Monitoring “foamy” magma gases can help with this

Collecting volcanic gas samples at Fumarole
Video: Hirochika Sumino (dark green jacket), Tomoya Obase (blue jacket) and Hiroshi Shinohara (orange jacket) collect gas samples from fumaroles in the Tateyama Jigokudani (“Hell Valley”) geothermal area, in Toyama Prefecture, Japan. Collecting gas samples from fumaroles is dangerous due to toxic gases and hot steam, so a gas mask, goggles, helmet and gloves are required. But Sumino says the results of this study show that the insight gained from the samples is worth the challenge.
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Credit: Yuki Hibiya

Volcanic eruptions are dangerous and difficult to predict. A team from the University of Tokyo found that the percentage of atoms in certain gases released from volcanic fumaroles (gaps in the Earth’s surface) can provide an indication of what’s going on with magma deep below — similar to taking a blood test to check your health. This can indicate when things might be “hot”. Specifically, changes in the ratio of argon-40 and helium-3 could indicate how foamy the magma is, indicating the risk of different types of eruptions. Understanding the proportions that the gases indicate for a particular type of magma activity is a big step. Next, the team hopes to develop portable equipment that can provide on-site and real-time measurements for a 24/7 volcanic activity monitoring and early warning system.

Does the thought of standing on a volcano make you shiver with excitement or fear? For many people, living in the shadow of a volcano is part of everyday life. Japan has 111 active volcanoes and an average of 15 volcanic “events”, including eruptions, each year. But these events are notoriously difficult to predict and can be fatal. In 2014, Mount Ontake, Japan’s second-highest volcano and popular tourist spot, unexpectedly erupted, killing 58 people and leaving five missing. Earthquake activity is usually an early warning sign, but some eruptions (including those in Ontake) can occur without obvious earthquake signals, so disaster mitigation agencies, such as the Japan Meteorological Agency, will take advantage of other reliable methods to warn residents of the disaster. next potential.

Fumaroles are holes and cracks in the Earth’s surface (crust), which release gas and steam and often occur around volcanoes. The gas released is made up of a mixture of chemicals. Its formation could provide us with insight into what’s going on beneath the Earth’s crust in the mantle, as magma (molten rock) forms and is pushed upward, eventually erupting as lava. Researchers already know that the ratio of isotopes (atoms of an element with the same chemical properties but a different mass) of certain gases can indicate hidden magma activity. “We learned that the helium isotope ratio sometimes changes from a low value, similar to helium in the Earth’s crust, to a high value, such as that in the Earth’s mantle, when magma activity increases. This was based on the observation of the helium isotope ratio of cold spring gas on El Hierro Island, In the Canary Islands (in the Atlantic Ocean off the northwest coast of Africa), where a volcanic eruption occurred in 2011,” explained Professor Hirochika Sumino of the Research Center for Advanced Science and Technology. “But we didn’t know why there was more mantle-derived helium during rock upheavals.”

To get more information, Sumino and his team decided to monitor gases from six fumaroles around the active Kusatsu-Shirane volcano, located about 150 kilometers northwest of Tokyo in Gunma Prefecture. The team collected samples every few months for seven years between 2014 and 2021. After collecting them, they took the samples back to the lab and analyzed them using state-of-the-art equipment called a noble gas mass spectrometer. This enabled them to accurately measure isotopic compositions, including very small (small but important) isotopes, such as helium-3, which are typically more abundant in the mantle than in the crust or air.

“We have been successful in detecting changes in the magma-derived argon-40/helium-3 ratio, which are associated with magma turbulence. Using computer models, we revealed that the ratio reflects the amount of foam underground, creating bubbles of volcanic gases that separate from liquid magma. Somino explained. “The amount of magma foams controls the amount of magma gas supplied to the hydrothermal system beneath the volcano and how much magma floats up. The former is associated with the risk of magma eruption, as increased water pressure in the hydrothermal system causes the volcano to erupt. The latter will increase the rate of magma ascent, causing to the eruption of molten rock.

When you compare a volcano to a human body, traditional geophysical methods of monitoring earthquakes and crustal deformation are like listening to the chest and taking measurements of body size. In these cases, it is difficult to know what health problem is causing some noise in your chest or a sudden increase in your weight without a detailed medical examination. On the other hand, analyzing the chemical and isotopic composition of the elements in fumarolic gases is similar to a breath or blood test. This means that we are looking at actual material that is derived directly from the magma to know exactly what is going on with the magma.”

Currently, gas samples must be collected from the field and returned to the laboratory for analysis, which is a difficult and time-consuming process. However, Sumino has experience improving noble gas mass spectrometers and hopes to develop a new instrument that will enable them to perform the same analysis, but in real time and in the field. “We want to be able to detect changes in magma activity as quickly as possible,” Somino said. “We are now developing a portable mass spectrometer for in situ and real-time monitoring of the noble gas isotope ratios of fumarolic gases. Our next step is to create a protocol for noble gas analysis using this new instrument, to make it a reality that all active volcanoes – at least those that have the potential to cause A disaster for the local population – it is monitored 24 hours a day, seven days. a week.”


Paper title:

Tomoya Obase, Hirochika Sumino, Kotaro Toyama, Kaori Kawana, Kohei Yamane, Muga Yaguchi, Akihiko Terada, and Takeshi Ohba. Observation of the hydrothermal magmatic system by noble gases and carbon isotopic compositions of fumarolic gases. Scientific reports (Posted online November 21, 2022). DOI: 10.1038/s41598-022-22280-3


This work was supported by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan, under its Integrated Next Generation Volcano Research and Human Resource Development Program (program grant number JPJ005391) and the Second Earthquake and Volcano Hazard Monitoring and Research Program (Earthquake and Volcano Risk Reduction Research ).

Useful Links:


RCAST Geochemistry and Environmental Chemistry:

Monitoring New Volcanoes Using the Helium Isotope Ratio: The Next Generation Volcano Research Project:

Research Contact:

Professor Hirochika Sumino

Research Center for Advanced Science and Technology,

tokyo university,
4-6-1 Komaba, Meguro, Tokyo 153-0041, Japan


Media communication:
Mrs. Nicola Borgall
Public Relations Group, University of Tokyo,
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan

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