11'1 Ocean Basins

1
11.1 Ocean Basins

• The surface of the ocean floor is as varied as
  the land.
• The five major oceans, from largest to smallest,
  are
• the Pacific
• the Atlantic
• the Indian
• the Southern
• the Arctic
• The low points in the oceans are called basins.
• Oceans are vital to life, as they control
  temperature, create weather patterns and provide
• water for water cycles.

See page 402
2
The Origin of Ocean Water

• Oceans have filled over hundreds of millions of
  years.
• Scientists believe the oceans are more than 3
  billion years old.
• Water may have originally been released from
  volcanic eruptions, or arrived on Earth via icy
  comets.

See page 404
3
Features of the Ocean Floor

• Although the word basin makes it sound flat,
  many features found on land, including mountain
  ranges, valleys, flat plains,
• canyons, and
• volcanoes also exist
• on the ocean floor.
• The basin is the large,
• flat middle part, while the
• continental margins are
• the edges rising up to
• the land.

The ocean topography of the Caribbean
See pages 404 - 405
4
Ocean Basins

• The largest changes to the ocean basin occur
  through the movement of tectonic plates, although
  there is also erosion via storms, earthquakes and
  icebergs.
• Mid-ocean ridges occur where new rock is forced
  up, and ocean floor spreads outward.
• The Mid-Atlantic Ridge is the largest example on
  Earth
• The Juan de Fuca plate lies
• 200 km off Vancouver Island
• A trench forms when
• the dense oceanic plates
• run into, and slide under,
• the continental plates.

See pages 406 - 407
5
Ocean Basins (continued)

• Abyssal plains are the pieces of oceanic crust
  between a spreading mid-ocean ridge and the
  trench it disappears into.
• These make up 30 of the Atlantic sea floor, and
  65 of the Pacific seafloor.
• Abyssal plains can be
• covered in 1 km of sediments
• Seamounts are old
• volcanic mountains
• found on abyssal plains.
• The Hawaiian Islands
• are an example.

See page 407
6
Continental Margins

• Continental margins are part of continental
  plates.
• Continental margins are made up of a continental
  shelf (averaging 80 km wide) and a
• continental slope down to the
• oceanic plate.
• Continental shelves were above
• water during the last ice age.
• Turbidity currents are slides on
• the slopes, and can create large
• submarine canyons in the shelf.

See pages 407 - 409
Take the Section 11.1 Quiz