Predicting volcanic eruptions is notoriously tricky. In large part this is because volcanos are unique, each with their own quirks and personalities: the lessons learned from studying one volcano may not apply directly to another. Luckily, researchers are getting better at finding warning signs that they can apply broadly. Some of the most well-known are heightened seismic activity, rising temperatures, expanding magma pools, and the release of gases. New research using satellite imagery now offers a new warning sign for underwater volcanos: a change in the color of the ocean.
The idea is simple: it has long been known that as underwater volcanos prepare to erupt, the gases and compounds they release affect the composition of the surrounding seawater. Iron-rich water looks yellowish or brown, for example, while aluminum and silicon turn the water white. The challenge has always been in systematically applying this information to make useful predictions. Measuring these color changes accurately isn’t easy.
Yuji Sakuno, associate professor at Hiroshima University, has been working on this problem. As an expert in remote sensing, his key tool in this endeavor is the Japanese Space Agency (JAXA)’s Global Change Observation Mission – Climate (GCOM-C) satellite. GCOM-C observes the ocean every 2-3 days at 250-meter resolution, giving Sakuno reliable data about changes in water color over time.
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By combining GCOM-C imagery with eruption information from Himawari-8 (a geostationary weather satellite) Sakuno was able to note changes in sea water colour about a month prior to volcanic activity on Nishinoshima Island.
One of the breakthroughs that made this possible involved finding a way to measure color accurately, despite the way that sunlight can distort and play tricks with apparent water color. Sakuno looked to other areas of research to find a solution: previous work done on hot spring water provided the tools needed to counteract the Sun’s distortions.
Sakuno has big plans for this technique: “In the future,” he said, “I would like to establish a system that can predict volcanic eruptions with higher accuracy in cooperation with the Japan Aerospace Exploration Agency (JAXA), the Maritime Security Agency, which is monitoring submarine volcanos, and related research.”
This research also underlines the value of Earth observation satellites. The vast majority of spacecraft launched into orbit are used not to study the Universe, but rather are turned to look back at Earth. Space missions like GCOM-C are designed to improve life here at home. Whether by enabling communications and GPS, or helping us understand and track climate change, or keeping us safe from dramatic events like volcanic eruptions, the world’s space infrastructure has very real value to all of us ground-bound Earthlings.
“To predict underwater volcano eruptions, scientist looks at images from space.” Hiroshima University
Sakuno, Y. “Trial of Chemical Composition Estimation Related to Submarine Volcano Activity Using Discolored Seawater Color Data Obtained from GCOM-C SGLI. A Case Study of Nishinoshima Island, Japan, in 2020.” Water.
Featured Image Credit: NOAA/National Science Foundation: Superheated molten lava from West Mata submarine volcano.