Final answer:
Earth's atmosphere is primarily composed of nitrogen and oxygen, and contains layers such as the troposphere and stratosphere. Temperature and air density generally decrease with altitude, while pressure also decreases as one moves higher up from the surface.
Step-by-step explanation:
The composition of Earth's atmosphere mainly consists of nitrogen (78.1%) and oxygen (21.0%), with other gases such as argon, carbon dioxide, water vapor, and others comprising approximately 1%. The atmosphere has various layers, including the troposphere, stratosphere, mesosphere, thermosphere, and the exosphere. The troposphere extends up to 12 km above sea level and contains most of the atmosphere's mass and weather events.
As you ascend in the troposphere, the air density and temperature decrease, a feature also observed in the mesosphere and the upper parts of the stratosphere. However, the temperature increases in the lowest part of the stratosphere due to the ozone layer and continues to increase through the thermosphere. Atmospheric pressure decreases with altitude, as the air becomes less dense away from Earth's surface.