3 Continental MarginsContinental Margin – the zone of transition between a continent and the adjacent ocean basin floorIn the Atlantic Ocean, thick layers of undisturbed sediment cover the continental margin. This region has very little volcanic or earthquake activityIn the Pacific Ocean, oceanic crust is plunging beneath continental crust. This force results in a narrow continental margin that experiences both volcanic activity and earthquakes
5 Continental Shelves, Slopes, and Rises Continental Shelf – the gently sloping submerged surface extending from the shorelineContinental shelves contain important mineral deposits, large reservoirs of oil and natural gas, and huge sand and gravel depositsContinental Slope – the seaward edge of the continental shelfThe continental slope is a relatively narrow feature along the continental shelf
6 Continental Shelves, Slopes, and Rises Submarine Canyon – deep, steep-sided valleys cut into the continental slopeTurbidity Currents – occasional movements of dense, sediment-rich water down the continental slopeTurbidity currents are known to be an important factor in sediment transfer in the oceanContinental Rise – a gradual incline which merges with the steep continental margin, occurs in regions where trenches do not exist
8 Ocean Basin FloorOcean Basin Floor – area between the continental margin and the mid-ocean ridgeDeep-ocean trenches are long, narrow creases in the ocean floor that form the deepest parts of the oceanTrenches form at sites of plate convergence where one moving plate descends beneath another and plunges back into the mantleAbyssal Plains – deep, extremely flat features and are the most level places on Earth
9 Ocean Basin FloorThe sediments that make up abyssal plains are carried there by turbidity currents or deposited as a result of suspended sediments settlingSeamounts – the submerged volcanic peaks which dot the ocean floorOnce underwater volcanoes reach the surface, they form islandsAfter millions of years, the tops are eroded away and the once active islands sink back into the ocean, forming guyots
11 Mid-Ocean RidgesMid-Ocean Ridge – found near the center of most ocean basins; an interconnected system of underwater mountains that have developed on newly formed ocean crustSeafloor Spreading – occurs at divergent plate boundaries where two lithospheric plates are moving apartNew ocean floor is formed at mid-ocean ridges as magma rises between the diverging plates and coolsHydrothermal vents form along mid-ocean ridges and are zones where mineral-rich water escapes through cracks in oceanic crust into the surrounding cooler water
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