Lava dome growth and mass wasting measured by a time series of ground‐based radar and seismicity observations

Abstract

Exogenous growth of Peléean lava domes occurs by addition of lava from a central summit vent and mass wasting on the flanks as rockfalls and pyroclastic flows, forming an apron of talus. We observed this process at the Soufrière Hills Volcano, Montserrat between 30 March and 10 April 2006 using a ground-based imaging mm-wave radar, AVTIS, to measure the shape of the dome surface. From a time series of range and intensity measurements at a distance of six kilometres we measured the topographic evolution of the lava dome. The locus of talus deposition moved to the southeast with time and the talus surface grew upwards on average at about 2 m/day. The AVTIS measurements show an acceleration in lava extrusion rate on 5 April, with a 2-day lag in the equivalent rockfall seismicity record. We account for the budget of lava addition and dispersal during the eleven days of measurements using: AVTIS range measurements to measure the talus growth (7.2 Mm 3 , 67%), AVTIS range and intensity measurements to measure the summit lava growth (1.7 Mm 3 , 16%), and rockfall seismicity and visual observations to measure the pyroclastic flow deposits (1.8 Mm 3 , 17%). This gives an overall dense rock equivalent extrusion rate of about 9.7 m 3 s -1 . These figures demonstrate how efficient non-explosive lava dome growth can be in generating large volumes of primary clastic deposits, and how this process could also reduce the propensity for large hazardous pyroclastic flows.

Satellite thermal observations of the Bezymianny lava dome 1993–2008: Precursory activity, large explosions, and dome growth

“…In addition, seismic activity associated with magma movement could destabilize talus that is at or near a critical angle. The critical angle of repose for talus on the Soufriere Hills dome varies from 33 to 42° [Wadge et al, 2008]. The explosion in this case could be triggered by sudden decompression of the upper Figure 11.…”

Muon tomography: Plans for observations in the Lesser Antilles

“…Time monitoring is also necessary to follow density variations associated with uid movements in the volcano and possibly related to liquid/vapour transformation in the shallow hydrothermal system. With respect to volcanoes in a magmatic eruption state like the Soufrière Hills, muon radiography could be an interesting alternative to radar techniques (Wadge et al, 2008) for real-time monitoring of dome growth and eventual collapse. Indeed, muon radiography would be an allweather operational technique unaffected by the opacity of ash clouds and electrostatic discharges.…”

Second generation of AVTIS FMCW millimeter wave radars for mapping volcanic terrain

“…The instrument was also used successfully to measure lava flows 12 and lava dome growth 13 . However, AVTIS1 suffered from long acquisition times, low signal-to-noise ratio (SNR) at long ranges, and limited operational duration due to battery consumption 14 .…”