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, including Mt. Hood, can go from dormant to active quickly

Mount Hood, in the Oregon Cascades, doesn't have a highly explosive history. -  Photo courtesy Alison M Koleszar
Mount Hood, in the Oregon Cascades, doesn’t have a highly explosive history. – Photo courtesy Alison M Koleszar

A new study suggests that the magma sitting 4-5 kilometers beneath the surface of Oregon’s Mount Hood has been stored in near-solid conditions for thousands of years, but that the time it takes to liquefy and potentially erupt is surprisingly short – perhaps as little as a couple of months.

The key, scientists 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 is the mixing of the two types of magma that triggered Mount Hood’s last two eruptions – about 220 and 1,500 years ago, said Adam Kent, an Oregon State University geologist and co-author of the study.

Results of the research, which was funded by the National Science Foundation, were published this week in the journal Nature.

“If the temperature of the rock is too cold, the magma is like peanut butter in a refrigerator,” Kent said. “It just 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 increases the viscosity of the magma and makes it easier to mobilize.”

Thus the scientists are interested in the temperature at which magma resides in the crust, they say, since it is likely to have important influence over the timing and types of eruptions that could occur. The hotter magma from down deep warms the cooler magma stored at 4-5 kilometers, making it possible for both magmas to mix and to be transported to the surface to eventually 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 postdoctoral 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, a professor in OSU’s College of Earth, Ocean, and Atmospheric Sciences. “A big glob kind of plops out the top, but in the case of Mount Hood – it doesn’t blow the mountain to pieces.”

The collaborative study between Oregon State and the University of California, Davis is important because little was known about the physical conditions of magma storage and what it takes to mobilize the magma. Kent and UC-Davis colleague Kari Cooper, also a co-author on the Nature article, set out to find if 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.

Thus 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. The diffusion rate of the element strontium, which is also sensitive to temperature, helped validate the findings.

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

In other words – even though 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 is encouraging from another standpoint is that modern technology should be able to detect when magma is beginning to liquefy, or mobilize,” Kent said, “and that may give us warning of a potential eruption. Monitoring gases, utilizing 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 their 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 Mt. Hood, can go from dormant to active quickly

Mount Hood, in the Oregon Cascades, doesn't have a highly explosive history. -  Photo courtesy Alison M Koleszar
Mount Hood, in the Oregon Cascades, doesn’t have a highly explosive history. – Photo courtesy Alison M Koleszar

A new study suggests that the magma sitting 4-5 kilometers beneath the surface of Oregon’s Mount Hood has been stored in near-solid conditions for thousands of years, but that the time it takes to liquefy and potentially erupt is surprisingly short – perhaps as little as a couple of months.

The key, scientists 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 is the mixing of the two types of magma that triggered Mount Hood’s last two eruptions – about 220 and 1,500 years ago, said Adam Kent, an Oregon State University geologist and co-author of the study.

Results of the research, which was funded by the National Science Foundation, were published this week in the journal Nature.

“If the temperature of the rock is too cold, the magma is like peanut butter in a refrigerator,” Kent said. “It just 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 increases the viscosity of the magma and makes it easier to mobilize.”

Thus the scientists are interested in the temperature at which magma resides in the crust, they say, since it is likely to have important influence over the timing and types of eruptions that could occur. The hotter magma from down deep warms the cooler magma stored at 4-5 kilometers, making it possible for both magmas to mix and to be transported to the surface to eventually 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 postdoctoral 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, a professor in OSU’s College of Earth, Ocean, and Atmospheric Sciences. “A big glob kind of plops out the top, but in the case of Mount Hood – it doesn’t blow the mountain to pieces.”

The collaborative study between Oregon State and the University of California, Davis is important because little was known about the physical conditions of magma storage and what it takes to mobilize the magma. Kent and UC-Davis colleague Kari Cooper, also a co-author on the Nature article, set out to find if 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.

Thus 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. The diffusion rate of the element strontium, which is also sensitive to temperature, helped validate the findings.

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

In other words – even though 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 is encouraging from another standpoint is that modern technology should be able to detect when magma is beginning to liquefy, or mobilize,” Kent said, “and that may give us warning of a potential eruption. Monitoring gases, utilizing 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 their 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.

Eruptive characteristics of Oregon’s Mount Hood analyzed

New research at Oregon State University has outlined the mechanisms that may lead to the next eruption of Mount Hood, the tallest mountain in Oregon. (Photo courtesy of Oregon State University)
New research at Oregon State University has outlined the mechanisms that may lead to the next eruption of Mount Hood, the tallest mountain in Oregon. (Photo courtesy of Oregon State University)

A new study has found that a mixing of two different types of magma is the key to the historic eruptions of Mount Hood, Oregon’s tallest mountain, and that eruptions often happen in a relatively short time – weeks or months – after this mixing occurs.

This behavior is somewhat different than that of most other Cascade Range volcanoes, researchers said, including Mount Hood’s nearby, more explosive neighbor, Mount St. Helens.

The research is being reported this week in Nature Geoscience by geologists from Oregon State University and the University of California at Davis, in work supported by the National Science Foundation.

It will help scientists better understand the nature of Mount Hood’s past and future eruptions, as well as other volcanoes that erupt by similar mechanisms. This includes a large number of the world’s active volcanoes.

“These data will help give us a better road map to what a future eruption on Mount Hood will look like, and what will take place before it occurs,” said Adam Kent, an OSU associate professor of geosciences. “It should also help us understand the nature of future eruptions and what risks they will entail.”

Mount Hood, at 11,249 feet tall, is the highest mountain in Oregon and fourth highest in the Cascade Range. The last major eruption was in the late 1780’s, and the effects of this eruption where viewed by members of the Lewis and Clark Expedition in 1805. It is considered potentially active and the Oregon volcano most likely to erupt, although the chances of that are still small.

Geologists are already able to use things like gas emissions, the chemistry of hot springs, ground deformation, local earthquakes and other data to help predict when a volcanic eruption is imminent, Kent said, and the new findings will add even more data toward that goal.

Two types of magma, or molten underground rock, are often involved in volcanic processes – mafic magma, which has less silica and is more fluid; and felsic magma, which has a higher silica content and a thicker consistency, like toothpaste. A third type of magma, called andesite, named after the Andes Mountains where it is often found, is composed of a mixture of both felsic and mafic magma.

Andesite is common in volcanoes that form at subduction zones – regions where one tectonic plate is sinking below another – and include those that form around the well-known Pacific Ocean “rim of fire”.

The rocks around Mount Hood, scientists say, are almost exclusively formed from andesitic magma. And research suggests that the recharge of mafic magma to mix with its thicker felsic counterpart often occurs just prior to an actual eruption.

“The intense mixing of these two types of magma causes an increase in pressure and other effects, and is usually the trigger for an eruption,” Kent said. “But this process doesn’t happen in all volcanic events. In the Cascade Range, Mount Hood appears to be one volcano where andesitic magma and recharge-driven eruptions are dominant.”

That may be because of local crustal conditions, Kent said. Even though the Cascade Range is linked to melting rock from the Cascadia Subduction Zone, some parts of the crust are more difficult than others for magma to move through. Mount Hood appears to be in a region where it takes the extra pressure of magma mixing to cause an eruption.

Kent said that researchers study these processes not only to improve their ability to predict eruptions, and to recognize precursors to eruption, but also to assess possible ore deposits associated with volcanic activity, and learn more about the fundamental dynamics of volcanic processes.