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The Ocean Floor 1 Description of 2 3 Atlantic Ocean Continental Shelf 4 Typical Oceanic Profile continental margin ocean basin coastal region continental shelf oceanic ridge Slope Abyssal plain Depth > 4000 m 5 The Continental Margin continental margin coastal region continental shelf ocean basin shelf break oceanic ridge Slope Abyssal plain continental rise > 4000 m 6 Continental Margin Fig. 2-3a 7 Continental Shelf 8 Coastal Region coastal region • Includes: •beaches •estuaries • lagoons • marshes • deltas Most important region to humans And marine birds and mammals 9 Beaches 10 Typical Salt Marsh 11 Mangrove Swamp 12 Continental Shelf continental margin • Definition: shallow part of ocean bottom next to coastline continental shelf Slope continental rise • SLOPE is less than 0.1° angle 13 Most exposed in Pleistocene 14 Continental Slope and Rise Slope Continental rise • Slope is 1° to 6° • Rise: less than 1° • Slope & rise can be cut by submarine canyons 15 Overlapping fans=cones See Fig. 2-3a 16 San Lucas Submarine Canyon 2 meters 17 Typical Oceanic Profile continental margin ocean basin shelf break continental shelf oceanic ridge Slope Abyssal plain continental rise 18 Ocean Basins Are the deep flat areas of the ocean 19 Deep Ocean Basins Fig. 2-3b 20 Seamounts and Guyots- undersea mountains that rise more than 1 km from the seafloor SEAMOUNT Top is rounded May rise above the surface and form an island GUYOT Top flattened by waves 21 3 Major Oceanic Ridges Mid-Atlantic Ridge E. Pacific Rise Carlsberg Ridge 22 Characteristics of Oceanic Mountain Ridges • Total length: 60,000 km • Present in all oceans • Between 1,000 and 4,000 km wide • mountains are 2 - 4 km high •The largest is the Mid Atlantic Ridge half that separatat 23 Mid-Ocean Ridges Fig. 2-3c 24 Mid-Atlantic Ridge Shallow valleys 20 - 30 km wide with high volcanic activity 25 Oceanic Trenches • 31 in the world; • Deep; U or V shaped •These form the deepest places on Earth • Max 130 km wide, 1500 km long 26 Distribution of Trenches 27 Kurile 10,500 m Mariana 11,000 m Tonga 10,880 m 3 _________ trenches 28 29 Island Arcs are associated with volcanoes 30 shelf Ridge shelf slope slope hills Atlantic Ocean plains island arc seamounts slope trench ridge plain Pacific Ocean 31 HYDROTHERMAL VENTS or BLACK SMOKERS • At a hydrothermal vent, sea water that has sunken into cracks in the ocean crust and been heated (sometimes to over 180 degrees!) by the interior of the earth escapes through crust cracks back into the ocean. • http://www.pmel.noaa.g ov/vents/nemo/explorer /multimedia.html 32 • The superheated water beneath the oceanic crust often dissolves minerals from nearby rocks. • The precipitating minerals often give vent fluids different colored “smoky” appearances. 33 • As hot vent fluids meet cold ocean water, minerals precipitate (fall) out of vent fluids. • The precipitating minerals form “chimneys” and other formations on the sea floor. 34 Hydrothermal Vent Sites 35
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