| Deeps |
| A 'deep' is a deep underwater valley. Sometimes the word 'deep' is used to describe the underwater canyons which cut across the continental shelf. In sonar images of the seafloor, these look just like rivers on land. Submarine canyons like these are thought to have formed by rivers but were submerged by sea-level rise.
Simulated perspective view of the Pacific Floor looking northeastward along the Mariana Trench. Generally though, deeps are deep-sea or 'oceanic' trenches. They are narrow, have steep sides, and depths of about 7,000 to 11,000 metres (19,000 to 30,000 feet). The deepest oceanic trench is the Pacific Ocean's Mariana Trench. Northwest of the Philippines is part of a very long deep trench which runs along the east coast of Japan toward Kamchatka in the northern Pacific. The Mariana Trench's deepest point - called Challenger Deep - lies 11,034 metres (30,000 feet) below sea level.
Submarine canyon in the sea floor off Monterey Bay, California. Running parallel to island arcs and mountain ranges, most of the Earth's deep trenches are found in the Pacific, having formed at the edge of the Pacific Plate. Oceanic trenches are formed by subduction, where one of the Earth's tectonic plates moves underneath another. For example, off the coast of South America the Pacific Plate is being pushed beneath the South American Plate. It is bent downwards and becomes incorporated into the Earth's crust. As the plate is drawn downward, it takes material with it, producing a very deep submarine valley. In the Atlantic Ocean deeps are found in parallel with island arcs: in the Caribbean there is the Puerto Rico Trench, and in the Southern Ocean is the South Sandwich Trench. These are associated with the subduction of the smaller Caribbean and Scotia plates. |
| Links | ||
|
