THIRD POSITION

Topic; Water cycle

The water in your glass may have fallen from the sky as rain just last week, but the water itself has been around pretty much as long as the earth has! When the first fish crawled out of the ocean onto the land, your glass of water was part of that ocean. When the Brontosaurus walked through lakes feeding on plants, your glass of water was part of those lakes. When kings and princesses, knights and squires took a drink from their wells, your glass of water was part of those wells.

Earth's water is always in movement, and the water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the Earth. Since the water cycle is truly a "cycle," there is no beginning or end. Water can change states among liquid, vapor, and ice at various places in the water cycle, with these processes happening in the blink of an eye and over millions of years.

Although the balance of water on Earth remains fairly constant over time, individual water molecules can come and go in a hurry. The water in the apple you ate yesterday may have fallen as rain half-way around the world last year or could have been used 100 million years ago by Mama Dinosaur to give her baby a bath.

There will never be any more freshwater on Earth than there is now. No new water is being made and water can’t escape from the Earth. The water we use is recycled over and over again. The water cycle is the simplest natural cycle on Earth. Solar energy evaporates water from the ocean, lakes and rivers. Millions of litres of water rise into the atmosphere as an invisible gas - water vapour. This process is called evaporation. As the water vapour is pushed over the land by winds and rises over mountains, the water vapour cools and turns back into tiny water droplets, forming clouds. The droplets joining together is termed condensation. These droplets fall to earth as rain (precipitation). The rain runs into streams and rivers, which eventually flow into lakes or the sea and the cycle begins all over again.

Millions of years ago there were no oceans on the planet. The surface of the Earth was so hot that water simply boiled away. But volcanoes poured huge amounts of steam into the atmosphere and as the Earth cooled down the steam turned to water vapor that condensed as droplets and began to fall as rain. This downpour lasted for many thousands of years filling great hollows in the land and thus forming the world's first seas.

condensation. Most of the water is immediately returned to the seas by rain (precipitation). The rest of the water vapor is carried inside clouds by wind over land where it rains or snows. (precipitation). Rain and melted snow is brought back to the oceans by rivers, streams, and run-off from glaciers and water underground. The water cycle is the only way that Earth can be continually supplied with fresh water. The heat from the sun is the most important part of renewing our water supply. This heat soaks up water from the oceans, lakes, rivers, trees and plants in a process called evaporation.evaporation. As the water mixes with the air it forms water vapor. As the air cools, the water vapor forms clouds. This is called

The water cycle is the way the Earth uses and recycles water. It's controlled by the sun, which produces energy in the form of heat. This heat energy causes the water in the world's oceans, lakes, and even puddles in your backyard to warm and evaporate. When water is heated, it changes from a liquid to a gas. This gas is called water vapor, and the process is called evaporation. When plants give off water vapor, it's called transpiration. When water evaporates, it rises into the cooler air, collects, and forms clouds. There, the water vapor molecules cool down and change back into liquid