Wednesday, January 5, 2011

Oceans

Oceans cover 71 percent of the Earth’s surface. Since the early Earth was probably too hot for liquid water to condense, all the water in today’s oceans probably came out of volcanoes and from falling comets. Today, the oceans average more than 3500 meter in depth and the deepest part, the Mariana Trench in the Pacific, goes down 11034 meter. The shallow shelves around many continents are, geologically, extensions of those continents. They support a wide range of marine life as well as concealing extensive oil deposits.




 They are bounded by the continental slope, down which sediments fall, producing graded beds of coarse to fine sediments fall, producing graded beds of coarse to fine sediment called turbidities.


The surface of the ocean provides an important source of moisture and warmth which controls the Earth’s climate. The deep ocean floor is relatively unexplored. It has been mapped by sonar to reveal ridges, canyons, volcanoes and sea mounts. Deep sea fishing and occasional visits by submersibles exploring the cold, dark and crushing pressure of the ocean deeps provide glimpses of bizarre life forms- giant invertebrates, fish that carry their own lanterns and entire communities that never see the Sun, depending for nutrients on hot submarine springs.