What is the lowest layer of Earth's atmosphere?

What is the lowest layer of Earth's atmosphere?

• A. Troposphere
• B. Stratosphere
• C. Mesosphere
• D. Thermosphere

Answer: (A)

The lowest layer is the troposphere. This layer sits directly above the Earth's surface and holds most of the atmosphere’s mass, which is why weather happens here. In the troposphere, temperature generally decreases with height (the lapse rate, about 6.5°C per kilometer), which helps drive weather patterns and cloud formation. It ends at the tropopause, where conditions change and the stratosphere begins. The stratosphere, mesosphere, and thermosphere sit above it, each with different temperature trends, so they aren’t the lowest layer.

The lowest layer is the troposphere. This layer sits directly above the Earth's surface and holds most of the atmosphere’s mass, which is why weather happens here. In the troposphere, temperature generally decreases with height (the lapse rate, about 6.5°C per kilometer), which helps drive weather patterns and cloud formation. It ends at the tropopause, where conditions change and the stratosphere begins. The stratosphere, mesosphere, and thermosphere sit above it, each with different temperature trends, so they aren’t the lowest layer.