The Volcanology Revolution

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Feature NURUL HIDAYAT/ANTARA FOTO/BISNIS INDONESIA VIA REUTERS FOTO/BISNIS HIDAYAT/ANTARA NURUL When Anak Krakatau in Indonesia erupted on 22 December 2018, part of the island collapsed into the ocean, causing a deadly tsunami. THE VOLCANOLOGY REVOLUTION Forty years after the Mount St Helens eruption galvanized volcano science, researchers are harnessing powerful new tools to forecast and understand eruptions. By Jane Palmer

arly in 2018, the volcano Anak Krakatau the mountain began showing obvious signs of killed at least 430 people along the nearby in Indonesia started falling apart. It was unrest. It spewed fiery ash and rocks into the sky coasts of Java and Sumatra. Although nobody a subtle transformation — one that in a series of small eruptions. And it was heating foresaw that disaster, a 2019 study found that nobody noticed at the time. The south- up. Another satellite instrument recorded ther- satellite and ground-based instruments had ern and southwestern flanks of the vol- mal emissions from Anak Krakatau that reached picked up a suite of precursory signals that cano were slipping towards the ocean 146 megawatts — more than 100 times the could help forecast similar events in the future at a rate of about 4 millimetres per normal value. With the increased activity, the at Anak Krakatau and other peaks. month, a shift so small that research- slippage jumped to 10 millimetres per month. The unexpected collapse at Anak Krakatau Eers only saw it after the fact as they combed Then, on 22 December, the southern flank shows some of the challenges facing research- through satellite radar data. By June, though, crashed into the sea, triggering a tsunami that ers as they try to monitor thousands of

potentially dangerous volcanoes around the time frame, much as meteorologists dole out hummocks — large hills and mounds that had world — each one unique. But it also highlights the chances of rain or snow on any specific day. been transported downslope in intact blocks. several advances in the field that promise to “I think that when people look back on this These features matched those found near give scientists a much better chance of fore- period, they will imagine this is the golden era many volcanoes around the world. And from casting disasters. of physical volcanology,” says volcanologist the historical record, volcanologists recog- Volcanologists are making substantial Christopher Kilburn at University College nized that around 1,000 similar landslides had headway, thanks to a torrent of data from sat- London. taken place on more than 550 volcanoes. “Tall ellites that can detect subtle movements of volcanoes collapse, they’re not just growing, mountains, ground-based sensors that track Historic blast they’re collapsing,” says volcanologist Thomas molten rock moving deep underground, and The first hints of trouble at Mount St Helens Walter at the German Research Centre for gas-sniffing devices that drones can carry over came on 16 March 1980, with a series of small Geosciences in Potsdam. seething mountains. And the theoretical under- earthquakes. Then, a week later, steam explo- The eruption of Mount St Helens taught other standing of volcanoes has grown markedly as sions burst through the ice on top of the volcano, lessons, such as the deadly impact of super- researchers have learnt to combine all these carving out a crater that grew to 400 metres heated volcanic ash and gas racing down the data into models of what is happening within across within days. Teams of researchers mountain at hurricane speeds, and the power volcanic systems. Researchers are now exper- arrived from the USGS and other institutions of mudslides that destroyed everything in their imenting with machine learning to sift through to keep vigil over the mountain. Planes flew path. The eruption also spurred a huge growth the flood of data to identify subtle patterns, in volcanology. In the decade after the blast, the such as the early movement of Anak Krakatau “Tall volcanoes collapse. USGS established volcano observatories in the months before it showed signs of waking. Pacific Northwest, Hawaii and Alaska. The field has made huge strides since the They are not just growing, Funding for the USGS’s volcanic hazards greatest volcanic crisis in US history exactly they’re collapsing.” programme today is nearly ten times what 40 years ago — the eruption of Mount St Helens it was before the Mount St Helens blast. And on 18 May 1980 in Washington state. That after a volcanic mudslide in Colombia killed event — which started with the largest land- over the smoking crater to measure the gases 23,000 people in 1985, the USGS established slide in recorded history — killed 57 people and escaping from the volcano, and seismometers the Volcano Disaster Assistance Program to blanketed much of Washington and nearby registered the tremors from magma — molten help other countries prepare for volcanic states with ash, shutting down the region for rock — moving beneath the surface. Volcanolo- crises — a project that soon proved its worth days. But it was also a turning point for vol- gists climbed the mountain’s slopes to measure when USGS researchers worked with scientists canic science, sparking a huge influx of money the bulging northern flank using tape measures in the Philippines in 1991 to assess the risk from and people into the field and setting the stage and laser-surveying equipment. Mount Pinatubo. Tens of thousands of people for rapid improvements in understanding. Magma was clearly rising high in the volcano were evacuated from the region before the Scientists had flocked to the mountain in and pushing against the slope, and research- volcano’s cataclysmic eruption. the months before the blast and had carefully ers warned that a major eruption could hap- Researchers today rely on many of the tracked its behaviour, including frequent pen soon. But what happened next caught lessons learnt at St Helens, Pinatubo and dozens earthquakes, gases fuming from its crater and scientists by surprise. of other volcanoes. Typically, seismic shaking an ominous bulge that swelled from its north- At 8:32 a.m. on 18 May, a massive landslide is the first sign that a volcano is stirring. Erup- ern flank. “It was the first really significant crashed down the mountainside, taking the tions occur when magma pushes to the surface, eruption that was captured by modern-day summit and snow and ice with it. The release but even as magma begins to rise from Earth’s scientific instrumentation,” says Seth Moran, in pressure uncorked the volcano, triggering mantle, it can trigger quakes. Today, seismic scientist-in-charge at the US Geological Sur- a powerful explosion. A blast of rocks, ash, gas networks are monitoring dozens of some of the vey (USGS) Cascades Volcano Observatory and steam was propelled upwards and out- most dangerous volcanoes around the world. in Vancouver, Washington. “And so, in a lot of wards at supersonic speeds, and travelled as That same magma movement can cause ways, it’s become a benchmark for the ways far as 25 kilometres northwards. volcanoes to inflate, as Mount St Helens did that people go about looking at volcanoes “We learnt from the May 18th eruption how before its blast. Researchers can now record around the world.” unstable steep-sided volcanoes are, and how movements safely and continuously, using The proliferation of ground- and space- they can fail and generate a big surge or lateral GPS receivers and, more recently, satel- based monitoring data since then, coupled blast,” says Don Swanson, a research geologist lite-borne radar — which detected the move- with increases in computing power, has revolu- at the USGS Hawaiian Volcano Observatory, ment at Anak Krakatau. tionized scientists’ understanding of volcanic who was involved in monitoring the 1980 Even before warning signs can be seen or systems. Ultimately, researchers are hoping eruption. “What seems so obvious now, wasn’t felt, rising levels of carbon dioxide from a that new tools and techniques will nudge them obvious before that time.” volcano’s crater or vents can hint at trouble closer to being able to assign probabilities to After the eruption, scientists analysed ahead. Magma contains dissolved gases and the chances of a volcano erupting in a given the landscape and found it littered with as this molten material rises and the pressure

10 s 42 s 52 s 60 s USGS On 18 May 1980, a giant landslide — the largest in recorded history — carried away the north flank of Mount St Helens, triggering an eruption.

Feature decreases, gases separate off and travel programmed the system to send automatic activity ever recorded,” says Walter. “So, this upwards. Carbon dioxide, one of the least e-mail and text-message alerts to the civil-pro- was clearly anomalous behaviour.” soluble of the volcanic gases, escapes first, tection department in Rome and to the city of The researchers also used satellite radar while the magma is still deep in the volcano. Catania close to the volcano. observations, which can detect small changes “In principle, you should get a gas signal The researchers’ original motivation for in vertical and horizontal motion, to find that long before the magma reaches the surface developing the system was to find a way to the volcano’s flank was already slipping at a rate in an eruption,” says volcanic-gas geochem- detect eruptions at unmonitored volcanoes, of 10 millimetres per month before it collapsed ist Alessandro Aiuppa at the University of because even remote blasts can have far-reach- (see ‘Island on the move’). Palermo in Sicily, Italy. ing impacts. The eruption of Eyjafjallajökull The research demonstrated how, even when Historically, scientists had to collect gas in Iceland in 2010 created an ash plume that ground instrumentation is limited, scientists samples from near the crater or vents — a disrupted air traffic across Europe for weeks. can learn about the lead-up to an eruption dangerous task that yielded only episodic “Volcanic risk has no borders,” says Maurizio or volcanic landslide from satellites. “As vol- bites of information. Then, in 2005, Italian Ripepe, a geophysicist at the University of canologists, we always used to say that we researchers designed an instrument — a Florence, Italy, who helped to create the were data poor,” says Michael Poland, scien- multicomponent gas analyser system (Mul- automated early-warning system on Etna. tist-in-charge at the USGS Yellowstone Volcano ti-GAS) — that is not much bigger than a shoe- Currently, fewer than half of the world’s Observatory in Vancouver, Washington. “But box. Volcanologists install these sensors near active volcanoes on land have any sort of now the satellite data really expand our ability vents, and also mount them on drones that ground instrumentation, and in many cases to see what volcanoes are doing.” fly over active craters to measure the levels of this consists of just a few seismometers. But Volcanology got a huge boost in 2014 and five key gases emitted by volcanoes. “This has in the past decade, researchers have gained 2016 with the launch of the European Space been a real revolution for volcanic-gas science new ways to monitor all volcanoes using Agency’s Sentinel 1A and 1B radar satellites. because it means you can have a measurement instruments mounted on satellites. Using the technique of interferometric of volcanic-gas composition every second, in synthetic-aperture radar, they can track real time, on your computer,” Aiuppa says. Data deluge movements of volcanoes at unprecedented On 10 April 2020, Indonesia’s Anak Krakatau resolution levels and at frequent time intervals Blast forecast spewed a column of ash 500 metres into the sky (see ‘Inflation watch’). “These satellites can The Multi-GAS instruments had their trial by and the Center for Volcanology and Geological detect subcentimetre deformation of ground fire on Stromboli, a volcano off the north coast Hazard Mitigation in Indonesia issued a level-2 surfaces, meaning that we can see when the of Sicily. Italian scientists installed these sen- alert, which signifies that the volcano has the volcano is swelling,” says volcanologist Charles sors, along with cameras and spectrometers, potential to erupt but poses limited hazards. Mandeville, programme coordinator of the on the volcano in 2005 and have collected gas After the deadly tsunami in 2018, German USGS Volcano Hazards Program. “There is a data ever since. In February 2007, lava began volcanologists had found a striking pattern whole fire hose of such data being collected to ooze out of the volcano in an effusive erup- at Anak Krakatau that was apparent in data now.” tion. The researchers saw that carbon dioxide recorded by the moderate-resolution imaging Researchers have combined radar data with levels rose tenfold over the two weeks before spectroradiometer (MODIS) on a NASA satel- satellite observations that record tempera- the volcano erupted explosively on 15 March1. lite. Infrared channels revealed that thermal ture and sulfur dioxide emissions to capture The findings allowed volcanologists to build emissions jumped in June 2018 (ref. 3). “The a multidimensional picture of what happens a conceptual model of this complex volcano, in whole volcano was hot, the most intense at volcanoes before and during eruptions. A which explosions emanate from a deep magma chamber 7–10 kilometres below the summit. The researchers determined that the chances ISLAND ON of an explosive eruption increase when carbon THE MOVE dioxide emissions top 2,000 tonnes per day. Satellite radar data reveal how N In August 2019, Stromboli oozed lava again, the ground surface of Anak Krakatau, a volcanic island, and for the next two weeks the Italians tracked shifted in the 12 months before a slow, progressive increase in carbon diox- an eruption on 22 December 2018. The southwestern region ide. “So, we knew that something was going to collapsed during the eruption, happen,” Aiuppa says. The team increased its triggering a deadly tsunami. vigilance and also closely monitored ground- Such observations could help to forecast when a volcano level changes using tiltmeters that measure will erupt. subtle changes in ground angle. Eventually, what they saw made them certain that an explosion was coming soon, and they alerted Vertical the local authorities minutes before a blast movement (mm yr–1) on 28 August. 100 (2019) , 4339 At Mount Etna on the Sicilian mainland, 10 0 Italian researchers are tracking low-frequency sound waves — infrasound waves — that some –100 volcanoes emit before they erupt. Scientists –200 installed the system on Etna in 2008 and ana- –300 lysed its performance for 59 eruptions in the Movement following 8 years. It successfully predicted East or West 57 of the events, and sent messages to the (mm yr–1) researchers about an hour before each erup- 2 100 tion . Given this success, in 2015 the team . COMMUN R ET AL. NATUE T. FIG. 3B WALTER,

lead to the installation of digital broadband N seismometers on 104 of the country’s vol- 5 km canoes and new digital-telemetry networks Kilauea with sufficient bandwidth to carry data from summit a number of different ground sensors. Future shocks In the past 40 years, scientists have successfully forecast the timing of many eruptions, from smaller blasts at Mount St Helens in the ft Zone East Ri early 1980s to the ash-rich lava fountains at Mount Etna. “A lot of progress has been made e n o on the timing aspect,” Poland says. “Perhaps Z t f in a very large part because of the amount of i R

t instrumentation, the advent of space-based s e monitoring and the increase in observations w h t that we have.” u Range o S change (cm) Nevertheless, volcanic eruptions still take people fatally by surprise. A small explosive 0 1.5 eruption at Mount Ontake in Japan in 2014 Pacific killed 63 people, and a violent eruption of the Ocean Fuego volcano in Guatemala in June 2018 killed hundreds. A minor eruption at White Island in New Zealand in 2019 claimed 21 lives. One challenge facing volcanologists is that INFLATION WATCH they are trying to infer what’s happening deep Parts of the Hawaiian volcano Kilauea are currently rising, which underground by looking at data such as gas can be seen in the coloured patterns in radar interferometry data taken from 6 April 2019 to 1 May 2020. Island of Hawaii emissions and shape changes on the surface.

MICHAEL POLAND, USGS MICHAEL POLAND, And each volcano has its own personality — its study of the 47 most active volcanoes in South half a million images from more than 1,000 own unique set of materials and structure. America, which used 17 years of satellite data, volcanoes. The individualistic nature of volcanoes showed that changes in at least one of these “You just can’t look at every image,” Poland highlights the limitations of using patterns variables, and sometimes in all three, precede says. “I see machine learning as having a real from past eruptions to forecast future ones. an eruption, sometimes years in advance4. impact in filtering through these massive When volcanologists see the first warning signs, To exploit these data, many of which are volumes of data.” they often think they’ve seen this before and freely available, Walter and colleagues have For the MOUNTS platform, scientists have know what happens, Poland says. “But the created a volcano-monitoring platform called also developed a neural network to search for volcanoes haven’t watched that movie,” he MOUNTS (monitoring unrest from space). The large shape changes. Other groups are trying to says. “They’ve evolved in ways that are incred- platform uses data from the current suite of develop algorithms that can sift through tem- ibly complex, and our understanding of the Sentinel satellites and ground-based earth- perature or gas-emission data from satellites. complexities are very cursory at this point.” quake information, and currently monitors 17 When Anak Krakatau sprang back into With more data and better understanding of volcanoes, including Anak Krakatau. action on 10 April this year, Walter was quick volcanic systems, researchers hope to develop As they started on the project, however, the to monitor the situation remotely by analysing dynamic models that can capture the physics researchers faced a new and unusual prob- the satellite data. Because visibility was low, he and chemistry of what happens below ground. lem — too much data. The satellites provide had to rely on the radar data, which can pen- In this way, the development of volcanology torrents of readings, more than researchers etrate thick clouds. The information will help could parallel that of meteorology, which uses can analyse using conventional methods. scientists understand the behaviour of Anak dynamic models of the atmosphere to forecast “There are so many volcanoes and so much Krakatau and in the future it might be used to weather many days in advance. data that we needed smarter ways of dealing help create a tsunami early-warning system But volcanic systems are so complex and so with the data set,” Walter says. for landslides from the Indonesian volcano, hidden that volcanic forecasts will never be In response to this challenge, researchers Walter says. as good as meteorological ones, says Poland. have turned to machine-learning techniques, Biggs says that the combination of satellite “It is a fun exercise to think that one day you a form of artificial intelligence in which com- data and AI is a useful tool for drawing atten- will open the newspaper and see the volcano puter algorithms such as neural networks can tion to possible risks and prioritizing the forecast next to the weather forecast,” he says. be trained to pick out patterns in data. Juliet installation of ground-based instruments. “But we are still a long way from that.” Biggs, a volcanologist at the University of Such remote-monitoring techniques provide Bristol, UK, and her colleagues have created valuable information and are safer for scien- Jane Palmer is a freelance writer based in a neural network that has churned through tists, but she thinks they are never going to Colorado. some 30,000 Sentinel-1 images of more than completely replace having instruments close 900 volcanoes and flagged about 100 images to the volcano itself. 1. Aiuppa, A. et al. Geophys. Res. Lett. 37, L17303 (2010). 2. Ripepe, M. et al. J. Geophys. Res. Solid Earth 123, as needing more attention. Of those images, In the United States, researchers will soon 9570–9585 (2018). 5 39 showed real ground distortions , meaning gain a large new source of ground-based data. 3. Walter, T. R. et al. Nature Commun. 10, 4339 (2019). that the AI system had reduced the workload In March 2019, US legislators passed a bill to 4. Reath, K. et al. J. Geophys. Res. Solid Earth 124, 195–218 (2018). for the volcanologists by a factor of nearly 10. fund the National Volcano Early Warning Sys- 5. Anantrasirichai, N., Biggs, J., Albino, F. & Hill, P. Now, they are testing their system on some tem (NVEWS). When implemented, NVEWS will J. Geophys. Res. Solid Earth 123, 6592–6606 (2018).