Abstract
We compare Worldview-3 (WV3) satellite imagery and Visible Near Infrared (VNIR) hand sample measurements from recent eruptions of two remote stratovolcanoes: Great Sitkin and Mount Veniaminof in Alaska, USA. Both are monitored through seismic and infrasound sensors, webcams, lightning detection, and satellite imagery. Great Sitkin, in the Aleutian Islands, has been erupting felsic material since May of 2021, producing ash/gas plumes and dome growth in the crater with lava flowing over the sides. Mount Veniaminof, located on the Alaskan Peninsula, is characterized by a glacier-filled crater, its last eruption was in 2018 producing ash and gas plumes, mafic lava flows, and lava fountaining. Great Sitkin's history of mass edifice failure on its northern side is potentially linked to dome growth and hydrothermal alteration. Mount Veniaminof's history of glacio-volcanic interactions, makes both interesting candidates for VNIR analysis. The VNIR portion of the electromagnetic spectrum ranging from 350-2500 nm collects the light reflected off material surfaces; useful for identifying clay minerals common in hydrothermal alteration while still sensitive to iron content. We aim to explore the accuracy of satellite imagery to identify the mineralogical assemblages and bulk compositions of volcanic material to assist in monitoring activity for hazard mitigation. Samples were collected by Alaska Volcano Observatory and VNIR measurements from the University of Idaho using an ASD HALO portable spectrometer. ArcGIS was used to process WV3 imagery to obtain reflectance values; corresponding imagery data was extracted from hand sample coordinates of the hand samples for comparison. Band ratios for argillic alteration ((SWIR3+SWIR6)/SWIR5), phyllic alteration ((SWIR5+SWIR7)/SWIR6), and iron oxides (green/red)can be used to map hydrothermal alteration areas, enhancing our insight into the alteration and contribute to hazard assessment. Composite images displaying Mafic vs. Felsic surfaces (SWIR3/SWIR5, SWIR3/SWIR7, NIR1/green) and Fresh vs. Altered surfaces (NIR1/red, SWIR8/green, SWIR8/SWIR5) can also be generated. The monitoring of alteration on volcanoes at risk of collapse, or the quick assessment of geochemistry without sampling could prove useful for entities responsible for remote volcanoes.