Cumbre Vieja volcano eruption, La Palma, activity update and field report: western portion of crater collapsed

Sun, 26 Sep 2021, 10:53
10:53 AM | BY: T
Lava fountain from the main vent at Cumbre Vieja last night; the collapsed crater area can be seen clearly if compared to similar photos from earlier updates (image: Tom Pfeiffer / VolcanoDiscovery)
Lava fountain from the main vent at Cumbre Vieja last night; the collapsed crater area can be seen clearly if compared to similar photos from earlier updates (image: Tom Pfeiffer / VolcanoDiscovery)
Lava fountain and the lava flow that had started Friday seen last evening (image: Tom Pfeiffer)
Lava fountain and the lava flow that had started Friday seen last evening (image: Tom Pfeiffer)
Tremor amplitude since the start of the eruption (green line; image: IGN)
Tremor amplitude since the start of the eruption (green line; image: IGN)
GPS measured deformation at LP03 station (IGN)
GPS measured deformation at LP03 station (IGN)
The eruption continues at fluctuating intensity and with significant changes at the morphology of the new crater:
During the course of yesterday, a significant portion of the western flank of the cone collapsed, likely during a series of rockfalls, leaving a narrow horse-show shaped breach, thus lowering the main vent, which continued to produce violent pulsating lava fountains at fluctuating intensity.
During periods, the jets of lava likely surpassed 500 m in height with individual bombs reaching perhaps up to around 1000 m in height. Jets usually were more or less vertical, but sometimes also oblique to the west, suggesting the presence of at least two closely-spaced vents.
The lava flow from the effusive vent on the NW flank of the cone seemed to almost cease during the evening, but later resumed, creating a new flow in the same channel. This lava flow was still active by the time we left the scene at around 10 a.m.
Violent spattering could be seen at the vent; the following video shows the high fluidity of the erupted lava:


Fluctuating intensity of lava fountains
The lava fountaining activity from the main vent changed somewhat as it became more fluctuating after late last night, switching from moderate to very intense during phases lasting several minutes.
After around 0.30 a.m. local time this morning, the fountains significantly decreased and switched to intermittent, weaker pulses. Later, they resumed and gained strength again, but decreased again in the early morning hours, only to pick up again a bit.
The associated ash plume was weaker than during the previous days, but still rose to approx. 3 km height and slowly drifted towards northeasterly directions.
In undisturbed areas around El Paso and Tacande, there is now a 3 cm thick deposit of black ash and lapilli from the ongoing eruption.

Seismic and deformation data
Tremor intensity remains high, but with significant fluctuations over periods of hours. Overall, its trend is either to be stable or even increasing. The latest GPS data suggest that ground deformation is slowing down and coming to a halt, suggesting that the overall magma effusion rate is now in balance with the supply of magma into the shallow reservoir feeding the eruption.
As to what might happen next, there can only be speculation at this point. For sure, it will be interesting...

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