Hannah Hickey
UW News
Roger Buick in 2004 at the Mount McRae Shale in Western Australia. Rocks drilled near here show “whiffs” of oxygen occurred before the Great Oxidation Event, 2.4 billion years ago. New analyses show a slightly earlier spike in the element mercury emitted by volcanoes, which could have boosted populations of single-celled organisms to produce a temporary “whiff” of oxygen.
A new analysis of 2.5-billion-year-old rocks from Australia finds that volcanic eruptions may have stimulated population surges of marine microorganisms, creating the first puffs of oxygen into the atmosphere. This would change existing stories of Earth’s early atmosphere, which assumed that most changes in the early atmosphere were controlled by geologic or chemical processes.
Though focused on Earth’s early history, the research also has implications for extraterrestrial life and even climate change. The study led by the University of Washington, the University of Michigan and other institutions was published in August in the Proceedings of the National Academy of Sciences.
“What has started to become obvious in the past few decades is there actually are quite a number of connections between the solid, nonliving Earth and the evolution of life,” said first author Jana Meixnerová, a UW doctoral student in Earth and space sciences. “But what are the specific connections that facilitated the evolution of life on Earth as we know it?”
In its earliest days, Earth had no oxygen in its atmosphere and few, if any, oxygen-breathing lifeforms. Earth’s atmosphere became permanently oxygen-rich about 2.4 billion years ago, likely after an explosion of lifeforms that photosynthesize, transforming carbon dioxide and water into oxygen.
UW News | July 2018: “Oxygen levels on early Earth rose and fell several times before the successful Great Oxidation Event“
But in 2007, co-author Ariel Anbar at Arizona State University analyzed rocks from the Mount McRae Shale in Western Australia, reporting a short-term whiff of oxygen about 50 to 100 million years before it became a permanent fixture in the atmosphere. More recent research has confirmed other, earlier short-term oxygen spikes, but hasn’t explained their rise and fall.
In the new study, researchers at the University of Michigan, led by co-corresponding author Joel Blum, analyzed the same ancient rocks for the concentration and number of neutrons in the element mercury, emitted by volcanic eruptions. Large volcanic eruptions blast mercury gas into the upper atmosphere, where today it circulates for a year or two before raining out onto Earth’s surface. The new analysis shows a spike in mercury a few million years before the temporary rise in oxygen.
These are drill-cores of rocks from the Mount McRae Shale in Western Australia. Previous analysis showed a “whiff” of atmospheric oxygen preceding the Great Oxidation Event, 2.4 billion years ago. New analyses show a slightly earlier spike in minerals produced by volcanoes, which may have fertilized early communities of microbes to produce the oxygen.Roger Buick/University of Washington
“Sure enough, in the rock below the transient spike in oxygen we found evidence of mercury, both in its abundance and isotopes, that would most reasonably be explained by volcanic eruptions into the atmosphere,” said co-author Roger Buick, a UW professor of Earth and Space Sciences.
Where there were volcanic emissions, the authors reason, there must have been lava and volcanic ash fields. And those nutrient-rich rocks would have weathered in the wind and rain, releasing phosphorus into rivers that could fertilize nearby coastal areas, allowing oxygen-producing cyanobacteria and other single-celled lifeforms to flourish.
“There are other nutrients that modulate biological activity on short timescales, but phosphorus is the one that is most important on long timescales,” Meixnerová said.
Today, phosphorus is plentiful in biological material and in agricultural fertilizer. But in very ancient times, weathering of volcanic rocks would have been the main source for this scarce resource.
“During weathering under the Archaean atmosphere, the fresh basaltic rock would have slowly dissolved, releasing the essential macro-nutrient phosphorus into the rivers. That would have fed microbes that were living in the shallow coastal zones and triggered increased biological productivity that would have created, as a byproduct, an oxygen spike,” Meixnerová said.
The precise location of those volcanoes and lava fields is unknown, but large lava fields of about the right age exist in modern-day India, Canada and elsewhere, Buick said.
“Our study suggests that for these transient whiffs of oxygen, the immediate trigger was an increase in oxygen production, rather than a decrease in oxygen consumption by rocks or other nonliving processes,” Buick said. “It’s important because the presence of oxygen in the atmosphere is fundamental – it’s the biggest driver for the evolution of large, complex life.”
Ultimately, researchers say the study suggests how a planet’s geology might affect any life evolving on its surface, an understanding that aids in identifying habitable exoplanets, or planets outside our solar system, in the search for life in the universe.
Other authors of the paper are co-corresponding author Eva Stüeken, a former UW astrobiology graduate student now at the University of St. Andrews in Scotland; Michael Kipp, a former UW graduate student now at the California Institute of Technology; and Marcus Johnson at the University of Michigan. The study was funded by NASA, the NASA-funded UW Virtual Planetary Laboratory team and the MacArthur Professorship to Blum at the University of Michigan.
For more information contact Meixnerová at janameix@uw.edu or Buick at buick@uw.edu. Note: Meixnerová is on European Time; Buick is on Pacific Time.
NASA: NNX16AI37G, 80NSSC18K0829
Volcanoes Have Been Acting As A Safety Valve For Earth's Long-term Climate: Research
Researchers of the University of Southampton have found concrete evidence to establish volcanoes are responsible for maintaining temperatures at Earth's surface
Image Credit: AP
Researchers of the University of Southampton have found concrete evidence to establish that volcanoes are responsible for maintaining temperatures at Earth's surface. The scientists also noted that it is the volcano that acts as a safety valve for Earth's long-term climate. The latest findings which were published in the journal 'Nature Geoscience' found that widespread series of volcanoes have been responsible for both emitting and then extracting climatic carbon dioxide (CO2) over geological time. According to the journal, scientists from the University of Leeds, University of Southampton, University of Sydney, Australian National University (ANU) and the University of Ottawa have contributed to the latest finding that explored the combined impact of processes in the Earth, oceans and atmosphere over the past 400 million years.
They found that the natural break-down and dissolution of rocks at Earth's surface (chemical weathering) flushes elements like calcium and magnesium via rivers to the oceans. Later, they form minerals that lock up CO2. "In this respect, weathering of the Earth's surface serves as a geological thermostat," said lead author Dr Tom Gernon, Associate Professor in Earth Science at the University of Southampton, and a Fellow of the Turing Institute. "But the underlying controls have proven difficult to determine due to the complexity of the Earth system," added Dr Gernon. "Many Earth processes are interlinked, and there are some major time lags between processes and their effects," explained Eelco Rohling, Professor in Ocean and Climate Change at ANU and co-author of the study.
Research throws uncertainty on a long-held theory
"Understanding the relative influence of specific processes within the Earth system response has therefore been an intractable problem," continued Rohling. The team, further constructed a novel "Earth network", combining machine-learning algorithms and plate tectonic restoration. The research throws uncertainty on a long-held theory that Earth's atmosphere balance over tens to hundreds of millions of years exhibits equilibrium between weathering of the seafloor and continental interiors. "The idea of such a geological tug of war between the landmasses and the seafloor as a dominant driver of Earth surface weathering is not supported by the data," stated Dr Gernon. "Unfortunately, the results do not mean that nature will save us from climate change," stressed Dr Gernon. "Today, atmospheric CO2 levels are higher than at any time in the past 3 million years, and human-driven emissions are about 150 times larger than volcanic CO2 emissions," explained Dr Gernon.
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