Asian in culture (East Asia, Southeast Asia, and South Asia) and that which is not (Southwest Asia, Central Asia, and Russian Asia). There is enormous cultural diversity within both regions, however.

II

THE NATURAL ENVIRONMENT

As the largest continent, Asia contains some of the world’s most spectacular natural features, including high mountain ranges, vast plateaus, majestic river basins, and lakes and inland seas. The centerpiece is the high mountains of the Himalayas and the associated Tibetan Plateau (Qing Zang Gaoyuan). To the far north are vast plateau regions of Siberia and open waterways such as Lake Baikal. Located in an arc around the eastern rim of the continent are the plateaus of China, dissected by great rivers, including the Yangtze River (Chang Jiang). In South Asia, the Deccan Plateau dominates India. Toward the west is the Arabian Peninsula, and in a northwesterly direction are the steppes of Central Asia.

A

Geological History

According to the theory of plate tectonics, the crust of the Earth’s surface is made up of vast continental and oceanic plates. These are in constant motion, rubbing and pushing against one another, moving only small amounts each year. The Eurasian continental plate is the largest. It is composed of some of the most ancient rocks on Earth, originating in Precambrian time from 4.65 billion to 570 million years ago. These ancient materials can today be found in eastern Siberia, throughout the Arabian Peninsula, and in India south of the Indus and Ganges rivers.

A huge sea called Tethys covered most of the interior of Eurasia during the Paleozoic and Mesozoic eras, which lasted from 570 million to 65 million years ago. Thick deposits of sediment formed on the seafloor, eventually becoming the layers of rock that form the geological features of the present day.

The Indian subcontinent broke off from the southeastern corner of the African continental plate during the Cretaceous period. It drifted in a northeasterly direction and collided with the larger Eurasian plate, slipping partly underneath it. The impact created an enormous “deep” that eventually filled with sediments and became the Gangetic Plain. The collision also generated enormous pressure on the southern edge of the Eurasian plate, causing this region to crumple; this forced an uplift of rock that created the Himalayas, the world’s highest mountain system.

The Pacific Ocean plate drifted westward, scraping along the Eurasian plate and slipping under its coastal edge. This created the islands of Japan, Taiwan, the Kurils, the Ryūkyūs, and the Philippines. Southeast Asia lies at the intersection of the Eurasian, Pacific Ocean, and Indian Ocean plates. Over time the contact between these plates created the mountain ranges of mainland Southeast Asia. The continued slow movement of the plates causes friction and instability deep below the Earth’s surface, producing volcanoes and earthquakes.

B

Surrounding Waters and Islands

Asia is bounded on three sides by oceans: the Arctic to the north, the Pacific to the east, and the Indian to the south. Many seas, bays, and gulfs indent the continent’s coastline, which is 62,000 km (39,000 mi) long.

The most prominent seas along the northeastern rim of Asia are the Bering Sea in the far north between Asia and North America; the Sea of Okhotsk, located west of the Kamchatka Peninsula and north of the Kuril Islands; the Sea of Japan (East Sea), which fills the gap between Japan and the Asian mainland; and the Yellow Sea, situated between China and Korea. The Kuril Islands, Japan’s major islands of Hokkaidō, Honshū, Shikoku, and Kyūshū and Taiwan run along a thread from north to south.

The South China Sea lies adjacent to Southeast Asia, linking mainland countries to the Philippines and Indonesia. The Gulf of Tonkin sits between Vietnam and China’s Hainan Island, while the narrow Strait of Malacca separates the Indonesian island of Sumatra from the Malay Peninsula. Java Island lies across the Java Sea from Borneo, the world’s third largest island after Greenland and New Guinea. To the southeast is the Timor Sea separating the Asian island of Timor from the Australian continent.

The Indian subcontinent is flanked by the Bay of Bengal on the east and the Arabian Sea on the west. The island of Sri Lanka and the much smaller Maldives and Nicobar Islands trail away to the south.

The Arabian Sea’s Gulf of Aden, the Red Sea, the Mediterranean Sea, and the Black Sea form an arc along the western rim of Asia, providing natural boundaries with Africa and Europe. The Suez Canal, an artificial waterway excavated in the mid-19th century, provides a passage for ships between the Mediterranean and Red seas. The Persian Gulf provides Saudi Arabia, Iraq, and Kuwait access to the Arabian Sea.

C

Plains and Deserts

Plains occupy more land area in Asia than any other type of physical feature. Most of the western and northeastern parts of Russian Asia consist of plains. Other large plains include those of the Tigris and Euphrates rivers in Southwest Asia, the Ganges River in northern India, the Mekong River in Southeast Asia, and the Yangtze River in China.

Deserts are a feature of the Asian interior north of the Himalayas and large parts of Southwest Asia, especially the Arabian Peninsula. There the Syrian Desert, a plateau strewn with rock and gravel, spreads through southern Syria, northeastern Jordan, and western Iraq. Farther to the south, in southern Saudi Arabia, lies the Rub‘ al Khali (Empty Quarter). It is the largest continuous body of sand in the world.

Large deserts are also spread throughout Central Asia. The Garagum (Turkic for “black sand”) occupies most of Turkmenistan. Southern Kazakhstan and northern Uzbekistan share the Qyzylkum (Turkic for “red sand”), which lies southeast of the Aral Sea.

Stretching east across Mongolia and into China’s Inner Mongolia Autonomous Region is the Gobi, a cold, high plateau with an average elevation of 900 m (3,000 ft). Southwest of the Gobi is the Takla Makan Desert in the Xinjiang Uygur Autonomous Region of China. Both deserts are in the rain shadow of the Himalayas, which blocks the movement of moist air from the Indian Ocean.

D

Mountain Ranges

Asia’s mightiest mountain ranges radiate in great sweeping arcs from the Pamirs of Central Asia, a highland region where Tajikistan, Afghanistan, and China intersect. Southeast of the Pamirs are the Himalayas, spanning 2,400 km (1,500 mi) from the border between India and Pakistan in the west to the border between India and Myanmar in the east. The Karakorum Range lies just north of the western Himalayas. These two ranges contain all but two of the world’s highest peaks, including Mount Everest, which lies on the border between Tibet and Nepal. Smaller mountain ranges extend southward from the eastern Himalayas into the Indochinese Peninsula.

East and northeast of the Pamir knot, the Kunlun Mountains and the Tian Shan extend for more than 1,600 km (1,000 mi) into China. To the west, extending into central Afghanistan, is the Hindu Kush. Ranges connected to the Hindu Kush then extend into northern Iran, where they are known as the Elburz Mountains. A branch of the Elburz becomes the Caucasus Mountains between Europe and Asia.

A low range of mountains extends southwestward from the Pamir knot into western Pakistan, where they are known as the Sulaimān Range. These mountains then continue northwestward through Iran into southern Turkey, where they are known as the Taurus Mountains.

Other important mountain ranges of Asia, such as the low Nan Ling hills in central and southern China, are not directly connected to the high mountain chains that meet at the Pamirs.

E

Plateaus

Several plateaus lie between the mountain ranges of Central Asia. The highest is the Tibetan Plateau, often referred to as the Roof of the World, which is bounded by the Kunlun Mountains and the Himalayas. About 1,300,000 sq km (500,000 sq mi) of this plateau lies at an elevation above 4,300 m (14,000 ft). The principal plateaus of Southwest Asia are the Anatolian Plateau of central Turkey, the Arabian Plateau, and the Iranian Plateau. In South Asia, most of the peninsula of India consists of the great triangular Deccan Plateau. The Yunnan Plateau extends over much of the Indochinese Peninsula and the southwestern part of China. Much of the northern part of Russian Asia is occupied by the Central Siberian Plateau.

F

Rivers, Lakes, and Inland Seas

East Asia is the location of the continent’s longest river, the Yangtze, which flows 6,300 km (3,900 mi) eastward from Tibet to the East China Sea. The Huang He (Yellow River) also rises in the Tibetan highlands, flowing east across central China to its mouth at the Yellow Sea. The Zhu Jiang (Pearl River) rises in southwestern China and flows through the southern part of the country on its route to the South China Sea.