WATER CYCLE REVIEWER
Earth’s Water Cycle
Water is always on the move. Rain falling where you live may have been water in the ocean just days before. And the water you see in a river or stream may have been snow on a high mountain top.Water can be in the atmosphere, on the land, in the ocean, and even underground. It is recycled over and over through the water cycle. In the cycle, water changes state between liquid, solid (ice), and gas (water vapor).( solid, liquid and gas. The state will change when the substance is heated. As a solid, a substance has a fixed volume and shape and is usually unable to flow, except in the case of glaciers. For instance, an ice cube or snowflake is the solid state of water. When a solid is heated, it turns into a liquid. When a liquid is heated, it turns into a gas. As a gas, a substance does not have a fixed volume or shape.)
Most water vapor gets into the atmosphere : The atmosphere is a mixture of nitrogen (78%), oxygen (21%), and other gases (1%) that surrounds Earth. High above the planet, the atmosphere becomes thinner until it gradually reaches space.
1) The troposphere is the first layer above the surface and contains half of the Earth’s atmosphere. Weather occurs in this layer.
2) Many jet aircrafts fly in the stratosphere because it is very stable. Also, the ozone layer absorbs harmful rays from the Sun.
3) Meteors or rock fragments burn up in the mesosphere.
4) The thermosphere is a layer with auroras. It is also where the space shuttle orbits.
5) The atmosphere merges into space in the extremely thin exosphere. This is the upper limit of our atmosphere.
(The atmosphere is an important part of what makes Earth livable. It blocks some of the Sun’s dangerous rays from reaching Earth. It traps heat, making Earth a comfortable temperature. And the oxygen within our atmosphere is essential for life.)
One process which transfers water from the ground back to the atmosphere is evaporation. Evaporation is when water passes from a liquid phase to a gas phase. (Rates of evaporation of water depend on things like the temperature, humidity, and wind.)Water vapor can also form from snow and ice through the process of sublimation and can evaporate from plants by a process called transpiration. -Transpiration is the process by which plants return water to the atmosphere.- (After absorbing water from the ground, plants release water through their leaves. Transpiration helps plants stay cool, in the same way perspiration keeps humans and animals cool. )
The water vapor rises in the atmosphere and cools, forming tiny water droplets by a process called condensation. -Condensation is the process by which water changes its state from a vapor or gas to a liquid.-( Condensation is responsible for the formation of clouds. Common examples of condensation are: dew forming on grass in the early morning, eye glasses fogging up when you enter a warm building on a cold winter day, or water drops forming on a glass holding a cold drink on a hot summer day.)
Those water droplets make up clouds. If those tiny water droplets combine with each other they grow larger and eventually become too heavy to stay in the air. Then they fall to the ground as rain, snow, and other types of precipitation. -Precipitation is any form of water that falls to the Earth’s surface. (Different forms of precipitation include drizzle, hail, sleet, and freezing rain. Precipitation is important because it helps maintain the atmospheric balance. Without precipitation, all of the land on the planet would be desert. Most of the precipitation that falls becomes a part of the ocean or part of rivers, lakes, and streams that eventually lead to the ocean. Some of the snow and ice that falls as precipitation stays at the Earth surface in glaciers and other types of ice. 7)
Water stays in certain places longer than others. A drop of water may spend over 3,000 years in the ocean before moving on to another part of the water cycle while a drop of water spends an average of just eight days in the atmosphere before falling back to Earth.
