The Great Oxidation Event in which oxygen levels rose and life on Earth flourished happened 100 million years later than previously thought, researchers claim.
Experts from the University of Leeds analyzed rocks from South Africa that were deposited in the ocean more than two billion years ago at the time of the Great Oxidation Event.
This event fundamentally changed Earth’s environment and habitability and was the first time that oxygen was significantly present in the planet’s atmosphere.
The Great Oxidation Event was a pivotal period in Earth’s history, and an international team now claims that it began 2.3 billion years ago, instead of 2.4 billion.
The study’s authors also say it should be called the Great Oxidation Episode because it ushered in a 1.5 billion year period of climate and environmental stability, enabling life form and resulting in multiple protracted ‘snowball-earth’ periods .
The Great Oxidation Event in which oxygen levels rose and life on Earth flourished happened 100 million years later than previously thought, researchers claim. Stock image
GREAT OXIDATION EVENT: THE MOST IMPORTANT TIME TO MAKE THE EARTH LIVEABLE
The Great Oxidation Event took place about 2.3 billion years ago.
It was a time when the Earth’s atmosphere and the shallow ocean first experienced an increase in oxygen.
This resulted in dramatic chemical changes on the planet that turned it from a reducing atmosphere to an oxidizing atmosphere.
This resulted in many early species becoming extinct, but the later ones allowed multicellular life.
The oxygen that spread was produced by cyanobacteria that obtained energy through photosynthesis.
Researchers from the University of Leeds worked with colleagues from the University of California-Riverside, Harvard University, the University of Southern Denmark and the University of St. Andrews to better understand this vital period in Earth’s history.
They say this 100-year difference also helps explain some of the most extreme climate episodes that have affected Earth.
This also includes ‘snowball earth’ when the planet was covered with ice repeatedly.
Although the Great Oxidation Event resulted in much lower oxygen levels than now, it drastically changed the chemical makeup of the planet’s surface.
It also paved the way for the further course of biological evolution on Earth, eventually leading to a planet that merged with plant and animal life.
By analyzing rocks from South Africa that had been deposited in the ocean at the time of the event, researchers were able to find that early oxygenation in the atmosphere was short-lived.
They also found that oxygen did not become a permanent feature of the atmosphere until much later in our planet’s evolution.
Simon Poulton, of the Leeds’ School of Earth and Environment, who led the research, said this event “fundamentally changed the environment and habitability of the Earth.”
“This early period of oxygenation was thought to have occurred about 2.43 to 2.32 billion years ago,” he explained.
However, our research shows that the oxygen supply to the atmosphere was in fact very unstable for a period of about 200 million years.
Adding to that, “permanent atmospheric oxygenation took place about 100 million years later, as previously thought.”
The study’s authors also say it should be called the Great Oxidation Episode because it ushered in a 1.5 billion year period of climate and environmental stability, enabling life form and resulting in multiple protracted ‘snowball-earth’ periods
KEY FINDINGS: OXYGEN DRAMATICALLY CHANGED THE EARTH
The rise of oxygen from the air has fundamentally changed the chemistry of the surface environments and the nature of the habitability of the Earth.
Early atmospheric oxygenation occurred over a prolonged period of extreme climatic instability characterized by multiple global ice ages.
These were related to the initial rise of the oxygen concentration above 10−5 from the current atmospheric level.
According to the study authors, this happened about 2.32 billion years ago.
This “represents the estimated timing of irreversible oxygenation of the atmosphere” rather than simply when it started and can still be reversed.
Their findings also suggest a direct link between fluctuations in atmospheric oxygen concentration and greenhouse gas concentrations.
University of California-Riverside professor Andrey Bekker, who co-authored the study, said the findings help explain four widespread ice ages.
These events coincided with the Great Oxidation Event, and some of them likely covered the entire Earth with ice for millions of years.
“Our new data shows that the permanent increase in oxygen actually occurred after the last great ice age of the period and not before,” explains Bekker.
This “had previously been a major puzzle in our understanding of relationships between early atmospheric oxygenation and intense climatic instability.”
The research team has renamed this period the Great Oxidation Episode.
It ushered in a 1.5 billion year period of subsequent climatic and ecological stability, which persisted until a second major period of increasing oxygen and climate instability at the end of the Precambrian period.
Professor David Johnston, a co-author from Harvard University, said the increase in oxygen in the air was a key factor in making the Earth habitable.
“By unraveling the history of atmospheric oxygenation, we can understand how oxygen rose to levels sufficient to allow for animal evolution,” he said.
Their findings also suggest a direct link between fluctuations in atmospheric oxygen concentration and greenhouse gas concentrations
“The Great Oxidation Episode, in which atmospheric oxygen rose to a significant level for the first time, represents a crucial step in this history.”
Professor Poulton said we need to know when permanent atmospheric oxygenation actually occurred to really understand its causes and effects.
“Now we finally have that piece of the puzzle,” he added.
The findings are published in the journal Nature
SNOWBALL EARTH: AN ICE CLIMATE COVERING OUR PLANET IN ICE
At various points in planet Earth’s history, the world was completely or almost completely frozen, covering the planet with ice.
Scientists say this explains evidence of glacial sedimentary deposits found in tropical regions of the Earth.
The name describes what the Earth looked like from space: a glittering white ball with a surface mostly covered with ice and ice crystals.
It would have resulted in gusty winds at low latitudes and a dark salty ocean moved by tides beneath the ice with heat slowly rising from geothermal vents on the ocean floor.
These global ice house events have occurred a number of times during the evolution of the planet.
Some of the earliest examples took place as early as 2.4 billion years ago, likely caused by the appearance of oxygen in the atmosphere.
This was during the Paleoproterozoic, where there was an Ice Age about 2.25 billion years ago, as seen through glacial deposits in tropical latitudes.
There were three or four major glacial events during the Neoproterozoic, about a billion years ago, some of which lasted millions of years at a time.
The thawing of these global glacial events may have resulted in a rapid explosion of life, particularly the early events shortly after the Great Oxidation.