On November 25, 2021, volcanologist Pablo J. González was walking through an amazing landscape.
He was near a new mouth of the Cumbre Vieja volcano that had opened at the door of a house already evacuated and covered under a mountain of black ash.
That scene was one of the most startling images of the eruption.
Shortly after, González saw another no less bleak as he entered the La Manchas cemetery.
“It was devastated”, recalls this CSIC volcanologist.
“The beams in the niches had collapsed and formed an arch.
In that place we discovered fractures in the ground that had not been detected until now.
There were tiny cracks, the size of a hair, and others that were up to 20 centimeters wide, ”he recalls.
In those days a new swarm of small earthquakes heralded the reactivation of the volcano, which had been spewing lava from the main cone for more than two months.
The new cracks also widened and modest flows began to flow that stopped at 10 or 20 meters.
The cracks are about two kilometers from the main crater.
The most interesting thing is that they do not have the same orientation as the main mouths, from northeast to southwest, but instead run from east to west.
This new focus —little studied— may be valuable to better understand one of the most unknown and destructive processes that can happen in an eruption: volcanic debris landslides, as González explains today in an analysis published in Science.
On December 23, 2018, a tsunami with waves of up to five meters hit the coast of Indonesia in the middle of the night.
More than 400 people died.
The cause was the collapse of one of the walls of the Anak Krakatoa volcano, which had erupted.
"That disaster occurred at night, so we do not have visual data on how and why it happened," says González.
The volcanologist believes that the enormous amount of data accumulated during the Cumbre Vieja eruption can provide new data on how and why disasters like these occur.
"In the Canary Islands, 32 landslides of volcanic origin have been identified that occurred in the last two million years," explains González.
“Some were huge.
The collapse of Anak Krakatoa was caused by a slide of 0.1 cubic kilometers of rock, while in Tenerife, for example, there were slides of up to 500 cubic kilometers”, he explains.
On March 27, 1980, the worst landslide in history was triggered.
Mount Saint Helena in the state of Washington (USA) had begun to deform under the pressure of the thriving magma until it exploded.
The north face of the volcano collapsed causing a terrible landslide in which 57 people died.
The most accepted theory is that these collapses happen when magma transforms underground pockets of liquid water into steam.
This causes the walls of the volcano to lose support and collapse.
The Cumbre Vieja eruption has been the longest recorded on the island of La Palma, 85 days.
It went out on December 13, about two weeks after González and his team found him in the cemetery.
“It had a very explosive end, the last day it spewed out a huge amount of ash that reached up to 4 kilometers high.
The new cracks are something unexpected and it is very important to study them because they can reveal important things about volcanic collapses and landslides, especially why they happen or not, as in the case of La Palma, despite the existence of that possibility, "he details. .
It is possible that the opening of this last mouth and the appearance of the cracks released tension and removed the risk of a greater accumulation of material in the main cone and, therefore, of a possible collapse, he points out.
"If we manage to clarify the sequence of events that led to the volcano not collapsing, we may be able to establish criteria that help alert us to these disasters," González points out.
"This is a very hot topic in the study of volcanoes," explains José Fernández, an expert in geodesy at the CSIC and director of González's thesis.
“It is very complicated to study because large landslides are rare.
Understanding why there was no landslide on La Palma can help understand why they occur in other areas”, he adds.
Now that the eruption has passed, the scientists are preparing to publish all the data that they have been amassing since the beginning of the seismic activity on La Palma.
The team led by Nieves Sánchez, a researcher at the Geological and Mining Institute of Spain (IGME-CSIC), hopes to soon publish a detailed catalog of all the faults on the Canary Island.
"This has been a unique eruption in many ways," says the volcanologist.
“I do not remember cases of volcanoes that affect urban areas in such a radical way and that have not caused victims.
In addition, everything that happened before, during and after the eruption has been monitored in great detail.
There is nothing like it in the Western Hemisphere,” she notes.
What has most surprised this geologist, who was a scientific adviser to politicians during the crisis, is the enormous complexity of an active volcano.
“Normally we volcanologists analyze the eruptions when they have already stopped and we try to infer what happened.
Here, on the other hand, we saw it evolve from the beginning, how the cone rose and collapsed several times, how the foci appeared and disappeared [there were more than 20 mouths];
and this only in the 85 days that it was active.
There are volcanoes that have been active for thousands of years!
This eruption is going to help us a lot to understand how the volcanoes in the Canary Islands work, especially those that are yet to come”, he concludes.
There are volcanoes that have been active for thousands of years!
This eruption is going to help us a lot to understand how the volcanoes in the Canary Islands work, especially those that are yet to come”, he concludes.
There are volcanoes that have been active for thousands of years!
This eruption is going to help us a lot to understand how the volcanoes in the Canary Islands work, especially those that are yet to come”, he concludes.
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