ASTER observations of thermal anomalies preceding the April 2003 eruption of Chikurachki volcano, Kurile Islands, Russia

Chikurachki volcano (Northern Kurile Islands Chain, Paramushir Island 50° 20′N, 155° 27′E; elevation 1816 m, stratovolcano) has been in a state of unrest for over twenty years. Its most recent eruption that began in April 2003 was preceded by an eruption between January and May 2002. Thermal infrared images from the Japanese–United Statesʹ Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER-5 TIR channels, 8–12 μm, 90 m/pixel, Noise Equivalent Delta Temperature [NEΔT] ∼0.1–0.3 K; onboard the U.S. National Aeronautics and Space Administrationʹs Terra polar-orbiting spacecraft) of a snow-covered Chikurachki Volcano taken in January 2003 show muted evidence of thermal activity. ASTER thermal infrared (TIR) images from February 2003, however, indicate warmer areas within the summit crater. Average whole-pixel temperatures of adjacent summit slopes are in the range of 250–252 K, while many summit-crater whole pixel temperatures are ∼2–6 K greater. A two component Planck solution for the warmer pixels yields a solution of 275–277 K for 10–15% of the Chikurachki summit crater and 285–295 K for 25–35% of a prominent “hotspot” on its flank. An interpretation of this enhanced pre-eruption heat flow is the presence of surface melt water. The detection in ASTER data of such subtle precursory heat-flow enhancement, even retrospectively, raises important issues for remote monitoring of “dormant” snow-capped volcanoes, especially those that threaten nearby populations, like Mt. Rainier.