Construction of probabilistic event trees for eruption forecasting at Sinabung volcano, Indonesia 2013-14

Eruptions of Sinabung volcano, Indonesia have been ongoing since 2013. Since that time, the character of eruptions has changed, from phreatic to phreatomagmatic to magmatic explosive eruptions, and from production of a lava dome that collapsed to a subsequent thick lava flow that slowly ceased to be active, and later, to a new lava dome. As the eruption progressed, event trees were constructed to forecast eruptive behavior six times, with forecast windows that ranged from 2. weeks to 1. year: November 7-10, December 12-14, and December 27, 2013; and January 9-10, May 13, and October 7, 2014. These event trees were successful in helping to frame the forecast scenarios, to collate current monitoring information, and to document outstanding questions and unknowns. The highest probability forecasts closely matched outcomes of eruption size (including extrusion of the first dome), production of pyroclastic density currents, and pyroclastic density current runout distances. Events assigned low probabilities also occurred, including total collapse of the lava dome in January 2014 and production of a small blast pyroclastic density current in February 2014

An initial comparison of the thermal anomaly detection products of MODIS and VIIRS in their observation of Indonesian volcanic activity

The Suomi National Polar-orbiting Partnership satellite was launched in 2011. On-board this satellite is the Visible Infrared Imaging Radiometer Suite (VIIRS) with thermal infrared detection capabilities similar to those of the earlier Moderate-Resolution Imaging Spectroradiometer (MODIS) sensors of the National Aeronautics and Space Administration Earth Observation System. Fire detection products have been developed using the thermal infrared data for both VIIRS and MODIS and, although having the observation of fire as their main objective, such products are also sensitive to the radiant emissions of active volcanic surfaces, but a comparison of their capabilities in this regard remains outstanding. Here, this comparison is conducted, with a focus on the volcanoes of Indonesia, and findings are initially promising, suggesting that the VIIRS fire detection capability is an improvement over that of its predecessor. For example, between 3 April 2012 and 14 July 2014, volcanic activity was detected on 519 days by the VIIRS product, as compared with 308 days for the MODIS-Aqua product (MYD14). Causes of this apparent enhanced sensitivity are explored and, with the examination of additional data from the MODIS-Terra product and the MODVOLC system, are shown to be the combined influence of spatial resolution, data processing steps, imaging scan width and the fire product algorithm used. As greater quantities of data become available, a more comprehensive comparison of these observations will be possible and will be undertaken at a global scale

Pyroclastic density currents resulting from the interaction of basaltic magma with hydrothermally altered rock:an example from the 2006 summit eruptions of Mount Etna, Italy

After 16 months of quiescence, Mount Etna began to erupt again in mid-July 2006. The activity was concentrated at and around the Southeast Crater (SEC), one of the four craters on the summit of Etna, and eruptive activity continued intermittently for 5 months. During this period, numerous vents displayed a wide range of eruptive styles at different times. Virtually all explosive activities took place at vents at the summit of the SEC and on its flanks. Eruptive episodes, which lasted from 1 day to 2 weeks, became shorter and more violent with time. Volcanic activity at these vents was often accompanied by dramatic mass-wasting processes such as collapse of parts of the cone, highly unusual flowage processes involving both old rocks and fresh magmatic material, and magma–water interaction. The most dramatic events took place on 16 November, when numerous rockfalls and pyroclastic density currents (PDCs) were generated during the opening of a large fracture on the SE flank of the SEC cone. The largest PDCs were clearly triggered explosively, and there is evidence that much of the energy was generated during the interaction of intruding magma with wet rocks on the cone’s flanks. The most mobile PDCs traveled up to 1 km from their source. This previously unknown process on Etna may not be unique on this volcano and is likely to have taken place on other volcanoes. It represents a newly recognized hazard to those who visit and work in the vicinity of the summit of Etna