A mass that died about 2.05 billion years ago destroyed more than 80 percent of life and dwarfs all mass extinctions – including what killed dinosaurs.
Unlike the large animals that have disappeared in these other events, however, the newly recognized dying involves small and simple microorganisms.
Researchers have found evidence of dying in rocks from Canada whose isotope ratios retain environmental information at the time they were formed.
Dying after an increase in the earth's levels of the atmospheric and oceanic oceans, which were accompanied by an increase in the abundance of life.
As the microorganisms have absorbed their nutrients over time, their numbers have to be reduced again.
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A mass dying about 2.05 billion years ago destroyed more than 80 percent of life – eclipsing all mass extinctions, including those, that killed the dinosaurs. Pictured rocks carrying barite from the Belcher Islands in Canada dating back to about 2 billion years ago
WHAT'S THE GREAT OXIDATION EVENT?
During the Great Oxidation Event, the earth's atmosphere and shallow oceans experience a dramatic rise in oxygen levels.
This was accompanied by an increase in the abundance of simple microbial life that lived at the time.
The episode lasted for about 2.4-2.1 billion years.
How the event ended earlier was not known.
Researchers now show that oxygen levels decrease with the mass death of life.
More than 80 percent of lives are estimated to have died – a dying event that goes beyond all mass extinctions.
Geologists Malcolm Hodgiskis of the University of California at Stanford, Peter Crockford of the Weizmann Science Institute, Israel, and colleagues have studied rocks collected from the Belcher Islands, southeast of Hudson Bay in Canada.
In particular, the team focuses on a sulfate mineral called barite, which can store information about the levels of oxygen found in the atmosphere and the degree of productivity of life at the time it was formed.
Studying isotopes of oxygen, sulfur and barium in rock samples, researchers have found that the Earth's biosphere – the regions of the planet occupied by life – has undergone tremendous changes, beginning about 2.4 billion years ago.
It was the time of the so-called Big Oxidation Event, when a huge amount of free oxygen was released into the atmosphere for the first time and ancient microbial life was breeding – but it was not clear how this event ended.
Researchers have found that there is a huge decline in the number of living organisms about 2.05 billion years ago – one that may be related to the decline in oxygen levels.
More than 80 percent of life may have died at this time, according to the team – this extinction is greater than both the event that killed the dinosaurs about 66 million years ago and the so-called "great dying" 252 19 million years ago.
"The fact that this geochemical signature was retained was very surprising," says Mr Hodgskiss.
"What was particularly unusual about these barites was that they obviously had a complex history."
The discoveries offer a rare window into life about two billion years ago, during a period before the complicated life of fossil life. fossils
"This shows that even when the biology of the Earth consists entirely of germs, it can still be considered as a huge extinction event that is not otherwise recorded in the fossils," says Mr Hodgiskis.
The discovery of a link between the proliferation of life and oxygen levels in the atmosphere of ancient Earth supports the hypothesis of the Big Oxidation event, called "oxygen ingestion".
This suggests that the weathering of rocks and the production of energy by ancient microorganisms release an enormous amount of oxygen into the earth's atmosphere.
However, these levels are thought to have fallen later as the oxygen-releasing organism interferes with depleted food supplies and reduced numbers.
This situation is in contrast to the stable atmosphere found on Earth today, where the amount of oxygen generated and the amount consumed essentially balance each other out.
studying oxygen isotopes, sulfur and barium in the rock they sample In the photo, researchers find that the Earth's biosphere – the regions of the planet occupied by life – has undergone tremendous changes, dating to about 2.4 billion years ago
Researchers' isotope data will help refine the size estimates Excess oxygen through reveals the impact it has on life.
"Some of these oxygen estimates probably require too many microorganisms living in the ocean in Earth in the past," Dr. Crockford said.
"So now we can begin to narrow what the composition of the atmosphere at this biological angle might look like."
"The size of the biosphere in geological time has always been one of our greatest questions in studying Earth's history," says Stanford University geologist Eric Sperling, who did not participate in this study.
"This new proxy demonstrates how in they link the biosphere and the levels of oxygen and carbon dioxide in the atmosphere. "
The full findings of the study were published in the journal Proceedings of the National Academy of Sciences.  Malcolm Hodgiskis Geologists at the Stanford University of California, Peter Crockford at the Weissman Institute of Science, Israel and colleagues have studied rocks collected from the Belcher Islands, southeast of Hudson Bay by Gadzogli Gawodzki ” class=”blkBorder img-share” />