Paleotempestology and 2011’s Hurricane Irene

Hurricane Irene made landfall in Onslow Bay, N.C., USA, on Aug. 27, 2011. Satellite image courtesy NASA. -  NASA
Hurricane Irene made landfall in Onslow Bay, N.C., USA, on Aug. 27, 2011. Satellite image courtesy NASA. – NASA

A new study published in the December issue of GSA Today examines the geological legacy of Hurricane Irene, not only in terms of its impact on current coastal conditions but also in what it can tell geoscientists about the past. Hurricane Irene made landfall in Onslow Bay, North Carolina, USA, on 27 August 2011, at which time it had been downgraded to a Category 1 hurricane after hitting the Bahamas at Category 3 strength.

In their GSA Today article, geoscientists Scott P. Hippensteel, Matthew D. Eastin, and William J. Garcia of the University of North Carolina at Charlotte call for a better understanding of the long-term record of storm frequency and impact, not only because of the increase in the strength of storms hitting coastal areas but also because of the high population density in vulnerable areas along the U.S. East Coast and Gulf Coast.

Those who study the paleo-storm record explain that gaining understanding of past events provides the context for future coastal vulnerability. Hippensteel and colleagues apply evidence of what they call the “lack of a definitive signature” from Hurricane Irene to a 1500-year paleostorm record at Onslow Bay. They write that fewer hurricanes could be found in the fossil and sedimentary records (through bioturbation or foraminiferal dissolution) than had actually made landfall there.

The authors infer that the lack of storm records in the marsh sediments from Onslow Bay means that only hurricane strikes of higher magnitude can provide proxies for understanding the paleostorm record, because only the most robust storm deposits are archived. The lack of definitive signs of Hurricane Irene in the area raises their concerns about the current understanding of hurricane deposition and preservation.

Paleotempestology and 2011’s Hurricane Irene

Hurricane Irene made landfall in Onslow Bay, N.C., USA, on Aug. 27, 2011. Satellite image courtesy NASA. -  NASA
Hurricane Irene made landfall in Onslow Bay, N.C., USA, on Aug. 27, 2011. Satellite image courtesy NASA. – NASA

A new study published in the December issue of GSA Today examines the geological legacy of Hurricane Irene, not only in terms of its impact on current coastal conditions but also in what it can tell geoscientists about the past. Hurricane Irene made landfall in Onslow Bay, North Carolina, USA, on 27 August 2011, at which time it had been downgraded to a Category 1 hurricane after hitting the Bahamas at Category 3 strength.

In their GSA Today article, geoscientists Scott P. Hippensteel, Matthew D. Eastin, and William J. Garcia of the University of North Carolina at Charlotte call for a better understanding of the long-term record of storm frequency and impact, not only because of the increase in the strength of storms hitting coastal areas but also because of the high population density in vulnerable areas along the U.S. East Coast and Gulf Coast.

Those who study the paleo-storm record explain that gaining understanding of past events provides the context for future coastal vulnerability. Hippensteel and colleagues apply evidence of what they call the “lack of a definitive signature” from Hurricane Irene to a 1500-year paleostorm record at Onslow Bay. They write that fewer hurricanes could be found in the fossil and sedimentary records (through bioturbation or foraminiferal dissolution) than had actually made landfall there.

The authors infer that the lack of storm records in the marsh sediments from Onslow Bay means that only hurricane strikes of higher magnitude can provide proxies for understanding the paleostorm record, because only the most robust storm deposits are archived. The lack of definitive signs of Hurricane Irene in the area raises their concerns about the current understanding of hurricane deposition and preservation.

Rain as acidic as lemon juice may have contributed to ancient mass extinction

Rain as acidic as undiluted lemon juice may have played a part in killing off plants and organisms around the world during the most severe mass extinction in Earth’s history.

About 252 million years ago, the end of the Permian period brought about a worldwide collapse known as the Great Dying, during which a vast majority of species went extinct.

The cause of such a massive extinction is a matter of scientific debate, centering on several potential causes, including an asteroid collision, similar to what likely killed off the dinosaurs 186 million years later; a gradual, global loss of oxygen in the oceans; and a cascade of environmental events triggered by massive volcanic eruptions in a region known today as the Siberian Traps.

Now scientists at MIT and elsewhere have simulated this last possibility, creating global climate models of scenarios in which repeated bursts of volcanism spew gases, including sulfur, into the atmosphere. From their simulations, they found that sulfur emissions were significant enough to create widespread acid rain throughout the Northern Hemisphere, with pH levels reaching 2 – as acidic as undiluted lemon juice. They say such acidity may have been sufficient to disfigure plants and stunt their growth, contributing to their ultimate extinction.

“Imagine you’re a plant that’s growing happily in the latest Permian,” says Benjamin Black, a postdoc in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “It’s been getting hotter and hotter, but perhaps your species has had time to adjust to that. But then quite suddenly, over the course of a few months, the rain begins to sizzle with sulfuric acid. It would be quite a shock if you were that plant.”

Black is lead author of a paper reporting the group’s results, which appears in the journal Geology. Co-authors include Jean-François Lamarque, Christine Shields, and Jeffrey Kiehl from the National Center for Atmospheric Research and Linda Elkins-Tanton of the Carnegie Institution for Science.

Lemon juice spike

Geologists who have examined the rock record in Siberia have observed evidence of immense volcanism that came in short bursts beginning near the end of the Permian period and continuing for another million years. The volume of magma totaled several million cubic kilometers – enough to completely blanket the continental United States. This boiling stew of magma likely released carbon dioxide and other gases into the atmosphere, leading to gradual but powerful global warming.

The eruptions may also have released large clouds of sulfur, which ultimately returned to Earth’s surface as acid rain. Black, who has spent several summers in Siberia collecting samples to measure sulfur and other chemicals preserved in igneous rocks, used these measurements, along with other evidence, to develop simulations of magmatic activity in the end-Permian world.

The group simulated 27 scenarios, each approximating the release of gases from a plausible volcanic episode, including medium eruptions, large eruptions, and magma erupted through explosive pipes in the Earth’s crust. The researchers included a wide range of gases in their simulations, based on estimates from chemical analyses and thermal modeling. They then tracked water in the atmosphere, and the interactions among various gases and aerosols, to calculate the pH of rain.

The results showed that both carbon dioxide and volcanic sulfur could have significantly affected the acidity of rain at the end of the Permian. Levels of carbon dioxide and other greenhouse gases may have risen rapidly at the time, in part because of Siberian volcanism. According to their simulations, the researchers found that this elevated carbon dioxide could have increased rain’s acidity by an order of magnitude.

Adding sulfur emissions to the mix, they found that acidity further spiked to a pH of 2 – as acidic as undiluted lemon juice – and that such acidic rain may have fallen over most of the Northern Hemisphere. After an eruption ended, the researchers found that pH levels in rain bounced back, becoming less acidic within one year. However, with repeated bursts of volcanic activity, Black says the resulting swings in acid rain could have greatly stressed terrestrial species.

“Plants and animals wouldn’t have much time to adapt to these changes in the pH of rain,” Black says. “I think it certainly contributed to the environmental stress which was making it difficult for plants and animals to survive. At a certain point you have to ask, ‘How much can a plant take?'”

Life as an end-Permian organism

In addition to acid rain, the researchers modeled ozone depletion resulting from volcanic activity. While ozone depletion is more difficult to model than acid rain, their results suggest that a mix of gases released into the atmosphere may have destroyed 5 to 65 percent of the ozone layer, substantially increasing species’ exposure to ultraviolet radiation. The greatest ozone depletion occurred near the poles.

Going forward, Black hopes paleontologists and geochemists will consider the results as a point of comparison for their own observations of the end-Permian mass extinction. In the meantime, he says he now has a much more vivid picture of that catastrophic time.

“It’s not just one thing that was unpleasant,” Black says. “It’s this whole host of really nasty atmospheric and environmental effects. These results really made me feel sorry for end-Permian organisms.”

Rain as acidic as lemon juice may have contributed to ancient mass extinction

Rain as acidic as undiluted lemon juice may have played a part in killing off plants and organisms around the world during the most severe mass extinction in Earth’s history.

About 252 million years ago, the end of the Permian period brought about a worldwide collapse known as the Great Dying, during which a vast majority of species went extinct.

The cause of such a massive extinction is a matter of scientific debate, centering on several potential causes, including an asteroid collision, similar to what likely killed off the dinosaurs 186 million years later; a gradual, global loss of oxygen in the oceans; and a cascade of environmental events triggered by massive volcanic eruptions in a region known today as the Siberian Traps.

Now scientists at MIT and elsewhere have simulated this last possibility, creating global climate models of scenarios in which repeated bursts of volcanism spew gases, including sulfur, into the atmosphere. From their simulations, they found that sulfur emissions were significant enough to create widespread acid rain throughout the Northern Hemisphere, with pH levels reaching 2 – as acidic as undiluted lemon juice. They say such acidity may have been sufficient to disfigure plants and stunt their growth, contributing to their ultimate extinction.

“Imagine you’re a plant that’s growing happily in the latest Permian,” says Benjamin Black, a postdoc in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “It’s been getting hotter and hotter, but perhaps your species has had time to adjust to that. But then quite suddenly, over the course of a few months, the rain begins to sizzle with sulfuric acid. It would be quite a shock if you were that plant.”

Black is lead author of a paper reporting the group’s results, which appears in the journal Geology. Co-authors include Jean-François Lamarque, Christine Shields, and Jeffrey Kiehl from the National Center for Atmospheric Research and Linda Elkins-Tanton of the Carnegie Institution for Science.

Lemon juice spike

Geologists who have examined the rock record in Siberia have observed evidence of immense volcanism that came in short bursts beginning near the end of the Permian period and continuing for another million years. The volume of magma totaled several million cubic kilometers – enough to completely blanket the continental United States. This boiling stew of magma likely released carbon dioxide and other gases into the atmosphere, leading to gradual but powerful global warming.

The eruptions may also have released large clouds of sulfur, which ultimately returned to Earth’s surface as acid rain. Black, who has spent several summers in Siberia collecting samples to measure sulfur and other chemicals preserved in igneous rocks, used these measurements, along with other evidence, to develop simulations of magmatic activity in the end-Permian world.

The group simulated 27 scenarios, each approximating the release of gases from a plausible volcanic episode, including medium eruptions, large eruptions, and magma erupted through explosive pipes in the Earth’s crust. The researchers included a wide range of gases in their simulations, based on estimates from chemical analyses and thermal modeling. They then tracked water in the atmosphere, and the interactions among various gases and aerosols, to calculate the pH of rain.

The results showed that both carbon dioxide and volcanic sulfur could have significantly affected the acidity of rain at the end of the Permian. Levels of carbon dioxide and other greenhouse gases may have risen rapidly at the time, in part because of Siberian volcanism. According to their simulations, the researchers found that this elevated carbon dioxide could have increased rain’s acidity by an order of magnitude.

Adding sulfur emissions to the mix, they found that acidity further spiked to a pH of 2 – as acidic as undiluted lemon juice – and that such acidic rain may have fallen over most of the Northern Hemisphere. After an eruption ended, the researchers found that pH levels in rain bounced back, becoming less acidic within one year. However, with repeated bursts of volcanic activity, Black says the resulting swings in acid rain could have greatly stressed terrestrial species.

“Plants and animals wouldn’t have much time to adapt to these changes in the pH of rain,” Black says. “I think it certainly contributed to the environmental stress which was making it difficult for plants and animals to survive. At a certain point you have to ask, ‘How much can a plant take?'”

Life as an end-Permian organism

In addition to acid rain, the researchers modeled ozone depletion resulting from volcanic activity. While ozone depletion is more difficult to model than acid rain, their results suggest that a mix of gases released into the atmosphere may have destroyed 5 to 65 percent of the ozone layer, substantially increasing species’ exposure to ultraviolet radiation. The greatest ozone depletion occurred near the poles.

Going forward, Black hopes paleontologists and geochemists will consider the results as a point of comparison for their own observations of the end-Permian mass extinction. In the meantime, he says he now has a much more vivid picture of that catastrophic time.

“It’s not just one thing that was unpleasant,” Black says. “It’s this whole host of really nasty atmospheric and environmental effects. These results really made me feel sorry for end-Permian organisms.”

Ancient minerals: Which gave rise to life?

The magnesium silicate forsterite was one of the most abundant minerals in the Hadean Eon, and it played a major role in Earth's near-surface processes. The green color of this mineral (which is also known as the semi-precious gemstone peridot, the birthstone of August) is caused by small amounts iron. The iron can react with seawater to promote chemical reactions that may have played a role in life's origins. -  Robert Downs, University of Arizona, Ruff Project
The magnesium silicate forsterite was one of the most abundant minerals in the Hadean Eon, and it played a major role in Earth’s near-surface processes. The green color of this mineral (which is also known as the semi-precious gemstone peridot, the birthstone of August) is caused by small amounts iron. The iron can react with seawater to promote chemical reactions that may have played a role in life’s origins. – Robert Downs, University of Arizona, Ruff Project

Life originated as a result of natural processes that exploited early Earth’s raw materials. Scientific models of life’s origins almost always look to minerals for such essential tasks as the synthesis of life’s molecular building blocks or the supply of metabolic energy. But this assumes that the mineral species found on Earth today are much the same as they were during Earth’s first 550 million years-the Hadean Eon-when life emerged. A new analysis of Hadean mineralogy challenges that assumption. It is published in American Journal of Science.

Carnegie’s Robert Hazen compiled a list of every plausible mineral species on the Hadean Earth and concludes that no more than 420 different minerals-about 8 percent of the nearly 5,000 species found on Earth today-would have been present at or near Earth’s surface.

“This is a consequence of the limited ways that minerals might have formed prior to 4 billion years ago,” Hazen explained. “Most of the 420 minerals of the Hadean Eon formed from magma-molten rock that slowly crystallized at or near Earth’s surface-as well as the alteration of those minerals when exposed to hot water.”

By contrast, thousands of mineral species known today are the direct result of growth by living organisms, such as shells and bones, as well as life’s chemical byproducts, such as oxygen from photosynthesis. In addition, hundreds of other minerals that incorporate relatively rare elements such as lithium, beryllium, and molybdenum appear to have taken a billion years or more to first appear because it is difficult to concentrate these elements sufficiently to form new minerals. So those slow-forming minerals are also excluded from the time of life’s origins.

“Fortunately for most origin-of-life models, the most commonly invoked minerals were present on early Earth,” Hazen said.

For example, clay minerals-sometimes theorized by chemists to trigger interesting reactions-were certainly available. Sulfide minerals, including reactive iron and nickel varieties, were also widely available to catalyze organic reactions. However, borate and molybdate minerals, which are relatively rare even today, are unlikely to have occurred on the Hadean Earth and call into question origin models that rely on those mineral groups.

Several questions remain unanswered and offer opportunities for further study of the paleomineralogy of the Hadean Eon. For example, the Hadean Eon differs from today in the frequent large impacts of asteroids and comets-thousands of collisions by objects with diameters from a mile up to 100 miles. Such impacts would have caused massive disruption of Earth’s crust, with extensive fracture zones that were filled with hot circulating water. Such hydrothermal areas could have created complex zones with many exotic minerals.

This study also raises the question of how other planets and moons evolved mineralogically. Hazen suggests that Mars today may have progressed only as far as Earth’s Hadean Eon. As such, Mars may be limited to a similar suite of no more than about 400 different mineral species. Thanks to the Curiosity rover, we may soon know if that’s the case.

Ancient minerals: Which gave rise to life?

The magnesium silicate forsterite was one of the most abundant minerals in the Hadean Eon, and it played a major role in Earth's near-surface processes. The green color of this mineral (which is also known as the semi-precious gemstone peridot, the birthstone of August) is caused by small amounts iron. The iron can react with seawater to promote chemical reactions that may have played a role in life's origins. -  Robert Downs, University of Arizona, Ruff Project
The magnesium silicate forsterite was one of the most abundant minerals in the Hadean Eon, and it played a major role in Earth’s near-surface processes. The green color of this mineral (which is also known as the semi-precious gemstone peridot, the birthstone of August) is caused by small amounts iron. The iron can react with seawater to promote chemical reactions that may have played a role in life’s origins. – Robert Downs, University of Arizona, Ruff Project

Life originated as a result of natural processes that exploited early Earth’s raw materials. Scientific models of life’s origins almost always look to minerals for such essential tasks as the synthesis of life’s molecular building blocks or the supply of metabolic energy. But this assumes that the mineral species found on Earth today are much the same as they were during Earth’s first 550 million years-the Hadean Eon-when life emerged. A new analysis of Hadean mineralogy challenges that assumption. It is published in American Journal of Science.

Carnegie’s Robert Hazen compiled a list of every plausible mineral species on the Hadean Earth and concludes that no more than 420 different minerals-about 8 percent of the nearly 5,000 species found on Earth today-would have been present at or near Earth’s surface.

“This is a consequence of the limited ways that minerals might have formed prior to 4 billion years ago,” Hazen explained. “Most of the 420 minerals of the Hadean Eon formed from magma-molten rock that slowly crystallized at or near Earth’s surface-as well as the alteration of those minerals when exposed to hot water.”

By contrast, thousands of mineral species known today are the direct result of growth by living organisms, such as shells and bones, as well as life’s chemical byproducts, such as oxygen from photosynthesis. In addition, hundreds of other minerals that incorporate relatively rare elements such as lithium, beryllium, and molybdenum appear to have taken a billion years or more to first appear because it is difficult to concentrate these elements sufficiently to form new minerals. So those slow-forming minerals are also excluded from the time of life’s origins.

“Fortunately for most origin-of-life models, the most commonly invoked minerals were present on early Earth,” Hazen said.

For example, clay minerals-sometimes theorized by chemists to trigger interesting reactions-were certainly available. Sulfide minerals, including reactive iron and nickel varieties, were also widely available to catalyze organic reactions. However, borate and molybdate minerals, which are relatively rare even today, are unlikely to have occurred on the Hadean Earth and call into question origin models that rely on those mineral groups.

Several questions remain unanswered and offer opportunities for further study of the paleomineralogy of the Hadean Eon. For example, the Hadean Eon differs from today in the frequent large impacts of asteroids and comets-thousands of collisions by objects with diameters from a mile up to 100 miles. Such impacts would have caused massive disruption of Earth’s crust, with extensive fracture zones that were filled with hot circulating water. Such hydrothermal areas could have created complex zones with many exotic minerals.

This study also raises the question of how other planets and moons evolved mineralogically. Hazen suggests that Mars today may have progressed only as far as Earth’s Hadean Eon. As such, Mars may be limited to a similar suite of no more than about 400 different mineral species. Thanks to the Curiosity rover, we may soon know if that’s the case.

Acid raid, ozone depletion contributed to ancient extinction

This photo taken along Kotuy River in Arctic Siberia shows the base of the Siberian Traps volcanic sequence. -  Benjamin Black
This photo taken along Kotuy River in Arctic Siberia shows the base of the Siberian Traps volcanic sequence. – Benjamin Black

Around 250 million years ago, at the end of the Permian period, there was a mass extinction so severe that it remains the most traumatic known species die-off in Earth’s history. Some researchers have suggested that this extinction was triggered by contemporaneous volcanic eruptions in Siberia. New results from a team including Director of Carnegie’s Department of Terrestrial Magnetism Linda Elkins-Tanton show that the atmospheric effects of these eruptions could have been devastating. Their work is published in Geology.

The mass extinction included the sudden loss of more than 90 percent of marine species and more than 70 percent of terrestrial species and set the stage for the rise of the dinosaurs. The fossil record suggests that ecological diversity did not fully recover until several million years after the main pulse of the extinction.One leading candidate for the cause of this event is gas released from a large swath of volcanic rock in Russia called the Siberian Traps. Using advanced 3-D modeling techniques, the team, led by Benjamin Black of the Massachusetts Institute of Technology, was able to predict the impacts of gas released from the Siberian Traps on the end-Permian atmosphere.

Their results indicate that volcanic releases of both carbon dioxide (CO2) and sulfur dioxide (SO2) could have created highly acidic rain, potentially leaching the soil of nutrients and damaging plants and other vulnerable terrestrial organisms. Releases of halogen-bearing compounds such as methyl chloride could also have resulted in global ozone collapse.

The volcanic activity was likely episodic, producing pulses of acid rain and ozone depletion. The team concluded that the resulting drastic fluctuations in pH and ultraviolet radiation, combined with an overall temperature increase from greenhouse gas emissions, could have contributed to the end-Permian mass extinction on land.

The team also included Jean-François Lamarque, Christine Shields, and Jeffrey Kiehl of the National Center for Atmospheric Research.

Acid raid, ozone depletion contributed to ancient extinction

This photo taken along Kotuy River in Arctic Siberia shows the base of the Siberian Traps volcanic sequence. -  Benjamin Black
This photo taken along Kotuy River in Arctic Siberia shows the base of the Siberian Traps volcanic sequence. – Benjamin Black

Around 250 million years ago, at the end of the Permian period, there was a mass extinction so severe that it remains the most traumatic known species die-off in Earth’s history. Some researchers have suggested that this extinction was triggered by contemporaneous volcanic eruptions in Siberia. New results from a team including Director of Carnegie’s Department of Terrestrial Magnetism Linda Elkins-Tanton show that the atmospheric effects of these eruptions could have been devastating. Their work is published in Geology.

The mass extinction included the sudden loss of more than 90 percent of marine species and more than 70 percent of terrestrial species and set the stage for the rise of the dinosaurs. The fossil record suggests that ecological diversity did not fully recover until several million years after the main pulse of the extinction.One leading candidate for the cause of this event is gas released from a large swath of volcanic rock in Russia called the Siberian Traps. Using advanced 3-D modeling techniques, the team, led by Benjamin Black of the Massachusetts Institute of Technology, was able to predict the impacts of gas released from the Siberian Traps on the end-Permian atmosphere.

Their results indicate that volcanic releases of both carbon dioxide (CO2) and sulfur dioxide (SO2) could have created highly acidic rain, potentially leaching the soil of nutrients and damaging plants and other vulnerable terrestrial organisms. Releases of halogen-bearing compounds such as methyl chloride could also have resulted in global ozone collapse.

The volcanic activity was likely episodic, producing pulses of acid rain and ozone depletion. The team concluded that the resulting drastic fluctuations in pH and ultraviolet radiation, combined with an overall temperature increase from greenhouse gas emissions, could have contributed to the end-Permian mass extinction on land.

The team also included Jean-François Lamarque, Christine Shields, and Jeffrey Kiehl of the National Center for Atmospheric Research.

Early-career investigator discovers current volcanic activity under West Antarctica

This image shows a researcher digging out a seismographic instrument in Antarctica. -  Douglas Wiens, Washington University in St. Louis
This image shows a researcher digging out a seismographic instrument in Antarctica. – Douglas Wiens, Washington University in St. Louis

Scientists funded by the National Science Foundation (NSF) have observed “swarms” of seismic activity–thousands of events in the same locations, sometimes dozens in a single day–between January 2010 and March 2011, indicating current volcanic activity under the massive West Antarctic Ice Sheet (WAIS).

Previous studies using aerial radar and magnetic data detected the presence of subglacial volcanoes in West Antarctica, but without visible eruptions or seismic instruments recording data, the activity status of those systems ranged from extinct to unknown. However, as Amanda Lough, a doctoral candidate at Washington University in St. Louis, points out, “Just because we can’t see …below the ice, doesn’t mean there’s not something going on there.”

“This [study] is saying that we have seismicity, which means [this system] is active right now,” according to Lough. “This is saying that the magmatic chamber is still alive; that there is magma that is moving around in the crust.”

Lough published her discovery in this week’s issue of Nature Geoscience along with her advisor Douglas Wiens, a professor of earth and planetary sciences at Washington University in St. Louis, and a team of co-authors.

NSF has a presidential mandate to manage the U.S. Antarctic Program, through which it coordinates all U.S. science on the Southernmost continent and in the Southern Ocean and the logistical support which makes the science possible.

The characteristics of the seismic events, including the 25- to 40-kilometer (15- to 25-mile) depth at which they occurred, the low frequency of the seismic waves, and the swarm-like behavior rule out glacial and tectonic sources, but are typical of deep long-period earthquakes. Deep long-period earthquakes indicate active magma moving within the Earth’s crust and are most often associated with volcanic activity.

The two swarms of seismic activity were detected by instruments deployed to obtain data on the behavior of the WAIS as part of the NSF-funded POLENET project, a global network of GPS and seismic stations. Wiens is a POLENET principal investigator.

Lough plotted the location of the swarms and realized their proximity to the Executive Committee Range, a cluster of volcanoes that were believed to be dormant, in Marie Byrd Land. She consulted with a volcanic seismologist to confirm that the frequency content and the waveforms of the seismic signals were indicative of a volcanic system.

The location of the current seismicity, about 55-60 kilometers (34-37 miles) south of Mt. Sidley, is where current volcanic activity would be predicted to occur based on the geographic locations and the ages of the lava of the known volcanoes in the Executive Committee Range. The seismic swarms were also located near a subglacial high-point of elevation and magnetic anomalies which are both indicative of a volcano.

In some volcanic systems, deep long period earthquakes can indicate an imminent eruption, but Lough sent samples of her data to volcano seismologists who “didn’t see seismic events that would occur during an eruption.” However, the elevation in bed topography did indicate to Lough and her colleagues that this newly discovered volcano had erupted in the past.

Radar data showed an ash layer trapped within the ice directly above the area of seismic and magmatic activity. Lough initially thought that the ash layer might have evidence of a past eruption from the volcano detected in this study, but based on the distribution of the materials and the prevailing winds, the ash most likely came from an eruption of nearby Mt. Waesche about 8000 years ago. The dating of the ash layer did confirm that Mt. Waesche, believed to have last been active around 100,000 years ago, erupted much more recently than previously thought.

Only an extremely powerful eruption from the active magmatic complex discovered in this study would break through the 1- to 1.5-kilometer (0.6-0.9 miles) thick ice sheet overlying the area, but this research extends the range of active volcanism deeper into the interior of the WAIS than previously known. Should an eruption occur at this location, the short-term increase in heat could cause additional melting of the bottom of the ice sheet, thereby increasing the bed lubrication and hastening ice loss from WAIS.

Early-career investigator discovers current volcanic activity under West Antarctica

This image shows a researcher digging out a seismographic instrument in Antarctica. -  Douglas Wiens, Washington University in St. Louis
This image shows a researcher digging out a seismographic instrument in Antarctica. – Douglas Wiens, Washington University in St. Louis

Scientists funded by the National Science Foundation (NSF) have observed “swarms” of seismic activity–thousands of events in the same locations, sometimes dozens in a single day–between January 2010 and March 2011, indicating current volcanic activity under the massive West Antarctic Ice Sheet (WAIS).

Previous studies using aerial radar and magnetic data detected the presence of subglacial volcanoes in West Antarctica, but without visible eruptions or seismic instruments recording data, the activity status of those systems ranged from extinct to unknown. However, as Amanda Lough, a doctoral candidate at Washington University in St. Louis, points out, “Just because we can’t see …below the ice, doesn’t mean there’s not something going on there.”

“This [study] is saying that we have seismicity, which means [this system] is active right now,” according to Lough. “This is saying that the magmatic chamber is still alive; that there is magma that is moving around in the crust.”

Lough published her discovery in this week’s issue of Nature Geoscience along with her advisor Douglas Wiens, a professor of earth and planetary sciences at Washington University in St. Louis, and a team of co-authors.

NSF has a presidential mandate to manage the U.S. Antarctic Program, through which it coordinates all U.S. science on the Southernmost continent and in the Southern Ocean and the logistical support which makes the science possible.

The characteristics of the seismic events, including the 25- to 40-kilometer (15- to 25-mile) depth at which they occurred, the low frequency of the seismic waves, and the swarm-like behavior rule out glacial and tectonic sources, but are typical of deep long-period earthquakes. Deep long-period earthquakes indicate active magma moving within the Earth’s crust and are most often associated with volcanic activity.

The two swarms of seismic activity were detected by instruments deployed to obtain data on the behavior of the WAIS as part of the NSF-funded POLENET project, a global network of GPS and seismic stations. Wiens is a POLENET principal investigator.

Lough plotted the location of the swarms and realized their proximity to the Executive Committee Range, a cluster of volcanoes that were believed to be dormant, in Marie Byrd Land. She consulted with a volcanic seismologist to confirm that the frequency content and the waveforms of the seismic signals were indicative of a volcanic system.

The location of the current seismicity, about 55-60 kilometers (34-37 miles) south of Mt. Sidley, is where current volcanic activity would be predicted to occur based on the geographic locations and the ages of the lava of the known volcanoes in the Executive Committee Range. The seismic swarms were also located near a subglacial high-point of elevation and magnetic anomalies which are both indicative of a volcano.

In some volcanic systems, deep long period earthquakes can indicate an imminent eruption, but Lough sent samples of her data to volcano seismologists who “didn’t see seismic events that would occur during an eruption.” However, the elevation in bed topography did indicate to Lough and her colleagues that this newly discovered volcano had erupted in the past.

Radar data showed an ash layer trapped within the ice directly above the area of seismic and magmatic activity. Lough initially thought that the ash layer might have evidence of a past eruption from the volcano detected in this study, but based on the distribution of the materials and the prevailing winds, the ash most likely came from an eruption of nearby Mt. Waesche about 8000 years ago. The dating of the ash layer did confirm that Mt. Waesche, believed to have last been active around 100,000 years ago, erupted much more recently than previously thought.

Only an extremely powerful eruption from the active magmatic complex discovered in this study would break through the 1- to 1.5-kilometer (0.6-0.9 miles) thick ice sheet overlying the area, but this research extends the range of active volcanism deeper into the interior of the WAIS than previously known. Should an eruption occur at this location, the short-term increase in heat could cause additional melting of the bottom of the ice sheet, thereby increasing the bed lubrication and hastening ice loss from WAIS.