The layers closer to Earth are filled with many different gases that are smooshed together. Ninety percent of all particles in the air are contained in the first 20 miles above Earth. The higher layers are filled with just a few particles that are more spread out. All of the layers together are called the atmosphere. The layer of air stretching from the ground to about ten miles above us is called the troposphere .
All weather occurs within the troposphere.
From 10 to 30 miles above us is the stratosphere . Sometimes airplanes fly in the lowest part of the stratosphere high above the thunderstorms, hurricanes, and wild weather of the troposphere. Oxygen molecules in the stratosphere form a protective blanket over the earth called the ozone. Harmful ultraviolet rays from the sun are absorbed by the ozone before they can burn us. At the same time, the ozone layer keeps heat from escaping the earth, so we don't freeze.