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An Undersea Volcano Is Building a New Island in Japan

An ongoing eruption from the volcano has created a small land mass less than a mile off Iwo Jima island. It’s a great case study of how volcanoes work.

By Hisako Ueno and Mike Ives

Reporting from Tokyo and Seoul

Three weeks ago, the view from Iwo Jima showed open ocean. Now there’s a tiny new island right offshore, billowing smoke as it grows and offering a rare glimpse at how volcanic islands emerge.

The new island is the product of an unnamed undersea volcano that began erupting on Oct. 21, less than a mile from Iwo Jima, the island in Japan where American and Japanese forces waged a fierce battle during World War II.

No injuries or damages have been reported on Iwo Jima, hundreds of miles from Tokyo in the Pacific Ocean, since the ongoing eruption began. The eruption is offering an eye-opening real-time view of a rare geological phenomenon .

Similar eruptions occurred last year in the same spot, but this time the eruption point is above the water’s surface, said Yuji Usui, a senior analyst for volcanic activity at the official Japan Meteorological Agency.

“Now that it’s visible,” he said, “people are paying attention.”

There are about 1,350 potentially active, land-based volcanoes around the world, according to the United States Geological Survey . Scientists have so far discovered thousands more active “submarine” volcanoes, and they believe that there may be many more — possibly hundreds for every one on land — lurking beneath the waves .

Undersea volcanic eruptions have occasionally formed major islands, including those of the Hawaiian archipelago, throughout geological history. But most of the time, we don’t get to witness these eruptions happening.

“The eruptions that formed Hawaii were all before our time,” said James White, a professor of geology at the University of Otago in New Zealand who has studied undersea volcanic eruptions. “But also, until it got up to the water’s surface, we wouldn’t have seen them even if we’d been sitting above them in a Polynesian canoe.”

The current eruption off Iwo Jima intensified for weeks and peaked last Friday and Saturday, said Mr. Usui of the Japan Meteorological Agency. The new island was about 100 meters, or 328 feet, in diameter as of Oct. 30, according to a report by the Earthquake Research Institute at the University of Tokyo.

Another small island formed in a similar way in the same region of Japan, near the Nishinoshima volcano, in 2013. That eruption lasted for a decade, but eruptions near Iwo Jima typically only last for a month, said Setsuya Nakada, a professor emeritus at the earthquake research institute.

“It’s hard to know when it will stop, but assuming the eruption continues, the island could grow higher and bigger,” he said.

Professor White said the current eruption appears to have started on the flank of a larger “parent” volcano that rises through about a third of a mile of seawater, and whose summit is exposed as Iwo Jima.

Instead of creating a sustained eruption column, the eruption is producing discrete explosions in fingerlike jets where large gray particles suck smaller ones along as they travel in a cannonball-like ballistic arc, Professor White said. The eruption also includes red-hot pieces of magma, and the mix of material illustrates the eruption’s complexity, he added.

“Even as volcanologists, it’s tricky to say exactly how that’s working,” he said.

Many Americans know Iwo Jima because the island, which is part of a chain, was the site of a deadly World War II battle in early 1945.

A Pulitzer Prize-winning photograph that the United States Marine Corps says shows six US. Marines raising the American flag over the island in February 1945 became an indelible image of the war for the American public.

Yuka Takahashi, who lives on Chichi Island, about 80 miles from the Nishinoshima volcano and about twice as far north from Iwo Jima, said she has sometimes smelled sulfur and smoke from the Nishinoshima eruption.

When Ms. Takahashi, 31, saw Iwo Jima in June during an overnight cruise that departed from Chichi, it was surrounded by water and she did not see — or smell — any sign of an eruption. All she saw was a facility run by Japan’s Self-Defense Forces and a handful of wrecked ships on the beach.

“I wonder if a new island will be formed there permanently or if it will just sink back under the water,” she said of the current eruption. “I’m curious.”

An earlier version of this article misidentified the United States service members who hoisted an American flag over the Japanese island of Iwo Jima in February 1945. According to the United States Marine Corps, all six men, not five of them, were U.S. Marines. 

How we handle corrections

Hisako Ueno has been reporting on Japanese politics, business, gender, labor and culture for The Times since 2012. She previously worked for the Tokyo bureau of The Los Angeles Times from 1999 to 2009. More about Hisako Ueno

Mike Ives is a reporter for The Times based in Seoul, covering breaking news around the world. More about Mike Ives

September 30, 2014

How a Deadly Volcano Erupted in Japan without Warning

The eruption that killed more than 30 people this weekend was a shallow steam explosion that is nearly impossible to predict

By Becky Oskin & LiveScience

The death toll at Japan's Mount Ontake volcano climbed to 36 today (Sept. 29), with rescue crews still searching for missing people.

The  eruption caught the hikers by surprise  this weekend. More than 250 people were exploring shrines and resorts at the 10,062-foot-high (3,067 meters) peak, the country's second-tallest volcano.

But just a month ago, in Iceland, anyone with an Internet connection knew exactly where new magma was tunneling underground before  the Bardarbunga eruption  began. Earthquakes, GPS and volcanic gas "sniffers" plotted out each new advance. (Magma is molten rock underground, whereas lava is molten rock flowing on the surface.) [ Stunning Pictures: Japan's New Volcanic Island ]

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Japan has a similar high-tech network for watching its volcanoes. But Saturday's killer outburst was likely a phreatic eruption, a shallow steam explosion that is nearly impossible to predict, experts told Live Science.

"If you have a monitoring system in place, it's very unlikely that deeper activity will go unnoticed," said Philipp Ruprecht, a volcanologist at Lamont-Doherty Earth Observatory in Palisades, New York. "We have very little information or science to help the monitoring people with phreatic eruptions."

Sudden surprise A phreatic eruption is just water and heat. Think of the inside of a volcano as a solid rock "oven" heated by magma. Earthquakes and shifting magma often jiggle and crack the rock. When a new crack opens in the oven, a blast of heat escapes, similar to opening a kitchen oven's door. If groundwater leaks into the crack, the water immediately flashes into steam from the intense heat. This violent transformation pulverizes the surrounding volcanic rock. Steam occupies much more space (or volume) than water, so it expands outward in all directions, punching a hole in the side or top of the peak.

"No magma actually erupts, it's just broken-up old rock that's been obliterated," said Margaret Mangan, scientist in charge at the U.S. Geological Survey's California Volcano Observatory in Menlo Park, California.

Cracks can open without warning, Mangan said. On the other hand, frequent or more severe earthquakes at a volcano with a history of phreatic eruptions could mean it's time for more vigilant monitoring, she added.

Earlier this month, the Japan Meteorological Agency (JMA) had warned of waxing and waning volcanic tremors at Mount Ontake. Tremors are small, nearly imperceptible earthquakes. Officials did not raise the volcano's alert level from normal, or Level 1. There were no signs of rising magma, such as changes in the ground surface or gases steaming from the peak, JMA said in a  Sept. 28 statement . 

Phreatic eruptions sometimes come before lava erupts, like a volcano clearing its throat. The incredible bang from  the 1883 Krakatau eruption  in Indonesia, heard "around the world" was from a phreatic eruption. Huge lava blasts followed. And similar explosions can occur when magma meets water, which volcanologists call phreatomagmatic eruptions. Some of these magma-water blasts leave behind giant, bomb-like craters called maars.

However, no one has seen fresh lava at Mount Ontake since Saturday's eruption.

The Japan Meteorological Agency currently has alerts and warnings for 11 volcanoes, including Ontakesan, as it is called in Japan. The last phreatic eruption at Mount Ontake was in 2007. Its last volcanic blast was in 1979.

Deadly ash flow Saturday's explosion triggered a pyroclastic flow, a mix of ash and volcanic gas that billows outward at hurricane speeds and crucible-like heat. It's likely that many of the hikers trapped in the pyroclastic flow survived either because they were on the edge of the ash cloud or because it was relatively cool, though no one knows at this time. Scientists will determine the conditions once the volcano is safer to approach.

A pyroclastic flow triggered by jetting lava can reach nearly 1,300 degrees Fahrenheit (700 degrees Celsius) and speeds exceeding 100 mph (161 km/h).

"It's a hazard that you don't run away from, because they're just moving too fast," Mangan said. [ Video – Crews Recover Bodies from Japan Volcanic Eruption ]

About 200 people are thought to have survived Saturday's deadly blast by scrambling down the mountain through the choking ash clouds or sheltering in huts and lodges. Their harrowing tales include eerie darkness, rocks raining from the sky and struggling to breath in the thick ash. A phreatic explosion tends to produce very fine ash particles, Ruprecht said. The ash covered 2 miles (3 km) of the mountain's south slope. 

"It's like being in a sauna while you're being blasted by a dust storm. It's hard to imagine how they were able to breathe," Ruprecht said.

Volcanic gases such as sulfur dioxide can also suffocate those trapped on the mountain, and rocks flung at high-speed can crush people and cause fatal head wounds. A phreatic explosion killed five people at  Mayon volcano in the Philippines last year.

Gallery: Beautiful Images of Bardarbunga's Volcanic Eruption

Explosive Images: Hawaii's Kilauea Erupts for 30 Years

Bodies Recovered From Japan Volcano Eruption | Video

Copyright 2014  LiveScience , a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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• National Research Institute for Earth Science and Disaster Resilience, Tsukuba, Japan

For the purpose of the development of volcanology and its practical application to volcanic hazard mitigation, we are conducting a new project named the Integrated Program for Next Generation Volcano Research and Human Resources Development (INeVRH). This project began in 2026 and will end in 2025 and consists of four themes focusing on observation, forecasting, countermeasures, and a data-sharing system. This data-sharing system is named the Japan Volcanological Data Network (JVDN), which will serve as a platform that combines observation, forecast, and countermeasure data to provide information for the judgment at branch nodes of event trees for volcanic crises in the coming decades in Japan.

Introduction

In Japan, there are 111 active volcanoes ( Figure 1 ), many of which potentially produce hazards and pose risks due to future eruption. Both for mitigation and research purposes, we operate volcano monitoring networks at 50 volcanoes that are managed by various agencies, universities, and institutions. As a consequence, data obtained through monitoring are dispersed across various institutions and in various data formats; therefore, we need to build a common platform to share these various datasets to improve mitigation techniques and to better understand volcanic processes. Doing so will allow us to enhance eruption forecast, hazard evaluation, and risk mitigation.

Figure 1. Distribution of active volcanoes in Japan.

Our main goal is to build event tree frameworks during volcanic crises to estimate probabilities of possible outcomes of volcanic unrest, which is supported by observational datasets and numerical simulation results, as well as taking into account exposure and vulnerability data. We will construct event trees for volcanic crises using the method proposed by Newhall and Hoblitt (2002) as a standard tool for evaluating volcanic activity to assess hazards and risks as a part of crisis management planning. The event tree systematizes a way to estimate the probabilities of various volcanic phenomena, of which nodes and branches express the subsequent relationships from prior events to final outcomes. In this way, we try to provide more information more quantitatively about the probability of branching at the nodes, i.e., which way the situation will develop. We categorize the event tree into three sections: observation, forecast, and countermeasures ( Figure 2 ). The observation section corresponds to the evaluation of volcanic activity, the forecast section corresponds to the branching of volcanic hazards, and the countermeasures section corresponds to the risk evaluation based on exposure and vulnerability.

Figure 2. Example of event tree for volcanic crises. We categorize this event tree into three parts: observation, forecast, and countermeasures. The quantitative threshold to judge the branching at each node is investigated by the new project, the Integrated Program for Next Generation Volcano Research and Human Resources Development. Our objective is to deal with all three categories and to propose an adequate countermeasure scheme.

The Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan, has recently launched a new research project, entitled the “Integrated Program for Next Generation Volcano Research and Human Resource Development (INeVRH)” to run from 2016 to 2025. This project consists of four themes, A: Developing a Data-Sharing System of Volcano Observation Data, B: Development of Cutting-edge Volcano Observation Technology, C: Development of Forecasting Technologies for Volcanic Eruptions, and D: Development of Volcano Disaster Countermeasure Technology. The data-sharing system distributed by theme A is the Japan Volcanological Data Network (JVDN). JVDN plans to archive various kinds of data, that is, seismic, geodetic, geochemical, geological, and petrological data. The design for the JVDN system and the data flow is shown in Ueda et al. (2019) . Details of the JVDN system are introduced in the next section. Theme B produces the observational data in various categories, namely, Muon, InSAR, optical remote sensing, volcanic gas, and geophysical campaign observation. These are also stored within JVDN. For the forecasting topic, theme C focuses on geological, petrological data, and also numerical simulation of volcanic phenomena, the details of which are explained in sections “Geological and Petrological Data” and “Numerical Simulation Data” of this paper. For the countermeasure information, real-time evaluation of volcanic activity and outreach information such as movies of lectures will be provided based on the research in theme D ( Nakada et al., 2019 ).

Currently, we are in the initial development stage of the JVDN database linking all of the observations, forecasting, and countermeasures, encompassing themes of A–D. We have developed a basic platform to share and to realize static linkage of these for risk management (e.g., hazard maps) and dynamic linkage for crisis management (e.g., updating information about ongoing damage). In this paper, we will summarize the outline of our ongoing project of JVDN database development.

Observation Data

We have various kinds of data from observation networks. The Japan Meteorological Agency (JMA) is responsible for issuing warnings and conducts volcanic observation at 50 volcanoes for the purposes of monitoring. Universities also operate observation networks at some active volcanoes for academic research. The National Research Institute for Earth Science and Disaster Resilience (NIED) manages a V-net at 16 volcanoes as a standard volcano observation network, equipped with a borehole high-sensitivity velocity seismometer, borehole tiltmeter, broadband seismometer, and Global Navigation Satellite System (GNSS). The Geospatial Information Authority of Japan (GSI) is responsible for GEONET, the GNSS network encompassing all of Japan. These data are shared between the related organizations, and some data are open to the public or can be used for scientific purposes through registration with each individual system ( Ueda et al., 2019 ).

For the evaluation of volcanic activity and scientific research, the analysis of multi-disciplinary data is pertinent for understanding the state of volcanoes. Our new data platform, JVDN, mainly provides these various kinds of volcanological data, some of which are raw data, while others are meta-data such as the indices about the location, data owner, and their instrument information ( Figure 3 ).

Figure 3. Schematic concepts of the Japan Volcanological Data Network (JVDN).

For example, raw seismic data is distributed in WIN or WIN32 format, a standard format in Japan ( Urabe, 1994 ). WIN/WIN32 data can be converted into international standard formats, like SAC, SUDS, ASCII, etc., using conversion tools, and users can treat the data as they wish. Ground deformation data from tiltmeters and strainmeters are also stored in WIN/WIN32 format, while GNSS data are stored in RINEX or in meta-data. Discussions are currently underway for other observation data such as magnetic, electric, and gravity observations to determine the most effective methods for analysis and storage.

All these data are designed to be compliant with WOVOdat ( Newhall et al., 2017 ), which has been prepared mainly by the Earth Observatory of Singapore, Nanyang Technological University. WOVOdat distributes data and also analysis visualization, query, and analysis tools with GUI interfaces. Experiences in each volcano observatory and historical volcanic eruptions at a singular volcano are not sufficient to judge forthcoming activity. Therefore, the sharing and comparison of such information between observatories worldwide provide more evidence upon which to judge volcanic activity. The JMA sets the threshold for volcanic warning levels. If we share the unrest/precursory data of a volcanic eruption, we can compare it to other similar events at other volcanoes to estimate the probabilistic outcome of the ongoing observation data for the unrest in question. For example, at Aso Volcano, Japan, the threshold from level 2 (Do not approach the crater) to level 3 (Do not approach the volcano) is defined as: volcanic tremor amplitude of 4 micro m/s in average tilt change, suggesting volcanic body expansion above 0.02 micro rad/h, and rapid increase in SO 2 gas in excess of 2,000 tons/day ( Japan Meteorological Agency, 2016 ). WOVOdat aims to support this data-sharing concept to improve eruption forecasting and for reaching a better understanding of volcanic processes, and our new JVDN database conforms to WOVOdat.

Geological and Petrological Data

Geological and petrological studies provide important information about long-term volcanic activity. We obtained many drilling cores during the installation of V-net borehole sensors ( Nagai et al., 2011 , 2012 , 2013a,b ) and by geological surveys conducted at many volcanoes by universities and other institutions ( Nakagawa et al., 2019 ). In addition, the INeVRT project is providing new drilling core data at other volcanoes. Precious core samples have to be preserved physically and archived digitally because they disintegrate easily.

National Research Institute for Earth Science and Disaster Resilience has established a drilling core center to manage and store drilling core samples and data in the JVDN database. Such cores can be utilized by researchers worldwide, and the database includes information on the locations, geologic and petrologic descriptions, column diagram, photographs, related background, analysis of results, and other information.

Geological data on units such as ashfall deposits provide information about eruption histories, including sequences of eruptions, modes and scales of eruption, and volumes and temporal development of each eruption (e.g., Suzuki et al., 2013 ). Drilling core and trench section analysis provide us with detailed information about individual historical eruptions, and we can estimate the branching probability based on multiple empirical data ( Nakagawa et al., 2019 ).

In addition, petrological and laboratory experiment studies provide us with a great deal of information about both the subsurface and surface characteristics of magma behavior. For example, chemical compositions, water content, vesicularity, texture, etc., are the keys to understanding magmatic characteristics as well as the eruptive styles of each volcano. This information can be stored in the database for comparative study ( Yoshimoto et al., 2004 ; Madarigal and Lucke, 2017 ).

FT-IR measurement of water content in a melt ( Yasuda, 2014 ) is one example of datasets representing magma reservoir characteristics of chemistry, mineralogy, temperature, and water contents for 11 representative active volcanoes that have been archived so far. These petrological data provide information about the conditions and pressure under which magma was stored and can be converted to depth information. From the geophysical observation point of view, we can detect volcanic earthquakes and volcanic tremors beneath volcanoes, as well as their source depth.

Geophysical and petrological data give us information on source depth individually. Then, we can choose plausible source mechanisms, for example, vaporized fluid flow for shallow regions and super-critical fluid flow for deeper regions. It may be possible to employ more quantitative models.

Not only is the database designed for the analysis of historical eruptions, it is also designed to help evaluation of ongoing volcanic eruptions. One important objective is to identify the type of eruption, whether it is magmatic or non-magmatic, and to evaluate the possibility of a successive larger eruption event. A quick analysis of volcanic ash, that is, whether it includes juvenile magmatic particles or not, is the key to forecasting the ongoing eruption (e.g., Gaunt et al., 2016 ). To this end, equipment for automatic ash collection and analysis is under development ( Miwa et al., 2018 ). This enables the precise sequence of the ashfall deposit to be analyzed with time stamping. In addition, ash particles are automatically analyzed and classified in terms of color and shape through an artificial intelligence (AI) system, and the equipment automatically reports the result of the component analysis, allowing the existence of magmatic particles to be assessed in real time. These results will also be uploaded to the JVDN database and will be used for the evaluation of ongoing volcanic activity as well as for countermeasure planning.

Numerical Simulation Data

Numerical simulation is used to evaluate complex volcanic phenomena consisting of both subsurface magmatic processes and surface hazards. In our project, we are building a volcanic hazard evaluation system that enables parallel evaluation of various volcanic hazards, including lava flow, ashfall, ballistics, and others, based on common input parameters such as flux rate ( Fujita et al., 2019 ). Each numerical simulation code is being developed, respectively, and the types of input parameters are set for each individual simulation code. Some background data, e.g., digital elevation maps (DEM) and wind profiles, can also be stored and shared for use in various numerical simulations.

In many cases, numerical calculation is time-consuming, especially for the simulation of complex phenomena like a volcanic plume and multi-phase lava flow. These outputs should also be stored in the relational SQL database associated with the calculation conditions. To express probability in volcanic hazard and risk, we conduct multiple sessions of numerical simulation under plausible sets of input parameters and process these results statistically.

This database of calculation results will also link volcanic hazard to exposures and vulnerability ( Fujita et al., 2019 ). The hazard information is expressed as the inundated area, time, velocity, and other characteristic properties for each type of hazard. As both databases are so-called big data, we need high-speed databases. We convert all of the information in these data into the OGC©, 2020 Moving Features Simple CSV format 1 , which enables quick and easy handling. They can also be visualized by using a Geographical Information System (GIS) to plot and overlay them on exposures and vulnerabilities, e.g., the distribution of residential areas, roads, and infrastructure. Through this visualized information, we can estimate the risk of volcanic hazard quantitatively at the target location, and this information is also useful for countermeasures such as the formulation of evacuation plans by disaster mitigation authorities.

Here we introduce some case examples. One of the most widespread and pernicious volcanic hazards is ashfall. Ashfall dispersion is calculated by the JMA-RATM model ( Shimbori, 2016 ). Here, we propose an example of an ashfall due to a Mt. Fuji eruption ( Figure 3 ) in which we assume the initial condition of being the same size as the Plinian eruption of Hōei in 1707. Ashfall distribution is strongly controlled by the height of plume and the local wind profile. In the JMA-RATM model, the numerical simulation refers to the weather-forecasting program and obtains detailed distributions. At present, the mesh size of the calculation is 5 km × 5 km, and this will be reduced to a 2 km × 2 km area to provide more detailed information.

We obtain quantitative information of the ashfall deposit for each mesh from the numerical simulation. For risk management, this hazard information can be coupled with the exposure and vulnerability information ( Figure 4 ). In general, the simulation mesh and archived mesh in the database are different from each other, so we need to match these different geometries to estimate the inundation area (Figure 4 in Fujita et al., 2019 ). The building distribution database provided by the Center for Spatial Information Science, The University of Tokyo (2010) is an example of static objects, and it has a much higher resolution than those of the numerical simulation. For the combination of hazard simulation and exposure databases, we need to synchronize the size and geometry of the meshes, applying intersection judgment and interpolation. Our future plan is to provide more quantitative information about the hazard and its risk, for example, using an agent-based model to integrate the ashfall simulation with dynamic information such as dynamic real-time data on humans and transportation. By doing so, we can propose efficient plans for logistics as part of crisis management.

Figure 4. An example of Mount Fuji ashfall simulation by JMA-RATM. The eruption plume was assumed to have the parameters of the Hōei eruption, and the wind profile in December 2016 was applied. The legend indicates the thickness of ashfall after 6 h from the onset of eruption. Gray makers show the buildings, while dark gray markers show those covered by ashfall.

In general, lava flows are less dangerous than the other volcanic hazards, since generally, the flow velocity is not very high, and the damage to human life itself is not very serious. However, a lava flow destroys the surrounding terrain permanently, so the damage inflicted on properties, public facilities, roads, and other infrastructure can be catastrophic. Some examples of lava flow simulation around Mount Fuji are also overlaid on the building infrastructure map ( Figure 5 ) using LavaSIM ( Hidaka et al., 2005 ). Most of the important transportation facilities in Japan go through this area, so there would be major economic ramifications if it is damaged by lava flow. A very threatening lava flow occurs when lava flows southward, destroying Shinkansen (bullet train) rail tracks and the Tōmei highway, which are the logistics arteries of Japan. We can delineate the impacted area and estimate the available time before the lava flow impacts and formulate a plan for countermeasures.

Figure 5. An example of Mount Fuji lava flow simulation using LavaSIM ( Hidaka et al., 2005 ). Blue markers indicate the location of buildings, and red markers show the lava-inundated cells. Yellow markers show the buildings damaged by lava flow. Eruption vent is assumed at the southern flank of Mount Fuji, and the lava flow runs toward the southern flank, damaging the important transportation facilities, Shinkansen (bullet train) and the Tōmei highway, the economic artery of logistics in Japan.

We experienced a tragedy caused by ballistics in the eruption of Ontake, Japan, in 2014. Unfortunately, there were many tourists around the summit crater when the phreatic eruption suddenly occurred ( Nagano Prefectural Police, 2014 ; Tsunematsu et al., 2016 ). Even though it is difficult to issue a warning for a sudden phreatic eruption, it will be essential to understand the risk of ballistic impacts and to make plans for evacuation and shelters around the summit area. We apply the ballistic simulation model using Ballista ( Tsunematsu et al., 2014 ), which can produce outputs regarding the deposits’ distribution, energy, and trajectories.

Volcanoes are popular tourist hotspots, and it is important to mitigate possible hazards that can affect volcano climbers. Lessons learned from the tragic Ontake eruption initiated an investigation to obtain real-time tracking of climbers along trails on Mount Fuji trails performed at different times ( Tanaka et al., 2018 ). Tracking devices (beacons) were distributed to each climber, whereby the receivers installed along the trails detected the real-time location of climbers. This dataset shows the speed of the climbers’ traffic flow during the most crowded season. A combination of ballistic simulation and this dataset provides a countermeasure plan against ballistics hazards, e.g., the adequate distribution and size of huts and the route to an evacuation path.

We will also evaluate other volcanic hazards such as pyroclastic flow, lahars, etc., and plan to add these to the volcanic disaster evaluation system ( Fujita et al., 2019 ).

Countermeasure Information Data

Volcanologists have information about observation and forecasts for volcanic activities and hazards; however, these outputs are too specialized and difficult to be understood by the general public and therefore are not useful in practical volcanic hazard mitigation procedures for authorities and the general public ( Nakada et al., 2019 ).

As an example, for the quick detection of ashfall distribution and component analysis, NIED developed an information-sharing system via SNS, named “Min’na de kazan,” meaning that everyone reports about volcanic activity. Users can upload ashfall information about thickness, ash color, etc., and plot this on a GIS system. We can grasp the distribution of ashfall in real time and can use this to produce contour maps to identify ashfall hazard distribution. This information can be applied to evaluating the damage by ashfall, e.g., against electric power supply lines, roads, railways, and agriculture.

In addition, we are also developing digital volcanic hazard maps, which are converted from the original paper-based volcanic hazard maps issued by individual local governments and are digitized in a GIS-applicable format. Using a combination of hazard maps and social and infrastructure geospatial layers, we can support the countermeasure planning of local governments.

Under our plan, the countermeasure database will also include instructions on how to interpret the observation data and numerical simulation results, some lecture materials about volcanoes for the general public, digital contents including movies of volcanic phenomena, and some standard operating procedure (SOP) information for volcanic disaster management, available for local governments.

The ultimate goal of the INeVRH project is to perform evaluation of forthcoming volcanic activity and hazards through the automatic assimilation of observation data. The observation data and its primary data analysis will be stored in the JVDN system. Together with geological and petrological data, these data will be set automatically and/or manually as input to execute various volcanic hazard simulations. Simulation results will then be combined with exposure and vulnerability data to evaluate the risk, which will be utilized on the system as countermeasure information for risk reduction. Since, in most cases, observation data are not sufficient to regulate all input parameters required to run volcanic hazard simulation, some assumptions are used. To obtain the uncertainty and the applicability of the model, we first performed various simulations using the possible range of input parameters. The hazard and risk evaluation are performed using event tree analysis. The most difficult but important part is to obtain threshold values that define toward which branch of the event tree the activity will continue, especially during volcanic crises. We must also remain cognizant that the threshold may not work for a specific volcano, so we should also obtain it at other volcanoes to determine the general applicability. Developing the new Japan volcanological database system capable of integrating observation, forecast, and countermeasure strategy is a challenging task.

Data Availability Statement

All datasets generated for this study are included in the article.

Author Contributions

EF conducted general management of INeVRH projects with colleagues, was leading theme C3, the numerical simulation project to develop the volcanic hazard evaluation system, and wrote the manuscript. HU developed the JVDN system and created the figure illustrating the JVDN system. SN managed the countermeasure database project. All authors contributed to the article and approved the submitted version.

This research was funded by the Integrated Program for Next Generation Volcano Research and Human Resource Development, Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan ( http://vivaweb2.bosai.go.jp/kazan-pj/next-generation-volcano-pj-2019-jun ).

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

We are grateful to all participants in the INeVRH. Yosuke Miyagi developed countermeasure tools and provided us with information.

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Keywords : event tree for volcanic crises, INeVRH, JVDN, observation, numerical simulation, countermeasures, database

Citation: Fujita E, Ueda H and Nakada S (2020) A New Japan Volcanological Database. Front. Earth Sci. 8:205. doi: 10.3389/feart.2020.00205

Received: 09 January 2020; Accepted: 18 May 2020; Published: 10 July 2020.

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Copyright © 2020 Fujita, Ueda and Nakada. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Eisuke Fujita, [email protected]

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Cause and risk of catastrophic eruptions in the Japanese Archipelago

Yoshiyuki tatsumi.

*1 Department of Earth and Planetary Sciences, Kobe University, Kobe, Hyogo, Japan.

*2 Research and Development Center for Ocean Drilling Science, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa, Japan.

Keiko SUZUKI-KAMATA

The Japanese Archipelago is characterized by active volcanism with variable eruption styles. The magnitude ( M )-frequency relationships of catastrophic caldera-forming eruptions ( M ≥ 7) are statistically different from those of smaller eruptions ( M ≤ 5.7), suggesting that different mechanisms control these eruptions. We also find that volcanoes prone to catastrophic eruptions are located in regions of low crustal strain rate (<0.5 × 10 8 /y) and propose, as one possible mechanism, that the viscous silicic melts that cause such eruptions can be readily segregated from the partially molten lower crust and form a large magma reservoir in such a tectonic regime. Finally we show that there is a ∼1% probability of a catastrophic eruption in the next 100 years based on the eruption records for the last 120 ky. More than 110 million people live in an area at risk of being covered by tephra >20 cm thick, which would severely disrupt every day life, from such an eruption on Kyushu Island, SW Japan.

Introduction

The Japanese Archipelago is built at convergent plate boundaries where oceanic plates are being subducted at trenches and is characterized by active volcanism with variable eruption styles. Even though catastrophic caldera-forming eruptions that produce more than 100 km 3 of tephra are rare in Japan (<0.01% in the frequency) they overwhelm smaller events in total erupted volume (>60%). Once such a catastrophic eruption occurs, it should have significant societal and environmental impacts. Understanding the cause of catastrophic eruptions is thus of primary importance for those living in volcano countries like Japan. However, the mechanisms that trigger these eruptions are elusive since the processes occurring in ‘normal’ volcanic systems cannot simply be scaled up to much larger magma reservoirs beneath calderas. Herein we analyze statistically the size and frequency of volcanic eruptions in Japan and discuss the mechanisms of catastrophic caldera-forming eruptions. We also evaluate the risks of such an eruption based on the geological record of a caldera-forming eruption that occurred at ∼28 ka in Japan.

Statistical analyses of volcanic eruption

The magnitude-frequency ( M - F ) relationships of volcanic eruptions provide a key to estimating the eruption frequency and help to assess associated hazards and risks. An inverse correlation between M and F is well known (Fig. ​ (Fig.1a) 1 a) and can be described by (ref. 1 ):

However, simple extrapolation of this relationship from small to large eruptions is not valid, and eruptions with M ≥ 9 have been extremely rare on this planet (Fig. ​ (Fig.1a). 1 a). The reason for this is that the volcanic eruption mechanism depends strongly on the scale of the system. 2 ) The scale and structure of volcanic systems that cause catastrophic eruptions depend on the tectonic regime, with those in subduction zones, such as Japan, different from those in other tectonic settings, such as hotspots ( e.g. , Yellowstone 3 ) ) and regional transtensional zones ( e.g. , Long Valley 4 ) ). Indeed, the M - F relationship for events in the Japan arcs (for events <120 ka; ref. 5 ) is not as simple as that for other eruptions elsewhere with similar amplitudes and defines two discrete lineations (Fig. ​ (Fig.1a). 1 a). Careful examination of the M - F relationship is thus needed to reveal the exact nature of catastrophic eruptions in Japan.

The magnitude-frequency ( M - F ) relationships of volcanic eruptions. (A). Although an inverse correlation between M and F is well known for volcanic eruptions worldwide, the relationships among Japanese eruptions are not simple and form two lineations. (B). The M - F relationships for Japanese eruptions (<120 ka). The overall relationship cannot be described by a single set of parameters. Instead, summit eruptions ( M ≤ 5.7) and caldera-forming eruptions ( M ≥ 7) are reproduced by separate Weibull parameters, suggesting that different mechanisms control the two eruption styles. The typical errors in magnitude and frequency are shown by error bars.

The M - F relationship that characterizes common eruptions must eventually break down at the extremes of the distributions, as there are physical limits to the size of eruptions. 2 ) To make a quantitative assessment of the size and frequency of volcanic eruptions in these regions, the extreme value theory has to be applied. 2 , 6 ) The Weibull function is the part of this theory that can be used for the upper limit of size 7 ) where the probability density function of amplitude S and the corresponding cumulative distribution function (fraction of amplitudes that are equal to or greater than S ) are given by:

respectively, where β and τ are fitting parameters. In the case of volcanic eruptions, the relative frequency F ( M ) of eruptions with magnitudes over M is then described by:

where a > 0, b > 1 (ref. 2 ).

The M - F relationship for eruptions <120 ka and with M ≥ 4 ( M given to one decimal place) in the Japanese arcs 5 ) (447 events in total) is analysed using the Weibull function in Fig. ​ Fig.1b. 1 b. The overall relationship exhibits three inflections and cannot be reproduced by a single set of Weibull parameters. Instead, the relationship requires two sets of Weibull parameters, one for eruptions with M ≤ 5.7 ( a = 2.81 × 10 −7 , b = 9.44) and the other for eruptions with M ≥ 7 ( a = 1.55 × 10 −13 , b = 14.4); eruptions with 5.7 < M < 7 can be expressed by the sum of above two functions. These magnitude thresholds correspond to changes in eruption style, with eruptions of M ≤ 5.7 characterised by summit eruptions, and all eruptions with M ≥ 7 catastrophic caldera-forming eruptions; events with intermediate M are hybrid eruptions including both eruption styles. Based on the Weibull parameters obtained here, the practical limit of the magnitude for normal summit eruptions is 6.9 for which the frequency falls to less than one event over 15 my, an elapsed time for the current tectonic setting around Japan. Thus the two eruption styles, summit eruptions and caldera-forming eruptions, reflect different mechanisms.

Two different mechanisms may operate even in a single volcano, as summit eruptions certainly took place at a volcano that caused catastrophic caldera-forming eruptions. The reason for these mechanism changes should be understood based on temporal variations in eruptive style, magma compositions, tectonic regime and so on for a single volcano. Such variations, however, have not been well documented at the present stage. We thus simply divide Japanese volcanoes into two groups, one solely with summit eruptions and the other with catastrophic eruptions and shall discuss the cause of operation of two different mechanisms for these two groups.

Mechanism of catastrophic caldera-forming eruptions

Over-pressurization of a magmatic reservoir generated by injection of magma is an essential trigger for relatively small eruptions, 8 , 9 ) in which the overpressure is proportional to the viscosity of the surrounding crust and the magma flux during a single recharge event, and inversely proportional to the volume of the reservoir. Injection of high-temperature magma into the reservoir may further heat the residing magma reducing the water solubility in that magma. Oversaturation of water and bubble growth in the magma in the reservoir may induce further overpressure and trigger an eruption. We suggest that this mechanism drives summit eruptions at Japanese volcanoes.

A catastrophic eruption discharges voluminous magmas from a large magma reservoir, causing the roof to collapse forming a caldera. Recent numerical and experimental approaches 9 , 10 ) show that silicic magma buoyancy in a large and rather flat magma reservoir can subject the roof to overpressures greater than the critical overpressure required for dyke propagation. This mechanism may further provide a qualitative explanation for the observation that the largest eruptions are rarer than smaller eruptions 9 ) (Fig. ​ (Fig.1a). 1 a). Thus, catastrophic caldera-forming eruptions in Japan could be triggered by melt buoyancy within large silicic magma reservoirs.

However, herein lies a problem: what controls whether a large silicic magma reservoir or a smaller reservoir that gives rise to a summit eruption forms? Partial melting of the lower crust caused by heat derived from basalt magmas and/or high-temperature mantle is widely accepted as a common mechanism to generate silicic magmas. 11 , 12 ) Indeed, crust-derived silicic magmas play a key role in magmatism in the NE Japan arc: they erupt directly as tholeiitic magmas or act as an end-member component in the mixing that generates calc-alkaline magmas. 13 , 14 ) However, in the last 120 ky there has been only two semi-catastrophic caldera-forming eruptions at Towada volcano ( M = 6.7) in the NE Japan arc, with most active volcanoes associated with summit eruptions (Fig. ​ (Fig.2). 2 ). Although silicic magmas are generally produced by crustal melting in this arc, these magmas tend not to form a large magma reservoir but to form a smaller reservoir.

Distributions of caldera-forming (red circles; <120 ka) and other active (black diamonds) volcanoes in Japan. Map also shows Ignimbrite distribution and tephra isopachs for a M = 8.4 catastrophic eruption that occurs in central Kyushu, and the number of people currently living within the areas covered by the isopachs. Caldera-forming volcanoes that caused catastrophic eruptions are located in regions of low strain rate (<0.5 × 10 8 /y, pink area; cf, regions of high strain rate beyond 0.5 × 10 8 /y in blue), suggesting that low strain-rate may encourage segregation and ascent of silicic magma, and enable it to collect in large magma reservoirs. VF, volcanic front.

To build a shallow-level large silicic magma reservoir, effective and continuous extraction of highly viscous silicic melts from the partially molten zone in the lower crust is required, otherwise partial melts evolve to intermediate and finally basaltic compositions as a result of a continuous heat supply. These high-degree, crust-derived partial melts are the source of tholeiitic andesites and basalts that cause summit eruptions at volcanoes in the NE Japan arc. 13 ) The factors that control whether melts segregate from the lower crust are the amount of partial melt, the viscosity and density contrast between melts and the residual solids, the applied stress pattern, and the strain rate. The first two factors, however, are not well constrained. We may thus have to assume an identical lower crust composition and constant heat supply as a first step. The highest density of volcanoes in arc settings occurs along the volcanic front; the boundary between the volcanic arc and the non-volcanic forearc (Fig. ​ (Fig.2). 2 ). The volcanic front is generally under compression 15 ) and both caldera-forming and summit eruptions occur (Fig. ​ (Fig.2). 2 ). This suggests that the stress regime may not be a critical factor in controlling eruption style. Instead, we here focus on the strain rate as an important factor controlling the formation of large silicic magma reservoirs. Analysing the strain rates of active faults, Japan can be divided into two regions (Fig. ​ (Fig.2): 2 ): one with relatively high strain rates (>0.5 × 10 8 /y), the other with relatively low strain rates. 16 ) Catastrophic caldera-forming eruptions have not taken place in the region with high strain rates. Instead, under tectonics with low strains rates the effective viscosity contrast between the melt and the solid is larger, developing instabilities that induce low-degree silicic partial melts to segregate, consistent with experimental and numerical analyses of partially molten rocks. 17 )

Risks of catastrophic eruptions

Our statistical analyses of the frequency of catastrophic eruptions using the Weibull function allow us to quantify the likelihood of future events in Japan. The best estimate for the frequency of M ≥ 7 eruptions is between 0.10 and 0.073 events per 1000 years, based on past eruption records and probability analyses applying the Weibull distribution to the M - F relationship (Table ​ (Table1). 1 ). Assuming an independent process for each catastrophic eruption and a constant mean occurrence rate, the occurrence of catastrophic eruptions can be described by a homogeneous Poisson distribution. 2 , 18 ) It is then possible to derive the probability of such eruptions recurring in the near future (Table ​ (Table1). 1 ). There is 0.73–1.0% probability of M ≥ 7 event, and 0.25–0.26% of M ≥ 8 event occurring in the next hundred years. Although these probabilities seem low, it should be stressed that immediately before the 1995 Kobe Earthquake the 30-year probability of such an earthquake occurring was 0.38–7.8% (ref. 19 ).

Table 1.

Likelihood of future catastrophic eruptions in Japan arcs

* Dense rock equivalent volume calculated assuming an uniform density of 2500 kg/m 3 .

In order to assess the risks associated with future catastrophic eruptions in Japan, we need to evaluate the hazards posed by past events. The Aira eruption ( M = 8.4) that occurred at ∼28 ka in Kyushu Island (Fig. ​ (Fig.2), 2 ), is used as a reference eruption, since the distribution of ignimbrite and tephra erupted is well documented. 20 , 21 ) This eruption resulted in formation of the Aira caldera with a diameter of 20 km. Major pyroclastics from this eruption cover areas of ∼30,000 km 2 (ignimbrite), ∼140,000 km 2 (≥50 cm tephra isopach), 530,000 km 2 (≥20 cm tephra isopach), 1,510,000 km 2 (≥10 cm tephra isopach), and 2,500,000 km 2 (≥5 cm tephra isopach). Although we are unable to identify exactly which volcano will cause such a catastrophic eruption in the future, we think it is likely to be located in central Kyushu. The reasons for this are twofold: (i) catastrophic caldera-forming eruptions have occurred repeatedly (seven times in the last 120 ky) in Kyushu Island, (ii) as tephra distribution is strongly influenced by the prevailing wind, which in Japan is from the west, an eruption on Kyushu would be the worst case scenario for disruption from the tephra in the most densely populated regions in Japan to the east. We provide a simple hazard map for this catastrophic eruption, including the areas of ignimbrite and tephra distribution and the population in each area (Fig. ​ (Fig.2). 2 ). Ignimbrite and ash fall thicker than 50 cm will cause immense disruption, leading to the areas affected being abandoned and mass migration. Currently ∼40 million people live in the areas that we predict would be covered by such thick amounts of ash and ignimbrites. Where ash fall is less than 50 cm but thicker than 20 cm, all utilities and transport will stop completely; we predict this would affect a further ∼70 million people.

Acknowledgements

We would like to thank Steve Sparks, Koji Kiyosugi, and Yukio Hayakawa for productive discussions and Alex Nicholls for his constructive comments on the manuscript. Comments by Takeshi Hashimoto, Tak Koyaguchi, Ichio Moriya, and Yasuaki Sudo were helpful in improving the paper.

Volcanic Emergency Management in Japan: Case Histories of Izu-Oshima and Unzen

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This chapter describes how scientists and civil authorities coped with two recent eruptive episodes in Japan, each of which led to mass evacuation, and significant economic disruption: (1) the 1986 fissure eruption of the basaltic volcano Izu-Oshima; and (2) the long-lived eruptive activity at the dacitic volcano Unzen that started in 1990. In both cases, distinct precursory data were observed, and the Japanese Coordinating Committee for Prediction of Volcanic Eruptions anticipated impending eruption and publicly expressed this view. However, in neither case was this Committee able to announce a specific prediction of the time and date of the first outbreak. Following the ordering of mass evacuations after the start of eruption, the critical question of when such orders could be cancelled was among the urgent and difficult issues for the concerned civil authorities. Because at present neither the onset nor the cessation of eruptive activity can be predicted with certainty, the Committee endured a severe trial from a scientific as well as political point of view during these two volcanic crises. Among the important lessons learned is that scientists must develop a common and unambiguous terminology for volcanic activity and associated hazards when communicating with the civil authorities, the news media, and the public.

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Shimozuru, D. (1996). Volcanic Emergency Management in Japan: Case Histories of Izu-Oshima and Unzen. In: Monitoring and Mitigation of Volcano Hazards. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-80087-0_24

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Eyjafjallajokull Case Study

What is Eyjafjallajokull?

Eyjafjallajokull is a volcano located in Iceland. The name is a description of the volcano with Eyja meaning island; fjalla meaning mountain; and jokull meaning glacier. You can find out how to pronounce Eyjafjallajokull on the BBC website .

Eyjafjallajökull consists of a volcano completely covered by an ice cap. The ice cap covers an area of about 100 square kilometres (39 sq mi), feeding many outlet glaciers.

What type of volcano is Eyjafjallajokull?

The mountain itself, a composite (stratovolcano) volcano, stands 1,651 metres (5,417 ft) at its highest point and has a crater 3–4 kilometres (1.9–2.5 mi) in diameter, open to the north.

When did Eyjafjallajokull erupt?

Eyjafjallajokull erupted between March and May 2010.

Why did Eyjafjallajokull erupt?

Iceland lies on the Mid-Atlantic Ridge, a constructive plate margin separating the North American and Eurasian plates. The two plates move apart due to ridge push along the Mid-Atlantic Ridge. As the plates move apart, magma fills the magma chamber below Eyjafjallajokull—several magma chambers combined to produce a significant volume of magma below the volcano. Eyjafjallajokull is located below a glacier.

The Eyjafjallajökull volcano erupted in 920, 1612 and again from 1821 to 1823 when it caused a glacial lake outburst flood (or jökulhlaup). It erupted three times in 2010—on 20 March, April–May, and June. The March event forced a brief evacuation of around 500 local people. Still, the 14 April eruption was ten to twenty times more powerful and caused substantial disruption to air traffic across Europe. It caused the cancellation of thousands of flights across Europe and to Iceland.

How big was the eruption of Eyjafjallajokull?

The eruption was only three on the volcanic explosivity index (VEI). Around 15 eruptions on this scale usually happen each year in Iceland. However, in this case, a combination of a settled weather pattern with winds blowing towards Europe, very fine ash and a persistent eruption lasting 39 days magnified the impact of a relatively ordinary event. The eruptions in March were mainly lava eruptions. On 14 April, a new phase began, which was much more explosive. Violent eruptions belched huge quantities of ash into the atmosphere.

The eruption of Eyjafjallajokull

What were the impacts of the eruption? (social / economic / environmental – primary and secondary effects)

Primary effects : As a result of the eruption, day turned to night, with the ash blocking the sun. Rescuers wore face masks to prevent them from choking on ash clouds.

Homes and roads were damaged, services were disrupted, crops were destroyed by ash, and roads were washed away. The ash cloud brought European airspace to a standstill during the latter half of April 2010 and cost billions of euros in delays. During the eruption, a no-fly zone was imposed across much of Europe, meaning airlines lost around £130m per day. The price of shares in major airlines dropped between 2.5 and 3.3% during the eruption. However, it should be noted that imports and exports are being impacted across European countries on the trade front, so the net trade position was not affected markedly overall.

Secondary effects : Sporting events were cancelled or affected due to cancelled flights. Fresh food imports stopped, and industries were affected by a lack of imported raw materials. Local water supplies were contaminated with fluoride. Flooding was caused as the glacier melted.

International Effects: The impact was felt as far afield as Kenya, where farmers have laid off 5000 workers after flowers and vegetables were left rotting at airports. Kenya’s flower council says the country lost $1.3m a day in lost shipments to Europe. Kenya exports typically up to 500 tonnes of flowers daily – 97% of which is delivered to Europe. Horticulture earned Kenya 71 billion shillings (£594m) in 2009 and is the country’s top foreign exchange earner. You can read more about this on the Guardian website .

What opportunities did the eruption of Eyjafjallajokull bring?

Despite the problems caused by the eruption of Eyjafjallajokull, the eruption brought several benefits. According to the Environmental Transport Association, the  grounding of European flights prevented some 2.8 million tonnes of carbon dioxide into the atmosphere (according to the Environmental Transport Association).

As passengers looked for other ways to travel than flying, many different transport companies benefited. There was a considerable increase in passenger numbers on Eurostar. It saw a rise of nearly a third, with 50,000 extra passengers travelling on their trains.

Ash from the Eyjafjallajökull volcano deposited dissolved iron into the North Atlantic, triggering a plankton bloom, driving an increase in biological productivity.

Following the negative publicity of the eruption, the Icelandic government launched a campaign to promote tourism . Inspired by Iceland was established with the strategic intent of depicting the country’s beauty, the friendliness of its people and the fact that it was very much open for business. As a result, tourist numbers increased significantly following the campaign, as shown in the graph below.

Foreign visitor arrivals to Iceland

What was done to reduce the impact of the eruption of Eyjafjallajokull?

In the short term, the area around the volcano was evacuated.

European Red Cross Societies mobilised volunteers, staff and other resources to help people affected directly or indirectly by the eruption of the Eyjafjallajökull glacier volcano. The European Red Cross provided food for the farming population living in the vicinity of the glacier, as well as counselling and psychosocial support, in particular for traumatised children. Some 700 people were evacuated from the disaster zone three times in the past month. In one instance, people had to flee their homes in the middle of the night to escape from flash floods.

The European Union has developed an integrated structure for air traffic management. As a result, nine Functional Airspace Blocks (FABs) will replace the existing 27 areas. This means following a volcanic eruption in the future, areas of air space may be closed, reducing the risk of closing all European air space.

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• 18 April 2024

Violent volcanoes have wracked Jupiter’s moon Io for billions of years

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Jupiter’s moon Io is the most volcanically active place in the Solar System. Credit: NASA/JPL/University Of Arizona

Jupiter’s moon Io has been continuously shaped by volcanic activity for billions of years — possibly even for the Solar System’s entire 4.57-billion-year history, a study suggests.

The findings, published in Science on 18 April 1 , have implications for the search for extraterrestrial life and for the understanding of volcanic moons and planets, including Earth.

Io is the most volcanically active place in the Solar System, with hundreds of volcanoes on its surface. This makes it difficult to study the moon’s past. The moon is continuously resurfaced by the constant flow of runny lava and ash settling from volcanic plumes, obscuring any physical evidence of its history. The volcanic activity arises because Io’s orbit of Jupiter is synchronized with the orbits of two neighbouring moons, Europa and Ganymede. The gravitational interactions between them make Io’s orbit elliptical and periodically squeeze the moon’s centre, causing friction and heating.

Sulfur studies

When Io’s volcanoes erupt, they spew sulfur-rich gases into the atmosphere. The researchers were able to use this sulfur as “a tracer for studying Io’s long-term evolution”, explains Katherine de Kleer, a planetary scientist at the California Institute of Technology in Pasadena and a co-author of the study.

Throughout the Solar System, the ratio between two sulfur isotopes — sulfur-32 and the slightly heavier sulfur-34 — is relatively constant, says de Kleer. Using the Atacama Large Millimeter/submillimeter Array, a radio telescope in Chile, she and her and colleagues measured sulfur emissions in Io’s atmosphere and calculated the ratio between the two isotopes.

Their observations revealed that Io has lost 94–99% of its originally available sulfur. At the top of its atmosphere, the ratio of sulfur isotopes is slightly skewed towards the lighter variant, and these gases rich in sulfur-32 are “being stripped off the top of the atmosphere at a loss of about one tonne per second”, de Kleer says. Over billions of years, this discrepancy has accumulated, and Io’s overall sulfur composition has become heavier. By extrapolating from the current rate at which the lighter sulfur is being lost, the researchers calculated that Io’s volcanoes have been erupting for most of its history.

Implications for Europa

The research also validates models that suggest Io, Europa and Ganymede have been caught in the same orbital dance since the birth of the Solar System, or soon afterwards. This raises the possibility that Europa has been experiencing similar heating for a similar amount of time, says de Kleer. Europa is a promising candidate for a place in the Solar System that has the potential to harbour life. Billions of years of heating “would enhance the habitability of Europa’s subsurface ocean over the long term”.

The very hot, runny lava on Io is much hotter than what found on Earth now, “but it’s thought to be the composition of magma that dominated in Earth’s early history, when we had these huge events laying down big regions of lava flows in a short period of time”, says de Kleer. “Io’s volcanism might be giving us a window into the mechanisms of volcanism and Earth’s early history.”

Jani Radebaugh, a planetary geologist at Brigham Young University in Provo, Utah, welcomes the findings. “That Io could be even more exciting — even more extreme — in its volcanism is mind-blowing,” she says. “The results reveal that further exploration of Io would help us uncover the unknown histories of other volcanic worlds, including our own planet.”

doi: https://doi.org/10.1038/d41586-024-01138-w

de Kleer, K. et al. Science https://doi.org/10.1126/science.adj0625 (2024).

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Japan's premodern concept of nature at root of distinctive mindset in early childhood education

by Osaka Metropolitan University

Observers of Japanese early childhood education and care have pointed to the mindset of educators watching over and waiting on preschoolers as being an intriguing tendency. This "mimamoru" approach has its roots in a premodern concept of nature, according to Professor Yosuke Hirota at the Graduate School of Literature and Human Sciences of Osaka Metropolitan University.

Professor Hirota looked into the works of Sozo Kurahashi (1882–1955) and Kitaro Nishida (1870–1945) to see how this concept of nature from the past made its way into education in the present day. Kurahashi's writing on education influenced early childhood education and care in Japan, while Nishida was one of the prominent philosophers of Kurahashi's time. The paper was published in History of Education .

It is well known in classical literary studies that the concept of nature in Japan had two meanings: voluntary, "from the self," and spontaneous, "beyond the self." What Professor Hirota found is that this concept has been carried over into modern education in Japan.

"Japanese educational philosophy has maintained a balance between acting by one's will and entrusting oneself to something beyond its will," stated Professor Hirota.

Kurahashi developed a theory of guidance (yūdō), likened to guiding the course of a river as it continues its inevitable flow. Professor Hirota said the achievement of his paper has been to find that this theory of guidance has its roots in Japan's traditional concept of nature.

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Chinese tourist dies after falling 250 feet into active volcano in Indonesia

The chinese tourist was posing for a photo when she lost her balance and fell into the volcano in east java..

Listen to Story

• Tourist went to watch 'blue fire' phenomenon near volcano Ijen
• She fell while walking backwards to pose for photos
• Body retrieved after two-hour operation

A 31-year-old Chinese tourist has died after falling 250 feet onto an active volcano in Indonesia. The incident happened when the woman, Huang Lihong (31), and her husband Zhang Yong, 32, were on a guided tour to Ijen - a volcano park in East Java - to watch its popular "blue fire" phenomenon, a report in The New York Post said.

While posing to get a photo, Lihong lost her balance and fell into the volcano. Her body was retrieved by rescuers after an operation of nearly two hours.

Local tour guides said Lihong initially maintained a safe distance from the edge of the live volcano but then started walking backwards while posing for the photos.

She then accidentally stepped on her clothing, tripped and fell into the mouth of the volcano, the tour guides said.