Wednesday , August 4 2021

Satellite Images Can Help Predict When Underwater Volcanoes Will Explode



Predicting volcanic eruptions is notoriously difficult. This is largely because volcanoes are unique, each with their own quirks and personalities: Lessons learned from one volcano study may not apply directly to another. Fortunately, researchers are getting better at finding warning signs that they can apply widely. Some of the best known are increased seismic activity, rising temperatures, expanding magma pools and gas release. New research using satellite imagery now offers a new warning sign for underwater volcanoes: a change in the color of the ocean.

The idea is simple: As underwater volcanoes prepare to erupt, the gases and compounds they release have long been known to affect the composition of the surrounding seawater. For example, iron-rich water will appear yellowish or brown, while aluminum and silicon will turn water white. The challenge has always been to apply this knowledge systematically to make useful predictions. It is not easy to accurately measure these color changes.

Yuji Sakuno, associate professor at Hiroshima University, is working on this problem. As a remote sensing specialist, his key instrument in this effort is the Japanese Space Agency’s (JAXA) Global Change Observation Mission – Climate (GCOM-C) satellite. GCOM-C observes the ocean at 250 meters resolution every 2-3 days, providing Sakuno with reliable data on changes in water color over time.

By combining GCOM-C images with eruption information from Himawari-8 (a geostationary weather satellite), Sakuno was able to note changes in the color of seawater about a month before volcanic activity on Nishinoshima Island.

This photo shows an example of the (Fe + Al)/Si distribution as an index of volcanic activity around Nishinoshima Island from May 16 to June 25: (a) May 16-23 2020, (b) May 24-31 2020, (c) 1-8 June 2020, (d) 9-16 June 2020, (e) 17-24 June 2020, (f) 25 June-2 July 2020. (( Fe+Al)/Si)=45.4(x )-13.3 SGLI (Second Generation Global Viewer – embedded GCOM-C device) data. From here, it can be seen that the distribution in the northeastern part of the island increased during this period and then moved towards the marine area around the island before the coloration disappeared. Nishinoshima Island is located approximately 1,000 km south of Tokyo, Japan. The original data used for this product was provided by JAXA’s JASMES (JAXA Satellite Tracking for Environmental Research). Credits: JAXA/Yuji Sakuno.

One of the breakthroughs that made this possible was finding a way to accurately measure color, even though sunlight plays with distortion and visible water color. Sakuno looked to other areas of research for a solution: Previous work on hot spring water provided the tools needed to counter the Sun’s distortions.

Sakuno has big plans for this technique: “In the future,” he said, “I would like to set up a system that can predict volcanic eruptions with greater accuracy, in collaboration with the Maritime Safety Agency, the Japanese Aerospace Exploration Agency (JAXA), submarine volcanoes and related research is watching.”

This image shows colorimetric data of colorless seawater in four directions (north, east, south and west) around Nishinoshima Island in 2020. The study investigated the color characteristics of the water to confirm whether the data obtained by SGLI accurately captured real conditions. colorless sea water. About a month before the volcano became active, it detected significant fluctuations in the distribution of chemicals on Nishinoshima Island, estimated from the SGLI data. Credits: Yuji Sakuno.

This research also highlights the value of Earth observation satellites. The vast majority of spacecraft launched into orbit are not used to study the Universe, but to return to Earth. Space missions like GCOM-C are designed to improve life here at home. Whether by enabling communications and GPS, helping us understand and monitor climate change, or protecting us from dramatic events like volcanic eruptions, Earth’s space infrastructure is of very real value to us land-bound Earthers.

Learn more:

“To predict underwater volcanic eruptions, the scientist looks at images from space.” Hiroshima University

Sakuno, Y. “Chemical Composition Estimation Trial of Submarine Volcano Activity Using Colorless Seawater Color Data from GCOM-C SGLI. A Case Study on Japan’s Nishinoshima Island in 2020.” That.

Featured Image Credit: NOAA/National Science Foundation: Superheated molten lava from the West Mata undersea volcano.


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