Chapter 7 The 11 February 2010 partial dome collapse at Soufrière Hills Volcano, Montserrat

Abstract

On 11 February 2010, a partial dome collapse, the largest since 20 May 2006, occurred at Soufrière Hills Volcano (SHV), Montserrat. The collapse is also the largest generated on the northern flank of SHV since the eruption began in 1995. Approximately 50×106 m3 was removed from the dome, resulting in widespread pyroclastic density currents (PDCs). Mapping revealed a complex stratigraphy that varied widely across the northern and NE flanks, and reflected the complex evolution of the collapse. The deposits included a range of fine-grained ash-rich and pumice-rich units deposited by dilute PDCs, and several types of coarse-grained, blocky deposits from dense PDCs. Several previously unaffected areas, including Bugby Hole, Farm River Valley, the village of Harris and Trants, suffered significant damage to the natural and built environments. The collapse lasted 107 min but the bulk of the activity occurred in a 15 min period that included five of the six peaks in PDC generation and two Vulcanian explosions. Although powerful, the PDCs generated were not associated with a lateral blast. The likely cause was the piecemeal collapse of a series of large, unstable lobes that had been extruded on the northern flank of the pre-existing dome.

Syn-eruptive, soft-sediment deformation of deposits from dilute pyroclastic density current: triggers from granular shear, dynamic pore pressure, ballistic impacts and shock waves

“…1). According to Stinton et al (2014), only three PDCs flowed in this drainage (stage 3-H, 4-K and 4-6), Wadge et al (2014) also mentioning PDCs in this zone for the 11 February 2010 collapse. Basal, small-scale pipes and attached potatoids intrude underlying diffusely cross-stratified ash from a massive lapilli-and-ash lens, whereas fines-poor, small-scale pipes are found in the otherwise ash-rich, massive, overlying layer ( Fig.…”

“…The 11 February 2010 partial dome-collapse event of Soufrière Hills (Montserrat) produced a series of six block and ash flows, five of them occurring within 15 min, and was the largest event since the 1995 awakening (Wadge et al, 2014;Stinton et al, 2014). Numerous degassing pipes were observed in block and ash flow deposits as well as massive ash units (Stinton et al, 2014).…”

“…Numerous degassing pipes were observed in block and ash flow deposits as well as massive ash units (Stinton et al, 2014). Other post-depositional structures are described by Stinton et al (2014) as "rootless phreatic explosion craters", i.e., structures related to hot blocks turning water into steam explosively.…”

“…Numerous degassing pipes were observed in block and ash flow deposits as well as massive ash units (Stinton et al, 2014). Other post-depositional structures are described by Stinton et al (2014) as "rootless phreatic explosion craters", i.e., structures related to hot blocks turning water into steam explosively. They can have diameters between 1 and 30 m, consist of "decimeter-sized blocks in a coarse ash-rich matrix derived from the underlying primary PDC deposits" and have a contact to underlying cross-bedded units or down to the pre-collapse surface.…”

Real-time prediction of rain-triggered lahars: incorporating seasonality and catchment recovery

“…The andesitic dome-forming eruption of SHV began in July 1995 and has featured several phases of activity consisting of dome growth, dome collapse and Vulcanian explosions as well as pauses in magma extrusion (Bonadonna et al, 2002;Komorowski et al, 2010;Stinton et al, 2014). Pyroclastic density currents (PDCs) have deposited fine-grained, ash-and pumice-rich, and coarser-grained blocky deposits around the volcano (Cole et al, 2002;Stinton et al, 2014), supplemented by tephra deposits from short-lived Vulcanian explosions and associated fountain-collapse flows and surges (Komorowski et al, 2010).…”