Volcanoes, including Mount Hood in the US, can quickly become active

Researchers have discovered that volcanoes can go from dormant to active very quickly. -  OSU
Researchers have discovered that volcanoes can go from dormant to active very quickly. – OSU

New research results suggest that magma sitting 4-5 kilometers beneath the surface of Oregon’s Mount Hood has been stored in near-solid conditions for thousands of years.

The time it takes to liquefy and potentially erupt, however, is surprisingly short–perhaps as little as a couple of months.

The key to an eruption, geoscientists say, is to elevate the temperature of the rock to more than 750 degrees Celsius, which can happen when hot magma from deep within the Earth’s crust rises to the surface.

It was the mixing of hot liquid lava with cooler solid magma that triggered Mount Hood’s last two eruptions about 220 and 1,500 years ago, said Adam Kent, an Oregon State University (OSU) geologist and co-author of a paper reporting the new findings.

Results of the research, which was funded by the National Science Foundation (NSF), are in this week’s journal Nature.

“These scientists have used a clever new approach to timing the inner workings of Mount Hood, an important step in assessing volcanic hazards in the Cascades,” said Sonia Esperanca, a program director in NSF’s Division of Earth Sciences.

“If the temperature of the rock is too cold, the magma is like peanut butter in a refrigerator,” Kent said. “It isn’t very mobile.

“For Mount Hood, the threshold seems to be about 750 degrees (C)–if it warms up just 50 to 75 degrees above that, it greatly decreases the viscosity of the magma and makes it easier to mobilize.”

The scientists are interested in the temperature at which magma resides in the crust, since it’s likely to have important influence over the timing and types of eruptions that could occur.

The hotter magma from deeper down warms the cooler magma stored at a 4-5 kilometer depth, making it possible for both magmas to mix and be transported to the surface to produce an eruption.

The good news, Kent said, is that Mount Hood’s eruptions are not particularly violent. Instead of exploding, the magma tends to ooze out the top of the peak.

A previous study by Kent and OSU researcher Alison Koleszar found that the mixing of the two magma sources, which have different compositions, is both a trigger to an eruption and a constraining factor on how violent it can be.

“What happens when they mix is what happens when you squeeze a tube of toothpaste in the middle,” said Kent. “Some comes out the top, but in the case of Mount Hood it doesn’t blow the mountain to pieces.”

The study involved scientists at OSU and the University of California, Davis. The results are important, they say, because little was known about the physical conditions of magma storage and what it takes to mobilize that magma.

Kent and UC-Davis colleague Kari Cooper, also a co-author of the Nature paper, set out to discover whether they could determine how long Mount Hood’s magma chamber has been there, and in what condition.

When Mount Hood’s magma first rose up through the crust into its present-day chamber, it cooled and formed crystals.

The researchers were able to document the age of the crystals by the rate of decay of naturally occurring radioactive elements. However, the growth of the crystals is also dictated by temperature: if the rock is too cold, they don’t grow as fast.

The combination of the crystals’ age and apparent growth rate provides a geologic fingerprint for determining the approximate threshold for making the near-solid rock viscous enough to cause an eruption.

“What we found was that the magma has been stored beneath Mount Hood for at least 20,000 years–and probably more like 100,000 years,” Kent said.

“During the time it’s been there, it’s been in cold storage–like peanut butter in the fridge–a minimum of 88 percent of the time, and likely more than 99 percent of the time.”

Although hot magma from below can quickly mobilize the magma chamber at 4-5 kilometers below the surface, most of the time magma is held under conditions that make it difficult for it to erupt.

“What’s encouraging is that modern technology should be able to detect when the magma is beginning to liquefy or mobilize,” Kent said, “and that may give us warning of a potential eruption.

“Monitoring gases and seismic waves, and studying ground deformation through GPS, are a few of the techniques that could tell us that things are warming.”

The researchers hope to apply these techniques to other, larger volcanoes to see if they can determine the potential for shifting from cold storage to potential eruption–a development that might bring scientists a step closer to being able to forecast volcanic activity.

Volcanoes, including Mount Hood in the US, can quickly become active

Researchers have discovered that volcanoes can go from dormant to active very quickly. -  OSU
Researchers have discovered that volcanoes can go from dormant to active very quickly. – OSU

New research results suggest that magma sitting 4-5 kilometers beneath the surface of Oregon’s Mount Hood has been stored in near-solid conditions for thousands of years.

The time it takes to liquefy and potentially erupt, however, is surprisingly short–perhaps as little as a couple of months.

The key to an eruption, geoscientists say, is to elevate the temperature of the rock to more than 750 degrees Celsius, which can happen when hot magma from deep within the Earth’s crust rises to the surface.

It was the mixing of hot liquid lava with cooler solid magma that triggered Mount Hood’s last two eruptions about 220 and 1,500 years ago, said Adam Kent, an Oregon State University (OSU) geologist and co-author of a paper reporting the new findings.

Results of the research, which was funded by the National Science Foundation (NSF), are in this week’s journal Nature.

“These scientists have used a clever new approach to timing the inner workings of Mount Hood, an important step in assessing volcanic hazards in the Cascades,” said Sonia Esperanca, a program director in NSF’s Division of Earth Sciences.

“If the temperature of the rock is too cold, the magma is like peanut butter in a refrigerator,” Kent said. “It isn’t very mobile.

“For Mount Hood, the threshold seems to be about 750 degrees (C)–if it warms up just 50 to 75 degrees above that, it greatly decreases the viscosity of the magma and makes it easier to mobilize.”

The scientists are interested in the temperature at which magma resides in the crust, since it’s likely to have important influence over the timing and types of eruptions that could occur.

The hotter magma from deeper down warms the cooler magma stored at a 4-5 kilometer depth, making it possible for both magmas to mix and be transported to the surface to produce an eruption.

The good news, Kent said, is that Mount Hood’s eruptions are not particularly violent. Instead of exploding, the magma tends to ooze out the top of the peak.

A previous study by Kent and OSU researcher Alison Koleszar found that the mixing of the two magma sources, which have different compositions, is both a trigger to an eruption and a constraining factor on how violent it can be.

“What happens when they mix is what happens when you squeeze a tube of toothpaste in the middle,” said Kent. “Some comes out the top, but in the case of Mount Hood it doesn’t blow the mountain to pieces.”

The study involved scientists at OSU and the University of California, Davis. The results are important, they say, because little was known about the physical conditions of magma storage and what it takes to mobilize that magma.

Kent and UC-Davis colleague Kari Cooper, also a co-author of the Nature paper, set out to discover whether they could determine how long Mount Hood’s magma chamber has been there, and in what condition.

When Mount Hood’s magma first rose up through the crust into its present-day chamber, it cooled and formed crystals.

The researchers were able to document the age of the crystals by the rate of decay of naturally occurring radioactive elements. However, the growth of the crystals is also dictated by temperature: if the rock is too cold, they don’t grow as fast.

The combination of the crystals’ age and apparent growth rate provides a geologic fingerprint for determining the approximate threshold for making the near-solid rock viscous enough to cause an eruption.

“What we found was that the magma has been stored beneath Mount Hood for at least 20,000 years–and probably more like 100,000 years,” Kent said.

“During the time it’s been there, it’s been in cold storage–like peanut butter in the fridge–a minimum of 88 percent of the time, and likely more than 99 percent of the time.”

Although hot magma from below can quickly mobilize the magma chamber at 4-5 kilometers below the surface, most of the time magma is held under conditions that make it difficult for it to erupt.

“What’s encouraging is that modern technology should be able to detect when the magma is beginning to liquefy or mobilize,” Kent said, “and that may give us warning of a potential eruption.

“Monitoring gases and seismic waves, and studying ground deformation through GPS, are a few of the techniques that could tell us that things are warming.”

The researchers hope to apply these techniques to other, larger volcanoes to see if they can determine the potential for shifting from cold storage to potential eruption–a development that might bring scientists a step closer to being able to forecast volcanic activity.

Volcanoes contribute to recent warming ‘hiatus’

Volcanic eruptions in the early part of the 21st century have cooled the planet, according to a study led by Lawrence Livermore National Laboratory. This cooling partly offset the warming produced by greenhouse gases.

Despite continuing increases in atmospheric levels of greenhouse gases, and in the total heat content of the ocean, global-mean temperatures at the surface of the planet and in the troposphere (the lowest portion of the Earth’s atmosphere) have shown relatively little warming since 1998. This so-called ‘slow-down’ or ‘hiatus’ has received considerable scientific, political and popular attention. The volcanic contribution to the ‘slow-down’ is the subject of a new paper appearing in the Feb. 23 edition of the journal Nature Geoscience.

Volcanic eruptions inject sulfur dioxide gas into the atmosphere. If the eruptions are large enough to add sulfur dioxide to the stratosphere (the atmospheric layer above the troposphere), the gas forms tiny droplets of sulfuric acid, also known as “volcanic aerosols.” These droplets reflect some portion of the incoming sunlight back into space, cooling the Earth’s surface and the lower atmosphere.

“In the last decade, the amount of volcanic aerosol in the stratosphere has increased, so more sunlight is being reflected back into space,” said Lawrence Livermore climate scientist Benjamin Santer, who serves as lead author of the study. “This has created a natural cooling of the planet and has partly offset the increase in surface and atmospheric temperatures due to human influence.”

From 2000-2012, emissions of greenhouse gases into the atmosphere have increased — as they have done since the Industrial Revolution. This human-induced change typically causes the troposphere to warm and the stratosphere to cool. In contrast, large volcanic eruptions cool the troposphere and warm the stratosphere. The researchers report that early 21st century volcanic eruptions have contributed to this recent “warming hiatus,” and that most climate models have not accurately accounted for this effect.

“The recent slow-down in observed surface and tropospheric warming is a fascinating detective story,” Santer said. “There is not a single culprit, as some scientists have claimed. Multiple factors are implicated. One is the temporary cooling effect of internal climate noise. Other factors are the external cooling influences of 21st century volcanic activity, an unusually low and long minimum in the last solar cycle, and an uptick in Chinese emissions of sulfur dioxide.

” The real scientific challenge is to obtain hard quantitative estimates of the contributions of each of these factors to the slow-down.”

The researchers performed two different statistical tests to determine whether recent volcanic eruptions have cooling effects that can be distinguished from the intrinsic variability of the climate. The team found evidence for significant correlations between volcanic aerosol observations and satellite-based estimates of lower tropospheric temperatures as well as the sunlight reflected back to space by the aerosol particles.

“This is the most comprehensive observational evaluation of the role of volcanic activity on climate in the early part of the 21st century,” said co-author Susan Solomon, the Ellen Swallow Richards professor of atmospheric chemistry and climate science at MIT. “We assess the contributions of volcanoes on temperatures in the troposphere – the lowest layer of the atmosphere – and find they’ve certainly played some role in keeping the Earth cooler.”

Volcanoes contribute to recent warming ‘hiatus’

Volcanic eruptions in the early part of the 21st century have cooled the planet, according to a study led by Lawrence Livermore National Laboratory. This cooling partly offset the warming produced by greenhouse gases.

Despite continuing increases in atmospheric levels of greenhouse gases, and in the total heat content of the ocean, global-mean temperatures at the surface of the planet and in the troposphere (the lowest portion of the Earth’s atmosphere) have shown relatively little warming since 1998. This so-called ‘slow-down’ or ‘hiatus’ has received considerable scientific, political and popular attention. The volcanic contribution to the ‘slow-down’ is the subject of a new paper appearing in the Feb. 23 edition of the journal Nature Geoscience.

Volcanic eruptions inject sulfur dioxide gas into the atmosphere. If the eruptions are large enough to add sulfur dioxide to the stratosphere (the atmospheric layer above the troposphere), the gas forms tiny droplets of sulfuric acid, also known as “volcanic aerosols.” These droplets reflect some portion of the incoming sunlight back into space, cooling the Earth’s surface and the lower atmosphere.

“In the last decade, the amount of volcanic aerosol in the stratosphere has increased, so more sunlight is being reflected back into space,” said Lawrence Livermore climate scientist Benjamin Santer, who serves as lead author of the study. “This has created a natural cooling of the planet and has partly offset the increase in surface and atmospheric temperatures due to human influence.”

From 2000-2012, emissions of greenhouse gases into the atmosphere have increased — as they have done since the Industrial Revolution. This human-induced change typically causes the troposphere to warm and the stratosphere to cool. In contrast, large volcanic eruptions cool the troposphere and warm the stratosphere. The researchers report that early 21st century volcanic eruptions have contributed to this recent “warming hiatus,” and that most climate models have not accurately accounted for this effect.

“The recent slow-down in observed surface and tropospheric warming is a fascinating detective story,” Santer said. “There is not a single culprit, as some scientists have claimed. Multiple factors are implicated. One is the temporary cooling effect of internal climate noise. Other factors are the external cooling influences of 21st century volcanic activity, an unusually low and long minimum in the last solar cycle, and an uptick in Chinese emissions of sulfur dioxide.

” The real scientific challenge is to obtain hard quantitative estimates of the contributions of each of these factors to the slow-down.”

The researchers performed two different statistical tests to determine whether recent volcanic eruptions have cooling effects that can be distinguished from the intrinsic variability of the climate. The team found evidence for significant correlations between volcanic aerosol observations and satellite-based estimates of lower tropospheric temperatures as well as the sunlight reflected back to space by the aerosol particles.

“This is the most comprehensive observational evaluation of the role of volcanic activity on climate in the early part of the 21st century,” said co-author Susan Solomon, the Ellen Swallow Richards professor of atmospheric chemistry and climate science at MIT. “We assess the contributions of volcanoes on temperatures in the troposphere – the lowest layer of the atmosphere – and find they’ve certainly played some role in keeping the Earth cooler.”

Oldest bit of crust firms up idea of a cool early Earth

A 4.4 billion-year-old zircon crystal is providing new insight into how the early Earth cooled from a ball of magma and formed continents just 160 million years after the formation of our solar system, much earlier than previously believed. The zircon, pictured here, is from the Jack Hills region of Australia and is now confirmed to be the oldest bit of the Earth's crust. -  John Valley
A 4.4 billion-year-old zircon crystal is providing new insight into how the early Earth cooled from a ball of magma and formed continents just 160 million years after the formation of our solar system, much earlier than previously believed. The zircon, pictured here, is from the Jack Hills region of Australia and is now confirmed to be the oldest bit of the Earth’s crust. – John Valley

With the help of a tiny fragment of zircon extracted from a remote rock outcrop in Australia, the picture of how our planet became habitable to life about 4.4 billion years ago is coming into sharper focus.

Writing today (Feb. 23, 2014) in the journal Nature Geoscience, an international team of researchers led by University of Wisconsin-Madison geoscience Professor John Valley reveals data that confirm the Earth’s crust first formed at least 4.4 billion years ago, just 160 million years after the formation of our solar system. The work shows, Valley says, that the time when our planet was a fiery ball covered in a magma ocean came earlier.

“This confirms our view of how the Earth cooled and became habitable,” says Valley, a geochemist whose studies of zircons, the oldest known terrestrial materials, have helped portray how the Earth’s crust formed during the first geologic eon of the planet. “This may also help us understand how other habitable planets would form.”

The new study confirms that zircon crystals from Western Australia’s Jack Hills region crystallized 4.4 billion years ago, building on earlier studies that used lead isotopes to date the Australian zircons and identify them as the oldest bits of the Earth’s crust. The microscopic zircon crystal used by Valley and his group in the current study is now confirmed to be the oldest known material of any kind formed on Earth.

The study, according to Valley, strengthens the theory of a “cool early Earth,” where temperatures were low enough for liquid water, oceans and a hydrosphere not long after the planet’s crust congealed from a sea of molten rock. “The study reinforces our conclusion that Earth had a hydrosphere before 4.3 billion years ago,” and possibly life not long after, says Valley.

The study was conducted using a new technique called atom-probe tomography that, in conjunction with secondary ion mass spectrometry, permitted the scientists to accurately establish the age and thermal history of the zircon by determining the mass of individual atoms of lead in the sample. Instead of being randomly distributed in the sample, as predicted, lead atoms in the zircon were clumped together, like “raisins in a pudding,” notes Valley.

The clusters of lead atoms formed 1 billion years after crystallization of the zircon, by which time the radioactive decay of uranium had formed the lead atoms that then diffused into clusters during reheating. “The zircon formed 4.4 billion years ago, and at 3.4 billion years, all the lead that existed at that time was concentrated in these hotspots,” Valley says. “This allows us to read a new page of the thermal history recorded by these tiny zircon time capsules.”

The formation, isotope ratio and size of the clumps – less than 50 atoms in diameter – become, in effect, a clock, says Valley, and verify that existing geochronology methods provide reliable and accurate estimates of the sample’s age. In addition, Valley and his group measured oxygen isotope ratios, which give evidence of early homogenization and later cooling of the Earth.

“The Earth was assembled from a lot of heterogeneous material from the solar system,” Valley explains, noting that the early Earth experienced intense bombardment by meteors, including a collision with a Mars-sized object about 4.5 billion years ago “that formed our moon, and melted and homogenized the Earth. Our samples formed after the magma oceans cooled and prove that these events were very early.”

Oldest bit of crust firms up idea of a cool early Earth

A 4.4 billion-year-old zircon crystal is providing new insight into how the early Earth cooled from a ball of magma and formed continents just 160 million years after the formation of our solar system, much earlier than previously believed. The zircon, pictured here, is from the Jack Hills region of Australia and is now confirmed to be the oldest bit of the Earth's crust. -  John Valley
A 4.4 billion-year-old zircon crystal is providing new insight into how the early Earth cooled from a ball of magma and formed continents just 160 million years after the formation of our solar system, much earlier than previously believed. The zircon, pictured here, is from the Jack Hills region of Australia and is now confirmed to be the oldest bit of the Earth’s crust. – John Valley

With the help of a tiny fragment of zircon extracted from a remote rock outcrop in Australia, the picture of how our planet became habitable to life about 4.4 billion years ago is coming into sharper focus.

Writing today (Feb. 23, 2014) in the journal Nature Geoscience, an international team of researchers led by University of Wisconsin-Madison geoscience Professor John Valley reveals data that confirm the Earth’s crust first formed at least 4.4 billion years ago, just 160 million years after the formation of our solar system. The work shows, Valley says, that the time when our planet was a fiery ball covered in a magma ocean came earlier.

“This confirms our view of how the Earth cooled and became habitable,” says Valley, a geochemist whose studies of zircons, the oldest known terrestrial materials, have helped portray how the Earth’s crust formed during the first geologic eon of the planet. “This may also help us understand how other habitable planets would form.”

The new study confirms that zircon crystals from Western Australia’s Jack Hills region crystallized 4.4 billion years ago, building on earlier studies that used lead isotopes to date the Australian zircons and identify them as the oldest bits of the Earth’s crust. The microscopic zircon crystal used by Valley and his group in the current study is now confirmed to be the oldest known material of any kind formed on Earth.

The study, according to Valley, strengthens the theory of a “cool early Earth,” where temperatures were low enough for liquid water, oceans and a hydrosphere not long after the planet’s crust congealed from a sea of molten rock. “The study reinforces our conclusion that Earth had a hydrosphere before 4.3 billion years ago,” and possibly life not long after, says Valley.

The study was conducted using a new technique called atom-probe tomography that, in conjunction with secondary ion mass spectrometry, permitted the scientists to accurately establish the age and thermal history of the zircon by determining the mass of individual atoms of lead in the sample. Instead of being randomly distributed in the sample, as predicted, lead atoms in the zircon were clumped together, like “raisins in a pudding,” notes Valley.

The clusters of lead atoms formed 1 billion years after crystallization of the zircon, by which time the radioactive decay of uranium had formed the lead atoms that then diffused into clusters during reheating. “The zircon formed 4.4 billion years ago, and at 3.4 billion years, all the lead that existed at that time was concentrated in these hotspots,” Valley says. “This allows us to read a new page of the thermal history recorded by these tiny zircon time capsules.”

The formation, isotope ratio and size of the clumps – less than 50 atoms in diameter – become, in effect, a clock, says Valley, and verify that existing geochronology methods provide reliable and accurate estimates of the sample’s age. In addition, Valley and his group measured oxygen isotope ratios, which give evidence of early homogenization and later cooling of the Earth.

“The Earth was assembled from a lot of heterogeneous material from the solar system,” Valley explains, noting that the early Earth experienced intense bombardment by meteors, including a collision with a Mars-sized object about 4.5 billion years ago “that formed our moon, and melted and homogenized the Earth. Our samples formed after the magma oceans cooled and prove that these events were very early.”

Current ice melt rate in Pine Island Glacier may go on for decades

A study of the Pine Island Glacier could provide insight into the patterns and duration of glacial melt.

The Pine Island Glacier, a major outlet of the West Antarctic Ice Sheet, has been undergoing rapid melting and retreating for the past two decades. But new research by an international team including researchers from Lawrence Livermore National Laboratory shows that this same glacier also experienced rapid thinning about 8,000 years ago.

Using LLNL’s Center for Accelerator Mass Spectrometry to measure beryllium-10 produced by cosmic rays in glacially transported rocks, Lawrence Livermore researchers Bob Finkel and Dylan Rood reported that the melting 8,000 years ago was sustained for decades to centuries at an average rate of more than 100 centimeters per year. This is comparable to modern-day melting rates.

The findings indicate that modern-day melting and thinning could last for several more decades or even centuries. The research appears in the Feb. 20 issue of Science Express.

“Pine Island Glacier has experienced rapid thinning at least once in the past. Once set in motion, rapid ice sheet changes in this region can persist for centuries,” said Finkel, one of the authors of the new findings.

Ice mass loss from the Pine Island-Thwaites sector dramatically contributes to the sea level of the West Antarctic Ice Sheet. The Pine Island Glacier is currently experiencing significant acceleration, thinning and retreat. The rate of thinning from 2002-2007 on the grounding line (the part where the glaciers export the ice down the continent and lose contact to the ground and become a floating ice shelf) was between 1.2 meters per year and 6 meters per year.

The change is likely tied to the increased influx of warm water to the cavity under the ice shelf at the glacial front.

Dramatic changes over longer timescales — from centuries to millennia — are somewhat limited, so there is considerable uncertainty associated with model projections of the future evolution of timing and ice loss of the Pine Island Glacier. Current geological research is tied to the grounding line retreat across the continental shelf. However, little is known about the terrestrial thinning history and how the ice stream evolved from 8,000 years ago to the onset of present-day thinning.

The team found that there was a direct correlation from glacial-geological samples consisting of cobblestones and granite boulders from the Hudson Mountains to rapid thinning in the Pine Island Glacier system about 8,000 years ago.

“The melting of the Pine Island Glacier at a rate comparable to that over the past two decades is rare but not unprecedented,” Rood said. “Ongoing ocean-driven melting of the glacial ice shelf in current times may result in continued rapid thinning and ground line retreat for several more decades or even centuries.”

Current ice melt rate in Pine Island Glacier may go on for decades

A study of the Pine Island Glacier could provide insight into the patterns and duration of glacial melt.

The Pine Island Glacier, a major outlet of the West Antarctic Ice Sheet, has been undergoing rapid melting and retreating for the past two decades. But new research by an international team including researchers from Lawrence Livermore National Laboratory shows that this same glacier also experienced rapid thinning about 8,000 years ago.

Using LLNL’s Center for Accelerator Mass Spectrometry to measure beryllium-10 produced by cosmic rays in glacially transported rocks, Lawrence Livermore researchers Bob Finkel and Dylan Rood reported that the melting 8,000 years ago was sustained for decades to centuries at an average rate of more than 100 centimeters per year. This is comparable to modern-day melting rates.

The findings indicate that modern-day melting and thinning could last for several more decades or even centuries. The research appears in the Feb. 20 issue of Science Express.

“Pine Island Glacier has experienced rapid thinning at least once in the past. Once set in motion, rapid ice sheet changes in this region can persist for centuries,” said Finkel, one of the authors of the new findings.

Ice mass loss from the Pine Island-Thwaites sector dramatically contributes to the sea level of the West Antarctic Ice Sheet. The Pine Island Glacier is currently experiencing significant acceleration, thinning and retreat. The rate of thinning from 2002-2007 on the grounding line (the part where the glaciers export the ice down the continent and lose contact to the ground and become a floating ice shelf) was between 1.2 meters per year and 6 meters per year.

The change is likely tied to the increased influx of warm water to the cavity under the ice shelf at the glacial front.

Dramatic changes over longer timescales — from centuries to millennia — are somewhat limited, so there is considerable uncertainty associated with model projections of the future evolution of timing and ice loss of the Pine Island Glacier. Current geological research is tied to the grounding line retreat across the continental shelf. However, little is known about the terrestrial thinning history and how the ice stream evolved from 8,000 years ago to the onset of present-day thinning.

The team found that there was a direct correlation from glacial-geological samples consisting of cobblestones and granite boulders from the Hudson Mountains to rapid thinning in the Pine Island Glacier system about 8,000 years ago.

“The melting of the Pine Island Glacier at a rate comparable to that over the past two decades is rare but not unprecedented,” Rood said. “Ongoing ocean-driven melting of the glacial ice shelf in current times may result in continued rapid thinning and ground line retreat for several more decades or even centuries.”

The ups and downs of early atmospheric oxygen

This photo shows one-billion-year-old weathering profiles from Michigan. Ancient soils like these provide evidence for low atmospheric oxygen levels through much of Earth's history. -  Noah Planavsky.
This photo shows one-billion-year-old weathering profiles from Michigan. Ancient soils like these provide evidence for low atmospheric oxygen levels through much of Earth’s history. – Noah Planavsky.

A team of biogeochemists at the University of California, Riverside, give us a nontraditional way of thinking about the earliest accumulation of oxygen in the atmosphere, arguably the most important biological event in Earth history.

A general consensus asserts that appreciable oxygen first accumulated in Earth’s atmosphere around 2.3 billion years ago during the so-called Great Oxidation Event (GOE). However, a new picture is emerging: Oxygen production by photosynthetic cyanobacteria may have initiated as early as 3 billion years ago, with oxygen concentrations in the atmosphere potentially rising and falling episodically over many hundreds of millions of years, reflecting the balance between its varying photosynthetic production and its consumption through reaction with reduced compounds such as hydrogen gas.

“There is a growing body of data that points to oxygen production and accumulation in the ocean and atmosphere long before the GOE,” said Timothy W. Lyons, a professor of biogeochemistry in the Department of Earth Sciences and the lead author of the comprehensive synthesis of more than a decade’s worth of study within and outside his research group.

Lyons and his coauthors, Christopher T. Reinhard and Noah J. Planavsky, both former UCR graduate students, note that once oxygen finally established a strong foothold in the atmosphere starting about 2.3 billion years ago it likely rose to high concentrations, potentially even levels like those seen today. Then, for reasons not well understood, the bottom fell out, oxygen plummeted to a tiny fraction of today’s level, and the ocean remained mostly oxygen free for more than a billion years.

The paper appears in Nature on Feb. 19.

“This period of extended low oxygen spanning from roughly 2 to less than 1 billion years ago was a time of remarkable chemical stability in the ocean and atmosphere,” Lyons said.

His research team envisions a series of interacting processes, or feedbacks, that maintained oxygen at very low levels principally by modulating the availability of life-sustaining nutrients in the ocean and thus oxygen-producing photosynthetic activity.

“We suggest that oxygen was much lower than previously thought during this important middle chapter in Earth history, which likely explains the low abundances and diversity of eukaryotic organisms and the absence of animals,” Lyons said.

The late Proterozoic-the time period beginning less than a billion years ago following this remarkable chapter of sustained low levels of oxygen-was strikingly different, marked by extreme climatic events manifest in global-scale glaciation, indications of at least intervals of modern-like oxygen abundances, and the emergence and diversification of the earliest animals. Lyons notes that the factors controlling the rise of animals are under close scrutiny, including challenges to the long-held view that a major rise in atmospheric oxygen concentrations triggered the event.

“Despite the new ideas about animal origins, we suspect that oxygen played a major if not dominant role in the timing of that rise and, in particular, in the subsequent emergence of complex ecologies for animal life on and within the sediment, predator-prey relationships, and large bodies” said Lyons. “But, again, feedbacks always rule the day. Environmental change drives evolution, and steps in the progression of life change the environment.”

No single factor is likely to be the whole story, and there is much more to be written in the tale. Lyons and coauthors, along with research groups from around world over, are focusing current efforts on the timing and drivers of oxygenation in the late Proterozoic, favoring a combination of global-scale mountain building, evolutionary controls on the way carbon is cycled in the biosphere, and concomitant climate events.

“We are faced with a lot of chicken-and-egg questions when it comes to unraveling the timing and sequence of oxygenation of the ocean and atmosphere,” Lyons said. “But now, armed with new and better data, more sophisticated numerical simulations, and highly integrated investigations in the lab and the field, Earth’s oxygenation history seems much longer and more dynamic than envisioned before, and we are getting closer to understanding the mechanisms behind such change.”

The ups and downs of early atmospheric oxygen

This photo shows one-billion-year-old weathering profiles from Michigan. Ancient soils like these provide evidence for low atmospheric oxygen levels through much of Earth's history. -  Noah Planavsky.
This photo shows one-billion-year-old weathering profiles from Michigan. Ancient soils like these provide evidence for low atmospheric oxygen levels through much of Earth’s history. – Noah Planavsky.

A team of biogeochemists at the University of California, Riverside, give us a nontraditional way of thinking about the earliest accumulation of oxygen in the atmosphere, arguably the most important biological event in Earth history.

A general consensus asserts that appreciable oxygen first accumulated in Earth’s atmosphere around 2.3 billion years ago during the so-called Great Oxidation Event (GOE). However, a new picture is emerging: Oxygen production by photosynthetic cyanobacteria may have initiated as early as 3 billion years ago, with oxygen concentrations in the atmosphere potentially rising and falling episodically over many hundreds of millions of years, reflecting the balance between its varying photosynthetic production and its consumption through reaction with reduced compounds such as hydrogen gas.

“There is a growing body of data that points to oxygen production and accumulation in the ocean and atmosphere long before the GOE,” said Timothy W. Lyons, a professor of biogeochemistry in the Department of Earth Sciences and the lead author of the comprehensive synthesis of more than a decade’s worth of study within and outside his research group.

Lyons and his coauthors, Christopher T. Reinhard and Noah J. Planavsky, both former UCR graduate students, note that once oxygen finally established a strong foothold in the atmosphere starting about 2.3 billion years ago it likely rose to high concentrations, potentially even levels like those seen today. Then, for reasons not well understood, the bottom fell out, oxygen plummeted to a tiny fraction of today’s level, and the ocean remained mostly oxygen free for more than a billion years.

The paper appears in Nature on Feb. 19.

“This period of extended low oxygen spanning from roughly 2 to less than 1 billion years ago was a time of remarkable chemical stability in the ocean and atmosphere,” Lyons said.

His research team envisions a series of interacting processes, or feedbacks, that maintained oxygen at very low levels principally by modulating the availability of life-sustaining nutrients in the ocean and thus oxygen-producing photosynthetic activity.

“We suggest that oxygen was much lower than previously thought during this important middle chapter in Earth history, which likely explains the low abundances and diversity of eukaryotic organisms and the absence of animals,” Lyons said.

The late Proterozoic-the time period beginning less than a billion years ago following this remarkable chapter of sustained low levels of oxygen-was strikingly different, marked by extreme climatic events manifest in global-scale glaciation, indications of at least intervals of modern-like oxygen abundances, and the emergence and diversification of the earliest animals. Lyons notes that the factors controlling the rise of animals are under close scrutiny, including challenges to the long-held view that a major rise in atmospheric oxygen concentrations triggered the event.

“Despite the new ideas about animal origins, we suspect that oxygen played a major if not dominant role in the timing of that rise and, in particular, in the subsequent emergence of complex ecologies for animal life on and within the sediment, predator-prey relationships, and large bodies” said Lyons. “But, again, feedbacks always rule the day. Environmental change drives evolution, and steps in the progression of life change the environment.”

No single factor is likely to be the whole story, and there is much more to be written in the tale. Lyons and coauthors, along with research groups from around world over, are focusing current efforts on the timing and drivers of oxygenation in the late Proterozoic, favoring a combination of global-scale mountain building, evolutionary controls on the way carbon is cycled in the biosphere, and concomitant climate events.

“We are faced with a lot of chicken-and-egg questions when it comes to unraveling the timing and sequence of oxygenation of the ocean and atmosphere,” Lyons said. “But now, armed with new and better data, more sophisticated numerical simulations, and highly integrated investigations in the lab and the field, Earth’s oxygenation history seems much longer and more dynamic than envisioned before, and we are getting closer to understanding the mechanisms behind such change.”