Washington’s Glacier Peak and its Secret History of Big Eruptions

By Erik Klemetti | November 16, 2017 3:19 pm
A view of Glacier Peak from the east, showing the snow-and-ice covered slopes and the wildness that surrounds the volcano. Jim Vallance, USGS.

A view of Glacier Peak from the east, showing the snow-and-ice covered slopes and the wildness that surrounds the volcano. Jim Vallance, USGS.

For a volcanic arc, the Cascade Range in Washington, Oregon, British Columbia and California uis pretty quiet. So quiet that it is an open question in geosciences why eruptions there seem to be so few and far between. The last eruption in the Cascades was the fairly benign 2004-08 eruptions at Mount St. Helens that, beyond an oddly H.R. Giger-looking lava dome, didn’t really impact much outside the crater carved by the 1980 eruption. In fact, in the past 100 years, only Mount St. Helens has erupted — we’re now past the 100th anniversary of the 1915 Lassen Peak eruption. Compare that to the volcanoes in Kamchatka, where there are three volcanoes currently showing different levels of eruption … and that’s on the quiet side of activity for the Russian volcanoes.

Does this mean we shouldn’t be worried about Cascade eruptions in the future? Far from it! We know that most will erupt again and many have erupted in the past 20,000 years, which is nothing in the lifespan of many volcanoes. Mount St. Helens is clearly the most famous of the bunch, but the proximity of volcanoes like Hood and Rainier to big cities (Portland and Seattle, respectively) mean they get much of the attention. However, one of the most remote volcanoes — and least known — might pose the biggest danger.

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CATEGORIZED UNDER: Rocky Planet, Science, Science Blogs

What Do Volcano Warning Signs Really Tell Us?

By Erik Klemetti | November 6, 2017 11:57 am

Glance at the news lately and you might see these headlines that would make Kent “ACTION NEWS” Brockman proud:

A snapshot at Google News from the weekend.

A snapshot at Google News from the weekend.

Let’s set something straight. No, we’re not around the corner from a VOLCANIC APOCALYPSE.

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CATEGORIZED UNDER: Rocky Planet, Science, Science Blogs

Impressive Eruption in the Solomon Islands

By Erik Klemetti | October 27, 2017 10:13 am
Himawari-8 loop from October 20, showing the two blasts from Tinakula in the Solomon Islands. Meteorological Service of New Zealand

Himawari-8 loop from October 20, showing the two blasts from Tinakula in the Solomon Islands. Meteorological Service of New Zealand

Over the last month, it has been Agung in Indonesia and Aoba in Vanuatu that have captured the media’s attention. However, it has been a volcano in the Solomon Island that might be the most hazardous right now.

So, what’s going on at the two volcanoes that prompted massive evacuations? At Agung, the seismicity has begun to drop compared to the last month. Now, this doesn’t mean it is getting any safer at the volcano. Some studies of previous periods of earthquakes prior to Agung’s other eruptions suggest that it can see earthquake swarms that last months. This explains why Indonesian officials are maintaining the highest alert status for the volcano even with diminishing earthquakes. Over 130,000 people remain evacuated from the danger zone around the volcano, but many are starting to break the evacuation order. Meanwhile, the Indonesian government is trying to keep tourists from avoiding Bali altogether (mostly due to unfounded rumors spread on the internet).

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CATEGORIZED UNDER: Rocky Planet, Science, Science Blogs

Where is the Most Fascinating Geology in the Solar System?

By Erik Klemetti | October 23, 2017 4:51 pm

I’ve spent the last few days at the Geological Society of America Annual Meeting in Seattle. What I’ve learned is that geology has definitely left the planet and there are some great questions and locations for studying geologic problems on other planets in our solar system.

This got me thinking about some of my favorite geologic sites in the solar system. Some of them are like features on Earth, others are like terrestrial deposits on steroids and others are like nothing we can find on our home planet.

So, here is a top 10 of cool geologic features across the solar system (in no particular order). By no means is this exhaustive, but it is at least a taste of the amazing geology off the Earth.

The seas of Titan: Cassini’s visit to Saturn recently met its fiery demise, but one of the most important aspects of that mission was the Huygens lander on the giant moon Titan. There, the orbiter and lander took a close look at the remarkable methane seas on Titan. I’m fascinated with what might lurk in those seas under the thick atmosphere — is there life? The ingredients of life? It might be awhile, but a robotic boat on the seas of Titan would be an amazing mission.

Composite Cassini image of Titan, with sunshine reflecting off the moon's methane seas. NASA

Composite Cassini image of Titan, with sunshine reflecting off the moon’s methane seas. NASA

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Kirishima in Japan Erupts for the First Time Since 2011

By Erik Klemetti | October 12, 2017 9:14 am
Kirishima in Japan erupting on October 12, 2017. Image by James Reynolds, used by permission.

Kirishima in Japan erupting on October 12, 2017. Image by James Reynolds, used by permission.

For the first time since September 2011, Kirishima in Japan has started erupting. On the morning of October 11, new ash emissions began from the Shinmoe-dake cone on the large, complex volcano on the north end of Kagoshima Bay. The eruption have been relatively small ash-and-gas plumes that reached less than 1 kilometer (~3,200 feet) over the volcano and spread shards of volcanic glass (aka ash) across the area. These new explosions have promoted the Japanese Meteorological Agency (JMA) to raise the alert status to Level 3 and declare an exclusion zone around the active vent. The plume from the eruption was clearly seen on Terra MODIS image (below) taken on October 11 (Universal time, so October 12 local). Read More

Could We Stop Geologic Disasters?

By Erik Klemetti | October 11, 2017 10:45 am
Damaged homes from the 2010 earthquake in Haiti. European Commission DG ECHO.

Damaged homes from the 2010 earthquake in Haiti. European Commission DG ECHO.

Geologic disasters are commonplace on Earth. Earthquakes, eruptions, tsunamis, floods — they occur all the time and not without consequence in terms of loss of life and property. Many times, they happen without warning and occasionally in places you might not suspect. So, what can we do to stop these disasters … and by that, I mean stop them, not prevent damage and destruction in their aftermath.

I get this question a lot: can we actually prevent geologic disasters from happening. That volcano looks like its going to erupt? Let’s make sure it doesn’t! That fault line has a record of big earthquakes and it has been longer than usual since the last one? Let’s get rid of the threat. Human ingenuity can solve many massive problems, so why not these?

That is the realm of what might be called “geoengineering“: attempts to solve problems by manipulating large Earth processes. It really sounds like science fiction, mostly because it is. The processes that drive massive geologic disasters are on such a scale that trying to prevent them with almost any human technology is like an ant trying to fix a Volvo.

But let’s speculate a bit. How would you even approach the problem? For the biggest geologic disasters (in terms of loss of life and property), the two big players are earthquakes and eruptions. With those events sometimes come tsunamis and landslides, which are massively destructive as well. However, they tend to be caused by earthquakes or eruptions, so they are best dealt with at the source.

And the source of all this is plate tectonics. This is the theory that the surface of the Earth is divided into plates of rock. These plates are massive — thousands to tens of thousands of kilometers across — thick, reaching 100 kilometers (62 miles) beneath our feet. These plates move on the slowly convecting (but still solid) mantle and at their fastest, only move tens of centimeters per year. These plates can collide to form mountain belts, spread apart to form huge rifts, dive under one another and slide past each other. All of these interactions have consequences: Friction, which cause earthquakes, and upwellings of magma, which forms volcanoes.

Luckily, much of the tectonic action of earthquakes and volcanoes are limited to the places where plates interact. This is why Indonesia is a very geologically active area but Ohio is not. It doesn’t mean that disasters don’t happen elsewhere (hello, Yellowstone or New Madrid), but those are much rarer events. However, day in and day out, the plates are moving.

Now, you might say “can we stop tectonics?” The answer to that is a very big NO and we wouldn’t want to anyway. So much of the habitability of Earth is likely linked to tectonics, so stopping mountain belts from rising or volcanoes from erupting would not be a good plan … or one even remotely possible as it is rooted in the convection of magma thousands of kilometers deep of the Earth’s mantle.

So, can we stop earthquakes and eruptions? We can start with earthquakes. They occur when stress builds on faults in the Earth’s crust (mostly) and when that stress exceeds the strength of the rock, then the rocks slip and an earthquake occurs. To get an idea of the energy released in an earthquake, we can compare it to other events. The first atomic bomb used in warfare released about the same amount of energy as a magnitude 6 earthquake. A lightning bolt might be the same energy as a magnitude 2 earthquake. The largest earthquakes on record (magnitude 8 and 9) released as much energy as almost 1 million Hiroshima bombs.

That’s a lot of stress stored in the faults and released when they rupture! Could we bleed off the stress somehow? One suggest might be to drill along the fault and try to measure stress along it. Then we could look for areas of high stress and create small earthquakes to reduce the potential for a massive destructive earthquake. Although that seems logical, the main problem is that the stress could be handed off to another part of the fault as a consequence, merely moving the threat rather than removing it. In any case, how would we trigger these small earthquakes? We already cause earthquakes (although not on purpose) in areas where we pump fluids into the crust (like Oklahoma), lubricating faults and changing the stress they feel. However, that is done by a Swiss cheese process of drilling rather than targeted drilling into faults — and right now, we have no idea what the impact of specifically trying to trigger these earthquakes might be.

For eruptions, I’ve heard similar suggestions about drilling to relieve pressure (see the recent spat of articles about Yellowstone caldera). As I’ve discussed in the past, drilling into a volcano is not likely to trigger an eruption (at least not with our technology) as we just don’t have much impact on a magma body … our drills are too small and the magma body is too large. Even after an eruption, we’ve tried bombing and blocking lava flows, mostly to little effect on the lava itself.

Oh, and we’d never want to nuke a volcano to try to prevent a larger eruption. If a volcano is showing signs of an eruption, nuking it is more likely to trigger a bigger eruption that’s also full of radioactive particles, so that would be even worse.

The source of magma under volcanoes is tens to hundreds of kilometers underground, so trying to prevent magma from rising in the first place isn’t feasible either. In places like the Andes or Japan (subduction zones), magma comes from the melting of the mantle due to the dehydration (loss of water) in the slab of oceanic crust that is being jammed into the mantle. You’d have to stop tectonics to end that. In other places, like the East African Rift, magma is formed by mantle rising and melting, so again, rooted in the deep convection inside the planet.

So, what is the point? Much like all geologic disasters, the key to save lives and property isn’t stopping the disaster from happening but rather planning so the impacts won’t be as consequential to those involved. For earthquakes, it might be strict building codes and early warning systems to help people stay out of harm’s way. For volcanoes, it might be preventing people from living too close to active volcanoes or preparing them for evacuations when signs of eruptions appear.

Geologic hazards are best handled by planning and mitigation. This takes organizations (usually governments) to handle the logistics and implementation of the plan. We can see what happens when that system breaks down, like what is currently happening in Puerto Rico. This takes an investment from society reaffirming the need to build better more robust infrastructure to withstand the hazard, even if it means spending money now that might not save anyone until 2060. If not, we leave ourselves exposed to increasing damage and death from geologic disasters. We live on an active planet and as residents of the planet, we need to learn to live with that change.

CATEGORIZED UNDER: Rocky Planet, Science, Science Blogs

Patience Wearing Thin as Unrest Continues at Agung but No Eruption

By Erik Klemetti | October 5, 2017 1:43 pm
A view of the crater at Agung on September 27, 2017. The increased steam and gas emissions can be seen on the right side of the crater. The dark scar on the slopes of the volcano come from a forest fire earlier in the month. Image by Planet Labs.

A view of the crater at Agung on September 27, 2017. The increased steam and gas emissions can be seen on the right side of the crater. The dark scar on the slopes of the volcano come from a forest fire earlier in the month. Image by Planet Labs.

We have likely entered the most dangerous period in the waiting game at Agung in Indonesia. It has been over 2 weeks since the volcano began to show signs of unrest and it has done very little other than shake and produce a small steam-and-gas plume. Upwards of 140,000 people have evacuated from the regions near the volcano and now all of them are watching and waiting for the volcano to do … something. The longer the wait, the more likely people may reject the assessment of volcanologists that an eruption is going to happen and try to move back to the homes near the volcano, potentially lining us up for a larger disaster. So, what can be done?

The signs of this impatience are already there: officials on Bali want tourist warnings rescinded as thousands of trips to the region have been cancelled (possibly leading to as much as a 30% decrease in tourism). Many people who live far out from the volcano who evacuated anyway have been asked to return to alleviate pressure on aid/housing for evacuees, yet they stay away out of fear. Even the media is beginning to ask questions about why the volcano hasn’t erupted and what happens if it doesn’t.

For a volcanologist, there is no easy answer. Much like meteorologists who get grief if you only get 2″ of snow instead of 20″, volcanologists must contend with residents who seem upset that they used an abundance of caution rather than put people in greater risk. However, once that trust is eroded, it is hard to rebuild. During the 1980’s, the USGS was very concerned that Mammoth Mountain in California was heading towards an eruption and took to the media to relay that potential threat. This severely impacted the people living in the tourist-heavy area, especially in terms of real estate prices and visits to the ski areas on the volcano. However, nothing came of the earthquake swarm at Mammoth, so the local residents claimed that the USGS oversold the threat.

As they say, hindsight is 20/20. During a crisis, you are presented with information and need to make the best interpretation possible that could prevent the most loss of life. You might be lulled into a sense of complacency if you sit through the period of unrest and see nothing change for days to weeks. Yet, if you were dropped into that situation in Day 10 of the crisis without any background, you would know the situation is highly hazardous.

The number of earthquakes at Agung has not really changed since the earthquakes began (see above) … and that isn’t a good thing. It means there is still a high level of unrest, so the threat remains. However, the perception might be that little has changed in the number of earthquakes, meaning that the threat has diminished. It has not. Instead, the longer the heightened unrest persist, even if it doesn’t increase, the greater the likelihood that an eruption could occur. This doesn’t say anything about the size of that eruption, but all that potential is still there.

Luckily, preparations are still underway to help with evacuations when an eruption happens. Ferries are being prepared to get tourists out of Bali if any eruption closes airports (author’s note: what about locals?) The PVMBG has deployed new webicorders to monitor the changing seismicity at Agung and there are webcams that are pointed at the volcano.

A small steam-and-gas plume from Aoba on Ambae in Vanuatu, seen on September 29, 2017. Although the eruption plume was small, the dark grey ash on the landscape betrays larger eruptions earlier in the week. Image by Planet Labs.

A small steam-and-gas plume from Aoba on Ambae in Vanuatu, seen on September 29, 2017. Although the eruption plume was small, the dark grey ash on the landscape betrays larger eruptions earlier in the week. Image by Planet Labs.

Meanwhile, in Vanuatu, the entirety of the population of Ambae have been asked to evacuate due to the increasingly large eruptions from Aoba. This is a massive operation involving all manner of transport, but luckily almost all of the island’s over 11,000 inhabitants have been moved. The government of Vanuatu has promised that people will be able to return when the threat diminishes, but no one has an idea of when that might be. Satellite images of the island show how much ash has impacted the idea, where great swaths of green have been turned grey due to the eruptions (see above). An evacuation this large in a nation like Vanuatu means that many people have been put into a dire situation, so calls for aid have been made — some of which have been heard by neighboring nations.

Both of these volcanic crises share traits: large populations of at-risk people need to be moved from the vicinity of the volcano. In one place, the threat is clear as eruptions coat the area with ash. In the other, unrest continues but patience is wearing thin as the volcano has not produced an eruption. You might think the latter is a better place to be, but as that patience disappears, we may see a larger crisis loom as people try to head back into areas where the volcano threat still remains.

CATEGORIZED UNDER: Rocky Planet, Science, Science Blogs

Why Are There Deadly Rockfalls at Yosemite?

By Erik Klemetti | September 29, 2017 10:11 am
Climbers on the shear granite face of El Capitan in Yosemite National Park. You can see areas where fresh (white) rock is exposed that likely experienced a recent rockfall. Image: Erik Klemetti, September 2012.

Climbers on the shear granite face of El Capitan in Yosemite National Park. You can see areas where fresh (white) rock is exposed that likely experienced a recent rockfall. Image: Erik Klemetti, September 2012.

The last few weeks have seen multiple rockfalls at Yosemite National Park in California, one of which produced a fatality to a climber on the iconic vertical wall. Yesterday, another rockfall that was ten times bigger than the fatal one earlier in the month occurred that injured a park visitor. So, why are these rock falls so common in Yosemite Valley? It all comes down to the fact that steep rock walls are not as permanent as they might seem.

Most of Yosemite Valley is lined with the remnants of magma bodies. El Capitan and Half-Dome are chunks of granite (or related rocks) that crystallized deep underground — likely over 3 kilometers down — during a time when a chain of volcanoes ran down the proto-California coastline. The solidified remains of the magma bodies that drove that volcanism are the beautiful granite that makes the valley so stunning. However, that granite isn’t stable.

Well, let me qualify that. Granite is stable — the Sierra Nevada itself is testament to that strength of the rock. However, granite doesn’t like being at the surface. It was formed under high pressure underground and processes like weathering, erosion and uplift bring that rock to the surface over millions of years. That granite encounters conditions very different than where it formed once it gets to where we can see it: the pressure is thousands of times lower, the temperature is hundreds of degrees cooler and there is all this stuff that keeps happening to it: rain! wind! animals! plants! frost! snow! boulders! It is an unpleasant place to be for granite.

So when the glaciers came through and carved Yosemite Valley, leaving these barren, steep slopes of granite, they also left an inherently unstable situation. Granite will naturally begin to split into sheets in a process called spalling (or exfoliation – think like an onion skin) as it is exposed to the low pressure of the Earth’s surface. That makes cracks in the rocks. Water or animals or plants roots get into those cracks and can help expand them. That water can work on destroying the rock multiple ways. Mixtures of water and natural acids can dissolve the minerals, making the rock weaker (geologists might call it “rotten”). Water can also get into cracks and freeze … and when it freezes, it expands, widening the cracks.

Eventually, that slab of rock isn’t attached to the rest of the granite and gravity can take over, causing it to fall. Maybe an earthquake or big rainstorm or the sun beating down on the rock causing it to expand and contract every day can help the process along. Then you get a rockfall, leaving new rock exposed (see below) to start the process all over again.

The whole Yosemite Valley is at high hazard for these rockfalls, especially underneath the stark cliffs. Without any vegetation to protect the rocks, the granite can be exposed to all the nastiness of the Earth’s surface and eventually, those slabs will fall away. You can see an NPS video on rockfalls here.

Unfortunately, it is really hard to predict exactly when that might happen. There are some ways we can start to make models of the places with the highest likelihood (a “hazard map“): carefully mapping the the cliffs, measurements of cracks in the rock walls using LIDAR or gauges, GPS measurements of parts of the cliffs, video surveillance looking for the start of falls. However, the only real way to be safe is to try to stay away from places of danger.

Which, of course, is a big problem for pesky humans. Climbers love the challenge of the sheer cliffs at Yosemite. Cabins sit at the bottom of these gorgeous geologic features. People want to be there even in the face of the potential that thousands of tons of rocks may come tumbling down on them while they climb or sleep.

You can see in the photo of yesterday’s rockfall that the area that the climber passed literally fell away. If you are under that, you are likely out of luck. Maybe if you are far enough away to hear/see the rockfall begin, you can get out of the way, but once they start, they move fast and are carrying potentially millions of cubic feet of rock.

The National Park staff has done multiple assessments of the rockfall hazard in Yosemite and produced hazard maps, showing where rockfalls have happened and where the highest likelihood of falls might be in the park. They can happen in all seasons, although early spring and late winter, with there abundant water, tends to have more rockfalls. The NPS has worked to reduce the usage of some places that have a higher occurrence of rockfalls so that we don’t have a large tragedy such as a rockfall heading through cabins full of visitors at night.

There really isn’t any way that rockfalls can be prevented at Yosemite National Park — they are part of the geologic process where rocks are destroyed at the Earth’s surface, only to be reburied as part of the rock cycle. The best way to prevent deaths or in juries is to be knowledgable of the hazard and try to avoid putting yourself into harms’ way. Now, not everyone is going to follow the advice of geologists and park officials to play it safe, but that is where society has to step in and decide how much value we want to put on keeping people safe.

CATEGORIZED UNDER: Rocky Planet, Science, Science Blogs

Rumbling Volcanoes in Indonesia and Vanuatu Still Have People Worried

By Erik Klemetti | September 27, 2017 11:20 am
Agung in Indonesia seen in 2009. Antoine Vasse Nicolas / CC by 2.0

Agung in Indonesia seen in 2009. Antoine Vasse Nicolas / CC by 2.0

This week, the focus is on the rumbling volcanoes in Indonesia and Vanuatu. Here are some updates (along with a tidbit at the end on Washington’s Rainier.)

Agung

The unrest at Indonesia’s Agung continues and now the total evacuated has reached almost 100,000 people. Now, this volcanic crisis has been going for almost a week with no eruption … and we begin to enter the long, dark teatime of volcano monitoring: how long until people stop believing your statement’s about an impending eruption? What if Agung waits 3 months to erupt instead of 2 days? Credibility is very hard to rebuild after a false start, so I’m sure Indonesian volcanologists and officials are biting their nails as Agung keeps experiencing heightened seismicity.

Comparisons of satellite images of Agung taken in early and late September (below) show the changes in fumaroles (gas emissions) from the volcano as it became more restless.

The latest BNPB (Indonesia’s disaster management agency) statement says that the earthquakes are getting more frequent and more are being felt, so they’re also getting stronger. All of this still supports the idea that magma is nearing the surface, making the likelihood of an eruption high (even though the steam plume is slightly smaller today). However, as any volcanologist would tell you, you trying to not only figure out the “when” but also the “how big“, and the latter is definitely much harder.

Indonesia officials are making plans to divert flights if/when the eruption begins and some airlines are planning to make extra fuel stops in case they have to turn back due to an eruption. Even without an eruption, the aviation alert level for Agung was raised to orange (from yellow) yesterday. Many people are making the evacuation on foot with the official exclusion zone around the volcano is currently set at 12 kilometers. Also, many countries are issuing travel warnings for people going to Bali because of the high potential of an eruption.

If you’re looking for lots of information and updates on the situation at Agung, check out Dr. Janine Krippner’s posts.

Ambae

In Vanuatu, the evacuations near Manaro Voui (Aoba)  are continuing, with the government of Vanuatu pledging $2 million to help with the preparations and evacuations. Ships have arrived with supplies for the evacuees, including water, food and essentials — however, more supplies are needed for the almost 8,000 people in 35 shelters which are rapidly becoming overcrowded. An official state of emergency has been announced for Ambae as well.

An overflight of the volcano’s summit showed vigorous explosions throwing ash and volcanic bombs. The volcano currently sits at alert level 4, which warns of the potential of volcanic bombs being thrown over 6 kilometers from the summit vent.

Rainier

On the far other end of the spectrum of concern, Washington’s Mt. Rainier experienced a small earthquake swarm over the past few weeks. You can read the full USGS statement on this earthquake swarm that can be summed up as “no indication that an eruption is in the works at the volcano”. This swarm might be related to the hydrothermal system under the volcano, where water warmed by magma deep below the surface circulates. Now, I bring this up not to scare people but rather to remind that the lower 48 states have potentially active volcanoes, including Rainier, lurking near Seattle You can check out the seismicity at Rainier on the PNSN page. The last known eruption of Rainier was likely in 1894.

CATEGORIZED UNDER: Rocky Planet, Science, Science Blogs

Over 8,000 People Evacuated on Ambae in Vanuatu

By Erik Klemetti | September 24, 2017 8:13 pm
Map of volcanic hazards for Ambae in Vanuatu. VMGD

Map of volcanic hazards for Ambae in Vanuatu. VMGD

One large-scale evacuation is already occurring in Indonesia as Agung remains restless, but in the South Pacific, another volcano is causing nearly as much trouble. Manaro Voui, on Ambae in the island nation of Vanuatu, has seen its eruptive activity increase dramatically, so much so that authorities have ordered over 8,000 people to evacuate (UPDATE: some of which have now left the island). The island itself has a total population of only ~11,500, so over 2/3 of the population has been asked to move to the far side of the island due to the activity at Ambae. Grey ash plumes (below) have been produced over the last few days as the activity has increased. UPDATE 9/25: New Zealand will be sending a team to survey the volcano. A state of emergency has been declared on Ambae with a large exclusion zone around the volcano.

Manaro Voui (also known as Aoba or Ambae) is one of the more active volcanoes in Vanuatu with frequent small Strombolian eruptions (bursts of lava from the erupting vent). However, the character of the eruptions has changed ion the last week, with a new lava fountain from the vent. Eruptions in 2005 caused people to leave one half of the island over 3 months while more violent explosions rocked the volcano.

The volcano also hosts a number of acidic lakes in the craters at the summit of the shield volcano. This mixture of lava and water meant many of the eruptions were more explosive than the basaltic nature of the lava might suggest. That eruption built an entirely new volcanic island inside the summit lake.

The volcanic hazard map for Ambae (above) shows how much of the island is potentially threatened by pyroclastic flows, while the areas near the volcano could see lava bombs or other volcanic debris (known as tephra). Volcanic mudflows (lahars) are also a potential hazard for the eastern side of the island. Unlike other shield volcanoes like Kilaeau on Hawaii, Aoba is more explosive in its character, with multiple calderas as part of the pyroclastic shield made of the debris of the volcano’s violent blasts.

CATEGORIZED UNDER: Rocky Planet, Science, Science Blogs
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Rocky Planet

Rocky Planet covers all the geologic events that made and will continue to shape our planet. From volcanoes to earthquakes to gold to oceans to other solar systems, I discuss what is intriguing and illuminating about the rocks beneath our feet and above our heads. Ever wonder what volcanoes are erupting? How tsunamis form and where? What rocks can tell us about ancient environments? How the Earth might change in the future? You'll find these answers and more on Rocky Planet.
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