The bounding waves

Stand at the seashore, or a lakeside, on a windy day. Watch the waves as they rush in toward you. They seem to come rolling at you as if pushed by a giant hand. With a great hiss and a swirl of foam, they surge up onto the beach. Then, almost at once, the water flows back out again. Only a last few sparkles are left on the wet sand.

Waves are made by wind blowing along the top of the water. The water seems to be moving forward-but it really isn't! It only moves up and down. A cork floating on the water would bob up and down as a wave moved under it. Unless pushed by the wind or tide, it would stay in the same place. This is because the water in a wave does not move forward. Only the shape of the wave moves forward.

You can see this for yourself. Tie a length of rope to a tree or post. Then wiggle the loose end of the rope. You'll see a wave shape travel down the rope. But the rope stays in the same place.

Where did the ocean come from

Scientists tell us that billions of years ago the earth was a ball of bare, sizzling-hot rock, with no air or water on it. The outside of the earth slowly cooled, but the inside stayed fiercely hot. Volcanoes roared and rumbled, throwing out tons of melted rock and enormous clouds of hot gases. One of these gases was steam-water so hot it is gas. When steam cools it turns into water.

Some scientists think the steam rose up in clouds. When these clouds cooled, they became water that fell as rain. Slowly, the low parts of the earth's rocky crust filled up with water, forming the ocean.

Other scientists think the steam cooled as it came out of the earth. When it became water, it trickled downhill. During many millions of years, the low places filled up to form the ocean.

Whichever way it happened, the ocean was formed by steam from inside the earth-steam that cooled and became water.

The deep blue sea

The sea! the sea! the open sea!
The blue, the fresh, the ever free!
Without a mark, without a bound,
It runneth the earth's wide regions round

From The Sea
Barry Cornwall

Sailors talk about "the seven seas", but there is really only one big ocean. The lands we live on, even giant continents such as North and South America, are really just islands in the huge ocean.

Large parts of this one big ocean lie between the continents. These parts have different names. The biggest part is called the Pacific Ocean. The next biggest part is called the Atlantic Ocean. There is also the Indian Ocean near India, the Arctic Ocean around the North Pole, and the Antarctic Ocean near the South Pole.

Smaller parts of the ocean, near islands or between pieces of land, are sometimes called seas. But we also call the whole ocean a sea - the deep, blue sea.