Tag Archives: volcano

The Bulge is back: Three Sister volcano in Oregon triggers swelling but is unlikely to erupt

Using satellite images and GPS instruments, geophysicists monitoring the Three Sister volcanoes have found a subtle but noticeable uplift around 3 miles (5 km) away from the South Sister volcano. While researchers are now keeping a closer eye on it, they say this type of uplift has happened before and there’s no need to worry.

Image credits: USGS.

The Three Sisters are closely spaced volcanic peaks in Oregon, USA. They stand over 10,000 feet (3,000 m) in elevation, being the 4th, 5th, and 6th highest peaks in Oregon, respectively. But researchers are more interested in their volcanic activity.

While the North and Middle sisters haven’t erupted in the past 14,000 years (and it’s considered unlikely that they will erupt again), the South Sister last erupted 2,000 years ago, and could easily do so again at some point in the not-very-distant future. In the 1990s, researchers detected tectonic uplift around this volcano, prompting the United States Geological Survey (USGS) to closely monitor the area.

The USGS is now tracking developments around the South Sister using GPS networks and satellite data. Radar satellites can highlight areas of uplifting (where the surface is bulging) or downwelling (where the surface is moving downwards). Then, ground-based GPS measurements are used for more precise measurements. Although the current uplifting isn’t as fast as the maximum rate observed in 1999-2000, it is “distinctly faster” than the normal rate of uplift, the USGS says.

Image credits: USGS.

The uplift is believed to be caused by pulses of magma accumulating under the volcano, some 4 miles (7 km) below the surface. While magma accumulation is associated with volcanic activity, eruptions are generally preceded by other detectable signs — most importantly, lots of small earthquakes, but also ground deformation and geochemical changes. There seems to be no sign of any of that around the Three Sisters.

All in all, this suggests that the volcano is still active, but there are no signs of an impending eruption. The volcano’s alert level and color code remain at Normal / Green.

How the USGS is tracking activity around the Three Sisters. Credit: USGS.

The Three Sisters volcanoes formed in the Pleistocene and belonged to a volcanic area that was very active from around 650,000 and about 250,000 years ago. The South Sister is the youngest and tallest of the three volcanoes, and unlike its sisters, it has an uneroded summit crater about 0.25 mi (0.40 km), which hosts a lake (called the Teardrop Pool).

An eruption from the South Sister would pose a significant threat to nearby life, with geologists estimating a proximal zone of danger extending from 1.2 to 6.2 miles (2-10 km) around the volcano summit. How flows would run down the sides of the volcano, threatening everything in its path, and the nearby city of bends would be covered by tephra some 2 inches (5 cm) thick.

The Teardrop Pool on South Sister is the highest lake in Oregon. Image via Wiki Commons.

Why don’t we throw all our trash into a volcano and burn it up?

Credit: Pixabay.

It’s true that lava is hot enough to burn up some of our trash. When Kilauea erupted on the Big island of Hawaii in 2018, the lava flows were hotter than 2,000 degrees Fahrenheit (1,100 Celsius). That’s hotter than the surface of the planet Venus, and hot enough to melt many rocks. It’s also as hot as waste incinerators, which usually burn garbage at 1,800 to 2,200 F (1,000-1,200 C).

But not all lavas are the same temperature. The eruptions in Hawaii produce a type of lava called basalt. Basalt is much hotter and more fluid than the lavas that erupt at other volcanoes, like the thicker dacite lava that erupts at Mount St. Helens in Washington state. For example, the 2004-2008 eruption at Mount St. Helens produced a lava dome with surface temperatures less than about 1,300 F (704 C).

There are 161 volcanoes in 14 U.S. states and territories. Scientists monitor them and warn nearby communities if they see signs that a volcano may erupt. USGS

Beyond temperature, there are other good reasons not to burn our trash in volcanoes. First, although lava at 2,000 degrees F can melt many materials in our trash – including food scraps, paper, plastics, glass and some metals – it’s not hot enough to melt many other common materials, including steel, nickel and iron.

Second, there aren’t many volcanoes on Earth that have lava lakes, or bowl-like craters full of lava, that we could dump trash into. Of all of the thousands of volcanoes on Earth, scientists know of only eight with active lava lakes. They include Kilauea, Mount Erebus in Antarctica and Nyiragongo in the Democratic Republic of the Congo. Most active volcanoes have craters filled with rocks and cooled lava, like Mount St. Helens, or with water, like Crater Lake in Oregon.

The third problem is that dumping trash into those eight active lava lakes would be a very dangerous job. Lava lakes are covered with a crust of cooling lava, but just below that crust they are molten and intensely hot. If rocks or other materials fall onto the surface of a lava lake, they will break the crust, disrupt the underlying lava and cause an explosion.

This happened at Kilauea in 2015: Blocks of rock from the crater rim fell into the lava lake and caused a big explosion that ejected rocks and lava up and out of the crater. Anyone who threw garbage into a lava lake would have to run away and dodge flaming garbage and lava.

An eruption from the Cumbre Vieja volcano on the Spanish island of La Palma on Sept. 30, 2021, produced clouds of toxic gas.

Suppose it was possible to dump trash safely into a lava lake: What would happen to the trash? When plastics, garbage and metals burn, they release a lot of toxic gases. Volcanoes already give off tons of toxic gases, including sulfur, chlorine and carbon dioxide.

Sulfur gases can create acidic fog, which we call “vog,” for “volcanic fog.” It can kill plants and cause breathing problems for people nearby. Mixing these already-dangerous volcanic gases with other gases from burning our trash would make the resulting fumes even more harmful for people and plants near the volcano.

Finally, many indigenous communities view nearby volcanoes as sacred places. For example, Halema’uma’u crater at Kilauea is considered the home of Pele, the native Hawaiian goddess of fire, and the area around the crater is sacred to native Hawaiians. Throwing trash into volcanoes would be a huge insult to those cultures.

Emily Johnson, Research Geologist, US Geological Survey. This article is republished from The Conversation under a Creative Commons license. Read the original article.

Scientists discover thousands of ancient massive volcanic eruptions on Mars

This image shows several craters in Arabia Terra that are filled with layered rock. Credit: NASA/JPL/University of Arizona.

Whether or not Mars is still volcanically active is still a matter of debate. What’s certain is true is that, in the past, the red planet was very volcanically active — and then some. Most of Mars’ volcanism occurred between three and four billion years ago, spawning giant geological features such as the 25-km-tall (16-mile) Olympus Mons, the highest mountain in the solar system.

Recently, NASA found evidence that a region of northern Mars called Arabia Terra experienced thousands of so-called “super-eruptions” over a 500-million-year period.

These kinds of eruptions, the most violent volcanic explosions known to science, were no joke. Relatively small volcanic eruptions on Earth are known to release carbon dioxide, sulfur dioxide, and other aerosols that can block sunlight and significantly reduce surface temperature.

The same happened on Mars, but only on a more massive scale. One single super eruption could have blasted out the equivalent of 400 million Olympic-size swimming pools worth of molten rock and gas.

“Each one of these eruptions would have had a significant climate impact — maybe the released gas made the atmosphere thicker or blocked the Sun and made the atmosphere colder,” said Patrick Whelley, a geologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who led the Arabia Terra analysis. “Modelers of the Martian climate will have some work to do to try to understand the impact of the volcanoes.”

Mars’ surface is littered with craters. Anywhere you go, you’re bound to find at least one within a couple of hundred kilometers. These craters are formed by one of two processes: impact (with a comet, meteorite, or asteroid), or by volcanic eruptions.

When very large volcanoes reach the end of their lifetimes, they collapse into a giant hole called a caldera, some of which can be dozens of kilometers wide. It was several of these calderas identified across Arabia Terra that prompted NASA scientists to look closer.

Unlike impact craters, which tend to be perfectly round, calderas bear signs of collapse such as deeper floors and benches of rock near the walls. However, there ought to be many other calderas in the region that haven’t been spared by the passage of time in the same way as these obviously visible formations.

The researchers decided to look for signs of ancient calderas by looking for ash “because you can’t hide that evidence,” Whelley said. So they used data from NASA’s Mars Reconnaissance Orbiter (MRO) to look for signs of ash across Arabia Terra, finding many well-preserved layers of the material.

When the researchers crunched the numbers, they figured that it would’ve taken thousands of supervolcanic eruptions to deposit the amount of ash registered in the data.

On Earth, volcanoes capable of super-eruptions are distributed around the globe, along with other volcano types. The last such cataclysmic eruption occurred 76,000 years ago in Sumatra, Indonesia. In contrast, Arabia Terra is littered with only one type of volcano, a mysterious oddity that scientists can’t yet explain. Arabia Terra is the only place on Mars where we found evidence of explosive volcanoes.

In the meantime, researchers are still busy combing through the MRO data to better understand the geological process that shaped the solar system’s planets and moons.

“People are going to read our paper and go, ‘How? How could Mars do that? How can such a tiny planet melt enough rock to power thousands of super eruptions in one location?’” said Jacob Richardson, a geologist at NASA Goddard. “I hope these questions bring about a lot of other research.”

The findings appeared in the journal Geophysical Research Letters.

Icelandic eruption attracts thousands of visitors, helicopter rides, over the weekend

What were probably the tastiest hot dogs made in all of Iceland this weekend were grilled over a volcanic eruption alongside marshmallows.

Aerial photo of the eruption. Image via Wikimedia.

In case it passed by below your radar, Iceland saw a new volcano start erupting late last Friday. Despite the island nation’s long history of volcanic activity and plane-grounding eruptions, this is the first time a member of this particular volcanic system has become active in around 9 centuries.

Still, the event attracted thousands of curious onlookers, and local media has even reported on some grilling marshmallows or hotdogs — which, scientifically speaking, is the best way to enjoy a volcano.

Mount Fagradalsfjall

The hard-to-pronounce volcano is situated around 40 kilometers (25 miles) from Reykjavik, Iceland’s capital. Despite the fact that the only way to reach it is to hike for around 90 minutes from the nearest road, locals came in droves to see the incandescent lava slowly pour down Fagradalsfjall’s slopes.

Luckily for everybody, the eruption has been very calm and small in scope so far, with experts estimating that around 300,000 cubic meters of lava have poured forth from the volcano’s lip now.

“It’s absolutely breathtaking,” said Ulvar Kari Johannsson, a 21-year-old engineer who spent his Sunday visiting the scene, for AFP. “It smells pretty bad. For me what was surprising was the colours of the orange: much, much deeper than what one would expect.”

Access to the area was blocked immediately after the eruption started, to keep everybody safe. After a few hours, however, the police allowed access to the public but were strongly discouraging visits (lava tends to be dangerous). By Saturday, however, visitors were allowed free access as long as they respected strict safety guidelines.

For the most part, however, the police are keeping an eye on visitors and occasionally asking those that get too close to “step back,” according to a local police officer. Emergency teams were also involved in helping people find their way back to the road on Sunday after weather conditions and visibility at the site deteriorated rapidly. These teams also carried devices to measure gas pollution levels in the atmosphere — especially sulfur dioxide, which can pose a danger to health and even be fatal.

High pollution levels on Monday morning prompted the authorities to close the site down for visitors yet again.

A volcanic eruption takes place in Iceland roughly once every five years on average and, due to the rugged nature of the island, they’re often far-removed from population centers. But this was the first such event in the Reykjanes peninsula, which is densely inhabited, in over 800 years, and the first member of the Krysuvik volcanic system to erupt in almost 900 years.

Given its relatively close proximity to people, many visitors went to admire the event, probably happy to break the dullness of staying at home all day after 2020. By Sunday, local media reported, hikers had already beaten a visible trail up to the volcano. Helicopter rides were also organized around it over the weekend.

For now, the site remains closed due to unsafe atmospheric conditions. Experts believe the eruption will die out possibly within a few days. But that doesn’t mean you have to miss out on the fun — here’s a live stream of Mount Fagradalsfjall doing volcano things.

Venus may still be volcanically active

Scientists have known for some time that the surface of Venus is dotted with volcanic features. However, due to the planet’s hazy atmosphere, it has always been uncertain whether Venus is still volcanically active — until now.

New compelling evidence suggests that Venus is volcanically active. This would make it only the second such planet that we know of, besides Earth.

Idunn Mons, a volcanic peak in the Imdr Regio area of Venus. The colored overlay shows heat patterns derived from data recorded by the European Space Agency’s Venus Express spacecraft. Credit: NASA.

In the early 1990s, NASA’s Magellan spacecraft beamed back radar images showing extensive lave flows. Subsequent studies and missions, such as ESA’s Venus Express orbiter, measured infrared light released by the planet’s surface at night to determine the age of the lava flows. Although the data was good enough for scientists to carry relative measurements between older and newer lava flows, their age couldn’t be accurately assessed.

Some have speculated from the data that Venus may have been volcanically active as recent as 2.5 million years ago — which is the blink of an eye in geologic time. But new evidence presented in a study led by Dr. Justin Filiberto, a researcher at the Lunar Planetary Institute in Houston, Texas, may mean that Venus may be volcanically active even now.

Researchers simulated Venus’ very dense atmosphere in the lab to assess its influence on lava flows over time. To their surprise, they found that olivine, a mineral that is abundant in some basaltic rocks (covering 90% of Venus), reacts rapidly with chemicals in Venus’ atmosphere, becoming coated with magnetite and hematite, both iron oxide minerals, within days.

The researchers also found that near-infrared light emitted by these minerals would disappear within days, something consistent with data recorded by the Venus Express mission.

“Our results indicate that lava flows lacking VNIR features due to hematite are no more than several years old. Therefore, Venus is volcanically active now,” the authors of the new study wrote in the journal Science Advances.

Maat Mons, a 5-mile-high volcano on Venus with lava flows. Credit: NASA/JPL.

Now, all that remains is for a new mission to confirm this hypothesis. Besides Earth, the only other confirmed volcanically active worlds that we know of are Io, a moon of Jupiter; Triton, a moon of Neptune; and Enceladus, a moon of Saturn.

However, Mars, Pluto, Jupiter’s moon Europa could also be volcanically active.

“If Venus is indeed active today, it would make a great place to visit to better understand the interiors of planets. For example, we could study how planets cool and why the Earth and Venus have active volcanism, but Mars does not,” Filiberto said.

The next missions bound for Venus are India’s Shukrayaan-1 orbiter and Russia’s Venera-D spacecraft, scheduled to launch by 2023 and 2026, respectively.

Researchers send drones to active volcanoes to improve early warning systems

There are about 300 active volcanoes on Earth, and anyone of them erupting could cause wide-scale disruptions. That’s why monitoring them is very important. Now, a group of researchers has created specially-adapted drones that can fly into volcanoes and gather data to warn of any upcoming eruption.

The Manam Volcano. Credit NASA

There are a few ways to forecast when a volcano is going to blow. Scientists can monitor earthquake activity in the area to detect tremors which almost always precede eruptions. With clear skies, satellites are also used to detect and measure the emissions of gases such as sulfur dioxide.

Drones can also help. Volcanologist Emma Liu from University College London and her team focused on the Manam volcano in Papua New Guinea. It’s one of the most active volcanoes in the country, located on an island that off its northeast coast. Manam erupted in 2014 and forced an evacuation of the entire island to the mainland.

“Manam hasn’t been studied in detail but we could see from satellite data that it was producing strong emissions,” said Liu, who led the research team of earth scientists and aerospace engineers. “We [also] wanted to quantify the carbon emission[s] from this very large carbon dioxide emitter.”

Liu and her team traveled to Manam Island and tested two types of long-range drones equipped with gas sensors, cameras, and other devices. The volcano’s slopes are very treacherous, so the drones allowed the researchers to measure volcanic gas emissions more safely and accurately.

The drones flew to over 2,000 meters (6,561 feet) altitude before dipping into Manam’s volcanic plumes some six kilometers (3.7 miles) away from their launching pad. The drones took images of Manam and its two craters, measured the gas composition right above the plumes, and collected four bags of extra gas for rapid analysis.

The images taken by the drones showed that degassing at Manam’s southern crater intensified between October 2018 and May 2019 (the volcano erupted in June). But volcanic emissions aren’t alone a reliable indicator of whether an eruption is likely. That’s why the researchers also looked at the ratio between different gases in the collected samples. Doing so can help detect the ascent of hot magma to the surface through the expulsion of CO2-rich emissions that reportedly precede big eruptions. However, the findings showed that the mixture of gases emitted from Manam was much the same during both field trips. The Manam ranks among the top 10 strongest degassing volcanoes in the world.

“Our novel approach – that is, long-range and high-altitude [drone] operations enabling in situ measurements – is presently the only feasible means by which we can characterize gas chemistry at steep, hazardous, and highly active volcanoes like Manam,” the research team concluded in their paper.

The researchers believe the drones could help local communities monitor nearby volcanoes and forecast future eruptions. At the same time, their measurements could also tell us more about the most inaccessible, highly active volcanoes on the planet and how volcanism in general contributes to the global carbon cycle.

The study was published in the journal Science Advances.

Iceland’s most active volcano may soon erupt, throwing air travel into turmoil — again

Iceland’s most active volcano, the Grímsvötn, could be close to erupting again, experts have shown, claiming there already are multiple indicators. The volcano has already seen 65 eruptions over the past 800 years. The last one occurred in 2011 when it released ash 20 kilometers into the atmosphere.

Credit Wikipedia Commons

Local authorities raised the Aviation Color Code from green to yellow after scientists recorded seismic activity indicating magma is swelling in the belly of the volcano. This doesn’t mean an eruption is imminent, but it does show that the Grímsvötn has reached a level of unrest, according to the Icelandic Met Office (IMO).

While an eruption would be unlikely to put anyone in immediate danger due to the remote location of the volcano, it could cause heavy local flooding. The Grímsvötn is buried in thick ice so a blast of heat from the volcano can create vast quantities of meltwater, according to Dave McGarvie, a UK volcano expert.

“Grímsvötn is a peculiar volcano, as it lies almost wholly beneath ice, and the only permanently visible part is an old ridge on its south side which forms the edge of a large crater. And it is along the base of this ridge, under the ice, that most recent eruptions have occurred,” wrote McGarvie in an article in The Conversation.

The ice might cause flooding, but also offers a layer of protection as it will absorb some of the force of the explosion. This means ash will be discharged tens of miles into the air, rather than hundreds, and will disperse more quickly. Still, this might be very bad news for the air travel sector, seeking to recover amid the pandemic.

The volcano is estimated to erupt every five to 10 years, and with nine years since its last eruption, scientists believe it could explode any time now. Usually, an eruption is hard to forecast for scientists, but as Grímsvötn erupts relatively frequently, scientists have been able to pick up on the signs.

First, the base of the volcano begins to expand as it fills with magma. This magma then causes intense heating, which leads to the ice arround the volcano to melt fairly quickly. Both signs have been noted in recent months by local volcano experts, as well as an uptick in earthquakes, another important indicator.

“A high frequency of eruptions at a volcano allows scientists to detect patterns that lead to eruptions (precursors). And if these are repeated each time a volcano erupts then it becomes possible for scientists to be more confident that an eruption is likely to happen in the near future. It’s, however, seldom possible to be precise about the exact day,” wrote McGarvie.

Iceland is home to a large number of volcanoes. While the Grímsvötn is the most active, others have also caused severe damage in the past. The Eyjafjallajökull erupted in 2010 and caused severe chaos in air travel, disrupting around 100,000 flights in April and May, with losses estimated at over $1.3 billion.

Iceland’s most active volcano likely headed towards eruption

The land of ice and fire is at it again, as one of Iceland’s ice-covered volcanoes starts to rumble.

A hole in the ice above Grímsvötn Volcano, Iceland, following the 2011 eruption. Image credits: NASA.

Ice and fire rarely go hand in hand, but at Iceland’s Vatnajökull ice cap, Europe’s largest by volume, the two are inexorably intertwined. Vatnajökull covers several active volcanoes, including Grímsvötn — the most active of them all.

Grímsvötn erupts, on average, every 5-10 years. Eruptions melt through the ice cap and in addition to the eruption itself, this process can form massive quantities of liquid water, triggering floods and landslides.

“The lava melts the ice, it flashes into steam. There is a tremendous amount of energy being released in split seconds,” Ronni Grapenthin, a geophysicist at the University of Alaska, described to GlacierHub.

When Grímsvötn erupts, Iceland gets nervous. In 1783, Grímsvötn caused the infamous seven-month Laki fissure eruption, which triggered a famine that killed 20% of Iceland’s population and temporarily lowered temperatures across the entire Northern Hemisphere by around 1°C.

Nowadays, famine is less of a concern in Iceland, but these eruptions can still cause serious problems. In 2011, an eruption at Grímsvötn sent plumes of ash 12 km (7 mi) high into the air — the strongest eruption at the site in over 100 years. The eruption forced the cancellation of 900 flights which, while less disruptive than the 2010 Eyjafjallajökull eruption, was still considerable in its own right.

Satellite image from 22 May 2011 of the volcanic plume above Iceland. Image credits: NASA.

In late June 2020, the Icelandic Meteorological Office (IMO) reported that Grímsvötn is stirring once again. The IMO reported over 3,000 tremors around the volcano, three with a magnitude greater than 5, one of which was even felt in the country’s capital Reykjavik, 265 kilometers away. No major damage was reported, although several landslides and rockfalls were noted in the area.

However, according to scientists at the IMO, this could be indicative of an impending eruption. While geologists are fairly certain another eruption is coming relatively soon, forecasting it with accuracy is extremely challenging because every volcano is different, and even within the same volcano, eruptions are not identical. However, because Grímsvötn erupts so often (which is unusual for volcanoes), researchers are starting to see a pattern, and the current state of the volcano seems similar to those before the 2011 and 2004 eruptions.

Keeping an eye on the beast

Currently, an international team of researchers is carefully monitoring Grímsvötn using several geophysical methods. A high precision GPS network on the ground measures any ground movement in real-time. As magma flows from below, the ground expands outwards like a balloon, and GPS offers a good image of this process. The same process also brings gases from magma to the surface, and gas measurements are also being carried out at the site. Of course, earthquake monitoring is also being carried out remotely.

Another piece of information comes from a process called jökulhlaup –a violent outburst of water from the volcano. Because Grímsvötn is covered by a glacier, the volcanic caldera is filled with a subglacial lake — as the volcano rumbles, it melts water beneath the ice. Every once in a while, the volume of water exceeds the capacity of the caldera, pouring and flooding the surrounding areas.

These jökulhlaups can actually trigger the eruption since the volcano is very sensitive to pressure release from the removal of the water. If this phenomenon happens this summer, it is quite likely to precede an eruption — so researchers are also monitoring the subglacial lake in real-time.

The window for an eruption seems to be opening in the near future, but if an eruption does happen, researchers expect it to be pretty tame. Grímsvötn only has a massive eruption around once in 100 years, and given how big the one in 2011 one was, the next one is expected to be relatively small.

Still, when a volcano erupts under ice, there’s bound to be fireworks. For now, all we can do is wait, monitor, and be prepared.

Scientists confirm Venus is still volcanically active

Artists rendition of Venusian volcano (Image Source: ESA/AOES)

The year 2020 started off on a good foot for Venusian lovers. Data from the European Space Agency’s Venus Express probe suggests that not all on the Solar System’s hottest planet is dead. A previous study published in Science Advances had found that active volcanoes most likely still existed on the surface of the planet. Now a new report published in the journal Nature Geoscience has identified 37 recently active volcanic structures.

“This is the first time we are able to point to specific structures and say ‘Look, this is not an ancient volcano but one that is active today, dormant perhaps, but not dead,'” said Laurent Montesi, a professor of geology at the University of Maryland (UMD) and co-author of the research paper. “This study significantly changes the view of Venus from a mostly inactive planet to one whose interior is still churning and can feed many active volcanoes.”

Venus has been found to harbor more volcanoes than any other planet in the solar system with over 1,600 major known volcanoes or volcanic features. Some say that there could be anywhere from 100,000 to one million smaller ones.

Scientists have known for quite some time that Venus has a younger surface than planets like Mercury and Mars, which have cold interiors. Evidence of a warm interior and geologic activity dots the surface of the planet in the form of ring-like structures known as coronae, which form when plumes of hot material deep inside the planet rise through the mantle layer and crust. This is similar to the way mantle plumes formed the volcanic Hawaiian Islands.

The 3D rendition above shows two coronae observed on the surface of Venus. The ring-like structures are formed when hot material from deep inside the planet rises through the mantle and erupts through the crust. Credit: University of Maryland.

However, it was originally believed that the coronae on the planet most likely pointed to signs of ancient activity, and that Venus had cooled enough to slow geological activity in the planet’s heart and harden the crust so much that any warm material from deep inside Venus would not be able to puncture through. The specific processes by which mantle plumes formed coronae on Venus and the reasons for variation among coronae have been matters for discussion.

Named after the Roman goddess of love and beauty, Venus is similar in structure and size to Earth, but the former planet’s thick, toxic atmosphere traps heat in a runaway ‘greenhouse effect.’ The scorched world is the hottest in our Solar System (the average temperature is 864 degrees Fahrenheit / 422 Celsius) and has temperatures high enough to melt lead. So hot, that the longest a probe was ever able to survive on the surface was the Russians’ Venera 13 which lastest just a shade over two hours.

The active coronae on Venus are clustered in a handful of locations, which suggests areas where the planet is most volcanically active, which can provide clues as to the workings of the planet’s interior. The study’s results can also help identify target areas where geologic instruments should be placed on future missions to Venus, such as Europe’s EnVision which is scheduled to launch in 2032.

In the global map of Venus above, active coronae appear in red and inactive coronae appear in white. Credit: Anna Gülcher.

In this latest study, the researchers used numerical models of thermo-mechanic activity beneath the surface of Venus to create high-resolution, 3D simulations of coronae formation. This helped identify features that are present only in recently active coronae. The UMD researchers were then able to match the observed features to those found on the surface of Venus, revealing that some of the variation in coronae across the globe represents different stages of geological development.

“The improved degree of realism in these models over previous studies makes it possible to identify several stages in corona evolution and define diagnostic geological features present only at currently active coronae,” said Montesi. “We are able to tell that at least 37 coronae have been very recently active.”

The report provides some of the first evidence that coronae on the planet are still evolving, indicating that the interior of the planet is still churning away.

Indonesian volcano erupted twice last Sunday

Mount Merapi, one of the world’s most active volcanoes, erupted twice on Sunday sending clouds of ash some 6 kilometers into the air, according to Indonesia’s geological agency.

Mount Merapi before the eruption.
Image credits Aditya Ananta Parameswara.

The eruptions lasted for around seven minutes and caused local authorities to ask residents to stay outside a three-kilometer zone around the volcano. Mount Merapi is close to Yogyakarta, the capital city of the Special Region of Yogyakarta in Indonesia on the island of Java, one of the country’s most important cultural areas. However, so far no damage to property or life has been reported.

A rumbling display

The first reports of something going on with the volcano came from locals in the neighbouring areas hearing strong rumbling sounds in the morning, according to Deutsche Welle.

With the memory of Merapi’s last eruption in 2010 still fresh (the event claimed 300 lives and forced the evacuation of 280,000 residents), authorities immediately instituted the no-go zone and prepared for the worst. The geological agency even advised commercial planes to proceed with caution in the area.

However, it was luckily all bark and no bite, so the authorities didn’t need to raise the volcano’s alert status. No loss of life or property was so far reported, despite this being the most powerful eruption of Mt. Merapi since 1930.

Air traffic is currently unrestricted across the region, but pilots are still advised to be cautious around the area.

Indonesia is made up of over 17,000 islands and islets created by tectonic movements across an active fault line on the Pacific “Ring of Fire”. This geological backdrop explains why the nation also has nearly 130 active volcanoes and lively seismic activity.

So while Indonesia will definitely see more eruptions like this in the future, we can only hope that they will all be just as harmless.

The 2018 eruption of Mount Kīlauea in Hawaii likely caused by rain

The 2018 eruption of Mount Kīlauea in Hawaii was likely triggered by excessive and sustained rainfall in the region, according to a new paper from the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science.

Kīlauea Erupting with lava at Hawaii Volcanoes National Park.
Image credits USGS.

Such findings have implications for volcanoes around the world, not just those in Hawaii, as they suggest local precipitation patterns could have an important role to play in the timing and frequency of eruptions.

Just add water

“We knew that changes in the water content in the Earth’s subsurface can trigger earthquakes and landslides. Now we know that it can also trigger volcanic eruptions,” said Falk Amelung, professor of geophysics at the UM Rosenstiel School and coauthor of the study.

“Under pressure from magma, wet rock breaks easier than dry rock. It is as simple as that.”

The team shows that the eruption was preceded by prolonged and at times extreme, rainfall in the months leading up to the event.

Kīlauea is an active shield volcano, one of the liveliest volcanoes in all of Hawaii. On May 3, 2018, it started spewing lava nearly two hundred feet in the air, eventually covering over 13 square miles of the well-populated east coast of Hawaii’s Big Island. The unprecedented event destroyed hundreds of homes and only ended four months later, in September, when the summit of the caldera (the volcano’s top) collapsed in on itself.

The researchers used data from ground- and satellite-based stations from NASA, the European Space Agency (ESA), and the Japanese Space Exploration Agency (JAXA), to model rainfall patterns in the area before the event and, from that, estimate the fluid pressure within the volcano over time.

This pressure is, essentially, what drives volcanoes to explode. Magma itself may be molten-hot, but it is generally quite harmless if left to its own devices. What actually pushes it out of the volcano is the buildup of fluids — gas and liquids — in the enclosed space. These fluids typically seep out of the magma as they escape the depths of the Earth, and thus encounter lower pressures. It’s the same mechanism that makes a can of soda pop if you shake it before opening.

All in all, the team explains that fluid pressure was highest just before the eruption — this wasn’t surprising. But they also calculated that it was the highest recorded pressure value in half a century at this point, which they argue helped move the magma and caused the eruption. Their hypothesis would also explain why there was no widespread uplift (from gas building up beneath the surface) at the volcano in the months prior.

“An eruption happens when the pressure in the magma chamber is high enough to break the surrounding rock and the magma travels to the surface,” said Amelung. “This pressurization causes inflation of the ground by tens of centimeters. As we did not see any significant inflation in the year prior to the eruption we started to think about alternative explanations.”

This is the first time that this mechanism has been invoked to explain deeper magmatic processes. In support of their theory, the team notes that Kīlauea’s historical eruption record shows it was almost twice as likely to erupt during the wettest parts of the year.

And, if this process is at work here, it’s likely to also take place at other volcanoes, the authors add. If such a link between rainfall and volcanism can be reliably determined, it “could go a long way towards advanced warning of associated volcanic hazards,” according to Jamie Farquharson, a postdoctoral researcher at the UM Rosenstiel School and lead author of the study.

“It has been shown that the melting of ice caps in Iceland led to changes of volcanic productivity,” said Farquharson. “As ongoing climate change is predicted to bring about changes in rainfall patterns, we expect that this may similarly influence patterns of volcanic activity.”

The paper “Extreme rainfall triggered the 2018 rift eruption at Kīlauea Volcano” has been published in the journal Nature.

The Earth was humming because a huge underwater volcano was forming

Something was brewing underneath the Comoros archipelago, and the Earth was rumbling.

Image credits: James Tuttle Keane.

All around the world, researchers have installed seismometers that captures the Earth’s minutest vibrations. When an earthquake takes place, it might rumble the area closest to it — but echoes of this rumbling are spread all around the world and can be detected by precise equipment.

This is actually how we know what the interior of the planet looks like: vibrations spreading from one point on the Earth to the other are affected by the environment they travel in, and they carry “fingerprints” of these environments.

So when researchers picked up an unusual “humming” coming from the inside of the Earth, they took it very seriously.

Mayotte. Image in public domain.

It all started with an unusual amount of earthquakes from the island of Mayotte in the Indian Ocean — one of the areas in the Comoros archipelago between Africa and Madagascar. Over 7,000 earthquakes were detected, the most severe of which had a magnitude of 5.9.

To make matters even more mysterious, some earthquakes exhibited an unusual type of oscillations: low-frequency and almost-harmonic vibrations, almost like those from a large bell.

Example of seismic oscillations. Image credits: Cesca et al (2020), Nature Geoscience.

Unfortunately, there were no seismic monitors on the ocean floor in the area where earthquakes were occurring, so researchers had to rely on seismographs farther away. But after a year of hard work, they managed to piece together what had happened. Although there was no previous indication of volcanism in that area, the seismic sign is indicative of an emerging underwater supervolcano, says Simone Cesca from the German GeoForschungsZentrum (GFZ).

“We interpret this as a sign of the collapse of the deep magma chamber off the coast of Mayotte,” explains Eleonora Rivalta, co-author of the scientific team. “It is the deepest (~30 km) and largest magma reservoir in the upper mantle (more than 3.4 cubic kilometers) to date, which is beginning to empty abruptly.”

The existence of the volcano was also confirmed by a separate investigation, but this research could help piece together what happened as the volcano was forming, and could help us make sense of similar events that would take in the future.

Luckily, despite the significant earthquakes, there were no casualties and major property damage. Nevertheless, researchers will keep a close eye to see how the volcano continues to develop.

“Since the seabed lies 3 kilometers below the water surface, almost nobody noticed the enormous eruption. However, there are still possible hazards for the island of Mayotte today, as the Earth’s crust above the deep reservoir could continue to collapse, triggering stronger earthquakes,” says Torsten Dahm, head of the section Physics of Earthquakes and Volcanoes at the GFZ.

The study “Drainage of a deep magma reservoir near Mayotte inferred from seismicity and deformation” has been published in Nature Geoscience.

Venus might still be volcanically active, according to its infrared emissions

Venus might still harbor active volcanoes, a new paper reports.

Image credits NASA.

Earth and Venus are similar enough in size and mass that they are sometimes referred to as being ‘sister planets’. But, apart from that, the two are very different. Venus is covered in a super-thick and opaque atmosphere, so we have had very few opportunities to actually see its surface. However, new research at the USRA’s Lunar and Planetary Institute (LPI) suggests that the second planet from the Sun may still be volcanically active.

So far, Earth has been the only planet in the solar system with confirmed volcanic activity. The other three bodies known to have active volcanoes are Io, a moon of Jupiter, Triton, a moon of Neptune, and Enceladus, a moon of Saturn.

Volcanoes near you

“If Venus is indeed active today, it would make a great place to visit to better understand the interiors of planets,” explains Dr. Justin Filiberto, a staff scientist with the LPI. “For example, we could study how planets cool and why the Earth and Venus have active volcanism, but Mars does not.”

“Future missions should be able to see these flows and changes in the surface and provide concrete evidence of its activity.”

Most planets and moons in the solar system show signs of ancient volcanism. Venus is no exception: readings in the 1990s showed that Venus had been volcanically active as recently as 2.5 million years ago and that its surface is littered with volcanic features to this day. However, because Venus is so hard to observe and visit, we’re not sure if its volcanoes are active or dormant.

The new study, led by Dr. Filiberto, drew on data recorded during the 2000s by ESA’s Venus Express orbiter, which measured infrared light coming from the planet’s surface at night. Through this data, the team was able to map the lava flows on Venus’ surface and, by comparing this against previous data, track how they evolved between the 1990s and 2000s. ESA’s data also allowed them to tease apart fresh lava flows from dormant ones.

One thing that prevented us from accurately determining when Venus’ volcanoes erupted was that we didn’t know how fast its (fresh) magma alters once on the surface. In order to determine this, Dr. Filiberto and his team simulated Venus’ atmosphere in their laboratory and then investigated how it impacts the evolution of lava.

They showed that olivine (a heavy, green mineral that’s very abundant in basalt rock) would rapidly react with gases in Venus’ atmosphere, becoming coated with magnetite and hematite (iron oxide minerals) within days. The near-infrared light emitted by these minerals are consistent with data obtained by the Venus Express mission, the team explains, and would disappear within days. This observation means that the lava flows seen on Venus must have only been a few days old at most, which would strongly indicate that the planet is still volcanically active

We won’t be able to fact-check the findings until we send a new craft to Venus. Several such missions are in the works for the future, including India’s Shukrayaan-1 orbiter and Russia’s Venera-D spacecraft, scheduled to launch by 2023 and 2026, respectively.

The paper “Present-day volcanism on Venus as evidenced from weathering rates of olivine” has been published in the journal Science Advances.

Underwater volcanoes can produce stadium-sized bubbles

An underwater volcano off the coast of Alaska has erupted more than 70 times over 9 months, producing a distinctive grumble before each eruption. The volcano also belched ungodly large gas bubbles.

Map of Bogoslof Volcano and two satellite images of the partially submerged summit and crater during the eruption. Image credits: Lyons et al / Nature.

Shallow submarine volcanoes are difficult to study as they are often remote; this can make data acquisition difficult and costly. The interaction between magma and surface water is also complex. It can create violent explosions, but because these interactions are so inaccessible, researchers don’t really understand the entire process. Furthermore, these explosions can also pose risks to nearby ships and planes.

To better understand these processes, researchers installed low-frequency microphones around the Bogoslof volcano to better study this interaction — of course, they couldn’t install the microphones right next to the volcano, so they installed them 59 kilometers to the south.

| Infrasound signals from an explosive eruption of Bogoslof on 13 June 2017. Image credits: Lyons et al / Nature.

The volcano has been known for a long time. Its peak forms Bogoslof Island, an uninhabited island that barely rises above the water surface (but which hosts a thriving seal colony). The first known emergence of the island above sea level was recorded during an underwater eruption in 1796, and since then, the volcano has been steadily adding more surface to the island through new eruptions. The volcano’s eruptive belches have also been documented.

In July 1908, a medium-sized cutter called Albatross was cruising around the island when the sea began to swell. The account of this event reports that the sea bulged and bulged until it ruptured, releasing a terrifying plume of gas and steam. It was a dazzling display that few humans have witnessed, and it’s exactly what researchers wanted to study with the microphones: how big do these bubbles really get?

Schematic depiction of how a bubble forms around a submerged eruption — it all starts with gases coming inside the magma and ends with a bubble collapse. At some point, the bubble reaches its maximum radius; that’s when the pressure is lowest. Image credits: Lyons et al / Nature.

Shallow submerged explosions are often described as beginning with a swelling of the water surface, but these descriptions are qualitative in nature (“giant”, “huge”), not quantitative; researchers wanted to put some numbers on those adjectives but obviously, hanging around a volcano and waiting for it to erupt is not exactly a safe idea. Previous research has shown that smaller bubbles produce infrasound when they oscillate, and their size can be calculated based on these oscillations. This is where the microphones kicked in — they picked up the infrasound and based on this, enabled the researchers to calculate how big the bubbles were without actually seeing them.

You can actually hear the bubbles below. The audio has been adjusted for human ears and sped up 300x. Each of the spikes is a signal from a separate bubble.

via Wired.

According to the calculations, volcanic bubbles reached up to 750 feet (228 meters) across, with a volume of over 180 million cubic feet (5 million cubic meters) of gas. The size of the bubble depended on the radius of the crater and the depth at which the bubbles form.

“The range of initial bubble radii thus varies from the vent radius, 25m, to 200m, or slightly smaller than the approximate radius of the crater area around the time of the observed signals. In our model, large bubbles most probably formed at or near the vent in the base of the shallow submerged crater and thus the height of the submerged portion of the bubble is controlled by the depth of the water,” the study concludes.

The study has been published in Nature Geoscience.

Human emissions are 100 times greater than those of volcanoes, study shows

The greenhouse gas emissions coming from human activity each year are 100 times greater than the emissions released by all the volcanoes on Earth, according to a decade-long study by the Depp Carbon Observatory.

The Misti volcano in Peru. Credit: Wikipedia Commons

The 500-strong international team of scientists released a series of papers outlining how carbon is stored, emitted and reabsorbed by natural and manmade processes.

According to their findings, manmade carbon dioxide emissions drastically outstrip the contribution of volcanoes—which belch out gas and are often fingered as a major climate change contributor—to current warming rates.

Just two-tenths of 1 percent of Earth’s total carbon—around 43,500 gigatonnes—is above the surface in oceans, the land, and in our atmosphere, the study showed. The rest—1.85 billion gigatonnes—is stored in our planet’s crust, mantle, and core, providing scientists with clues as to how Earth formed billions of years ago.

The Deep Carbon Observatory measured the prominence of certain carbon isotopes in rock samples around the world and was able to create a timeline stretching back 500 million years to map how carbon moved between land, sea, and air.

They discovered that, in general, the planet self-regulated atmospheric levels of carbon dioxide, a key greenhouse gas, over geological timeframes of hundreds of thousands of years. The exceptions to this came in the form of “catastrophic disturbances” to Earth’s carbon cycle, such as immense volcanic eruptions or meteorites.

“In the past, we see that these big carbon inputs to the atmosphere cause warming, cause huge changes in both the composition of the ocean and the availability of oxygen,” said Marie Edmonds, Professor of Volcanology and Petrology and Ron Oxburgh Fellow in Earth Sciences at Queens’ College, Cambridge.

The team analyzed the impact of the Chicxulub meteorite that impacted the Earth 66 million years ago and killed off three-quarters of all life on Earth. The meteorite released between 425 and 1,400 gigatonnes of CO2. They also looked at volcanoes, whose CO2 emissions hovered around 0.3 and 0.4 gigatonnes—roughly 100 times less than manmade emissions.

“The amount of CO2 pumped into the atmosphere by anthropogenic (manmade) activity in the last 10-12 years (is equivalent) to the catastrophic change during these events we’ve seen in Earth’s past,” Edmonds said.

Whereas Earth’s atmosphere has frequently contained higher concentrations of CO2 than the present day, outside of catastrophic eruptions it has taken hundreds of thousands of years for such levels to accumulate. In contrast, manmade carbon emissions have seen CO2 levels rise two thirds in a span of a few centuries.

Celina Suarez, Associate Professor of Geology at the University of Arkansas, said modern manmade emissions were the “same magnitude” as past carbon shocks that precipitated mass extinction. “We are on the same level of carbon catastrophe which is a bit sobering,” she said.

“Climate skeptics really jump on volcanoes as a possible contender for top CO2 emissions but it’s simply not the case,” said Edmonds. “It’s also the timescale.”

Loki volcano.

Io volcano is surprisingly predictable, and will likely erupt this month

While volcanic eruptions are next to impossible to predict, researchers have found a volcano that blows up on a relatively regular schedule — on Io, one of Jupiter’s largest moons.

Loki volcano.
Voyager 1 image showing the volcano Loki and its “lava lake,” a U-shaped dark area about 200 kilometers across.
Image credits NASA/JPL.

Christened Loki, the volcano on Io is expected to erupt in mid-September, according to a poster by Planetary Science Institute Senior Scientist Julie Rathbun presented today at the EPSC-DPS Joint Meeting 2019 in Geneva.

Spacecanoes

“Loki is the largest and most powerful volcano on Io, so bright in the infrared that we can detect it using telescopes on the Earth,” Rathbun said.

Based on over 20 years’ worth of observations, Loki undergoes periodic brightenings as it erupts — and these brightenings follow a relatively regular schedule. One of Rathbun’s previous studies showed that this schedule was roughly once every 540 days during the 1990s; currently, it appears to be once every 475 days.

“If this behavior remains the same, Loki should erupt in September 2019, around the same time as the EPSC-DPS Joint Meeting 2019. We correctly predicted that the last eruption would occur in May of 2018,” said Rathbun.

Volcanic eruptions are difficult to predict because many different factors have to come together for them to take place. The rate of magma upwelling, its chemical composition, the presence of gas bubbles in said magma, what type of rock the volcano sits on top of, as well as how fractured or massive that rock is, all have an impact on when a volcano erupts.

What Rathbun thinks sets Loki apart is its sheer size. Because it’s so large, the effects of these individual factors, overall, are secondary to those of “basic physics” — which are much more easily-predictable.

“However, you have to be careful because Loki is named after a trickster god and the volcano has not been known to behave itself. In the early 2000s, once the 540 day pattern was detected, Loki’s behavior changed and did not exhibit periodic behavior again until about 2013,” she explains.

The paper “Io’s Loki volcano: An explanation of its tricky behavior and prediction for the next eruption” has been presented today, 17 September, at the EPSC-DPS Joint Meeting 2019 and can be read on the Meeting’s journal here.

Tamu Massif is an intriguing new type of hybrid volcano

Tamu, the largest volcano on Earth, shares characteristics of both a mid-ocean ridge and a shield volcano. Its unique characteristics may force us to rethink a classic volcano formation theory.

A 3D map of Tamu Massif, the largest known volcano on Earth. It is around 4 miles high from its base and around 120,000 square miles across — approximately the size of New Mexico. Image credits: IODP.

When the Tamu Massif was discovered in September 2013, researchers suspected that it might be a single volcano. If this were, in fact, the case, it would make Tamu the single largest shield volcano on the globe. A new study, however, casts doubt on that idea — but shows that Tamu might be even more interesting than we thought.

Tamu is an extinct volcano, dating from the Mesozoic, some 145 million years ago. It is located 1,600 km (990 mi) east of Japan at a spreading ridge triple junction, where three tectonic plates are diverging from each other. However, Tamu was considered to be a shield volcano, comprising almost entirely of fluid lava flows from an emerging mantle plume.

This might not be the case.

Spreading ocean ridges typically form large volcanoes themselves. They also have a very distinct magnetic signature, which researchers can analyze. Essentially, whenever lava comes up the surface it solidifies, and the magnetic minerals inside it tend to align to the Earth’s magnetic poles — like compass needles frozen in time.

The magnetic poles are in constant movement, so when the next generation of lava bubbles up, those minerals will have a slightly different magnetic alignment, and so on. This magnetic analysis can also highlight polarity changes in the magnetic poles, which researchers can then detect.

Depiction of polarity around an ocean ridge. Image credits: WHOI.

Linear magnetic anomalies formed by the three ridges had previously been found around Tamu Massif, but it was unclear whether they continued within the volcano itself. Existing information seemed to suggest that this was not the case, hence the argument for Tamu being a shield volcano.

Now, a team of researchers from Texas, China, and Japan analyzed data from 4.6 million magnetic field readings carried over 54 years by ship tracks carrying magnetic measurement equipment. They also had new surveys over the area, finding that linear magnetic anomalies around Tamu Massif blend into linear anomalies over the mountain itself, indicating that the ridge is directly connected to the volcano formation.

“For Tamu Massif, we find dominantly linear magnetic field anomalies caused by crustal blocks of opposite magnetic polarity. This pattern suggests that Tamu Massif is not a shield volcano, but was emplaced by voluminous, focused ridge volcanism,” the study reads.

This is important because it suggests that the Tamu Massif (and potentially other similar areas) were formed through entirely different processes than we thought. A commonly accepted model in volcanology suggests that a hotter (and therefore, lighter) blob of magma, called a mantle plume, slowly rises through the mountain. This plume creates a volcano when it reaches the surface through a vertical succession of lava flows.

But in the case of Tamu, this succession is lateral, not vertical, which the mantle plume theory struggles to incorporate.

Depiction of a mantle plume. This explains many of the earth’s volcanic systems, but not Tamu. Image via Wikipedia.

William Sager, a geophysicist at the University of Houston and senior author for the paper, was one of the authors of the study which concluded that Tamu is likely a shield volcano, but he says questioning old ideas and putting them to the test is an essential part of science.

“Science is a process and is always changing. There were aspects of that explanation that bugged me, so I proposed a new cruise and went back to collect the new magnetic data set that led to this new result.”

“In science, we always have to question what we think we know and to check and double check our assumptions. In the end, it is about getting as close to the truth as possible—no matter where that leads.”

Also, in light of these findings, Tamu also can’t be considered the world’s largest shield volcano, since it’s not a shield volcano. That honor flows back to Mauna Loa, on the island of Hawaii. As for the largest overall volcanic system in the world, that is dominated by the mid-ocean ridges.

“The largest volcano in the world is really the mid-ocean ridge system, which stretches about 65,000 kilometers around the world, like stitches on a baseball,” Sager said. “This is really a large volcanic system, not a single volcano.”

The study ‘Oceanic plateau formation by seafloor spreading implied by Tamu Massif magnetic anomalies’ has been published in Nature Geosciences

Monitoring Volcanic Craters with Infrasound “Music”

Volcanic craters act as giant horns that emit intense low-frequency sounds. Changes in this infrasound may be used to track rising lava lakes and identify signals of future eruptions.

Eruption of Villarrica Volcano. Credit: Wikimedia Commons.

Eruption of Villarrica Volcano. Credit: Wikimedia Commons.

Chile’s Villarrica volcano erupted suddenly on 3 March 2015, disgorging a lava fountain more than 2 kilometers high. The eruption—Villarrica’s first in 30 years—was unexpected in terms of its rapid onset and its violence. It was also remarkably short-lived. Within an hour, the explosive activity had ended. Within about a month, the volcano had returned to its usual state, which featured a roiling lava lake situated deep within the steep-walled summit crater.

Forecasting such violent eruptions is the holy grail for applied volcano science. Toward this objective, volcanologists deploy seismometers to detect tremors, tiltmeters and GPS to identify swelling, and multispectral detectors to monitor gas and heat output. Infrasound sensors, which record the low-frequency sounds produced by volcanoes, are an increasingly important component of this diverse tool kit.Volcanologists traditionally have used infrasound surveillance to both count explosions and track eruption intensity, important capabilities when the view of the volcano is obscured [Fee and Matoza, 2013; Johnson and Ripepe, 2011]. Recent studies have demonstrated that infrasound monitoring can also be used to identify important eruption precursors [e.g., Ripepe et al., 2018]. Villarrica gave indications of its unrest through the changing character of its infrasound. We now recognize that Villarrica’s changing sounds provided a warning that lava was rising within the crater [Johnson et al., 2018a].

These observations were made serendipitously as part of a National Science Foundation–sponsored research project, Volcano Acoustics: From Vent to Receiver, that studied the long-distance propagation of the infrasound produced at Villarrica. During the 2015 field expedition, we installed sensors on the summit and flanks of the volcano. Although the 3 March eruption destroyed the summit deployment, sensors outside the damage zone collected data that yielded a full chronology of the volcano’s increasing unrest.

Volcanoes as Giant Musical Instruments

Volcanoes generate infrasound, low-frequency sounds below the threshold of human perception. Despite varied eruptive behaviors, many volcanoes radiate their most intense sounds within a few octaves of 1 hertz, corresponding to sound wavelengths of hundreds of meters. It is no coincidence that this dimension is similar to the dimension of volcanic craters, which play a critical role in modulating the radiated sound [e.g., Kim et al., 2015].

In many ways, a volcano is like a giant musical instrument. As with volcanoes, the size of a musical horn controls the pitch of the sound it makes: Bigger horns make lower-pitched sounds. Musical sounds tend to be pleasing because of the horn’s resonance; air pressure waves sloshing back and forth within a length of brass tube project sonorously from the horn’s bell. The shape of the bell’s flare is important and controls whether a note is sharp and short or rich and reverberating. This quality, which is independent of a note’s frequency or loudness, is referred to broadly as its timbre.As with a musical horn, a volcano’s timbre and pitch are particular to a crater’s shape. Volcanoes with deep craters have a tendency to produce low-frequency sounds, whereas shallow craters radiate higher-frequency sounds [Spina et al., 2014; Richardson et al., 2014]. Narrow conduits often resonate for extended periods, but broad, dishlike craters might not reverberate at all. Although volcanic sound sources can be varied, vents at the bottom of a crater acting as mouthpieces often generate infrasound. The violent expulsion of gas from vents or from a lava lake surface can induce the crater to resonate.

Volcanic Unrest and Changing Sound Quality

Fig. 1. During the few days leading up to Villarrica’s 3 March 2015 explosion, the volcano’s characteristic explosion infrasound changed (top and bottom). Colored disks represent the spatial equivalents of the respective infrasound time series, which were recorded 4 kilometers from the vent; oscillations are mostly absent on 2 March. Waveforms on 27 February had well-defined oscillations that were mostly absent by 2 March (middle). Draped topography was created by the authors from the Shuttle Radar Topography Mission digital elevation model using an image from NASA Earth Observatory. VID and VIC are the stations that recorded the waveform data.

Volcano infrasound merits particular attention when it changes over time. This can happen when volcanoes change their shape as crater walls slump, floors collapse, or a lava lake rises and falls. Villarrica’s lava lake dynamism, for instance, is considered to be responsible for changing infrasound leading up to the violent eruption in 2015. Frequency fluctuations had previously been attributed to oscillating lava lake stages [Richardson et al., 2014], but in 2015, scientists noted a systematic variation that led up to the violent eruption on 3 March. A study by Johnson et al. [2018a] reported two primary observations: The frequency content of the sounds increased around 1 March (from 0.7 to 0.95 hertz), and the timbre changed (Figure 1). Prior to 1 March, reverberations were evident, but afterward, the sound became like a thunk. In other words, the crater’s acoustic source had dampened.

Villarrica’s crater resembles a funnel, with a conical upper section and a narrow conduit beneath. The absence of resonance in early March is important because according to numerical models, it signifies a high stand of the lava lake situated near the flaring section of the crater. During Villarrica’s typical background state, the surface of the lava lake is deeper—and often hidden—within the vertical-walled shaft. By 2 March, the infrasound signals suggest that the lava lake was approaching the crater rim; the horn had become a loudspeaker, as illustrated in the video below.

The trigger for the dramatic 3 March lava fountain, which started at 3:00 a.m. local time, remains enigmatic, but the end result was a violent paroxysm that caused property damage, forced thousands of people to evacuate the area, and made worldwide headlines. Infrasound observations told us that the surface of the lava lake had reached a high level several days before the eruption. These insights may help us to anticipate future eruptions at open-vent volcanoes.

Volcano Resonance on Steroids

Every volcano has a unique infrasound signature. Compared with Volcán Villarrica, whose resonance evolved during a few days from noticeable to absent, infrasound from Ecuador’s Cotopaxi volcano was notable because it rang consistently in 2016 (Figure 2). Villarrica’s infrasound oscillations lasted cumulatively for a few seconds, but a single oscillation at Cotopaxi lasted for 5 seconds. As many as 16 oscillations were detected in some of the infrasound signals, which, incredibly, lasted more than a minute (Figure 3).

Fig. 2. Cotopaxi and Villarrica volcano photos and satellite imagery from NASA Earth Observatory show the relative size of their summit craters, which produce discrete infrasound signals. Yellow squares in both satellite images are 1 square kilometer. Credit: NASA International Space Station photo archive (Cotopaxi satellite photo), NASA Earth Observatory
Fig. 3. The infrasound signal time series illustrates the nature of the resonance at Villarrica and Cotopaxi (top left). Each waveform is a composite stack of 50 events, which occurred during 1 day at Villarrica and during 6 months at Cotopaxi. A detail of the first 10 seconds from this time series shows the contrast in sound signatures from the two volcanoes (top right). Frequency spectra peak at 0.2 hertz for Cotopaxi and 0.75 hertz for Villarrica; damping factors α indicate the time constant for characteristic decay in reciprocal seconds (bottom).

 

A study of the Cotopaxi events recorded in 2016 refers to these beautiful signals as infrasound tornillos, the Spanish word for screws, because the pressure recording resembles a screw’s profile [Johnson et al., 2018b]. Such waveforms attest to an exceptionally low damping and thus a high quality factor of the crater acoustic source. (Sources with higher quality factors have less damping, and they ring or vibrate longer.)

If Villarrica is like a large trombone, with a leadpipe length that changes over time, then Cotopaxi is like a giant tuba, with relatively unchanging dimensions during much of 2015 and 2016. After explosions in August 2015 opened up Cotopaxi’s crater, the visible conduit extended steeply downward from its 5,900-meter summit. Throughout the first half of 2016, the crater bottom was not visible to aircraft flying over the summit. Aerial observations showed a vertical-walled crater at least 200 meters deep, a dimension corroborated by the modeled infrasound, which suggested a 350-meter shaft.

Sources of Crater Resonance

Infrasound’s journey from volcano source to receiver can be understood only by considering the dramatic modulating effects produced by crater topography [Kim et al., 2015]. It is most plausible that both Cotopaxi’s impressive tornillos and Villarrica’s subdued oscillations are induced by short-duration impulses occurring at the bottom of their craters. An abrupt explosion, or an impulse, contains a broad spectrum of frequencies; however, only those that excite the crater in resonance are well sustained.

Typically, volcano scientists who analyze remote infrasound recordings are generally less interested in the oscillatory “breathing” of the crater outlet (i.e., its infrasound resonance) than in extracting important information about the explosion’s source, such as its duration or mass flux. It is this information that contributes to our growing understanding of how gas accumulates and separates from magma and how it powers volcanic explosions.

However, with recent developments in the understanding of crater acoustic effects, we are better poised to recover important parameters related to the sources of explosions. Cotopaxi and Villarrica represent just two of the dozens of volcanoes active worldwide where infrasound is contributing to our fundamental understanding of eruption dynamics and to our ability to forecast future paroxysms.

Acknowledgments

This work was funded in part by National Science Foundation grants EAR-0838562 and EAR-1830976 and by the Fulbright Scholar Program.

About the authors: This article was written by Jeffrey B. Johnson (jeffreybjohnson@boisestate.edu), Boise State University, Idaho; and Leighton M. Watson, Stanford University, Calif. The article originally appeared on Eos, 100, https://doi.org/10.1029/2019EO123979. Published on 17 June 2019.

References

Fee, D., and R. S. Matoza (2013), An overview of volcano infrasound: From Hawaiian to Plinian, local to global, J. Volcanol. Geotherm. Res., 249, 123–139, https://doi.org/10.1016/j.jvolgeores.2012.09.002.

Johnson, J. B., and M. Ripepe (2011), Volcano infrasound: A review, J. Volcanol. Geotherm. Res.206, 61–69, https://doi.org/10.1016/j.jvolgeores.2011.06.006.

Johnson, J. B., et al. (2018a), Forecasting the eruption of an open-vent volcano using resonant infrasound tones, Geophys. Res. Lett., 45(5), 2,213–2,220, https://doi.org/10.1002/2017GL076506.

Johnson, J. B., et al. (2018b), Infrasound tornillos produced by Volcán Cotopaxi’s deep crater, Geophys. Res. Lett., 45(11), 5,436–5,444, https://doi.org/10.1029/2018GL077766.

Kim, K., et al. (2015), Acoustic source inversion to estimate volume flux from volcanic explosions, Geophys. Res. Lett., 42(13), 5,243–5,249, https://doi.org/10.1002/2015GL064466.

Richardson, J. P., G. P. Waite, and J. L. Palma (2014), Varying seismic-acoustic properties of the fluctuating lava lake at Villarrica volcano, Chile, J. Geophys. Res. Solid Earth, 119(7), 5,560–5,573, https://doi.org/10.1002/2014JB011002.

Ripepe, M., et al. (2018), Infrasonic early warning system for explosive eruptions, J. Geophys. Res. Solid Earth, 123(11), 9,570–9,585, https://doi.org/10.1029/2018JB015561.

Spina, L., et al. (2014), Insights into Mt. Etna’s shallow plumbing system from the analysis of infrasound signals, August 2007–December 2009, Pure Appl. Geophys., 172(2), 473–490, https://doi.org/10.1007/s00024-014-0884-x.

Huge underwater eruption created giant volcano off the coast of Africa

The beautiful island of Mayotte was shaken by numerous volcanic temblors. Image credits: Yane Mainard.

Volcanic shake

About half a year ago, seismologists noticed something unusual off the coast of Mayotte, an overseas French territory between Africa’s eastern coast and Madagascar. Sensors all around the world picked up seismic waves coming from around the island, but the source was largely unknown.

The locals felt it too. Almost every day, they felt small rumbles, stressing out about what the source might be, and authorities had little answers. French researchers had a hunch what the source might be, but without an on-site expedition, it was impossible to confirm. In February, such an expedition was launched. Nathalie Feuillet of the Institute of Geophysics in Paris (IPGP) and colleagues installed six seismometers on the seafloor, 3.5 kilometers beneath the surface, to monitor the seismic activity.

They pinpointed the seismic area, triangulating a region some 20-50 km deep — but this was only the first step. After the area was identified, researchers mapped it using sonar, finding evidence of a tall volcanic mountain formed underwater, and a huge quantity of solidified lava around it.

The outline of the volcano (in red) was excellently outlined by the sonar beams. The 800-meter (half a mile) volcano was built from nothing in just six months. The eruption was so dramatic that the island of Mayotte sank by about 13 centimeters (5 inches) and moved eastwards about 10 centimeters (4 inches). The sonar also revealed 5 cubic km (1.2 cubic miles) of magma on the seafloor Image credits: MAYOBS TEAM (CNRS/IPGP-UNIVERSITÉ DE PARIS/IFREMER/BRGM).

Competing theories

Mayotte is part of the Comoros archipelago, an archipelago formed through volcanic eruptions. However, although some areas of the Comoros are still very active, the last eruption around Mayotte took place about 7,000 years ago. It’s not just the location of this new volcano that’s a bit puzzling, its nature is also a mystery.

There are several competing theories regarding the nature of this volcanic range. Most volcanoes are found along mid-ocean ridges — underwater mountain ranges formed where the Earth’s tectonic plates are pulling apart, and where convection currents from the mantle are bringing magma closer to the surface. However, this isn’t really the case in the Comoros.

Another possibility is that of a hotspot. A volcanic hotspot is an area where a rising mantle plume comes really close to the surface, producing volcanic activity. The classic example is Hawaii, although the nearby island of Reunion was also formed this way. Hot spots aren’t affected by plate tectonics, and they stay in place while tectonic plates move about, typically leaving a “trail” of volcanoes on the surface. This is consistent with the fairly deep earthquakes observed around Mayotte, which would also suggest that the volcanic magma chamber is also very deep. But the evidence isn’t convincing enough to definitively say that there’s a hotspot there.

Depiction of a rift breaking down into multiple rigid blocks. Image credits: Italian Institute for Geosciences.

Another likely culprit is the geological process of rifting. East Africa is one of the world’s most active rift zones, with the African tectonic plate splitting into two separate plates. The rifting area isn’t exactly close to Mayotte, but rifting tends to break large areas into rigid blocks, and this might be responsible for the volcanic events.

Most intriguingly, it could be a combination of some (or all) of the above, making Mayotte one of the most exciting volcanic areas to study.

As for the island’s inhabitants, they still have reason to worry. The volcano is probably too deep to threaten the island in any way — the eruptions are too deep to affect the surface and even a potential collapse of one of its flanks would likely be too deep to generate a tsunami. However, the earthquakes seem to be slowly migrating towards the island, which could potentially lead to a collapse of the island’s flank itself — which would, of course, be much more dangerous. Given this turn of events, Feuillet wants to extend the mission for a few months and get a much better view of what’s happening with this volcanic activity in order to assess the potential risk to the locals. After this is done, results will also be published in a journal, Feuillet says.

Bermuda might hold the key to a whole new type of volcano

Researchers studying a volcano in Bermuda report that it is unlike anything else we’ve seen on Earth — it formed through a mechanism we knew nothing about until now.

About 30 million years ago, a disturbance in the mantle’s transition zone supplied the magma to form the now-dormant volcanic foundation on which Bermuda sits. Image credits: Wendy Kenigsberg/Clive Howard.

With its turquoise seas and pink beaches, Bermuda draws almost 1 million tourists every year. But far beneath the crystalline water, something draws a completely different crowd: scientists.

Cornell researchers had a hunch that there was something off about Bermuda’s volcanoes, so they analyzed a 2,600-foot (800-meter) core sample taken back in 1972. They were looking for isotopes, trace elements, evidence of water content, volatile materials — anything that would give some indication as to how the volcanoes were formed.

“I first suspected that Bermuda’s volcanic past was special as I sampled the core and noticed the diverse textures and mineralogy preserved in the different lava flows,” Mazza said. “We quickly confirmed extreme enrichments in trace element compositions. It was exciting going over our first results … the mysteries of Bermuda started to unfold.”

When the team analyzed the materials from the core, they found a clear signature of the “transition zone” — a layer rich in water, crystals and melted rock that lies beneath the outer and inner mantle. Before now, researchers didn’t know that volcanoes can form from the transition zone.

“We found a new way to make volcanoes. This is the first time we found a clear indication from the transition zone deep in the Earth’s mantle that volcanoes can form this way,” said senior author Esteban Gazel, associate professor in the Department of Earth and Atmospheric Sciences at Cornell University.

Cross-polarized microscopic slice of a core sample. Blue-yellow mineral is augite. Credits: Gazel lab.

Volcanoes were thought to form through one of two mechanisms: either when two tectonic plates subduct (one moves beneath the other), or when there is a deep mantle upwelling, as is the case in Hawaii. Surprisingly this wasn’t the case in Bermuda.

“We were expecting our data to show the volcano was a mantle plume formation — an upwelling from the deeper mantle — just like it is in Hawaii,” Gazel said. However, 30 million years ago, a disturbance in the transition zone caused the magma to flow towards the surface of what is now Bermuda.

Although geochemical studies of this type have been carried out in most volcanic parts of the world, Bermuda had escaped trialing until now. Now that they know what to look for, researchers say that there’s a good chance they might find these chemical signatures in other volcanic areas as well.

This suggests that the transition zone, which is located at a depth of 410-660 km (250 to 400 mi), is an important chemical reservoir for the Earth, bringing material from that depth and onto the surface.

The study has been published in Nature. DOI:10.1038/s41586-019-1183-6.