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Transcript
Ocean Topography What is Ocean Topography? The shapes, patterns and physical configuration of the ocean surface. Side-scan sonar is used to create an image of large areas of the ocean floor. This tool is used for mapping the seabed. In conjunction with seafloor samples it is able to show differences in material and texture type of the seabed. Ocean Basin: Structures 1.Continental Margin: (near continent) Continental Shelf Continental Slope Continental Rise Submarine Canyons 2. Deep Ocean Basin: Abyssal Plains Oceanic Ridges Trenches Seamounts & Guyots Atolls 3. Others: Definitions Continental Shelf – An extension of the continent under water. There is a fairly abrupt drop off at the edge. Has hills, valleys, canyons and other features. This is very wide off of Atlantic Canada. Grand Banks & Scotian Shelf Continental Slope – The portion of the ocean bed between the edge of the continental shelf and the deepsea floor. The average angle displayed by the slope is about 5 degrees. Abyssal Plain – The largest portion of the earth’s sea bed. It is covered with a thick layer of sediment, beneath which is relatively dense basalt rock. Vast, empty and usually boring. Seamounts and Guyots • Both are underwater volcanic mountains that originated at a hotspot or along a ridge. • Guyots: have reached the surface of the ocean and have flat, eroded tops. Seamounts: have never reached the surface, so they have pointy tops. • Example : Hawaii Submarine Canyons V-shaped indentations in the continental shelf, usually ending in a fan shaped wedge of sediments. How do submarine canyons form? Fast moving currents and underwater landslides. The Gully Submarine canyon off Nova Scotia Marine Protected Area (MPA) because of the rare corals found there & a resident population of approximately 280 Northern Bottlenose Whales. The natural gas pipeline goes right by it…problems? Mid-Ocean Ridge A large underwater mountain chain. Part of a vast system extending some 40,000 miles through four of the world’s oceans. Caused by divergent plate boundaries. NS Mid-Atlantic Ridge Trench – Deep gap in ocean floor, formed by movement of plates. Eg: Mariana Trench is 10,668 meters deep Deepest areas of the Earth’s crust. 90% of trenches are found around the Pacific rim. Atolls A ring shaped island of coral reefs and coral debris. These often form over sinking inactive volcanoes. Major Sea Floor Structures H Major Sea Floor Structures A. Continental Slope B.Sea Mount D. Mid Ocean Ridge E. Island F. Continental Shelf C. Abyssal Plain G. Oceanic Trench H. Guyot