Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

Which layer of the atmosphere is closest to the Earth's surface?

1. Stratosphere

2. Mesosphere

3. Troposphere

4. Thermosphere

The correct answer is: Troposphere

The troposphere is the layer of the atmosphere that is closest to the Earth's surface. It extends from the Earth's surface up to about 8 to 15 kilometers (5 to 9 miles) in altitude, depending on where you are on the planet. This layer contains most of the atmosphere's mass, including the majority of its water vapor, which is crucial for weather phenomena. The troposphere is characterized by a decrease in temperature with altitude, which is the foundation of weather patterns and climatic conditions we experience daily. In contrast, the other layers mentioned are positioned above the troposphere: the stratosphere, which is located above the troposphere, contains the ozone layer and is where temperature increases with altitude; the mesosphere, which lies above the stratosphere, is where temperatures again drop with altitude and is where most meteorites burn up upon entering the atmosphere; and the thermosphere, the uppermost layer, characterized by very high temperatures and the presence of the ionosphere. Each of these layers serves different functions and experiences unique atmospheric conditions, making the troposphere distinct in its proximity to human life and weather development.