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Lecture 2
The Study of the Oceans

THE OCEAN WORLD -- Just the Facts

The ocean covers 71% of the Earth's surface.

Over 97% of the water on the Earth is in the ocean.

The average depth of the ocean is about 3,800 meters.

The Mariana Trench is 11,022 meters deep, the deepest spot in the ocean.

Mauna Kea, on the Big Island of Hawaii, measures ~10,600 m from the ocean floor, making it the tallest mountain on the planet (surpassing even Mt. Everest).

If the Earth's contours were leveled to a smooth ball, the ocean would cover it to a depth of 2,686 meters (8,810 feet).

The world ocean contains some 5 trillion tons of salts; if dried and spread evenly, that mass would cover the entire planet to a depth of 45 meters (150 feet).

On a planetary scale, however, the ocean itself is insignificant. Its average depth is a tiny fraction of the Earth's radius: The blue ink representing the ocean on an 8-inch paper globe is proportionally thicker.

Why Study the Oceans? (a perspective from UC-Santa Cruz)


Oceanography is a broad science that has the understanding of the oceans as its common goal. The field is so broad that oceanography is broken down into several disciplines based on the nature of the investigations:

Geological Oceanography (Marine Geology) -- the study of rocks and sediments found within the oceans, and of the processes responsible for their formation;

Marine Geophysics -- the study of the rock structure within the ocean basins, the properties of rocks such as their magnetism, and the occurrence and cause of earthquakes;

Physical Oceanography -- investigates how and why ocean currents flow, and air-sea interactions such as the generation of waves by the wind;

Chemical Oceanography -- the study of the composition of sea water and the processes that control and alter this composition, including marine pollution;

Biological Oceanography (Marine Biology) -- concerned with the organisms that live in the oceans, and their relationships to the environment;

Ocean Engineering -- the branch of engineering that designs equipment and installations to be used in the oceans.

Although such categories exist, individual oceanographers tend to be broad in their outlooks and often are not easily placed into one of these "boxes". In addition, oceanographic research tends to be highly interdisciplinary, involving a team of investigators that combine their expertise to better understand the oceans.


  • Modern Oceanography
  • Current and Future Oceanographic Research
  • Chapter Summary - What is Oceanography?


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