The oceans cover two thirds of our Earth and hold all but 3% of the Earth`s water.  The oceans contain every natural element known, but its main element is sodium (salt).  New water is not created on Earth, but the same supply is recycled over and over through the water cycle.

The sun heats the ocean waters.  As millions of gallons evaporate, clouds form.  As clouds drift over the land, water is released to flow down streams and rivers to the oceans.       There are four oceans:  the Pacific Ocean, the Atlantic Ocean, the Arctic Ocean, and the Indian Ocean.  But, some scientists believed that long ago there was only one ocean, Panthalassa, surrounding one huge continent, Pangaea.  When this huge continent slowly split into our seven continents today, the four oceans were formed.

Winds cause the oceans to have currents.  Currents are bodies of water that always flow in the same direction.   One type of wind is called the Westerlies that blow from west to east.  The Trade Winds blow from east to west.  The Gulf Stream is another current that runs along the east coast of the United States.

Waves are made by the wind blowing across the oceans.  The stronger the wind, the bigger the waves.  A wave is made up of a lot of water particles going around and around.

The sea holds most of the life on Earth.  Living things in the sea can be microscopic, like plankton, as well as enormous, like whales.

Each year fishermen harvest over 70,000,000 tons of seafood to feed the people of the world.

The sea also provides us with other resources like oil.

Five thousand years ago, ancient Egyptians were the first people to navigate the seas.  Their sails were square and made out of reeds, a kind of plant.  Early navigators used the stars to guide them.  Later, sailors used an instrument called a sextant to plot their position on the ocean.  It measured the distance between the sun or moon above the horizon

Today, sea navigation is made much more accurate through the use of computers, radios, radar, and satellite links.

The deepest ocean is the Pacific.  It has the Marianas Trench which is over 36,000 feet deep.  If you dropped a two pound anchor, it would take over an hour before it would come to rest at the bottom of this deep trench.

We measure the depth of the ocean with an echo sounder that measures the length of time it takes for sound waves to bounce off the ocean floor and back up to a ship that holds the equipment.  This is how scientists can draw a map of the ocean floor.

The Pacific Ocean is also the largest ocean located between the Western Hemisphere, Asia, and Australia.   It covers about one third of the Earth`s surface.  It is about 18 times the size of the United States.

The coldest ocean is the Arctic Ocean.  It is also the smallest ocean. It is located at the northern tip of our Earth.

The Atlantic Ocean is the second largest ocean in the world.  It is bordered by North America and South America on the west and by Europe and Africa on the east.

The warmest as well as the saltiest ocean is the Indian Ocean.  It is the third largest ocean being less than half the size of the Pacific Ocean.