Oceans

The earth’s oceans make up more than 70% of its total surface area. More than half of this area of salt water is more than 9000 feet deep!

There are actually just three distinctly separate oceans in the world today; the World Ocean, the Black Ocean and the Caspian Sea. The largest ocean on earth is the World Ocean, measuring in at an immense 361 million square kilometers. The World Ocean is continentally divided into five smaller parts, which include the Atlantic Ocean, the Pacific Ocean, the Indian Ocean, the Arctic Ocean and the Antarctic Ocean. Smaller portions of these oceans are typically classified as either seas, gulfs or straits.

The Mediterranean Sea unofficially became the world’s fourth ocean when the sea’s only outlet to the World Ocean, the Strait of Gibraltar, was closed due to the movement of the African continent.

The oceans of the world are home to the vast majority of the plant and animal species on earth, millions of which have yet to be discovered by man.

Source :www.livescience.com

Atlantic Ocean

The second largest of the world's four oceans is located between the continents of North and South America, Europe, Africa and Antarctica. It is also the youngest of the oceans and probably did not exist 100 million years ago. It covers about 20% of the Earth's surface, with an area of 82,362,000 sq km. It has an average depth of 3,926 m. The deepest spot is the Puerto Rico Trench which is 8,381 m. Other notable trenches in the Atlantic are the South Sandwich Trench (8,428 m) and the Romanche Trench (7,760 m). The farthest distance across the Atlantic occurs between the United States and North Africa at 4,830 km. The shortest distance is between Senegal and Brazil at 2,575 km. The S shape of the Atlantic ocean results in two distinct basins with their own circulation systems. In the Northern Atlantic currents flow in a clockwise direction, while in the Southern Atlantic currents flow in a counterclockwise direction. use of the c.

Arctic Ocean

This, the smallest of the four oceans, lies almost entirely above the Arctic Circle (66.5? N). Nearly surrounded by land, its only outlets are the Bering Strait between Alaska and Russia, Davis Strait between Greenland and Canada, and Denmark Strait and the Norwegian Sea between Greenland and Europe. The Arctic Ocean has an area of 14,090,000 sq km and an average depth of 3,658 m off of the continental shelf. The lowest point is Fram Basin which is 4,665 m deep. The Artic Ocean has the widest continental shelf of all the oceans.

The Arctic Ocean is divided into two basins, the Eurasian Basin, and the North American Basin, by the Lomonosov Ridge. There are also submarine ridges between the Arctic and Atlantic Oceans. This results in a large stagnant pool of cold water at the bottom of the Arctic Ocean, since land and submarine ridges block water from flowing out. The main current in the Arctic Ocean is the East Greenland current. This current is strong due to the number of rivers that flow into the Arctic Sea, the low rate of evaporation, and the land and submarine ridges surrounding the ocean. Two other weak currents flow out of the Arctic Ocean, the Labrador Current which runs through Smith Sound and Baffin Bay, and one that runs out of the Bering Straight. There is also a circular current in the Arctic Basin which is created by water deflecting off of Northern Greenland.

The central part of the ocean is permanently covered in about ten feet of ice. Pressure ridges in the ice can sometimes reach three times that height. In the summer months, the icepack is surrounded by water and free-floating. During the winter, the icepack expands to nearly twice its summer area, reaching the land on all sides. Due to the extreme temperatures people thought that non-oceanic life didn't exist in the Arctic.

Indian Ocean

The Indian Ocean is the third largest ocean. It is surrounded by southern Asia, the Arabian Peninsula, Africa, the Malay Peninsula, the Sunda Islands, Australia and Antartica. The 20? E meridian divides it from the Atlantic and the 147? E meridian divides it from the Pacific below Australia. The Continental Shelves of the Indian Ocean are narrow compared to those of the other oceans. The Indian Ocean has an area of 73,556,000 sq km. At its widest point, between Southern Africa and Australia, it is nearly 10,000 km wide.

The Indian Ocean is divided into three major sections by the Mid-Oceanic Ridge which runs from Asia to Antarctica in an upside down Y shape. The sections are, the African, the Antardis, and the Australasian. The Mid-Oceanic Ridge rises to an average of 3,000 m, with some of its peaks rising to form islands. Many deep sea basins are enclosed by the Mid-Oceanic Ridge. The deepest among these is the Java Trench which reaches a depth of 7,450 m.

The Indian Ocean has two water circulation systems. The northern system circulates clockwise except during the winter monsoon season when the currents are reversed. Low atmospheric pressure over southwest Asia from hot, rising, summer air results in the southwest monsoon and clockwise winds and currents. High pressure over northern Asia from cold, falling, winter air results in the northeast monsoon and counterclockwise winds and currents. In the southern portion of the Indian Ocean, currents travel in a counterclockwise direction.

The main importance of the Indian Ocean has been as a trade route between Africa and Asia. Petroleum, extracted mainly from the Persian Gulf area is also important. Relatively warm surface temperatures keep the growth of phytoplankton low, which limits ocean life. Fishing is only done at the subsistence level.

Pacific Ocean

Located between the continents of North America, South America, Asia, Antarctica and Australia the Pacific Ocean is the largest of the world's four oceans. It covers approximately one-third of the surface of the earth, more surface area than all the continents combined. It is commonly divided at the Equator into the North Pacific and the South Pacific. The southern portion is dotted with thousands of small volcanic islands and coral atolls (i.e. Fuji, Tahiti). The western rim is lined with large lines of volcanic islands (i.e. Japan, the Philippines). To the north lies the Aleutian Islands- another line of volcanoes- and the Bering Sea. The eastern coast is marked by the Americas.

The tallest mountain in the world is found in the Pacific Ocean: Mauna Kea of the Hawaiian Islands. From the base of the volcano on the ocean floor it is 33,476 feet. That is 4,441 feet higher than Mount Everest. The deepest trench in the world is also housed in the waters of the Pacific. At 36,198 feet deep, the Mariana Trench would submerge Mount Everest with 1.4 miles of water above to spare.

The volcanic regions on the West, North and East rims collectively are known as the Ring of Fire. These areas of volcanic activity are caused by seduction of tectonic plates. In addition to the threat of volcanic eruption, earthquakes are a common occurrence along the Ring of Fire. Many of the earthquakes are among the strongest in the world.

With the threat of earthquakes comes the threat of tsunamis (also incorrectly called tidal waves). These giant waves can travel at speeds of up to 500 miles per hour, appearing as little more than a small wave in the deep sea. Often these waves go undetected by ships they pass beneath.

In the inner regions of the ocean, volcanic islands can also be found. These are either formed over magma tic hot spots or along oceanic rift zones. The Hawaiian chain is over a hot spot. Only the large island of Hawaii is volcanically active. The rest of the islands have moved past the hot spot and drifted off in a north by northwest direction. Remnants of former Hawaiian Islands can be seen as far away as the Aleutian Islands. Much eroded and millions of years old, they are known as the Emperor Seamounts. The oldest of the seamounts are around 70 million years old.

Source : http://www.mnsu.edu