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Volcanoes show signs of large-scale thermal unrest for years prior to eruption
  • Társilo Girona,
  • Vincent Realmuto,
  • Paul Lundgren
Társilo Girona
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA., ​Geophysical Institute, University of Alaska Fairbanks, ​Alaska 99775,​ USA

Corresponding Author:[email protected]

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Vincent Realmuto
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA., Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
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Paul Lundgren
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA., Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
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Abstract

Identifying the observables that warn of volcanic eruptions is a major challenge in natural hazard management. An important, but under-investigated, observable is the release of heat through volcano surfaces, which represents a major energy source at quiescent volcanism. However, it remains unclear whether surface heat emissions respond to pre-eruptive processes and vary before eruption. Here we show that the last magmatic and phreatic eruptions of five different volcanoes were preceded by subtle but significant long-term (~years), large-scale (10s of km2), increases of their radiant heat flux (up to ~1 of median radiant temperature). This pre-eruptive thermal unrest is found through a new statistical analysis of satellite-based long-wavelength (10.780–11.280 ) infrared data, and is attributed to the enhancement of underground hydrothermal activity. Large-scale thermal unrest is detected even before eruptions that were impossible to anticipate through other geophysical/geochemical methods (e.g., the 2014 phreatic eruption of Ontake, Japan; the 2015 magmatic eruption of Calbuco, Chile), thus opening new horizons to better constrain the thermal budget of volcanoes and improve eruption forecasts.