Abstract:

We propose to carry out the first phase of a multi-faceted remote sensing study of the hazards associated with the growth and collapse of silicic volcanoes. Most volcanologic remote sensing studies to date have focused on basaltic shields because of ease of access, frequency of eruptions, and relevance to ancillary planetary geologic studies. However, many more people have been killed or are at risk from the typical hazards of silicic volcanoes: pyroclastic flows and surges generated by lava dome collapse; silicic fissure eruptions fed by dikes; debris avalanches, lahars, and other mass movements; and catastrophic magma chamber evacuation and caldera collapse.

We will initially focus on the most common of these processes: the growth and collapse of silicic domes and lava flows. The framework for these studies will be a theoretical model, previously developed by the P.I., that relates the velocities and kinetic energies of pyroclastic flows generated by dome collapse to five properties of the dome and its setting: volatile content, temperature, chemical composition, thickness of cooled carapace, eruption rate, and underlying topography. We will use several different remote sensing techniques to evaluate these variables. (1) Linear deconvolution of thermal infrared (TIR) spectroscopic data (employing a model developed by the Co-PI.) will be used to assess lava vesicularity, which can be related to volatile content. (2) For lavas of a given vesicularity, similar analysis can reveal chemical composition, which correlates with lava eruption temperature and rheology. (3) SAR can be used to calculate surface block sizes, which reflect the thickness of the dome's cooled carapace. (4) DEMs will be used to measure sub-flow topography and changes in flow volume.

Field testing of our remote sensing analyses will be carried out at several Holocene silicic lava flows in the western U.S. and at three or more sites of recent dome emplacement characterized by pyroclastic flow generation (Unzen, Japan; Santa Maria, Guatemala; Soufriere Hills, Montserrat; and other sites that may become active within the next 3 years).