Seas and Lakes

More than three quarters of the surface of the Earth is covered by water in the form of oceans, seas and lakes. The volume of water from these bodies is drawn up into the clouds by the effect of the heat received from the sun and it descends as rain, keeping life in existence, today. Several parts of the ocean floors are more than ten miles, stretching below the surface and some abysses are even deeper than that. There are many wonders in the oceans that are even found close the land shores and they include deep harbours, coral reefs, sandbars and gravel banks which are built by the action of the ocean waves and the ebb and flow of the tides which is caused by the pull of the Moon. Most of the islands that are found in the middle of the oceans emerge from the sea floor directly. The coral reefs are made up of small coral animals that are also known as polyps or planktons and they are related to sea anemones and jellyfish. They occur in seas that have temperatures exceeding eighteen degrees Celsius or sixty-five degrees Fahrenheit. These corals exist in colonies and they build external skeletons from calcium that is extracted from the seawater. These combined skeletons build huge deposits that turn into atolls and reefs. The Power of Seas and Lakes The seas and lakes have the power to change the face of Planet Earth. It has to be noted that the waves crash on to already heavily eroded rocky shores. Atolls also begin as fringing reefs around volcanic islands. They emanate from the rims of craters. On account of the subsidence, the centres of islands are left submerged to form lagoons and the reefs form atolls. The longer reefs appear off continental coasts. A fine example is the Great Barrier Reef, off the North-Eastern coast of Australia. Many people imagine lakes to be limited in size and area. There are some lakes in this world that look as big as the oceans, themselves. Take Lake Superior or the Caspian Sea for example. Caspian Sea is the largest in the world and it covers an area of one hundred and forty-four thousand square miles. It is located in a great depression, east of the Caucasus Mountains and it lies about ninety feet below the sea level. In contrast, the Aral Sea is located about two hundred and twenty miles to its east and lies about one hundred and sixty-five feet above the sea level. The Great Salt Lake in Utah in the United States of America is the saltiest in the world. Lake Eyre, the largest lake in Australia is often wholly dry and is covered with a thick crust of salt, covering its bed. It gets filled only in times of heavy rainfall. Lake Baikal in Southern Siberia is the deepest lake in the world. It fills a deep rift valley with its bed being close to five thousand feet below the sea level at the lowest point. Lake Superior is the largest freshwater lake in the world. It forms one of the five great lakes in North America. The Tarn House in Cumbria to the north of England is a fine example of a mountain lake, occupying a hollow that was created by snow and ice. Lake Titicaca in Bolivia is the highest situated lake in the world. Its surface is at around twelve thousand feet above the sea level.