Topography of the Ocean Floor

Continental Margin Includes: Continental Shelf Continental Slope Continental Rise Submarine Canyon

Continental Shelf Gently sloping part of the continent that is underwater. The Atlantic shelves are wide b/c they are passive margins. The Pacific shelves are narrow b/c they are active margins.

Continental Slope Continental Rise The edge of the cont. shelf, which slopes steeply to the ocean floor. “Active” plate boundaries = steeper slopes “Passive” plate boundaries = not as steep Continental Rise A mound of sediments at the bottom of the cont. slope.

Turbidity Currents – An underwater mudslide of sediments down the cont Turbidity Currents – An underwater mudslide of sediments down the cont. slope. Submarine Canyon – A deep, eroded area on the cont. slope carved out by turbidity currents.

OCEAN BASIN The part of the ocean that is oceanic crust. Made primarily of basalt.

Abyssal Plain The flattest areas on the planet. Covered by a layer of sediment about 1 km thick.

Mid-Ocean Ridges The largest tectonic feature on the earth. Associated with rift valleys (divergent plate boundaries). Where new seafloor is being formed.

Seamounts Underwater mountains, usually volcanic. The biggest mtn. on earth is Mauna Loa (Hawaii). Build-up underwater (over a hot spot), & when they break the ocean surface they turn into islands. Start to “deflate” & sink as the crust carries it away from the hot spot.

Atolls When a seamount becomes an island, coral reefs typically form around the island. When the island deflates back underwater & the coral reef is still intact, it becomes an atoll.

Guyots Flat-topped seamounts, formed from being weathered flat when above sea level. Guyots are the “deflated” seamounts that have subsided back underwater (the coral reef is no longer present). Guyot Seamount/Volcanic Island

Trenches Long, narrow, deep depression of the sea floor caused by __________. (deepest place on Earth- ________ Trench - 7 miles deep). subduction Marianas