Practice Test

Question 10 • Earth and Space Science

Why is atmospheric pressure highest in the troposphere?

Answer

Gravity pulls air molecules toward Earth's core, and the force of gravity is stronger closer to the planet’s surface than it is farther away.

The troposphere contains the ozone layer, which is a concentrated layer of gas that exerts atmospheric pressure.

The other layers contain the same number of gas particles, but they press down on the troposphere, reducing the volume of the troposphere.

The troposphere contains greenhouse gases like water vapor and carbon dioxide that exert strong atmospheric pressure.

Explanation

Gravity pulls air molecules toward Earth, so the air is densest near the surface and becomes thinner at higher altitudes. The weight of the air above creates pressure, making atmospheric pressure highest in the troposphere, closest to Earth’s surface. Choice B states this gravitational cause; greenhouse gases and the ozone layer do not explain why pressure is greatest there.

AI-written and checked against the verified answer.

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