La Palma volcano eruption update: high lava effusion rates, new lava arm at the sea, speculation about seismic activity
Mon, 11 Oct 2021, 10:3310:33 AM | BY: T
Lava fountain, ash emission and lava flow today at noon (image: Live webcam)
Map of lava flows as of yesterday afternoon (image: x_y_es / twitter)
Today, the eruption continues with steady lava fountaining from the lower vent and strong degassing and ash emission from the upper vents, but is much less noisy compared to yesterday, to the relief of people living in the area many of whom were terrorized by the extreme noise of the eruption in recent days.
Seismic spectrum at TBT station yesterday showing the tremor at 18 Hz (image: IGN)
The decrease of sound intensity is however not an indication of what state the eruption is in its deeper underground. It is mostly reflecting how gasses can escape and interact with the ambient air at the very surface. The decrease of eruption sound is likely due to an enlargement of the upper conduits after several collapses and other changes occurred at the vents, which now are in a more stable configuration to allow the passage of magma in a more unobstructed way. It probably has no significance as to the eruption's effusion rate, which continued to be very high. The past day's activity changed the morphology of the main cone quite a bit, by accumulation of falling material from the mountains, as well as overlapping lava flows.
The result is that the cone overall grew significantly and most lava now is going into the northern flow, which has been following the northern margin of the flow field, causing lots of additional damage in the past 48 hours. It reached the sea last night around 22.55 p.m., after passing north Montaña de Todoque (the cinder cone near Todoque, already half circled by lava flows on the southern side).
Lava threatens La Laguna
Forming a rather narrow front, its rate of advance was very fast, at about 500-700 m per hour. It is now hoped that its channel or tube system will remain stable to direct the lava straight into the ocean instead of widening the flow or branching off, which would put the town of La Laguna at risk.
Seismic activity shows worrying signs
According to a post of a geoscience page VolcanesyScienciaHoy on facebook based in Tenerife, the current seismic activity points towards that more magma is moving upwards, as indicated by 3 factors:
- several earthquakes appeared at depths less than 7-8-9 km;
- after the 4.2 quake two days ago, there have been episodes of spasmodic tremor with many earthquakes in a row that indicate movement of magma in depth;
- since yesterday, the appearance of strong volcanic tremor at around 18 Hz frequency thought to be caused by depressurization of fluids at great depth around 10 km;
If these interpretations hold, there should soon be noticeable ground uplift visible in the GPS stations (which, so far, is not the case). What will next happen, when this new magma pulse reaches the surface, is unknown. In the best scenario, the current conduits will continue to cope with it and the magma will erupt from the existing vents. In the worst scenario, magma could open new fissures in a different area, even after another potential pause of the eruption should it occur. In a scenario in between, new fissures might open near the existing vents, and new lava would erupt onto existing lava fields.
No one can predict the future, but for sure the evolution of the eruption will be a highly interesting one and the experience intense for everyone involved, in one way or another.
Mon, 11 Oct 2021, 09:50
The seismic activity under the island remains intense, but the quakes remain clustered in the same areas as before with no clear trend visible. ... Read all
Mon, 11 Oct 2021, 09:15
La Palma Volcano Volcanic Ash Advisory: ERUPTION AT 20210919/1410Z ONGOING EMISSION OBS VA DTG: 11/0900Z to 10000 ft (3000 m)