Earth's atmosphere plays a critical role in regulating our climate. There are countless invisible processes occurring each second in the air around and above us.

The atmosphere can be described as having of four "layers" with different densities and molecular compositions. Open the Earth's Atmosphere learning tool and you will see a weather balloon sitting on the Earth. Move it up with your mouse to learn about the different layers of the atmosphere. As you do so, work through the material on the right side of the image and answer the following questions:

• What are the layers of the atmosphere called?
• What are the most abundant gases in Earth’s atmosphere?
• How does temperature vary from layer to layer?