Weather Review

Earth is wrapped in a layer of gases called the atmosphere.

The atmosphere helps make the Earth suitable for living things and is divided into layers.

The Troposphere is the layer closest to the ground.

It contains almost all of Earth's carbon dioxide, water vapor, air pollution, clouds, and organisms.

All of Earth's weather takes place in the troposphere.

Above the troposphere is the stratosphere.

The ozone layer is located in the stratosphere. Oxone is a form of oxygen gas that helps protect the Earth from the Sun's UV rays.

The middle layer of the atmosphere is the mesosphere.

Meteoroids falling to the Earth burn up in this layer.

Beyond the mesosphere is the thermosphere.

The Space Shuttle and Satelites orbit Earth in this layer.

The outermost part of the atmosphere is the exosphere. Some satellites orbit in this layer as well.

The water cycle is a never-ending movement of water between Earth's surface and the atmosphere. The cycle has no start and no end. It goes on without stopping every second of every day.

Heat energy from the sun causes water on Earth's surface to change from a liquid to a gas. This gas is called water vapor.

The process that changes gas to a liquid is called evaporation.

Transpiration is a process in which plants release wator vapor, mainly through their leaves.

The next step in the water cycle is called condensation.

Condensation is the process in which water vapor condenses when it cools.

Condensation turns the water vapor into water droplets.

After water condenses in the atmosphere, it falls to Earth as precipitation.

Forms of precipitation include: rain, snow, freezing rain, sleet, and hail.

When water falls to the ground, the water may flow over land and collect in rivers, streams , ponds, and lakes.

This happens when the ground cannot absorb water, or the water is falling too fast to soak into the ground.

Clouds form due to the process of condensation.

They are made of water droplets or ice particles and bits of dust that stick together as the water vapor cools and condenses.