The Ocean Basins Physical Oceanography
Plate Tectonics Results in Sea Floor Features
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 Photic Zone Relatively flat with a gradient of 2 m drop per km
Features of the Ocean Basins The average angle displayed by the slope is about 5 degrees.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 90% of trenches are found around the Pacific rim.trench: deep narrow valleys along the edges of subduction zones in the ocean floor; 90% of trenches are found around the Pacific rim. 10,668 meters 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 of slope 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
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) Still growing and may become an island
Atolls Features of the Ocean Basins Atolls A ring shaped island of coral reefs and coral debris. These often form over sinking inactive volcanoes.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 This is what old islands turn into
Features of the Ocean Basins rift valley: deep crevice in between mountain ranges
Which coast has the wider shelf?