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Volcanic activity and changes in Earth's mantle were key to rise of atmospheric oxygen
Tuesday, June 9, 2020
Oxygen first accumulated in the Earth's atmosphere about 2.4 billion years ago, during the Great Oxidation Event. A long-standing puzzle has been that geologic clues suggest early bacteria were photosynthesizing and pumping out oxygen hundreds of millions of years before then. Where was it all going?
Something was holding back oxygen's rise. A new interpretation of rocks billions of years old finds volcanic gases are the likely culprits. The study led by the University of Washington was published in June in the open-access journal Nature Communications.
"This study revives a classic hypothesis for the evolution of atmospheric oxygen," said lead author Shintaro Kadoya, a UW postdoctoral researcher in Earth and space sciences. "The data demonstrates that an evolution of the mantle of the Earth could control an evolution of the atmosphere of the Earth, and possibly an evolution of life."
Multicellular life needs a concentrated supply of oxygen, so the accumulation of oxygen is key to the evolution of oxygen-breathing life on Earth.
"If changes in the mantle controlled atmospheric oxygen, as this study suggests, the mantle might ultimately set a tempo of the evolution of life," Kadoya said.
The new work builds on a 2019 paper that found the early Earth's mantle was far less oxidized, or contained more substances that can react with oxygen, than the modern mantle. That study of ancient volcanic rocks, up to 3.55 billion years old, were collected from sites that included South Africa and Canada.
Robert Nicklas at Scripps Institution of Oceanography, Igor Puchtel at the University of Maryland, and Ariel Anbar at Arizona State University are among the authors of the 2019 study. They are also co-authors of the new paper, looking at how changes in the mantle influenced the volcanic gases that escaped to the surface.
The Archean Eon, when only microbial life was widespread on Earth, was more volcanically active than today. Volcanic eruptions are fed by magma - a mixture of molten and semi-molten rock - as well as gases that escape even when the volcano is not erupting.
Some of those gases react with oxygen, or oxidize, to form other compounds. This happens because oxygen tends to be hungry for electrons, so any atom with one or two loosely held electrons reacts with it. For instance, hydrogen released by a volcano combines with any free oxygen, removing that oxygen from the atmosphere.
The chemical makeup of Earth's mantle, or softer layer of rock below the Earth's crust, ultimately controls the types of molten rock and gases coming from volcanoes. A less-oxidized early mantle would produce more of the gases like hydrogen that combine with free oxygen. The 2019 paper shows that the mantle became gradually more oxidized from 3.5 billion years ago to today.
The new study combines that data with evidence from ancient sedimentary rocks to show a tipping point sometime after 2.5 billion years ago, when oxygen produced by microbes overcame its loss to volcanic gases and began to accumulate in the atmosphere.
"Basically, the supply of oxidizable volcanic gases was capable of gobbling up photosynthetic oxygen for hundreds of millions of years after photosynthesis evolved," said co-author David Catling, a UW professor of Earth and space sciences. "But as the mantle itself became more oxidized, fewer oxidizable volcanic gases were released. Then oxygen flooded the air when there was no longer enough volcanic gas to mop it all up."
This has implications for understanding the emergence of complex life on Earth and the possibility of life on other planets.
"The study indicates that we cannot exclude the mantle of a planet when considering the evolution of the surface and life of the planet," Kadoya said.
This research was funded by the National Science Foundation.
Analysis: It's time to rethink the disrupted US food system from the ground up | The Conversation
Friday, June 5, 2020
"The COVID-19 pandemic and resulting economic shutdowns have severely disrupted and spotlighted weaknesses in the U.S. food system. Farmers, food distributors and government agencies are working to reconfigure supply chains so that food can get to where it's needed. But there is a hidden, long-neglected dimension that should also be addressed as the nation rebuilds from the current crisis," write the UW's David Montgomery, professor of Earth and space sciences; Jennifer Otten, associate professor of environmental and occupational health sciences; and Sarah Collier, assistant professor of environmental and occupational health sciences. Read More
NSF Plots a Course for the Next Decade of Earth Sciences Research
Thursday, May 21, 2020
ESS faculty Kate Huntington is highlighted today for her leadership on the decadal vision for Earth Sciences at NSF, produced by the National Academies. A new report released this week by the National Academies of Sciences, Engineering, and Medicine, "A Vision for NSF Earth Sciences 2020–2030: Earth in Time", lays out recommendations for how the National Science Foundation (NSF) should invest in the next decade of Earth sciences research. The report highlights 12 priority questions for the field to explore from 2020 to 2030, from the deceptively simple “What is an earthquake?” to the more urgent “How can Earth science research reduce the risk and toll of geohazards?”
Link to full report:
https://www.nap.edu/catalog/25761/a-vision-for-nsf-earth-sciences-2020-2030-earth-in?mc_cid=042f9a6a09&mc_eid=9b486ee580 Read More
How routine monitors weather the pandemic storm | Eos
Tuesday, May 19, 2020
Much of routine monitoring can be done remotely these days, but networks aren't completely immune to COVID-19's society-halting symptoms. Harold Tobin, director of the UW-based Pacific Northwest Seismic Network and professor of Earth and space sciences at the UW, is quoted. Read More
Scientist killed in Mount St. Helens eruption remembered 40 years after deadly blast | KING 5
Monday, May 18, 2020
David Johnston, a scientist studying Mount St. Helens when it erupted in 1980, was killed in the blast. His body was never recovered. Steve Malone, emeritus research professor of Earth and space sciences at the UW, is quoted. Read More
A plate boundary emerges between India and Australia | Eos
Monday, May 18, 2020
Tectonic plates blanket the Earth like a patchwork quilt. Now, researchers think they've found a new plate boundary -- a line of stitching in that tectonic quilt -- in the northern Indian Ocean. Kevin Kwong, a postdoctoral scholar in Earth and space sciences at the UW, is quoted. Read More
2.9 earthquake out of Mead, WA felt across the Inland Northwest on Friday afternoon | KREM
Monday, May 18, 2020
A 2.9 magnitude earthquake hit Mead, Washington around 2:30 p.m. on Friday according to the United States Geological Survey. Paul Bodin, UW research professor of Earth and space sciences and network manager of the UW-based Pacific Northwest Seismic Network, is referenced. Read More
40 years after Mount St. Helens eruption, pandemic sparks parallels | Geekwire
Sunday, May 17, 2020
Seismologist Steve Malone, emeritus research professor of Earth and space sciences at the UW, feels a magnitude-5.1 rumble of deja vu whenever he hears the latest developments in the debate over reopening businesses amid the coronavirus outbreak. It reminds Malone of the debate that raged in the days before Mount St. Helens blew its top on May 18, 1980. Read More
1,000-year-old bones represent oldest tsunami victims in East Africa | National Geographic
Wednesday, May 13, 2020
A thousand years ago, a thriving early Swahili village bustled on the banks of Tanzania's Pangani River a few miles inland from the Inidan Ocean. Residents built their houses out of wood lattices daubed with earth. They filled their nets with fish and crafted beads from shells. And then one day, a tsunami barreled in, triggered by an earthquake on the other side of the Indian Ocean. Jody Bourgeois, professor emeritus of Earth and space sciences at the UW, is quoted. Read More
Seismologists to host virtual event on 40th anniversary of Mount St. Helens eruption
Tuesday, May 12, 2020
The Pacific Northwest Seismic Network, based at the University of Washington, will host an online event on the 40th anniversary of the eruption of Mount St. Helens, featuring seismologists from the UW and other institutions who can explain the events before, during and after the historic blast.
The virtual event will take place from 6:30 to 8 p.m., Monday, May 18, on the PNSN's YouTube channel — exactly 40 years after the blast. The group will stream prerecorded talks from four speakers and then host a live Q&A of questions on the network's Facebook page. Moderator Harold Tobin, director of the PNSN and a UW professor of Earth and space sciences, will select audience questions.
Mount St Helens 40th Anniversary
- Attend the virtual event
- Read "After the Ashes" in UW Magazine’s March issue — an excerpt from "After The Blast: The Ecological Recovery of Mount St. Helens" published by UW Press
- View historical photos of Mount St. Helens from UW Libraries Special Collection
The presenters will review the region's tectonics, volcanoes and volcanic hazards, and summarize how the science and monitoring has evolved over the past four decades.
Steve Malone, research professor emeritus of Earth and space sciences, was intimately involved with recording and interpreting the earthquake buildup to the massive eruption. His personal story of the two months leading up to the 1980 eruption will illustrate the difficulty and uncertainty of dealing with a developing natural disaster in real time.
Seth Moran did his doctorate at the UW with Malone and is now scientist-in-charge at the U.S. Geological Survey's Cascade Volcano Observatory. He will describe the more recent activity at Mount St. Helens and the USGS work on volcano monitoring throughout the Cascades.
Jackie Caplan-Auerbach, a professor of geophysics at Western Washington University whose research focuses on volcanoes and landslides, will discuss plate tectonics and the origin of the Cascade volcanoes.
Josef Dufek, professor at the University of Oregon, will discuss the individual character of different volcanoes and volcanic hazards.
For more information on the event, contact PNSN communications director Bill Steele at email@example.com or 206-685-5880.