Select Page

11 million cubic meters of magma creates “push zone” causing continued surface deformations on La Palma

11 million cubic meters of magma creates “push zone” causing continued surface deformations on La Palma

La Palma island, the north-western-most in the Canary Islands archipelago, has continued to tremble all week as a result of a seismic swarm registered in the area known as Cumbre Vieja, with citizens, seismologists and vulcanologists continuing to monitor the situation.

The Canary Islands Volcanological Institute say that the source of this swarm, which began last Saturday, September 11, 2021, has now been shown to have a magmatic origin, related to the intrusion of a small volume of magma inside the Cumbre Vieja volcano, producing more than 4,200 detected tremors so far.

Involcan has repeated in a statement this Thursday that the Canary Islands Geodetic Network has registered a significant deformation in the terrain, of volcanic origin, over recent days, saying that seismicity in the coming days has the potential to intensify, depending on the evolution of the activity.

La Palma is currently on yellow alert for volcanic activity in the municipalities of El Paso, Los Llanos de Aridane, Mazo and Fuencaliente de La Palma; The population have been asked to remain attentive to the information provided by the corresponding Civil Protection authorities.

Up until Tuesday night and the early hours of Wednesday morning the surface deformations had been measured at up to 1.5cm, and over that period of approximately 12 hours, Spain’s National Geographic Institute (IGN) registered more than 200 individual seismic events. During this period of time, anything up to five earthquakes occurred at a depth of just one kilometre below the surface,  reaching up to a maximum intensity of 2.1 on the mbLg scale, measuring seismic magnitude, with various others at two and three kilometres, mainly around Fuencaliente and also in the El Paso area.

The biggest earthquake, with the greatest intensity, was recorded at a magnitude of 3.1, and took place in El Paso, at 6:15 am on Wednesday morning, at 9 kilometres deep, and was felt by the population. Tremors have moved within a depth range of between 19 and 1 kilometre.

The National Geographic Institute (IGN) registered, on Wednesday, an elevation of the surface reaching up to 6 centimetres, at some points on the southwest of La Palma, data that sources from the Canary Islands Volcanological Institute (Involcan) confirmed. Also, on Wednesday, some low-magnitude earthquakes were registered at shallow depths (between one and three kilometres below ground).

IGN announced that “the GNSS network has registered an accumulated deformation since the beginning of the seismic series. The geometric pattern of the deformation obtained is compatible with a pressure centre located at the area where the seismicity is being located”.

According to Involcan, this deformation is caused by magma “that is trying to rise to the surface.” This change in surface terrain is known as the “push zone”, the point where the greatest pressure is being exerted to escape, going on to say that “it is necessary to continue observing the evolution of the seismic swarm and of the changes in the terrain” describing this process as “accelerated and energetic”, confirming there is the possibility of an eruption, although they add that there is still no clear evidence that it is imminent. “We must continue to monitor,” they concluded.

The director of the Central Geophysical Observatory of the National Geographic Institute (IGN), Carmen López, told Canarias Ahora this Wednesday morning that the Cumbre Vieja seismic swarm earthquakes registered during the night, at a depth of one kilometre “are being analysed, though some will remain at that [detected] depth, between one and two kilometres, others may go to six.”

López explained that “the seismic series is migrating and deformations are appearing, already registered by the Geodetic Network that we have and the process underway is intrusive, so continuous monitoring is necessary, assessing day by day and moment by moment”.

The scientific coordinator of the Canary Islands Volcanological Institute (Involcan), Nemesio Pérez, was reported on Tuesday as saying “what we currently have is a process of magmatic intrusion, more or less like previous ones, we are going to see how it evolves.

He described the Cumbre Vieja Volcano, as “the most active in the Canary Islands, with seven eruptions recorded in the last 600 years, it is relatively young, so it is still under construction, but we do not know when this process will occur”, he stressed.

He explained that “knowing when a volcano is going to erupt is not an easy task, although it can be forecast a few days in advance, as long as sufficient work is done to monitor volcanic activity.”

“We are making all the necessary efforts to do a good job of monitoring and alert the population early,” said Pérez.

The Cabildo de La Palma, island government, have been holding meetings with essential services coordinators, in light of the increased seismic activity in Cumbre Vieja. La Palma’s president, Mariano Zapata, indicated that “we have to be working, we cannot stop because we are in a yellow alert situation, we must keep calm, but be prepared for what may happen, if it happens, most likely not, but you have to keep the Cabildo machinery always greased and that is why we have held a meeting to review the different reports and plans to keep them fresh, up to date, for what may happen ”

This series of events may not necessarily end in an eruption. There is also the possibility that it will just stop.

That is why the volcanic risk “traffic light” on La Palma remains at yellow (level 2 of 4) , at least until pre-eruptive phenomena have been detected, which would raise the bar to orange (3).  But there is no way to know, until it is already happening.

The magmatic intrusion itself is still being described as small, measuring 11 cubic hectares, 11 million cubic meters (11 Hm3), it is just over 2/3 of the capacity volume of the Canary Islands’ largest fresh water reservoir, Soria.

The latest news on Thursday is the there has been a decrease in seismic activity, but that the deformation now extends to 10cm

INVOLCAN Information update on earthquake-volcanic activity at the Cumbre Vieja volcano (La Palma, Canary Islands):
11 million cubic meters of magma have already been injected.
The Canary Islands Geodetic Network, operated by the Canary Islands Volcanological Institute (INVOLCAN), has registered, in recent days, a significant deformation of the terrain of volcanic origin.
The figure shows the horizontal (red arrows) and vertical (black arrows) displacement at some of the GNSS stations that are part of the network. This deformation pattern can be interpreted as the effect of the pressurisation of a small magmatic reservoir, with a volume of approximately 11 million cubic meters, located inside Cumbre Vieja in the same area as where most of the earthquakes, in the recent swarm, [have been detected] and at a depth of about 6-7 km.
This observation confirms that the source of this swarm, which began last Saturday, September 11, 2021, has a magmatic origin and is related to the intrusion of a small volume of magma inside the Cumbre Vieja volcano.
INVOLCAN will continue to stay informed about the evolution of this new seismic swarm at the Cumbre Vieja volcano. Remember that it cannot be ruled out that the seismicity felt in the coming days will intensify, depending on the evolution of the activity.
The current situation of the volcanic traffic light is in YELLOW for the municipalities of El Paso, Los Llanos de Aridane, Mazo and Fuencaliente de la Palma; therefore, keep an eye on the information provided by the corresponding Civil Protection authorities.

https://en.wikipedia.org/wiki/Cumbre_Vieja_tsunami_hazard

About The Author

1 Comment