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Just like us can often spot the beginnings of a disease from a number of signs, there are symptoms of volcanic activity that may indicate an increasing likelihood of an eruption. Monitoring them may involve detecting surface changes and small earthquakes caused by the movement of magma within a volcano, or measure changes in gas emitted by the vents. Signs like these are used to trigger alerts and trigger evacuations, and they have saved lives. But they are not always perfect.
Mount Ontake in Japan erupted in 2014 without warning, for example, killing more than 60 people. So, additional methods of detecting volcanic activity are always welcome, especially if they involve more subtle signs that could be overlooked. A new study from a Jet Propulsion Laboratory group led by Társilo Girona highlights the possibility that currently available Satellite data could provide a whole new way to warn of eruptions.
Heat is obviously a relevant parameter for volcanic activity, but it can be quite variable in individual places where you might install a thermometer. If we could instead measure all the heat coming out of a volcano, that would be quite significant, as the majority of volcanic energy is released as heat.
To attempt this, the team turned to heat radiation data NASA’s Terra and Aqua satellites. Combined, these two offer twice-daily passes with worldwide coverage, and each metric is embedded on a 1-mile-by-1-mile pixel. There are five volcanoes which have both had major eruptions since 2002 (when these satellites first came online) and are not located on islands too small to cover enough pixels for a good signal. These include Ontake in Japan, Ruapehu in New Zealand, Calbuco in Chile, Redoubt in Alaska, and Pico do Fogo in Cape Verde.
Upward trends in temperature were observed in the two to four year periods leading up to each eruption, including the surprise eruption of Ontake in 2014. Temperatures have only risen by 1 degree C or less prior to eruption. each event, but these were statistically significant trends and not just noise. The maximum temperatures of each record were associated with an eruption.
The researchers say it could represent a combination of two processes. First, magma advancing closer to the surface – and releasing gases – could stimulate hydrothermal circulation, carrying heat to warm the surface from below. Second, if this pushes more moisture into the soil layer, the soil could emit heat radiation more efficiently and thus appear “brighter” to satellites. Either way, these subtle changes seem easily detectable in satellite data.
This provides another significant metric helping to fill in a complete picture of volcanic activity. It could also facilitate the study of a volcano’s total heat balance – the balance of energy coming from below, and when and where everything is released. Combined with other monitoring tools, satellite data could easily be used to increase confidence in alert levels, placing short-lived events in a longer-term context. And the more symptoms we watch, the less likely we are to miss important warning signs.
This story originally appeared on Ars Technica.
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