Describe the atmosphere's structure from base to top. What characteristics define the boundaries between layers?

This is the lowest layer of the Earth's atmosphere, extending approximately 8 to 14.5 kilometers (5 to 9 miles) above the Earth's surface. It contains about 75% of the atmosphere's mass and is where most weather phenomena occur. The temperature in this layer generally decreases with altitude, and the boundary separating the troposphere from the stratosphere above is called the tropopause, characterized by a temperature inversion (temperature increases with altitude).

The stratosphere extends from the tropopause to a height of about 50 kilometers (31 miles) above the Earth's surface. The ozone layer, which absorbs and scatters ultraviolet sunlight, is located in the stratosphere, providing crucial protection for life on Earth. In this layer, the temperature rises with altitude due to the absorption of UV radiation by ozone molecules. The stratopause marks the boundary between the stratosphere and the mesosphere above, where the temperature stops increasing with altitude.

The mesosphere extends from the stratopause to approximately 85 kilometers (53 miles) above the Earth's surface. Within the mesosphere, the temperature decreases with altitude, and it is the layer where meteors typically burn up upon entering Earth's atmosphere. The mesopause separates the mesosphere from the thermosphere above, characterized by the lowest temperatures in the atmosphere.

The thermosphere extends from the mesopause to about 600 kilometers (373 miles) above the Earth's surface. In this layer, the temperature increases with altitude due to the absorption of high-energy solar radiation by atoms and molecules, resulting in extremely high temperatures. It is also the layer where auroras occur and where the International Space Station orbits the Earth. The boundary between the thermosphere and the exosphere above is called the thermopause, characterized by the gradual transition of atmospheric particles into space.

The exosphere is the outermost layer of the Earth's atmosphere, extending from the thermopause to the edge of space, at around 10,000 kilometers (6,214 miles) above the surface. It is a very thin layer with extremely low density, and it is where Earth's atmosphere gradually fades into space. The exosphere contains mainly light gases such as hydrogen and helium, and satellites typically orbit within this layer. In summary, the Earth's atmosphere is structured into five primary layers: troposphere, stratosphere, mesosphere, thermosphere, and exosphere. The boundaries between these layers are characterized by changes in temperature trends with altitude (tropopause, stratopause, mesopause, and thermopause), reflecting the different physical and chemical processes occurring within each layer.