ASVAB General Science: Layers of the Atmosphere
Earth's atmosphere is a complex system that plays a crucial role in supporting life on our planet. It is divided into five main layers, each with unique characteristics and functions. These layers, from closest to Earth's surface to farthest, are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
The troposphere is the lowest layer of the atmosphere and the one we interact with most directly. It extends from the Earth's surface to about 10-15 kilometers high, depending on location and weather conditions. This layer contains most of our weather phenomena, including clouds, rain, and wind. As you ascend through the troposphere, the temperature generally decreases, which is why mountaintops are often cooler than valleys.
Above the troposphere lies the stratosphere, which extends to about 50 kilometers above the Earth's surface. This layer is notable for containing the ozone layer, which absorbs much of the sun's harmful ultraviolet radiation. Unlike the troposphere, temperature increases with altitude in the stratosphere due to this absorption of solar energy. The stratosphere is also where many jet aircraft fly, taking advantage of its stable conditions.
The mesosphere starts above the stratosphere and extends to about 85 kilometers high. It's the coldest layer of the atmosphere, with temperatures dropping as low as -90°C (-130°F) at its upper boundary. This layer is where many meteors burn up as they enter Earth's atmosphere, creating the streaks of light we call "shooting stars."
Next is the thermosphere, extending from about 85 to 600 kilometers above Earth's surface. Despite being very thin, this layer absorbs high-energy X-rays and UV radiation from the sun, causing temperatures to rise dramatically with altitude. The aurora borealis and aurora australis (Northern and Southern Lights) occur in this layer. The International Space Station orbits Earth within the thermosphere.
The outermost layer of Earth's atmosphere is the exosphere, which gradually thins out into the vacuum of space. It extends from the top of the thermosphere to about 10,000 kilometers above the Earth's surface. This layer contains only scattered particles of atmosphere, and many satellites orbit Earth within the exosphere.