What is the thin layer of gases surrounding Earth?

• A. Fossils
• B. Geologic time scale
• C. Law of Superposition
• D. Atmosphere

Answer: (D)

The atmosphere is the thin layer of gases surrounding Earth. It’s held in place by gravity and extends from the surface up into space, composed mostly of nitrogen and oxygen with smaller amounts of other gases and water vapor. This gaseous blanket protects living things by filtering harmful solar radiation, moderating climate and weather, and supplying the air we breathe. It’s structured into layers, like the troposphere where weather occurs and the stratosphere that contains the ozone layer. The other terms—fossils, the geologic time scale, and the law of superposition—relate to Earth’s history and rock layers, not to a gaseous shell around the planet.