The Earths OceansPart I

1
The Earths Oceans-Part I

• The Water Planet

2
The Blue Planet

• The world is dominated by interconnected oceans.
  It just depends on your viewpoint.

3
The Blue Planet

• Nearly 71 of the Earths surface is covered by
  the global ocean.

4
How Big is the Ocean

• The ocean covers about 360 million square miles
  of the Earths surface. Oceanographers divide
  the oceans into four major ocean basins
• The Pacific
• The Atlantic
• The Indian
• The Arctic

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The Pacific Ocean

• The Pacific Ocean is the largest ocean. It is
  the largest single geographic feature on the
  Earth. It comprises more than half on the
  worlds oceans. With an average depth of about
  3,900 meters, it is the deepest ocean in the
  world as well.

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The Atlantic Ocean

• The Atlantic Ocean is about half the size of the
  Pacific Ocean. The Atlantic is slightly
  shallower than the Pacific. Both the Atlantic
  and Pacific Oceans are bounded on their eastern
  and western sides by continents.

7
The Indian Ocean

• While the Indian Ocean is slightly smaller than
  the Atlantic, it is about the same depth. Unlike
  the Atlantic and Pacific, the Indian Ocean is
  located almost entirely in the southern
  hemisphere.

8
The Arctic Ocean

• The Arctic Ocean accounts for only about 7 of
  the worlds oceans. It is also only about one
  fourth as deep as the other oceans of the world.

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Bathymetry

• The study of the oceans topography is called
  bathymetry.

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Oceanographic History

• The first serious look at the ocean came in the
  1870s. The Challenger conducted an 6-year
  voyage to study the worlds oceans. The
  Challenger sailed approximately 128,000 miles on
  its journey.

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Current Technologies for Exploring the Ocean

• Today, there are various technologies available
  to explore the ocean. These include sonar,
  satellites and submersibles. This allows modern
  scientists to explore the ocean floor more
  efficiently and accurately than ever.

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Sonar

• Sonar stands for Sound Navigation and Ranging.
  Sound waves are bounced off the ocean bottom and
  timed as they arrive. The difference in arrival
  time can be translating into a depth.

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Sonar

• Today, modern multibeam radar sends out multiple
  sound signals and receivers to establish the
  depth of wide bands along the ocean floor as
  opposed to narrow points.

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Satellites

• Satellites are able to compensate for waves,
  tides, currents and atmospheric effects to
  produce ocean surface and topographic features
  images. Scientists have discovered that the
  ocean is not flat. Where seamounts and ridges
  occur the ocean bulges up. Where undersea
  canyons occur, the ocean has depressions.
• SEAsat

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Satellite Images

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Submersibles

• Submersibles are small underwater craft capable
  of diving to great depths. Submersibles such as
  Alvin and Sea Cliff II can reach ocean depths of
  between 4,000 and 6,000 meters, respectively.

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Submersibles

• More modern versions of submersibles are
  unmanned an operated with computers and joy
  sticks. These submersibles operate longer and
  cheaper because they have no crews that require
  life support or comforts.
• Autosub

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Warm Up

• What are the three major divisions of the sea
  floor?
• Define the parts and characteristics of each
  division.
• What is a seamount?
• What is a guyot?
• What is a turbidity current?
• Where do you find convergent boundaries?
• Where do you find divergent boundaries?

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Ocean Topography

• The ocean floor has been divided into three
  major regions
• the continental margins
• the ocean basin floor
• the mid-ocean ridge

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The Continental Margins

• The continental margin includes the continental
  shelf, the continental slope and the continental
  rise. It does not include the abyssal plain.

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The Continental Margins The Continental Shelf

• Continental shelves contain mineral deposits,
  oil reservoirs, natural gas, and huge sand and
  gravel deposits.

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The Continental MarginsThe Continental Slope

• The continental slope is located just seaward of
  the continental shelf. Averaging only about 20
  kilometers in width, it marks the boundary
  between the continental and oceanic crusts.
• The slope often has
• deep channels cut into
• them. These occur
• at time when the
• worlds oceans are
• Low and rivers cut
• deeply into the exposed
• sediment. Sometimes
• Large underwater land-
• Slides occur here that
• Create turbidity currents.

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Turbidity Currents

• Artificially created turbidity current

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The Continental MarginsThe Continental Rise

• The continental rise marks the area of the ocean
  floor where the incline of the sea floor is
  reduced. The continental rise may be hundreds of
  kilometers wide.

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The Ocean Basin Floor

• Between the continental margin and the mid-ocean
  ridges, lies the ocean basin floor. Some of the
  features of the ocean floor basin include
  deep-ocean trenches, abyssal plains and seamounts
  and guyots.

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Deep-ocean Trenches

• Deep-ocean trenches are long, narrow creases in
  the ocean floor that form in the deepest parts of
  the ocean. Most of the trenches form along the
  margins of the Pacific and exceed 10,000 meters
  in depth. The deepest know point on the planet
  is located in the Marianas Trench and is over
  11,000 meters deep.
• These mark convergent
• plate boundaries.

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Abyssal Plains

• Abyssal plains are huge expanses of extremely
  flat sediments. They are possibly the flattest
  places on the planet. These plains are formed
  from sediment carried by turbidity currents and
  settling suspended sediments.

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Seamounts and Guyots

• Seamounts are undersea volcanic peaks that dot
  the ocean floor. They are volcanoes that have
  yet to reach the surface.

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Seamounts and Guyots

• Once volcanic islands break the oceans surface
  the begin to erode and form flat-topped, once
  active structures called guyots.

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The Mid-Ocean Ridge

• Mid-Ocean ridges are found at the center of most
  ocean basins. It is an interconnected system of
  underwater mountains that develop above newly
  formed ocean crust.

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The Mid-Ocean Ridge

• Mid-Ocean ridges are areas of seafloor spreading
  or divergent plate boundaries that we talked
  about earlier. This is where new land is formed.