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OCEAN TOPOGRAPHY FEATURES OF THE OCEAN FLOOR What do you think the ocean floor looks like? It actually looks like this… It has the same mountains, valleys, plains, trenches, and pits that we find on land. Features of the Ocean Floor • Continental shelf: surrounds the continent as a shallow extension of continental crust extending out to the continental slope. Features of the Ocean Floor • Continental slope: steep drop-off at the end of the continental shelf that connects the continental crust to the oceanic crust. Because variations in ocean depths are often noticeable, that means the divisions of the lithosphere are commonly seen. Continental Shelf Continental Slope Features of the Ocean Floor • Continental rise: area of accumulated sediments that marks the absolute boundary between the continental crust and the oceanic crust. Features of the Ocean Floor • Abyssal plain: the deepest part of the ocean. Features of the Ocean Crust Abyssal plains are the flattest areas on earth Features of the Ocean Crust • Seamounts: isolated volcanic mountains which erupt under the ocean. Large ones are islands. • Guyots: are extinct volcanoes with eroded flat tops. Features of the Ocean Crust • Ocean ridges: are long mountain ranges formed when magma seeps or erupts between pieces of the Earth’s crust (tectonic plates). Features of the Ocean Crust The ocean ridges form a mountain chain that extends 40,000 miles through all the oceans. Features of the Ocean Crust • Trenches: are the deepest part of the ocean. Trenches form where one tectonic plate is forced under another plate. Earth’s HIGHEST mountains, DEEPEST valleys, and FLATTEST plains are all on the ocean floor! The highest mountain on Earth is Mauna Kea, Hawaii, a seamount. The average depth of the ocean is around 12,200 feet or 3,730m. The Trieste and the Mariana Trench Exploration The Mariana Trench In 1960, the US Navy sent down a small submersible (minisub) that sat on the bottom at 35,838 ft. (10,923 m.) The sailors had 7 miles of water over their heads! For Help: AMSTI-GLOBE www.amsti.org/globe The GLOBE Program www.globe.gov Jerry Cobbs AMSTI-GLOBE Lynn Vaughan AMSTI-GLOBE Technology Specialist [email protected] Resource Specialist [email protected] Robin Nelson AMSTI-GLOBE Administrator [email protected]