REMOTELY MONITORING VOLCANIC ACTIVITY AT MOUNT ST. HELENS WITH THERMAL INFRARED DATA

Thermal infrared (TIR) data from the MASTER airborne imaging spectrometer were acquired over Mount St. Helens in Sept and Oct, 2004, before and after the onset of recent eruptive activity. Pre-eruption data show no measurable increase in surface temperatures before the first eruption on Oct 1. MASTER data acquired during the eruptive episode on Oct 14 show maximum temperatures of ~330 C and TIR data acquired concurrently from a Forward Looking Infrared (FLIR) camera show maximum temperatures ~675 C, in narrow (~1-m) fractures of molten rock on a new resurgent dome. MASTER and FLIR thermal flux calculations indicate a radiative cooling rate of ~694 J/m2/s over the new dome, corresponding to a radiant power of ~23-25 MW. MASTER spectral emissivity data indicate the new material is dacitic, and the plume contains low SO2 concentrations. Digital elevation data derived from LIDAR acquired concurrently with MASTER show the dome growth correlated with the areas of elevated temperatures. The results demonstrate that airborne TIR data provide information on the temperature and composition of both the surface and plume during eruptive episodes. Given sufficient resources, the airborne instrumentation could be deployed rapidly to a newly-awakening volcano and provide a means for remote volcano monitoring.