REMOTE SENSING OF VOLCANO STREAM TEMPERATURES PRIOR TO ERUPTIVE PHASES

Mt. Redoubt (60.49^o N, 152.74^o W, elevation 3108 m, stratovolcano) is an active volcano at the eastern end of the Aleutian arc on the west side of Alaska’s Cook Inlet, and has been active for over a century. Thermal-infrared (TIR) images from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER, band 13, 10.25-10.95 um, 90 m/pixel, NEΔT~0.25° C) aboard NASA’s Terra spacecraft show an increase in thermal activity inside the snow-covered crater over a six-month period prior to the eruption, which began on March 15th, 2009. This increase in thermal activity developed a meltwater drainage stream down the north flank of the volcano. Comparisons of visible/near-infrared (VNIR, band 0.5-0.9 um, 15 m/pixel) and TIR bands identify the area of the under-resolved stream and its temperature relative to the background snow-covered terrain (Gustafson, 2003). The crater outflow stream was 3^o C warmer than background snow and warmer than the non-volcanogenic water in the Drift River on February 26th, 2009, as well as other dates prior to eruption. The temperature difference between the water sources is indicative of thermal output from the volcano, and may be applied to other volcanoes around the world. Streams and crater lakes may offer better opportunities than fissures and fumaroles for detecting increased thermal activity remotely because they typically are larger and less likely to be associated with obscuring clouds of condensing vapor. These advantages outweigh the loss of thermal contrast due to in-mixing of cold water.

While Mt. Redoubt is also monitored with a proximal seismic network, many other volcanoes in the Aleutian Island chain are not directly seismically monitored at all. The development of reliable remote-sensing indicators for eruptions could be a key component of reliable regional eruption monitoring (Pieri, 2005), and the use of streams from volcanoes to detect any increased thermal flux can be a part of a complete set of tools for predicting eruptions.