The oldest group of mountains on earth are the Mid-Pacific Mountains, a submarine range extending from Necker Island of the Hawaiian group to the vicinity of Wake Island. They contain coral about 100,000,000 years old.

 

Oceanographers are the scientists of the world ocean.  

The shore of the Dead Sea, on the border between Israel and Jordan, is the deepest land depression on earth and lies about 1,300 feet below sea level. Climatic changes have raised the level of the sea some 20 feet since the 1880's. 

Drake Passage, 500 miles of treacherous icy waters between the southern tip of Chile and the Antarctica Peninsula, is considered the most dangerous place in the oceans of the world.

 

America's inland waters cover an enormous area. The Great Lakes cover nearly 100,000 square miles. Huge river systems are composed of the 2,340-mile Mississippi and its largest tributary the Missouri which combined have 4,000 to 5,000 miles of waterways in addition to some 250 tributaries, such as the 900-mile Ohio River.

 

The salinity of the oceans varies according to depth and location.   The highest concentrations of salty water are in the subtropics.

 

Ocean water is salty because the ocean catches water flowing from lakes and rivers. As this water makes its way down a river it picks up various minerals, one being salt. As the water evaporates in the ocean it leaves the salt behind.

 

Antarctica has no land areas below sea level.

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