Detecting fluctuations in the lava-lake level of Villarrica Volcano, Chile using MODIS thermal imagery from 2003--2005

Villarrica Volcano, Chile hosts a small lava-lake within its summit crater. Repeated fluctuations of the lava-lake level (¡¾80 m) of Villarrica Volcano have been taking place since the last eruption in 1984 . 1985. These cycles comprise gradual build up and increase of the free surface height over weeks until the height approaches the crater rim, usually followed by sudden withdrawal (days). Filling and draining of magma in the lake reflects the dynamic behavior and volume charging in the conduit and magma chamber. At Villarricca Volcano, magma is thought to convect freely with escaping volatiles playing an important driving role in the upper conduit dynamics. In this work, thermal data are extracted from Moderate Resolution Imaging Spectroradiometer (MODIS) satellites. Thermal radiance anomaly data are compared with photographic documentation of the summit crater for the three-year period of 2003 . 2005, and the hot-spot alerts provided by Hawai'i Institute of Geophysics and Planetology (HIGP) at the University of Hawai'i and their MODVOLC algorithm. Radiance for each lava-lake pixel in successive images is used to generate a time series with respect to the thermal state of the lake. Increases in the lava-lake area or level will be reflected by increases in thermal radiance. Visual inspection methods are used to establish a time-series of lava-lake heights from a photographic archive. The lake height data will then be compared and correlated with thermal radiance data from satellites; the intensity of the radiance also reflects the height of the lava-lake within the crater. The combined time series allows some constraints to be placed on the physical processes responsible for the lava-lake fluctuations at Villarrica Volcano.