Deep Ocean Trenches

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Deep Ocean Trenches Essay, Research Paper

Deep Ocean Trench

A trench is any long, narrow, steep-sided depression in the ocean bottom. The deepest known depression of this kind is

the Mariana Trench, which lies east of the Mariana Islands in the western North Pacific Ocean . Of the Earth’s 20 major trenches, 17 are found in the Pacific. The only Atlantic trenches are the Puerto Rico Trench north of the Caribbean islands and the South Sandwich Trench east of Drake Passage between South America and Antarctica. The single major Indian Ocean trench is the Java Trench south of Indonesia.

The cross sections of trenches generally are V-shaped with steeper landward sides. Geophysical data provide important

clues concerning the origin of trenches. No abnormalities in the flow of internal Earth heat or variations in the Earth’s magnetic

field occur at trenches. Precision measurements reveal that the force of gravity generally is lower than normal. Small quantities of brown or red clay, which are signs of organic remains, volcanic ash and lapilli, and coarse, graded layers are found in the trench. Large amounts of remains cannot build up because they either are dragged into the Earth’s interior or are distorted into folded masses and molded into new material of the continents.

Deep trench in the sea bed indicating the presence of a destructive margin (produced by the movements of plate tectonics). The dragging downwards of one plate of the lithosphere beneath another means that the ocean floor is pulled down. Ocean trenches are found around the edge of the Pacific Ocean and the northeastern Indian Ocean; minor ones occur in the Caribbean and near the Falkland Islands.

Ocean trenches represent the deepest parts of the ocean floor, the deepest being the Mariana Trench which has a depth of

11,034 m/36,201 ft. At depths of below 6 km/3.6 mi there is no light and very high pressure; ocean trenches are inhabited by

crustaceans, coelenterates (for example, sea anemones), polychaetes (a type of worm), molluscs, and echinoderms.

Mariana Trench (depression in the floor of the Pacific Ocean), the deepest seafloor depression in the world. It is located just east of the Mariana Islands in the western part of the ocean basin. The Mariana Trench is an arc-shaped valley extending generally northeast to southwest for about 2500 km ;its average width is about 70 km. The Mariana is one of many deepwater ocean trenches formed by the geologic process of subduction near its southwestern extremity, about 338 km southwest of the island of Guam, is the deepest point on earth. This point, the Challenger Deep, is estimated to be 11,033 m deep. The Challenger Deep was named after HMS Challenger II, the vessel of those who discovered the point in 1948.

In January 1960 Swiss ocean engineer Jacques Piccard and United States Navy Lieutenant Donald Walsh descended into the Challenger Deep in the French-built, U.S. Navy-operated bathyscaphe Trieste. Piccard whose father, Auguste Piccard, invented the bathyscaphe and Walsh took the Trieste to a depth of 10,915 m, the deepest descent in history.

Caribbean Sea, (arm of the Atlantic Ocean), partially enclosed on the north and east by the islands of the West Indies, and bounded on the south by South America and Panama, and on the west by Central America. The name of the sea is derived from the Carib people, who inhabited the area when Spanish explorers arrived there in the 15th century. The Caribbean is approximately 2415 km long east and west and between about 640 and 1450 km wide. It has an area of about 1,942,500 sq km. At the northwestern it is connected with the Gulf of Mexico by the Yucat n Channel, (a passage about 193 km wide between Cuba and the Yucat n Peninsula). The Windward Passage between Cuba and Haiti is a major shipping route between the United States and the Panama Canal. Many gulfs and bays indent the coastline of South America, notably the Gulf of Venezuela, which carries tidal waters to Lake Maracaibo in Venezuela. With a few exceptions the entire Caribbean Basin is more than 1830 m (more than 6000 ft) deep. Large areas of the sea exceed 3660 m (12,000 ft) in depth; the greatest depth measured thus far is Cayman Trench (7535 m/24,720 ft) between Jamaica and Cayman Islands. Navigation is open and clear, making the Caribbean a major trade route for Latin American countries. The main oceanic current in the Caribbean Sea is an extension of the North Equatorial and South Equatorial currents, which enter the sea at the southeastern extremity and flow in a generally northwestern direction. A popular resort area, the Caribbean Sea is noted for its mild tropical climate.

Trenches exist in the ocean floor running beside the continents surrounding the Pacific Ocean. How does expansion explain these? Certain channels discovered on lake bottoms appear to be created by the roots of ice floats, so heavy that they deeply scraped the bottom as they moved. It is prudent to assume that the mountain ranges around the Pacific Ocean also have roots. It appears that an expulsion event in this area has forced the surrounding land up into mountains through a side thrust. The mountain roots may have prevented the magma to fill in the areas — the trenches — left along the shifted land. As well, quick cooling after the event, caused by water with high salt content (after expulsion the ocean water would cover the continents up to 12,000 feet, according to numerous sources) made the top magma too sluggish to fill up to the general level, thus leaving the trenches empty. If subduction did occur, there would be no trenches. They would be filled with the sedimentary debris of the ocean floor (Carey).

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