digital surface model of new cone
Digital Surface Model (DSM) is a commonly implemented geospatial feature generated with UAV mapping systems and captures both the natural and built/artificial features of the environment.
eruptive episode ended after almost three months
The eruption that started on 19 September, lasted exactly 85 days and 8 hours.
The activity was dominated by strombolian activity and lava-fountaining episodes (paroxysm).
The low-level seismic activity continues including no signs of tremor signals although quakes are not ruled out.
The newly born basaltic scoria cone has reached 1,121 meters altitude with an estimated volume of about 200 million m3 of lava and tephra.
Volcano remains calm, but small quakes continue
Official confirmation when the eruption is declared over will likely need to wait a little longer. Some doubt remains as to the significance of the continuing earthquake activity: although of low energy and overall on a decreasing trend, it remains significant, and could indicate that magma at depth is still able to pressurize and fracture rocks at depth and create intrusions that might eventually allow it to rise further. However, this is far from certain - it could also be adjustments of the system triggered by the massive shifts of masses that has occurred during the eruption. In the latter case, the quakes should slowly die out.
During the past 24 hours, there were 3 quakes of magnitudes 3.3-3.5 at 35-36 km depth, in addition to many more smaller quakes (22 quakes of magnitudes 2.0-2.9 and 48 quakes below magnitude 2.0). If looking at the various maps published of recent quakes, it might seem that there is a a strong increase of quakes. This apparent increase, however, is mostly in the number of quakes, especially for those in the deeper region around 30-40 km. This is mostly an artifact caused by the absence of volcanic tremor, which acted as noise during the eruption and was simply hiding smaller quakes in its signal. Now, the very sensitive seismic devices are again able to pick up very small quakes below magnitudes 2, as well as quakes deeper down (whose signals at the surface are much weaker). In other words, most of the apparent increase of quakes is only an increase in detection sensitivity. Still, a weak increase in the total energy of the seismic activity remains visible for the past 48 hours or so. With most likelihood, it is part of a normal fluctuation, but nobody can be sure.
No new activity - pause of eruption or end?
The calm allowed scientists to actually approach the crater to take gas measurements and film the craters from close:
Un equipo del INVOLCAN accede por primera vez a la boca activa de la erupción para realizar geoquímica de gases, a las 13:00 hora canaria / An INVOLCAN team access for the first time to the main active vent to perform gas geochemistry at 13:00 Canarian time pic.twitter.com/1p4wVdbn0V— INVOLCAN (@involcan) December 15, 2021
Primeras imágenes del interior del cráter más activo donde hay desgasificación, donde uno de nuestros equipos ha conseguido acceder a las 13:00 hora canaria / First footage of the interior of the strongest degassing crater, where one of our teams reached at 13:00 Canarian time pic.twitter.com/kKtnSOdZAa— INVOLCAN (@involcan) December 15, 2021
Is the eruption over?
Whether the eruption has ended or not will depend on whether magma still stored in the reservoir beneath the surface is able to ascend or not, which in turn is likely depending on two main factors:
First, whether the shallow reservoir is being re-supplied by magma from the deeper source, which should become visible with the occurrence of deeper earthquakes - lately, these have been mostly absent, suggesting that supply from the deep source has ended.
Second, the ascent of magma from the shallow reservoir is driven by gasses dissolved in the magma and forming bubbles to increase volume and pressure and eventually make the magma rise to erupt as lava.
If, and this is maybe a likely scenario, most of the gasses have already left the system or if the remaining gasses can separate efficiently from the liquid (magma), and rise and degas at the vents and through the surface, the magma will slowly start cooling down and eventually crystallize over a very long period of time.
It is also very much possible that the current pause of the eruption leads to a blockage of the upper conduits, which disables the degassing process and generates conditions that could lead to sudden explosions and allowing probably smaller batches of remaining magma to erupt in short phases of re-activation.
Nobody knows for now - the situation remains volatile and care should be taken to make any predictions of whether activity will resume or not.
La Palma volcano: activity drops sharply, eruption might have ended or is pausing
After a temporary strong increase yesterday producing lava fountaining and tall ash plumes, visible activity decreased drastically and more or less ceased today. No significant explosions or lava flows can be seen on any of the available images from the vents or on this morning's drone surveillance flight. Volcanic tremor has dropped to its lowest levels since the eruption began, and is close to absent now.
The absence of tremor in the signal in turn allows to detect tiny quakes of magnitudes below 2, which leads to an increase in the number of total detected quakes - IGN reported 129 events, but only 5 of them were at least of magnitude 3 and none above 3.2, which is among the lowest-by-energy combined values counts since the beginning of the eruption.
Whether or not the eruption is now already at its end is hard to say, but it is most likely at least close to it.
Más imágenes de la zona cercana a la fisura a las 12.45 hora canaria / More footage of the area near the fisure at 12.45 pm Canarian time pic.twitter.com/xi1rixC1ZL— INVOLCAN (@involcan) December 14, 2021