Table 7.1.

Chronology and timing of activity prior to and during the partial dome collapse at the SHV on 11 February 2010

StageTime and date (UTC)Time since onsetFig. 7.4ActivityDescription
09:30 (10 February 2010)−1800 minSeismic cycle peakPeak of seismic cycle (on 10 February 2010) at which time there appears to have been a switch in the focus of growth on the lava dome from the west to the north. Flows occurred on Gages, Farrell's Plain and to the NE
14:50 (11 February 2010)−163 minSeismic cycle peakPeak of the last seismic cycle before dome collapse. PDC activity in the cycle was to the west, north and NE. The level of seismic activity was down to about half the peak by the start of the collapse activity. The gaps between the last four peaks were 6.7, 7.5 and 8.1 h
115:53:230 minAStart of PDC activityBeginning of near-continuous PDC activity to the north on Farrell's Plain. The first PDC was preceded by a LP earthquake
15:585 minBLarge PDC on Farrell's PlainFirst PDC on Farrell's Plain to travel behind the ridge. Small–moderate PDC reached the bottom of Tyre's Ghaut
16:007 minCFlows close to W. H. Bramble airportObservers at Jack Boy Hill report flows reached to within 300 m of Bramble Airport
216:1017 minDLarge PDCAppears to have been a larger PDC on Farrell's Plain
16:2330 minELarge PDCAppears to have been a larger PDC on Farrell's Plain
316:4249 minIncrease in PDC activityStart of steady increase in PDC activity, as recorded on seismic network
16:4451 minFIncrease in activityIncrease in visible activity. Lateral expansion of active flow area
16:5663 minGIncrease in activityIncrease in visible activity. Lateral expansion of active flow area. More PDCs in Farrell's and the NE, with lots of convecting ash
16:5663 min1First peak in PDC activityFirst peak in PDC activity, as recorded on the seismic network
17:0471 minHIncrease in activity, first PDC in Belham ValleyIncrease in visible activity. Lateral expansion of the active flow area. First PDC into the upper Belham, reaching to the kink in the river seen from the MVO at 17:11:51 UTC
417:0673 min2Second peak in PDC activity
17:1077 min3Third peak in PDC activity
17:1481 min4Fourth peak in PDC activity
17:15:1682 minIMBHA downLast data from the seismic station at Harris Lookout (MBHA)
17:1683 min5Fifth peak in PDC activityFifth and largest PDC peak, as seen on seismic data.
17:16:0383 minJExplosionHeard at the MVO. Infrasound sensors show a single pulse
17:1784 minKIncrease in activity, second PDC in Belham ValleyIncrease in visible activity. Second PDC in Belham reached Corkhill at approximately 13:33. This is possibly two flows as it seemed to pause by the Waterworks
17:18:5885 minVigorous convecting plume from Harris?Vigorously convecting plume appears to originate from low down on Farrell's Plain or from Harris. Observed from the MVO
17:1986 minPDCs moving across the sea at TrantsEyewitnesses in the village of Lookout recorded video of numerous PDCs moving over the sea and vigorously convecting plumes
17:20:2987 minLExplosion(s)Infrasound sensors show three or four pulses. This explosion is larger than the 13:16 LT explosion. Thermal camera shows several large explosions directed to the NE
17:2188 min6Sixth peak in PDC activitySixth peak in PDC activity, as recorded on the seismic network
517:25:3992 minMLarge LP eventLarge LP event
17:40107 minSeismic activity levels offSeismic activity begins to level off, with mainly rockfalls detected
  • Compiled from visual observations, seismic and infrasound records and thermal imagery. Labels A–M and 1–6 correspond to the labels in Figure 7.4. For information on the stages, see the discussion in the text.