What does this island mean?

Islands are naturally formed land areas, surrounded by water, which rises above the water surface at high tide (according to the United Nations Convention on the Law of the Sea). In a narrow area, more than two islands are concentrated, that is, an "island group", and the larger island group is called "archipelago" or "archipelago". If all the territory of a country is located on one or more islands, it can

Island (island)

Definition: Natural land scattered in oceans, rivers or lakes, surrounded by water, exposed at high tide. A group of islands close to each other are called islands.

Land smaller than the mainland and completely surrounded by water can appear in oceans, lakes or rivers. The islands are called islands.

Classification: Islands in the ocean vary in size, and the smallest is less than 1 square kilometer, which is called "island"; Millions of square kilometers are called "islands". According to the causes, it can be divided into mainland island, island or volcanic island, coral island and alluvial island. According to the number and distribution characteristics of islands, they can be divided into isolated islands and islands (islands) that are close to each other.

Islands can be divided into continental type or marine type. Ocean islands refer to those islands that rise from the bottom of the ocean basin to the sea surface. Continental islands are those parts of the continental shelf that are surrounded by water but not submerged. Many large islands in the world are continental. The largest Greenland, with an area of 2175,600 square kilometers (840,000 square miles), is made of the same material as the neighboring North American continent, and is separated from the North American continent by a narrow shallow sea. Similarly, New Guinea (000 square miles, the second largest island in the world) is a part of the Australian mainland platform, separated from it by a very shallow and narrow Torres Strait. As long as the seabed near the Torres Strait is slightly tilted, it will be enough to connect New Guinea with Australia. On the contrary, if the sea level rises slightly, the hilly coast will be flooded, and the remaining hilltops will be offshore islands (such as offshore islands near Boston, Massachusetts and offshore islands in Maine).

The island rising from the bottom of the ocean basin is a volcanic island. Lava keeps piling up until it is quite thick and finally protrudes out of the sea. The lava piles that make up the Hawaiian Islands are 9700 meters (32000 feet) higher than the bottom of the sea.

The largest island in the world is Greenland, with an area of 2 175600 square kilometers.

The largest archipelago in the world is the Malay Archipelago, which is located in the vast sea area between the Pacific Ocean and the Indian Ocean in Southeast Asia. It consists of more than 20,000 islands, including Sumatra, kalimantan island, Java and Philippine Islands. It extends 6100km along the equator, with a maximum width of 3,500km from north to south and a total area of about 2.43 million square kilometers. It accounts for about 20% of the world's island area. [Edit this paragraph] Basic overview There are more than 50,000 islands in the world, with a total area of about 9.97 million square kilometers, which is similar to that of China, accounting for about115 of the total land area of the world. Geographically, there are islands on seven continents, of which North America has the largest island area, reaching 4 15. Antarctica has the smallest island area, only 70,000 square kilometers, accounting for only 0.5% of the whole continent. Tierra del Fuego, the largest island in South America, is located at the southernmost tip of the South American continent and is owned by Argentina and Chile, covering an area of 48,400 square kilometers. The largest island in Antarctica is Alexandria Island, which is located in the waters near bellingshausen, covering an area of 43,200 square kilometers.

As a result, islands can be divided into mainland islands and islands. The mainland island is the "home" of the mainland. Most of them are distributed in color chains around the continental margin. They are connected with nearby continents in geological structure, but some lands are surrounded by water due to crustal changes or rising sea water. China Taiwan Province Island is the most typical mainland island. Islands can be divided into volcanic islands, coral islands and alluvial islands according to their causes. It was erupted by a submarine volcano. The island formed by volcanic eruption and accumulation is called volcanic island. Hawaii Island in the Pacific Ocean is a typical volcanic island. Coral is the main force to shape coral island. The island formed by the accumulation of coral remains is called coral island. Coral islands are mainly distributed in tropical shallow waters between 20 north and south latitudes, and the shallow seas in the Pacific Ocean are relatively concentrated, such as the Great Barrier Reef in northeastern Australia. Most islands in the South China Sea are coral islands. Alluvial islands are islands formed by rivers or waves.

The standards of islands and continents are relative. Usually, people define Australia as the smallest continent, so Greenland becomes the largest island in the world.

The life on the island presents very interesting characteristics. The ocean is an obstacle for some creatures, but it is a carrier for others. Once settled in a new base, these creatures often evolve and develop new characteristics in an isolated environment. Long-standing sea barriers have caused significant differences between animals and vegetation, even between adjacent islands. From this difference, we can infer the origin of the island. In addition, any detailed map of the global biological distribution area can explain the importance of islands in determining the distribution boundary of animals and vegetation types. For example, west of a line (Wallace line) between Bali and Lombok and between Borneo and Celebes, the creatures on the island are Asians; To the east of that line, although the Lombok Strait is very narrow, the vegetation and animals are Australian. Marine islands often have only a few kinds of animals, mainly seabirds and insects. There are often a lot of vegetation on the island, and plant seeds are brought to the island by wind and water or birds. However, the species of plants are limited. [Edit this paragraph] Formation reasons ① Due to crustal movement, land subsidence or sea level rise, some land and mainland are separated into islands, such as Taiwan Province Island in China.

② The eruption materials (mainly lava) produced by submarine volcanism are piled up, or coral reefs are composed of coral secretions and remains. The former is like most of the Hawaiian Islands, while the latter is like Xisha and Nansha Islands in China.

③ It is formed by sediment accumulation in rivers and lakes, such as Chongming Island in China.

How are the islands in the ocean formed?

In the vast ocean, there are more than 50,000 islands, large and small, like countless colorful jadeites embedded in the blue sea 1. How were these islands formed? Some islands were originally a part of the mainland. Due to the movement of the earth's crust, a fault subsidence zone appeared between them, so they became islands facing the mainland across the sea, such as Taiwan Province Island in China, Hainan Island, Madagascar Island in Africa and so on. That's how they are formed. Sometimes, due to the action of the earth's tension, the mainland will produce some deep and large cracks, and the material in the deep underground will squeeze in, which will gradually open the cracks and form a new seabed. Fragments of the divided mainland have become islands far from the mainland. For example, Greenland, the largest island in the world, was separated from the European continent in this way. Sometimes the global warming and the melting of ice and snow will increase the water volume of the whole ocean and raise the sea level, so the low-lying parts of the continental margin will be submerged, and the highlands and peaks that are not submerged will become islands. Many islands in the Arctic Ocean were formed in this way.

The above islands are called mainland islands.

There are many islands, which are not land originally, but are formed by lava and debris ejected from submarine volcanoes. For example, the Hawaiian Islands in the Pacific Ocean are formed by a group of volcanoes exposed on the sea. These islands are called volcanic islands.

Corals living in warm seawater are also active builders of islands. Coral can continuously secrete calcium, and hundreds of millions of corals secrete calcium together with their remains to form coral islands. For example, most islands in the South China Sea belong to coral islands.

In addition, there are some islands where rivers enter the sea, which are formed by alluvial sediment carried by rivers. They are called alluvial islands, such as Chongming Island in China.

(1) Greenland in North America: 2175,000 square kilometers.

(2) Hiran Island in Oceania (also known as New Guinea): 785,000 square kilometers.

(3) kalimantan island in Asia: 734,000 square kilometers.

(4) Madagascar, Africa: 595,000 square kilometers.

(5) baffin island in North America: 507,000 square kilometers.

(6) Sumatra Island in Asia: 434,000 square kilometers.

(7) The island of Great Britain in Europe: 230,000 square kilometers.

(8) Honshu Island in Asia: 227,000 square kilometers.

(9) Victoria Island in North America: 210.5 million square kilometers.

(10) ellesmere island, North America: 200,000 km2.

Islands in the world

There are more than 50 major islands in the world, distributed in four oceans. Pacific islands are the most,19; There are 17 islands in the Atlantic Ocean, 9 islands in the Indian Ocean and 5 islands in the Arctic Ocean. The largest archipelago in the world is the former Malay archipelago in the western Pacific Ocean. There are more than 20,000 islands in the whole archipelago, belonging to Indonesia, Malaysia, Brunei, Philippines, East Timor and other countries. It is 4,500 kilometers wide from east to west and 3,500 kilometers long from north to south, with a total area of 2.407 million square kilometers. There are many mountains on the island. The crust is unstable, and earthquakes and volcanic eruptions often occur. There are many straits, which are important passages from Southeast Asia to all parts of the world.

In addition to the Malay Archipelago, the larger archipelagos in the world are: the Canadian Arctic Archipelago in the Arctic Ocean in northern North America, with an area of 6.5438+0.3 million square kilometers; Japanese archipelago, located in the western Pacific Ocean, with an area of 377,500 square kilometers; The nine British Isles located in the northeast of the Atlantic Ocean, covering an area of 325,000 square kilometers; The Philippine Islands in the southwest Pacific Ocean, covering an area of 299,700 square kilometers; The West Indies is located in the northwest of the Atlantic Ocean, covering an area of 240,000 square kilometers.

The smallest archipelago in the world is Tokelau, which is located in the northern part of Samoa in the South Pacific. It is composed of three coral atolls, with an area of only 10 square kilometer, which is called "pocket islands". [Edit this paragraph] China, an island in China, has more than 5,000 islands, with a total coastline of1.4000 km. The area of China exceeds 100. Taiwan Province Island, Hainan Island and Chongming Island can be divided into three types according to their causes: bedrock island, alluvial island and coral reef island. The East China Sea accounts for about 60% of the total islands, the South China Sea accounts for about 30%, and the Yellow Sea and Bohai Sea account for about 10%. [Edit this paragraph] Bedrock islands account for more than 90% of the total number of islands in China, and are controlled by the Neocathaysian tectonic system.

Taiwan Province Island and Taiwan Province Island, with an area of 35,780 square kilometers, are the 1 largest island in China. Mountains account for 2/3 of the island, and plains account for 1/3. Taiwan Province Island is located in the island arc zone of the western Pacific Ocean. From Oligocene to Pliocene, it returned to the young fold zone from the geosyncline. The neotectonic movement on the island is strong and the seismic activity is frequent. When the sea level was low during the Quaternary Ice Age, Taiwan Province Island was connected with the mainland. In the east, there are mountains. The main mountain ranges are Taitung Coast Mountain, Central Mountain, Yushan Mountain and Alishan Mountain. The highest peak of Yushan Mountain is 3997 meters above sea level. The whole island and mountains are northeast-northeast. Rivers develop along faults. The turbid water stream forms Tainan alluvial plain, the largest snail in Taiwan Province Province, and the fresh water stream forms Pingtung plain. The east coast of Taiwan Province Province is a fault coast with straight coastline and steep cliffs.

With an area of 34,380 square kilometers, Hainan Island is the second largest island in China. Hainan Island is high in the middle and low around, and its water system is radial. Platform plains account for 65% of the total area, and mountains and hills account for 35%. Wuzhishan, the main peak, is1.867m above sea level. In the early and middle Pleistocene, Hainan Island was separated from Leizhou Peninsula. Basalt is widely distributed in the northern part of Hainan Island, with complete craters. There are many typical sand dunes along the coast.

Other bedrock islands are distributed in the following areas:

① Coastal areas of Liaodong Peninsula. Changshan Archipelago is located in the southeast coast of Liaodong Peninsula, with more than 50 islands, which can be divided into three island groups: the northern Shicheng Archipelago, including Shicheng Island and Wang Jia Island; The southwest is Changshan Islands, including Changshan Island and Guanglu Island. To the south are the Waichangshan Islands, including the island and Zhangzi Island, of which Dachangshan Island is the largest and the highest, with an altitude of 388 meters. The bedrock that constitutes Changshan Islands is Sinian-Cambrian strata. Restricted by the checkerboard structure, the arrangement of islands has certain rules. In addition, there are some small islands scattered in Liaodong Bay.

(2) Coastal areas of Shandong Peninsula. Miaodao islands is located in the Bohai Strait, with more than 30 islands, which can be divided into three island groups: North Island Group includes South and North Huangcheng Island, and Qinxiao Island; Among the islands, there are rocky islands and alpine islands. The South Island Group consists of Changshan Island in the south and Changshan Island in the north, Xiaoheishan Island and Miaodao. South Changshan Island is the largest, with an area of 20.4 square kilometers. The islands are mainly composed of pre-Sinian metamorphic rocks, and the arrangement direction of the islands is consistent with the tectonic line, showing a NNE. In addition, there are Liu Gongdao, Tian Heng Island and Lingshan Island along the coast of Shandong Peninsula, and some land-bound islands such as Zhifu Island have also been developed.

(3) Coastal areas of Zhejiang and Fujian. Zhoushan Archipelago is the largest archipelago in China, consisting of 1339 islands, of which Zhoushan Island is the largest and the fourth largest island in China, with an area of 472 square kilometers, followed by Liuheng Island, Zhujiajian Island Island, Putuo Island, Daishan Island and Sijiao Island. The islands are the seaward extension of the Zhejiang-Fujian uplift belt, and are mainly composed of Mesozoic volcanic rocks. Zhejiang Province

④ South China coast. Wanshan Islands is located outside the Pearl River Estuary, with more than 150 islands, mainly including Hong Kong Island, Gaolan Island, Shangchuan Island, Xiachuan Island, Dangan Island and Wanshan Island. These islands are mainly composed of Yanshanian granite. In addition, the East China Sea, Weizhou Island and Sunset Island are scattered along the coast of South China.

⑤ Sea area near Taiwan Province Province. Penghu Islands, located in the south of Taiwan Province Strait, has 64 islands, which are divided into South Island Group and North Island Group. The North Island Group consists of Penghu, Fisherman and Baisha Island, forming Penghu Port. South Island Group consists of Bajiao Island, Huayu Island and Dayu Island. Penghu Island is a volcanic island mainly composed of basalt, surrounded by moraine reefs. Diaoyu Island, located about 65,438+000 nautical miles northeast of Taiwan Province Province, consists of Diaoyu Island, Huangwei Island and chiwei yu. In addition, there are Green Island and Lan Yu Island. Rivers in alluvial islands flow into the sea, and sediments often accumulate near the entrance, forming sand islands or alluvial islands.

Chongming Island is located at the mouth of the Yangtze River, covering an area of 65,438+0,083 square kilometers. It is the third largest island in China and the largest alluvial island in China. Dongsha and Xisha appeared at the mouth of the Yangtze River before the 7th century A.D., and then the sandbars drifted. Now Chongming Island was developed on the basis of16th century Changsha. Since 1950s, it has reinforced the dam and stabilized the collapse. At the same time, land reclamation has expanded the area of Chongming Island by 80%. Changxing and Hengsha Islands in the south of Chongming Island used to be a group of sandbars. 65,438+000 years ago, there were several scattered estuarine swamps. Reclamation began in the second half of the 65,438+09 century. In the past twenty or thirty years, it has gradually become the status quo to build dams and artificially promote siltation.

The sand island at the mouth of the Pearl River is either developed from the central beach at the mouth of the river, or blocked by bedrock island and accumulated sand under its protection. At first, the entrance of the Pearl River Estuary was wide, and sandbars were scattered all over the place. However, after reclamation and siltation, the entrance bundle was narrow, and gradually the Pearl River Delta with vertical and horizontal entrances was formed. Today, the sand island is still expanding, especially in Wanqingsha and Denglangsha.

The sand islands on the west coast of Taiwan Province Province and several sand islands outside the Zhuoshuixi and Zengwenxi deltas on the west coast of Taiwan Province Province are typical sand islands developed from estuarine sand mouths. Sand islands are distributed intermittently, and there is a lake between the interior and the land.

In addition, there are sand islands in the Luanhe River, the Yellow River and the Hanjiang River Delta.

Heixiazi Island is also an alluvial island. [Edit this paragraph] Coral reef island is located in the South China Sea in the south of Chinese mainland. They are scattered in the blue waves, and their distribution position is divided into four island groups from north to south, which are called Xisha Islands, zhongsha islands and Nansha Islands in Dongsha Group, and these island groups are also called South China Sea Islands. Among them, dongsha islands is the closest to Chinese mainland; Xisha Islands are in the middle; Zhongsha islands, near the southeast of Xisha, is an underwater atoll, and only Huangyan Island is exposed to the sea. Nansha Islands is located in the south, farthest from Chinese mainland. Except for Gaojianshi Island in Xisha Islands, all the South China Sea islands are coral islands.

There are many coral islands in the South China Sea, but their areas are very small. There are more than 200 islands and reefs in the South China Sea, with a total area of 12 square kilometers. There are different forms of existence, which are commensurate with islands, reefs, sand and beaches. Generally speaking, an island or sand-injecting continent with a large area exposed to the water during the spring tide is called an island; A reef with small exposed surface area is called an open reef; Exposing reefs at high tide and reefs at low tide are called reefs; What is submerged under water for a long time is called the sum of dark water; An underwater platform with a deep dive and flat surface is called a shoal. At present, there are 258 named islands, reefs, sands and beaches, including 35 islands, sandbars 13, reefs 13, 60 beaches and 3 beaches1.