Ocean
Ocean
Oceans are large bodies of saltwater that surround the continents and occupy the basins between them. Ocean basins are the part of the seafloor that lies beyond the margins of the continents, generally in water deeper than 600 feet (183 meters).
As Earth formed in a cloud of gas and dust more than 4.5 billion years ago, a huge amount of lighter elements, including hydrogen (H) and oxygen (O), became trapped inside the planet as the gases condensed and formed molten rock. Materials of different densities separated out; in the young planet’s molten interior, heavy elements sank and light elements rose.
Gases rose through thousands of miles of molten and melting rock, to erupt on the surface through volcanoes and fissures. Within the planet and above the surface, oxygen combined with hydrogen to form water (H20). Enormous quantities of water—enough to fill oceans if it were liquid—shrouded the globe as an incredibly dense atmosphere of water vapor. Near the top of the atmosphere, where heat could be lost to outer space, water vapor condensed to liquid and fell back into the water vapor layer below, cooling the layer. This atmospheric cooling process continued until the first raindrops fell to Earth’s surface. Over thousands of years, and perhaps at different times during the life of Earth, the surface depressions filled to create the oceans.
It may be that most of the water on Earth today has been cycling between the oceans, the land, and Earth’s atmosphere for more than four billion years. However, small amounts of “new” water escape the planet’s interior, from volcanoes, even today.
Water absorbs a large amount of heat energy before its temperature changes. Put the other way round, water must lose a large amount of heat energy before it cools noticeably. The net result of this phenomenon is that water, more than air or earth, tends to remain at the temperature at which it is already. Water is not given to sudden, wild extremes of temperature. Therefore water has a strong moderating effect on climates. Where there is water, there are more moderate temperatures. A maritime (oceanlike) climate tends to be moister and subject to less fluctuation in temperature than regions far from the ocean such as the interior of the United States.
Nearly all coasts experience this maritime effect, but it is especially apparent along coasts where there are large ocean currents. The moderating effects of the Gulf Stream are a good example. Caribbean sunshine warms the waters of the Gulf Stream in the tropics. This warm water then flows up the east coast of the United States and Canada until crossing the Atlantic to the coast of Western Europe. This warm current is why England’s climate is so much warmer than areas at about the same latitude in North America. However, when the Gulf Stream is diverted southward, Western Europe experiences extreme cold—the last such event, during the fourteenth through nineteenth century, is known as the “Little Ice Age.”
The moderating influence of the Gulf Stream may be changing. Evidence published in 2005 suggests that the flow of the Gulf Stream may be diminishing. If this proves to be the case, the climate of regions like England could be profoundly affected.
KEY TERMS
Continental shelf —A relatively shallow, gently sloping, submarine area at the edges of continents and large islands, extending from the shoreline to the continental slope.
Maritime climate —A moist climate that is neither too hot nor too cold, caused by the moderating effect of water on temperatures.
Pelagic sediment —Sediment in the open ocean.
Pillow lava —The shape adopted by lava when it erupts deep under water.
Trenches —Deep, trough-like depressions in the ocean floor.
Resources
BOOKS
Dinwiddie, Robert, Louise Thomas, and Fabien Cousteau. Ocean. New York: DK Adult, 2006.
Hutchinson, Stephen and Lawrence E. Hawkins. Oceans: A Visual Guide. Tonawanda: Firefly Books, 2005.
MacInnis, Joe and James Cameron. James Cameron’s Aliens of the Deep: Voyages to the Strange World of the Deep Ocean. Washington, DC: National Geographic Press, 2005.
Stow, Dorrick. Oceans: An Illustrated Reference. Chicago: University of Chicago Press, 2006.
Clinton Crowley