---
title: "Ozone Layer — AP Environmental Science Definition & Review"
description: "The ozone layer is the band of O3 in the stratosphere that absorbs harmful UV radiation. Learn how AP Enviro tests it in Units 4 and 9, from CFCs to HFCs."
canonical: "https://fiveable.me/ap-enviro/key-terms/ozone-layer"
type: "key-term"
subject: "AP Environmental Science"
---

# Ozone Layer — AP Environmental Science Definition & Review

## Definition

The ozone layer is a region in Earth's stratosphere that contains a high concentration of ozone (O3) molecules. It plays a crucial role in absorbing and filtering out most of the sun's harmful ultraviolet (UV) radiation before it reaches the Earth's surface.

## Related Study Guides

- [4.4 Earth's Atmosphere](/ap-enviro/unit-4/earths-atmosphere/study-guide/7Z9K5q4df3Hvtvuh33x9)
- [9.4 Increases in the Greenhouse Gases](/ap-enviro/unit-9/increases-greenhouse-gases/study-guide/xy8sIvBYMxVP54em0thk)

## Review

### Related Terms

- [Stratosphere](/ap-enviro/key-terms/stratosphere): The stratosphere is the second major layer of Earth's atmosphere located above the troposphere and below the mesosphere.
- [Ozone Depletion](/ap-enviro/key-terms/ozone-depletion): Ozone depletion refers to the thinning or reduction of the ozone layer due to human-made substances like CFCs.
- UV Radiation: UV radiation stands for ultraviolet radiation, which is a type of electromagnetic radiation emitted by the sun that can cause harm to living organisms.