What is the Atmosphere?

The atmosphere is the layer of gases that surrounds the Earth. It is held in place by the force of gravity and consists of several different layers.

Composition of the Atmosphere

The Earth's atmosphere is composed mainly of nitrogen (about 78%) and oxygen (about 21%). The remaining 1% consists of other gases such as carbon dioxide, water vapor, and trace amounts of other gases.

Layers of the Atmosphere

The atmosphere is divided into five main layers: the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. Each layer has its own unique characteristics and plays a different role in the Earth's systems.

Troposphere

The troposphere is the lowest layer of the atmosphere and is where all weather occurs. It is also the densest layer and contains the majority of the atmosphere's mass.

Stratosphere

Above the troposphere is the stratosphere, which contains the ozone layer. The ozone layer helps to absorb and block harmful ultraviolet radiation from the sun.

Mesosphere

The mesosphere is the layer where meteors burn up upon entering the Earth's atmosphere. It is also the coldest layer of the atmosphere.

Thermosphere

The thermosphere is the layer where the International Space Station orbits. Temperatures in this layer can reach extremely high levels, but the air is very thin, so it would not feel hot to our skin.

Exosphere

The exosphere is the outermost layer of the atmosphere and gradually transitions into space. It is composed of very thin air and extends out to the edge of the Earth's gravitational influence.

Functions of the Atmosphere

The atmosphere serves several important functions, including:

• Protecting the Earth from harmful solar radiation
• Regulating the Earth's temperature
• Supporting life by providing the air we breathe and the gases necessary for photosynthesis

Study Guide

Here are some key points to remember about the atmosphere:

1. The atmosphere is the layer of gases that surrounds the Earth.
2. It is composed mainly of nitrogen and oxygen, with small amounts of other gases.
3. The atmosphere is divided into five layers: troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
4. Each layer has unique characteristics and plays a different role in the Earth's systems.
5. The atmosphere serves important functions such as protecting the Earth from solar radiation and supporting life.

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