A strong earthquake swarm started under Cumbre Vieja volcano, La Palma, Canary Islands at 03:18 UTC on September 11, 2021.
From the beginning of the seismic series until 08:00 UTC on September 13, a total of 1 570 earthquakes have been detected, of which 354 were located. 315 earthquakes have been detected (90 located) to 17:45 UTC on September 12.
The magnitude of earthquakes have been increasing in recent hours, with a maximum magnitude of 3.4 mbLg.
The depth of the earthquakes remains between 8 and 13 km (5 - 8 miles).
Since October 2017 there have been 10 seismic series with similar characteristics in this area of the island of La Palma.
"The occurrence of events of this type in an active volcanic zone is within normality and does not present any risk to the population," the Spanish National Geographic Institute (IGN) said.1
Only 15 earthquakes (M0.9 - 2.6) have been detected on the island during the entire month of August. 10 of these earthquakes have been part of a small seismic series that occurred on August 27 and 28 located in the south of the island.
Shallow depths suggest that new magma is currently intruding into a reservoir under the volcano, volcanologist Dr. Tom Pfeiffer said.2
"Whether or not this might be leading up to new volcanic activity is impossible to say at this stage, as there seem not to be other signs of significant volcanic unrest at this stage."
Earthquakes registered in the previous two earthquake swarms under the volcano -- December 20203 and February 20214, were deeper (20 - 30 km / 12 - 18 miles, and 15 - 20 km / 9 - 12 miles, respectively), which could indicate that magma has now risen higher in the volcano's underground storage systems.
"Without a doubt, the current seismic swarm represents a significant change in the activity of the volcano and is related to a process of magmatic intrusion beneath La Palma Island," the Volcanology Institute of the Canaries (INVOLCAN) said.5
"Our geochemical monitoring program for volcanic surveillance in La Palma has allowed us to detect in 2020 (16/09/2020), the highest emission value of helium-3 observed in La Palma over the past 30 years, and after this detection, not only the largest number of seismic swarms in La Palma since 2017 (7 of a total 10) but also a year before recording the most important seismic swarming of the 10 occurred in La Palma."
"For these reasons described above, the PEVOLCA Management has been advised to raise the volcanic light for La Palma from GREEN to YELLOW."
The Ministry of Public Administrations, Justice and Security, the Government of the Canary Islands convened the Scientific Committee of the Special Plan for Civil Protection and Attention to Emergencies due to Volcanic Risk (PEVOLCA) to assess the situation, and agreed to activate this Plan in a situation of Alert for Fuencaliente, Los Llanos de Aridane, El Paso and Mazo and the change of the traffic light from Green to Yellow for said municipalities.6
The 47-km-long (29 miles) wedge-shaped island of La Palma, the NW-most of the Canary Islands, is composed of two large volcanic centers. The older northern one is cut by the massive steep-walled Caldera Taburiente, one of several massive collapse scarps produced by edifice failure to the SW.
The younger Cumbre Vieja, the southern volcano, is one of the most active in the Canaries.
The elongated volcano dates back to about 125 000 years ago and is oriented N-S. Eruptions during the past 7 000 years have originated from the abundant cinder cones and craters along the axis of Cumbre Vieja, producing fissure-fed lava flows that descend steeply to the sea.
Historical eruptions at La Palma, recorded since the 15th century, have produced mild explosive activity and lava flows that damaged populated areas.
The southern tip of the island is mantled by a broad lava field produced during the 1677-1678 eruption. Lava flows also reached the sea in 1585, 1646, 1712, 1949, and 1971.7
1 The seismic series activity located in the south of the island of La Palma continues - 09-13-2021 08:00 UTC - IGN
2 La Palma volcano (Canary Islands): strong seismic swarm suggests magma intruding at depth - VolcanoDiscovery
3 New earthquake swarm under Cumbre Vieja volcano, La Palma, Canary Islands - The Watchers
4 Earthquake swarm under Cumbre Vieja volcano, Canary Islands - The Watchers
5 INVOLCAN - FB
6 The Canarian Government activates the special plan for volcanic risk in La Palma - Then24
7 La Palma - Geological summary - GVP
Featured image credit: IGN
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