Multidisciplinary Studies of the 2015-2016 Eruption of Momotombo Volcano

Momotombo volcano, Nicaragua, began erupting in December 2015 after 105 years of dormancy. Within weeks of the eruption onset, an international team of scientists began interdisciplinary studies investigating the geophysical and geochemical processes of the eruption. Our work included the installation of new seismic and geodetic networks, sampling of lava flows and ashes for geochemical and petrographic analyses, and the collection and analysis of space and ground-based radar data. Momotombo volcano has been seismically restless since at least the 1980's, when modern records are first available. Beginning in September 2013, discrete seismic swarms including events up to M4 and depths of 20 km occurred periodically. On April 10, 2014 an M6.1 earthquake occurred in Lake Managua displacing the southern flank of the volcano more than 5 cm as measured at a continuous GPS (cGPS) site. A major seismic swarm, which included an M4.7 earthquake, began on November 24, 2015, and culminated in gas and ash eruptions beginning at 7:49 am (local time) on December 1, 2015. By the evening of December 1, Momotombo was in strombolian eruption with columns to ~1 km and a lava flow advancing down the northern flank. To date, there have been over 435 explosions as detected by seismic data and visually on webcam imagery, with the last explosion on April 7, 2016. Utilizing cGPS and episodic GPS observations and radar interferometry (InSAR), we did not detect any significant pre-, co-, or post-eruptive magmatic deformation. Lava samples collected from the 2015, 1905, and pre-1905 eruptions are all basaltic andesites with nearly identical major and trace element compositions, suggesting a long-lived magma body. Concentrations of metals and volatiles in ash leachates decrease over time in the first two days of the eruption. Our interdisciplinary studies allow for an integrated analysis of this strombolian eruption and its hazards.