---
source: https://iinventedlight.com/library/notes/ozone-layer.md
title: "The ozone layer: what it is and why it matters"
license: CC-BY-4.0
license_url: https://creativecommons.org/licenses/by/4.0/
source_license: "US government work, public domain; restated in our own words"
attribution: "Summary by iinventedlight (AI-assisted). Sources: NASA, Nasa Ozone Watch: Ozone facts, US government work, public domain; US EPA, Basic Ozone Layer Science, US government work, public domain."
author: "iinventedlight (synthesis of cited sources); text drafted with AI assistance"
date: 2026-11-04
status: published
checked_on: 2026-11-04
as_of: 2026-11-04
confidence: medium
untested: "No observation or experiment was done; only the fetched government pages were read."
category: coverage-gaps
topic_area: "science-explain: atmosphere"
tags: science, atmosphere, ozone, uv
sources:
  - id: S1
    title: "Nasa Ozone Watch: Ozone facts"
    publisher: NASA
    url: https://ozonewatch.gsfc.nasa.gov/facts/SH.html
    accessed: 2026-11-04
    license: "US government work, public domain"
  - id: S2
    title: "Basic Ozone Layer Science"
    publisher: US EPA
    url: https://www.epa.gov/ozone-layer-protection/basic-ozone-layer-science
    accessed: 2026-11-04
    license: "US government work, public domain"
---
# The ozone layer: what it is and why it matters

## Short answer
Ozone is a molecule of three oxygen atoms (O3). Most of it sits in the stratosphere, roughly 15 to 30 km up, where it absorbs much of the Sun's ultraviolet (UV) radiation. [S1][S2]

## Key points
- **Good up high, bad nearby:** near the ground, ozone forms from vehicle and other pollution and is a pollutant. [S1]
- **UV bands:** UVA is not absorbed by ozone, UVB is mostly absorbed, UVC is fully absorbed. [S2]
- **Damage:** human-made ozone-depleting substances have thinned the layer. [S2]

## Claims
- id: C1
  claim: Ozone is a gas made of three oxygen atoms.
  source: S1
  evidence: "Ozone is a gas made up of three oxygen atoms (O3)."
- id: C2
  claim: Ozone protects life on Earth from the Sun's UV radiation.
  source: S1
  evidence: "Ozone protects life on Earth from the Sun’s ultraviolet (UV) radiation."
- id: C3
  claim: UVA is not absorbed by ozone.
  source: S2
  evidence: "UVA is not absorbed by ozone."
- id: C4
  claim: Most atmospheric ozone is concentrated in a stratospheric layer.
  source: S2
  evidence: "Most atmospheric ozone is concentrated in a layer in the stratosphere"

## Sources
- [S1] Nasa Ozone Watch: Ozone facts. NASA. https://ozonewatch.gsfc.nasa.gov/facts/SH.html . License: US government work, public domain. Accessed 2026-11-04.
- [S2] Basic Ozone Layer Science. US EPA. https://www.epa.gov/ozone-layer-protection/basic-ozone-layer-science . License: US government work, public domain. Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).