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An underwater volcanic eruption off the Vava u island group in Tonga on 7 August 2019 resulted in the creation of floating pumice on the ocean s surface extending over an area of 150 km2 The pumice s far-reaching effects from its origin in the Tonga region to Fiji and the methods of automatic detection using satellite imagery are described making it possible to track the westward drift of the pumice raft over 43 days Level 2 Moderate Resolution Imaging Spectroradiometer MODIS Visible Infrared Imaging Radiometer Suite VIIRS Sentinel-3 Ocean and Land Color Instrument OLCI and Sentinel-3 Sea and Land Surface Temperature Radiometer SLSTR imagery of sea surface temperature chlorophyll-a concentration quasi-surface i e Rayleigh-corrected reflectance and remote sensing reflectance were used to distinguish consolidated and fragmented rafts as well as discolored and mesotrophic waters The rafts were detected by a 1 to 3 5 C enhancement in the MODIS-derived sea surface temperature due to the emissivity difference of the raft material Large plumes of discolored waters characterized by higher satellite reflectance backscattering of particles in the blue than surrounding waters and corresponding to either submersed pumice or associated white minerals were associated with the rafts The discolored waters had relatively lower chlorophyll-a concentration but this was artificial resulting from the higher blue red reflectance ratio caused by the reflective pumice particles Mesotrophic waters were scarce in the region of the pumice rafts presumably due to the absence of phytoplanktonic response to a silicium-rich pumice environment in these tropical oligotrophic environments As beach accumulations around Pacific islands surrounded by coral shoals are a recurrent phenomenon that finds its origin far east in the ocean along the Tongan trench monitoring the events from space as demonstrated for the 7 August 2019 eruption might help mitigate their potential economic impacts

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Automatic detection of optical signatures within and around Floating Tonga-Fiji pumice rafts using MODIS, VIIRS, and OLC...

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