Paleoproterozoic Era · Siderian Period
Earth 2.4 Billion Years Ago: Oxygen Arrives and Ice Spreads
Earth 2.4 billion years ago: oxygen from microbes floods the air in the Great Oxidation Event, the methane haze clears and ice sheets reach low latitudes.
Spin it in 3D and move through timeNo map of the land exists this far back: the globe is an illustration of what Earth was like.
Map: Ancient maps: PALEOMAP PaleoDEMs (Scotese & Wright 2018), CC BY 4.0.
Around 2.4 billion years ago, oxygen made by photosynthesising cyanobacteria finally began to build up in the atmosphere: the Great Oxidation Event. Before it, the air held almost none. Iron dissolved in the sea reacted with the oxygen and settled out as the rusty layers of banded iron formations.
The oxygen destroyed much of the methane that had kept the planet warm. Between about 2.45 and 2.22 billion years ago, the Huronian glaciation spread ice sheets to low latitudes, perhaps close to the equator.
Over the following hundreds of millions of years an ozone layer formed and the oceans began to change, setting the stage for complex cells. The globe shows an illustration of this time.
Events of the time
The Great Oxidation Event
2.4 billion years ago · The whole planet
Cyanobacteria had been making oxygen for hundreds of millions of years; around 2.4 billion years ago it finally built up in the air, changing the planet’s chemistry for good.
▶ Watch it happen on the globe
Part of the Origin of Life & Proterozoic Eon.