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The Greenland
In July, 1834, Darwin went for inspection along with the Bigger ship. During the inspection, different phenomena kept refreshing Darwin’s understanding of the earth. At Verde of San Diego, he found that there was a strip of white settled layer with bare coral and shell fragments high up in a volcanic rock cliff, this discovery brought about brand new angle of view for him on thinking about the island geologic history. In the next journey, Darwin had more discoveries. In Patagonia, he saw stratums mixed with roundstones and shells spreading along the level up. After the chile earthquake, he found the earthquake elevated the land, piling the mussel bed base on the tide. High on the Andes, he found fossil trees standing on a beach, with masses of seashells scattering around. After exploring the Cocos (keeling) islands, he inferred that these coral islands were formed above the submerged volcanoes.
The Maldives islands
The Maldives islands include 26 atolls and 1192 coral islands. Coral islands are islands piled up with the remains of corals, spreading mostly in the tropical ocean.
There are mainly two forming processes of the coral islands, one is the hunching of coral reefs, another one is the growth in length of the coral reefs. The hunching of coral reefs means theoceanic crust movement pushing the coral reefs out of the sea surface; the growth in length of the coral reefs means that in the oceanic cyclonic storm, rocks, macadam and sands are driven by the storm and gradually pile on the top of the coral reefs. Under the combined action of seawater and storm, they are fixed firmly with other concretionary materials to form the islands. Then the consolidation is strengthened by the powerful roots of the island plants.
The Fiji islands
The Fiji islands locate in the south Pacific ocean, with 332 island, most of them are volcanic islands surrounded by coral reefs. Most of Fiji’s islands were formed under the volcanic movements of 1500 thousand years ago, these volcanoes has stopped eruption long time ago. In geology (sometimes archaeology), “ high island” is always used to represent volcano island, which is named through its forming reason, means the island piled by the eruptive materials. While the islands caused by the uplifting of the coral reefs are called “low island”. The altitudes of most high islands are just one or two meters, always classified into “islet or rock”. While the low islands, such as Nauru and Panama, are always one or two hundred meters in altitude.
The high islands and low islands are always close to each other, especially in the south Pacific ocean, the low islands are always surrounding the high islands.
The Chongming Island
The Chongming island locates at China’s Yangtze river’s estuary, the area of the whole island is 1225 square kilometers. It’s the largest river alluvial island in the world, more than 90% of the land elevation (taking Wusong’ elevation of 0 meter as reference) on this island are from 3.21 to 4.20 meters. The Chongming island heaved out in the first year of Tang Wude( the year of 618), they were two small shoals in the river at beginning, called Dongsha and Xisha. In Song Dynasty, Yaoliusha, Majiabang, Pingyangsha and other shoals formed. Then many shoals leaned on the north one by one or rushed away by water, the Dongsha and Xisha were also rushed away in succession. Then Changsha appeared, today’s Chongming island was accumulated by the Changsha. As the Changsha carried lots of sediments, the Chongming island extends to the East China Sea at a speed of 143 meters per year.