The Seafloor (69)

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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
  Earths interior forms new ocean crust.
• New ocean floor forms along mid-ocean ridges as
  lava erupts through cracks in Earths 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?vwP380-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?vXotF9fzo4Vo

• 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
  producers?are 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?vwbNeIn3vVKM

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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 Earths 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