Our planet has not always been a suitable place for life, and even though our atmosphere has changed throughout eons to provide the air we breathe, the process in which it has undergone was intense according to a new study.
HOW WAS EARTH ABLE TO PRODUCE BREATHABLE OXYGEN?
The new study, which was published in Nature Geoscience, explains how volcanic eruption caused by shifting tectonic plates could have contributed to the dramatic changes in the planet's atmosphere. The spike in oxygen production is attributed to how the crust and the mantle are moving and how their movements trigger chemical reactions.
Researchers from Rice University created a new model that can possibly explain the Great Oxidation Event and the Lomagundi event. Both of these are two long-standing geological mysteries that occurred 2.4 billion and 100 million years ago, respectively.
WHAT IS THE GREAT OXIDATION EVENT?
To understand how life came to be, it is important to note the atmospheric history of the planet, which allowed life to succeed. One of the important events in atmospheric history is the Great Oxidation Event, wherein the Earth's shallow oceans experienced a dramatic increase in oxygen. Millions of years, later the planet experienced a drop in oxygen in the atmosphere, and this was called the Lomagundi event, the most prominent carbon isotope event in the planet's atmospheric history. The causes of the said oxidation events were unclear until recently.
The researchers would like to focus on carbon isotopes in explaining these events. Since carbon has three naturally-occurring isotopes (variants can be determined based on the number of neutrons), the ratio of carbon-12 and carbon-13 isotopes becomes a useful tool for studying natural systems, especially in the atmosphere. This is because carbon-12 and carbon-13 come from different sources. Geoscientist James Eguchi from the University of California Riverside explains, "what makes this unique is that it's not just trying to explain the rise of oxygen. It is also trying to explain some closely associated surface geochemistry, a change in the composition of carbon isotopes that are observed in the carbonate rock record shortly after the oxidation event."
Eguchi also explained that the team is trying to explain how the events occurred by using a single mechanism that involves the interior of the Earth, tectonics, and enhanced degassing of carbon dioxide from volcanoes. Prior to this study, the most accepted explanation is that photosynthesis was behind the Great Oxidation Event through cyanobacteria which excrete oxygen as a waste product. Eguchi and his team recognize the validity of that explanation and how it played a big part, but something bigger is occurring within the planet's crust and mantle.
HOW THE EARTH'S INTERIOR PLAYED A MAJOR ROLE IN THE PLANET'S OXIDATION
Scientists behind the study used detail modeling and discovered that an increase in tectonic activity produced new volcanoes prior to the Great Oxidation Event which pumped big amounts of carbon dioxide in the air which led to the warming of the climate, increased rainfall, and leading to more minerals washed into the ocean. These phenomena led to the boom of cyanobacteria and carbonates. The increase in photosynthesis is attributed to the rise in the population of cyanobacteria and in turn, the carbon present in the atmosphere was buried underground. Eguchi said that it's kind of a big cyclic process. He also explained that carbon-rich in inorganic-derived carbon-13 isotopes would have reappeared first through volcanic activities meanwhile carbon-12-rich carbon appeared later via other volcanic hotspots. "We're proposing that carbon dioxide emissions were very important to this proliferation of life," he says. "It's really trying to tie in how these deeper processes have affected surface life on our planet in the past."
