Atmosphere Timeline by Madeleine Mercer

4.6 billion years ago (bya)

mercermo27_1 — 2025-07-09 20:52:02 UTC

Earth formed from dust and gas in space. The early Earth had no oxygen, and its atmosphere was made of deadly gases like methane and ammonia.

4-2.5 bya

mercermo27_1 — 2025-07-09 20:52:39 UTC

Volcanoes released water vapor and the first oceans formed. Sunlight caused chemical reactions in the air, that broke apart the methane and ammonia. Nitrogen and carbon dioxide became more common and bacteria (cyanobacteria) appeared and started photosynthesis, making oxygen.

2.6 bya- 400 million years ago (mya)

mercermo27_1 — 2025-07-09 20:52:55 UTC

Oxygen from photosynthesis kept building and some oxygen formed ozone which created the ozone layer. This layer blocked UV rays, making it safe for life to move out of the ocean.

400 mya- 290 mya

mercermo27_1 — 2025-07-09 20:53:02 UTC

Green plants grew all across the land and made even more oxygen. Animals came out of the water and began to live on land.

290 mya- present

mercermo27_1 — 2025-07-09 20:53:08 UTC

The atmosphere became more like it is today. The levels of oxygen and carbon dioxide became steady. People started using fossil fuels, which added more carbon dioxide and began to change the climate.

mercermo27_1 — 2025-07-09 21:12:01 UTC

mercermo27_1 — 2025-07-09 21:13:13 UTC

mercermo27_1 — 2025-07-09 21:13:42 UTC

mercermo27_1 — 2025-07-09 21:14:06 UTC

mercermo27_1 — 2025-07-09 21:14:23 UTC