* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project
Download Features of the Ocean Basins
Document related concepts
The Ocean Basins Physical Oceanography Features of the Ocean Basins • Continental margin: portion of ocean made up of continental crust Features of the Ocean Basins • continental shelf: flat part of continental margin covered by shallow ocean water Formed by changes in sea level Avg depth = 60 m Shelf • Relatively shallow • 0 – 200 m • Relatively flat with a gradient of 2 m drop per kilometre Features of the Ocean Basins • continental slope: boundary between continental crust and oceanic crust - The average angle displayed by the slope is about 5 degrees. Features of the Ocean Basins • submarine canyons: deep, v-shaped valley that cuts through shelf & slope Features of the Ocean Basins • continental rise: wedge of sediments that separates slope from ocean floor Features of the Ocean Basins • abyssal plain (floor): very flat areas at depths of 3-5 km Features of the Ocean Basins • mid-ocean ridge: mountain range on ocean floor due to seafloor spreading Features of the Ocean Basins • trench: deep narrow valleys along the edges of subduction zones in the ocean floor; 90% of trenches are found around the Pacific rim. Marianas Trench in Pacific ocean is the deepest point on earth - 10,668 meters Bathymetric Charts – show the contours and depths of the seafloor topography General Slope Features • Sharp break from the shelf • Angle is gentle, averaging less than 5 degrees • Continues to a depth of 3600 m • Often carved by deep canyons - Hudson Canyon is famous in N.A. Submarine Canyons • V-shaped • Hudson Canyon steeper than the Grand Canyon • Form deep sea fans from sediments • Originated from rivers during ice ages The Gully! Submarine canyon off Nova Scotia • • Marine protected area because of the rare corals found there • The natural gas pipeline goes right by it…problems? The Gully Turbidity currents • Turbidity currents are caused by the slumping of sediments from the continental slope. • can travel at over 55 km/h • can spread 700 km+ • Can damage underwater pipelines, transatlantic cables Rise • Slope about ½ degree toward the abyssal plain • Sediment deposition from continent • Range from 100 to 1000 km in width • Only occur along passive margins, often off the mouth of large rivers Another look Features of the Ocean Basins • seamount: underwater volcanic mountain (some more than 1000 m high) • Features of the Ocean Basins Atolls A ring shaped island of coral reefs and coral debris. These often form over sinking inactive volcanoes. Features of the Ocean Basins • coral reef: limestone structures containing shells of animals that surround volcanic islands Features of the Ocean Basins • guyot: a flat-topped submerged seamount due to erosion Features of the Ocean Basins • rift valley: deep crevice in between mountain ranges Which coast has the wider shelf?