Atlantic and Pacific Oceans Help

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By — McGraw-Hill Professional
Updated on Sep 4, 2011

Atlantic Ocean

There are several differences between the Atlantic and Pacific Oceans, but here are some of the highlights. The Atlantic Ocean is divided into two sections by the Mid-Atlantic Ridge; the margins of the North American and Eurasian plates. The Atlantic is also a spreading ocean except for a small subduction zone in the Caribbean Sea. The Atlantic continental margins are considered passive by geologists, since volcano and earthquake activity across the plate is rare.

The continental shelf in the Atlantic Ocean is a fairly flat, wide, sandy, area. It stretches gently out from the land mass of North and South America for 50 to 100m before dropping down to the continental slope (4° angle) for a distance of around 1km. The depths are between 2000 and 3000m here.

Eventually, the continental slope begins to rise slowly. This large area, hundreds of kilometers wide, is called the abyssal plain . It is found at depths of 4000 to 6000m with only the occasional seamount (extinct volcano) for interest. The plain rises until it comes to a hot, active volcanic gap and ridge area, the Mid-Atlantic Ridge.

The Mid-Atlantic Ridge (nearly 2000 m) is the margin of divergent plates where new seafloor is created and being pushed up from the magma below.

The other side of the ridge, closest to Europe and Africa is pretty much a mirror image of the first half as far as ocean depths and landscape is concerned.

Pacific Ocean

The first thing that most people notice about the Pacific Ocean is its size. It is huge! But because of its many subduction zones along the Ring of Fire, the Pacific Ocean is actually getting smaller. In many millions of years, barring other problems, North America and South America will be a lot closer to Asia and Australia. Who knows, by then it may be only a day trip by speed boat!

However, when people think of the Pacific Ocean, they usually think of balmy days, tropical islands, volcanic fireworks, and white beaches. That is fairly accurate, but to geologists, the Pacific Ocean is the hot spot of tectonic plate activity. It has active continental margins.

Comparing the Atlantic Ocean to the Pacific Ocean, the main structural difference is probably depth. Some places in the Pacific are nearly twice as deep as the Atlantic Ocean.

For example, if you start out from the west coast of South America, the continental shelf is short, only 20–60m wide and at its edge, the slope drops off to 8000m (like a ball rolling off a table) into the Peru–Chile trench. On the other side of the trench, the depth rises up onto the Nazca plate around 4000 m, until it gets to the East Pacific Rise (2200 m).

On the far side of the East Pacific Rise, the Pacific Ocean floor stays around 4000m in depth, with a number of volcanoes, seamounts, and guyots jutting up abruptly from the sea floor. Still traveling east, the Tonga Trench drops the ocean depth to nearly 11,000m in depth. The ocean floor comes back up from this gash to 4000m until it comes to the short continental shelf of Australia.

The Future

The oceans are critical to life on Earth. Considering climate, medicines, fish, and transported goods, the ocean plays an important role in everyone’s life in some way. The oceans unite people and landmasses of the Earth. In fact, one in every six jobs in the United States is thought to be marine-related and attributed to fishing, transportation, recreation, and other industries in coastal areas. Ocean routes are important to national security and foreign trade. Military and commercial vessels travel the world on the oceans.

To acknowledge the importance of the world’s oceans, the United Nations declared 1998 the International Year of the Ocean . This designation gave organizations and governments an important chance to increase public awareness and understanding of marine environments and environmental issues.

Practice problems of this concept can be found at: Oceans Practice Test

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