ASTER- and field-based observations at Bezymianny Volcano: Focus on the 11 May 2007 pyroclastic flow deposit

Abstract

Bezymianny (Kamchatka Peninsula, Russia) is an active stratovolcano, characterized by a summit lava dome and overlapping pyroclastic flow (PF) deposits to the southeast. Three explosive eruptions (24 December 2006, 11 May 2007, and 14 October 2007) generated PFs that were dominated by juvenile material and were emplaced primarily due to column collapse. Following this, a gravitational lava flow front collapse event generated block and ash flow on 5 November 2007. Moderate spatial resolution data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument were collected between October 2006 and December 2007 to assist in post-eruption monitoring and interpretation of the volcanological processes that produced the PF deposits. Using multitemporal ASTER thermal infrared (TIR) data, three periods of increased activity were observed that coincided with each eruption and subsequent activity. During a field campaign in August 2007, the May 2007 PF deposit was investigated in detail. Eight ASTER TIR pixels (90 m spatial resolution) were selected from the 30 June 2007 ASTER TIR image, seven of which were accessible in the field. Forward-Looking Infrared (FLIR) image and thermocouple data over these areas were collected to observe thermal heterogeneities with distance along the PF deposit. Although synchronous ASTER data were not possible at the time of fieldwork due to cloud cover, a field survey of blocks versus ash in each pixel was carried out to investigate thermal and textural variation with distance from the vent and to provide preliminary field results. Based on the field-derived temperature data and surface block percentages, the May 2007 PF deposit was more block-rich in the medial portion of the flow surface, but more ash-dominated at the PF terminus region, which promoted more rapid cooling. We present multitemporal ASTER data spanning a 14 month period and highlight ground-based observations acquired within the same period of eruptive and dome-growth activity. These data collectively provide thermal radiative and emissivity information on an actively changing explosive volcanic system and specifically documents changes over recently-emplaced and cooling PF deposits.