Ocean LandformsOcean Landforms

The Ocean FloorThe Ocean Floor

Revealing the Ocean FloorRevealing the Ocean Floor

•If you could travel to the bottom If you could travel to the bottom of the ocean, you would see the of the ocean, you would see the world’s largest mountain chain world’s largest mountain chain and canyons much deeper than and canyons much deeper than the Grand Canyon.the Grand Canyon.

•How can the ocean floor be How can the ocean floor be mapped?mapped?

Revealing the Ocean FloorRevealing the Ocean FloorSonarSonar (stands for Sound (stands for Sound

Navigation and Ranging)Navigation and Ranging) Invented in the 1920s Invented in the 1920s Primary instrument for Primary instrument for measuring depth measuring depth

Reflects sound from ocean Reflects sound from ocean floor floor

Revealing the Ocean FloorRevealing the Ocean Floor Use of satellites for mappingUse of satellites for mapping

Employs satellites equipped with Employs satellites equipped with radar altimetersradar altimeters

Scientists are able to measure the Scientists are able to measure the direction and speed of ocean direction and speed of ocean currents.currents.

Measure the different heights of the Measure the different heights of the ocean surface to make maps of ocean ocean surface to make maps of ocean floor.floor.

Can cover more territory using Can cover more territory using satellites rather than ship sonar. satellites rather than ship sonar.

Continents EdgeContinents Edge•Called the continental marginCalled the continental margin

•Three parts Three parts –Continental shelfContinental shelf–Continental slopeContinental slope–Continental riseContinental rise

Continental ShelfContinental Shelf•Begins at the shorelineBegins at the shoreline•Continues until it begins to Continues until it begins to slope more steeply slope more steeply downwarddownward

•Depth can reach 200 metersDepth can reach 200 meters•This is what you walk on at This is what you walk on at the beach.the beach.

Continental SlopeContinental Slope•Begins at the edge of Begins at the edge of shelf and continues to shelf and continues to flattest part of ocean flattest part of ocean floorfloor

•Depth ranges from 200 Depth ranges from 200 meters to 4000 metersmeters to 4000 meters

•Continent ends at Continent ends at bottom of continental bottom of continental slopeslope

Continental RiseContinental Rise•Slopes more gentlySlopes more gently

•Made of sediments that Made of sediments that come off the shelfcome off the shelf

•Like underwater Like underwater avalanches of avalanches of sediment and sediment and waterwater

Abyssal PlainAbyssal Plain

•Broad, flat portion of the Broad, flat portion of the deep-ocean floor.deep-ocean floor.

•Covered with mud and Covered with mud and remains of marine remains of marine organisms.organisms.

•Average depth is 4,000 Average depth is 4,000 metersmeters

Mid-Ocean RidgesMid-Ocean Ridges

•Mountain chains formed where Mountain chains formed where tectonic plates pull apart.tectonic plates pull apart.

•Pulling motion creates cracks Pulling motion creates cracks in the crust called rift zones.in the crust called rift zones.

•Rift Valley forms between Rift Valley forms between mountains in the mid-ocean mountains in the mid-ocean ridge.ridge.

SeamountsSeamounts•Individual mountains of Individual mountains of volcanic material.volcanic material.

•If a seamount builds up If a seamount builds up above sea level, it above sea level, it becomes an island.becomes an island.

•A guyot is a flat-topped A guyot is a flat-topped seamount.seamount.

Actual footage of an erupting underwater volcano.

Ocean TrenchOcean Trench•Seemingly bottomless Seemingly bottomless cracks in the ocean basin.cracks in the ocean basin.

•Formed where one oceanic Formed where one oceanic plate is forced underneath plate is forced underneath another plate.another plate.

•Most famous: Most famous: Marianas TrenchMarianas Trench