Pacific Ocean

The Pacific Ocean is the largest of all the oceans and covers nearly one-third of the globe.  All the continents could be placed into it with room left over!  This is a very geologically active area with many volcanoes.

Atlantic Ocean

The Atlantic Ocean is considered a passive margin ocean with most of its geological activity centered along the Mid-Atlantic Ridge. Most of its coastal regions are low and geologically quiet. The Atlantic's major marginal seas include the Mediterranean Sea, the North Sea, the Baltic Sea, Hudson Bay, the Gulf of Mexico, and the Caribbean Sea.  Its greatest depth is in the Puerto Rico Trench at 8,605 meters (28,231 feet).

Indian Ocean

The Indian Ocean is often thought of as a tropical ocean, however, it extends from India in the north, all the way to Antarctica in the south.  It contains about 20% of the earth's water. It's deepest point is the Java trench at 7725 m.

Arctic Ocean

The Arctic Ocean is centered on the North Pole and is the smallest of the oceans.  This ocean is unique in that it has permanent to semi-permanent ice.

The ocean is salty because of the gradual concentration of dissolved chemicals eroded from the Earth's crust and washed into the sea. Solid and gaseous ejections from volcanoes, suspended particles swept to the ocean from the land by onshore winds, and materials dissolved from sediments deposited on the ocean floor have also contributed. Salinity is increased by evaporation or by freezing of sea ice and it is decreased as a result of rainfall, runoff, or the melting of ice.

The average salinity of sea water, 35 parts per thousand (ppt or o/oo), occurs at the Equator. But concentrations as high as 40 o/oo are observed in the Red Sea and the Persian Gulf. Salinities are much less than average in coastal waters, in the polar seas, and near the mouths of large rivers.

If the salt in the sea could be removed and spread evenly over the Earth's land surface it would form a layer more than 500 feet thick, about the height of a 40-story office building. The saltiness of the ocean is more understandable when compared with the salt content of a fresh-water lake. For example, when 1 cubic foot of sea water evaporates it yields about 2.2 pounds of salt, but 1 cubic foot of fresh water from Lake Michigan contains only one one-hundredth (0.01) of a pound of salt, or about one sixth of an ounce. Thus, sea water is 220 times saltier than the fresh lake water.