the seafloor (69). contiental shelf ocean basins, which are low areas of earth that are filled with...
TRANSCRIPT
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The Seafloor (69)
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Contiental Shelf
• Ocean basins, which are low areas of Earth that are filled with water, have many different features.
• The continental shelf is the gradually sloping end of a continent that extends under the ocean as deep as 350 meters.
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• Beyond the shelf, the ocean floor drops more steeply, forming the continental slope.
• The continental slope extends from the outer edge of the continental shelf down to the ocean floor.
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• Beyond the continental slope lie the trenches, valleys, plains, mountains, and ridges of the ocean basin.
• In the deep ocean, sediment, derived mostly from land, settles constantly on the ocean floor.
• These deposits fill in valleys and create flat seafloor areas called abyssal plains.
• Some areas of abyssal plains have small hills and seamounts.
• Seamounts are underwater, inactive volcanic peaks.
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Ridges and Trenches
• Mid-ocean ridges can be found at the bottom of all ocean basins. They form a continuous underwater ridge approximately 70,000 km long.
• A mid-ocean ridge is the area in an ocean basin where new ocean floor is formed
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• As crustal plates move, the ocean floor changes.
• When ocean plates separate, hot magma from Earth’s interior forms new ocean crust.
• New ocean floor forms along mid-ocean ridges as lava erupts through cracks in Earth’s crust.
• When the lava hits the water, it cools quickly into solid rock, forming new seafloor.
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Subduction Zone• On the ocean floor,
subduction zones are marked by deep ocean trenches.
• A trench is a long, narrow, steep-sided depression where one crustal plate sinks beneath another.
• http://www.youtube.com/watch?v=wP380-Iaoos
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Life in the Ocean• Marine organisms such as plants and algae use
energy from the Sun to build their tissues and produce their own food.
• This process of making food is called photosynthesis.
• Chemosynthesis involves using sulfur or nitrogen compounds as an energy source, instead of light from the Sun, to produce food.
• Bacteria that perform chemosynthesis using sulfur compounds live along mid-ocean ridges near hydrothermal vents where no light is available.
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http://www.youtube.com/watch?v=XotF9fzo4Vo
• Marine organisms that drift with the currents are called plankton.
• Plankton range from microscopic algae and animals to organisms as large as jellyfish.
• Most phytoplankton plankton that are producersare one-celled organisms that float in the upper layers of the ocean where light needed for photosynthesis is available.
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Plankton
• One abundant form of phytoplankton is a once-celled organism called a diatom.
• Diatoms and other phytoplankton are the source of food for zooplankton, animals that drift with ocean currents.
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Coral Reefs• Corals thrive in clear, warm water that receives a
lot of sunlight.• Each coral animal builds a hard capsule around
its body from the calcium it removes from seawater.
• Each capsule is cemented to others to form a large colony called a reef.
• A reef is a rigid, wave-resistant structure built by corals from skeletal material.
• https://www.youtube.com/watch?v=wbNeIn3vVKM
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• What is the continental shelf?
• The continental shelf is the gradually sloping end of a continent that extends under the ocean.
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• Which structure extends from the outer edge of the continental shelf to the ocean floor?– A. abyssal plain– B. continental slope– C. oceanic trench– D. seamount
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• What is the area in an ocean basin where new ocean floor is forming?
• New seafloor forms at mid-ocean ridges as lava erupts through cracks in Earth’s crust.
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• Which process involves using sulfur or
• nitrogen compounds as an energy source to produce food?– A. chemosynthesis– B. nitrosynthesis– C. photosynthesis– D. sulfurosynthesis