Millions of people live within 100 kilometers of an active volcano, in danger from volcanic bombs, lava flows, and clouds of ash. Predicting when a volcano will erupt is incredibly difficult, even with heavy monitoring. The pools of molten rock that feed volcanoes—such as the behemoth magma reservoir below Yellowstone—are underground, where scientists can’t directly observe their behavior. Instead, researchers rely on indirect signals to predict when a volcano will erupt, such as the exhalation of volcanic gases like sulfur dioxide and seismic rumbles, which may or may not indicate an impending eruption.
Without long-term, ground-based observations, scientists often can’t determine whether these signals are normal disturbances or harbingers of a dangerous eruption, yet half the world’s active volcanoes have no ground-based monitoring systems.
New research suggests satellite data could help to fill that gap and improve scientists’ understanding of the complex warning signs a volcano may issue before it erupts. Reath et al. analyzed 17 years of remote sensing observations of 47 volcanoes in Latin America, where more than 60% of active volcanoes are unmonitored. They looked at three types of data: sulfur dioxide gas emissions, which often increase before a volcano erupts; thermal measurements; and radar data that show how a volcano is changing shape. In 2010, for example, radar measurements revealed that the volcanic dome on Mount Merapi in Indonesia was growing larger, prompting an evacuation that saved thousands of lives.
Satellite observations do have drawbacks that prevent satellites from being an accurate predictive tool, however. Although NASA collects data on sulfur dioxide emissions over the Colima volcano in Mexico, for example, the volcanic emissions are often masked by pollution from Mexico City. When all three types of satellite data are used together, however—ideally in combination with ground measurements—they can provide valuable information on normal cycles of volcanic behavior.
On the basis of their analysis of the satellite data, the team found that the majority of the 47 volcanoes were on a spectrum between open systems—able to release gas and pressure—and closed systems, which are likely building up internal pressure. In addition, an in-depth study of the Copahue volcano on the Chile-Argentina border showed that its eruptions are preceded by a regular cycle of ash plumes, gas venting, and increased thermal activity and internal pressure, all of which can be effectively tracked from space. Examining the long-term behavior of volcanoes with satellite data is an important step toward a better understanding of the scientific tools available to predict eruptions. (Journal of Geophysical Research: Solid Earth, https://doi.org/10.1029/2018JB016199, 2018)
—Emily Underwood, Freelance Writer