G5 The Water Cycle & Earth’s Spheres – 02_Approaching

Both the north and south pole of the Earth are covered by ice. In warm regions, water can be found as a liquid in lakes, streams, and oceans. As ice forms in winter months in colder climate and turns back into a liquid in warmer months. In this way, water can be traded between the hydrosphere and the cryosphere. As water moves back and forth from the hydrosphere to the cryosphere it can have a major influence on climate. The hydrosphere and the cryosphere are obvious places for water to exist, but what are others?

Even the atmosphere contains water in the form of a gas. Water in a gaseous state is called water vapor. Water in the air is usually considered to be in the atmosphere. You may be wondering, what does this have to do with water being really old? It is the Sun that powers the recycling process of the water cycle.

Energy from the Sun causes water to evaporate. Most evaporation is from the oceans because they cover so much area. The water vapor rises into the atmosphere. Wind currents carry the water vapor to other locations. Another way liquid water is changed into a gas is transpiration. Transpiration occurs in plants, which are part of earth’s biosphere. The biosphere is made up of the parts of Earth where life exists. Plants release water vapor through their leaves. This water vapor also rises into the atmosphere. Once in the air as a gas, water needs a way to turn back into a liquid. Can you think of a way this could happen?

Condensation is the opposite of evaporation and changes water vapor back to liquid water. As air rises higher into the atmosphere, it cools as it expands. Cool air can hold less water vapor than warm air. This causes some of the water vapor to condense into water droplets. Those water droplets may form the clouds you see in the sky. In the clouds, water droplets join with other droplets becoming bigger and bigger. Water droplets in clouds fall to Earth when they become too heavy for the wind currents to hold them aloft. The water falls as rain if the air is warm. If the air is cold, the water may freeze and fall as snow, sleet, or hail. Most precipitation falls into the oceans. Some falls on land. When water falls from clouds it is called precipitation.