After 50 years of slumber, the volcano that forms the Cumbre Vieja on the island of La Palma in the Canary Islands in Spain roared back to life on Sept. 19, 2021. The last eruption on the island occurred in 1971 when a relatively diminutive outburst lasting about a month caused damage to roads, banana crops, and some homes in the southern portion of the island and led to the tragic loss of two lives.
The 2021 eruption, by contrast, has lasted 45 days so far, is the largest on record for La Palma, and has consumed whole towns and more than 2,500 homes. Most remarkably and happily, there has not been a single loss of life. The 2021 eruption is also one of the best-monitored basaltic eruptions of all time, offering lessons and insight into how to manage volcanic risk, as well as how eruptions take place and why volcanism occurs in ocean islands like La Palma.
On the Canary Islands, a range of governmental bodies maintain seismic stations as well as monitor gases emanating from the volcanoes to provide precursor information on likely eruptions. When reports of minor tremors occurring beneath La Palma appeared in the news in early September 2021, I was intrigued. In 2011, there had been a significant seismic crisis and eruptive event offshore of the neighboring southerly island of El Hierro. There had also been plenty of small seismic events under La Palma in the past without a volcanic eruption. Despite these “false starts,” something about the September 2021 events felt different. To me, having researched a major part of my PhD dissertation on La Palma and El Hierro in the early 2000s, I feel a strong connection with the islands, their incredible geology, mesmerizing landscapes, and wonderful people. The observations from the seismic data suggested not just a rumbling beneath the Cumbre Vieja, but a sense that the volcano was about to burst into life once more.
At 15:12 local time on Sept. 19 the ground was wrenched apart beneath a region of the Cumbre Vieja known as the Cabeza de Vaca, and molten rock was expelled to the surface. Preceding this event, geophysicists had noticed that tremors occurring roughly 25 miles beneath the volcano had migrated both upwards and northwestwards, first to about seven miles depth and then, roughly five hours before the eruption, a major seismic rupture occurred just beneath the Cabeza de Vaca region. Remarkably, authorities on the island had already begun a major mobilization and evacuation of people so that when the lavas and incandescent lava fountains eventually poured forth from the broken Earth, no one was in harm’s way. The authorities, consulted by a body of experts known as PEVOLCA (Plan de Emergencias Volcánicas de Canarias), have done a remarkable job of preventing loss of life and minimizing damage to property.
After the initial ash had settled on La Palma, I joined a group of volcanologists and geochemists invited to investigate and observe the 2021 eruption. Our team, made up of volcanology experts from Scripps Institution of Oceanography, the University of Gran Canaria Las Palmas, the University of Barcelona, Cornell University, Uppsala University (Sweden) and Freiburg University (Germany), seeks to understand both the inner workings of the earth and how volcanism occurs on ocean islands, as well as the hazards associated with basaltic volcanism. Studying basaltic volcanism is important for many reasons. Basaltic volcanoes are the most prevalent on Earth, with much of the ocean floor covered in this dark rock. The magmas that make basaltic volcanoes tend to come from direct melting of the Earth’s interior and so tell us about the inner workings of the earth. Basaltic rocks have not undergone very much crystallization of minerals, leading to generally lower viscosity and more fluid magmas that are poorer in water than magmas that form arc volcanoes like those in the Andes or the Cascades. This means generally less explosive volcanism and an opportunity to get close to the volcano to understand how it operates.
Our investigations began by studying the lava fountains and deposits of volcanic material that fall to the ground as sand to small pebble-sized particles known as volcanic tephra. These deposits are important for retrieving a history of volcanic eruptions. On La Palma, with both detailed observations of wind direction, seismic evidence and the ability to collect tephra from underneath the eruption plume, we will be able to piece together both the workings of the volcano, but also provide information on how historical volcanic eruptions might be better understood. A particularly important observation that we made was that of fast-moving red-hot “spallation bombs” that were ejected from the volcano and fell first ballistically and then by gravity.
We are also interested in the lavas erupting from the volcano. The lava flows from the volcano have been extensive, covering towns and vast swaths of land covered in banana plantations on the island. While we might refer to dark volcanic rocks as “basaltic,” there are many varieties of basalt. The 2021 La Palma eruption has produced two of these different varieties, the first rich in a water-rich mineral called ‘amphibole’ and the second richer in olivine (the gem quality variety of which is known as peridot). We will be examining these rocks to understand how the volcanism changed and to link this with the geophysics that provides a geological ‘CAT-scan’ of the shallow interior beneath La Palma.
My experience on La Palma has personally been rewarding, but for the people of La Palma, and those directly affected by the volcano, it has been an extremely challenging time. While no loss of human life has occurred, personal suffering has been exacerbated by the unpredictability of the volcano which has posed immense challenges for the authorities as they try to juggle safety with providing accurate information. By far the biggest challenge is predicting when the eruption will end. Historical eruptions on La Palma have lasted between one and three months. On the other hand, no prior historical eruption has been as big as the 2021 event. So, perhaps the eruption will end in a few weeks, but perhaps not. The event may be unprecedented.
Another challenge is communication. Anxiety surrounding the eruption for individuals comes in many guises, from being forced to abandon pets, not having insurance or property deeds, or simply not speaking the language. La Palma is a wonderful tourist destination and a significant fraction of the individuals affected by the eruption are retirees who do not speak Spanish. Communication with the entire population is an important lesson in continuing to manage the eruption.
The silver lining of the dark eruption cloud for La Palma is the potential for investment that should follow the eruption. The people of La Palma should be allowed to capitalize on the incredible volcanic landscape produced by the 2021 eruption to draw tourists who wish to see the remains of this incredible natural spectacle. La Palma is a wonderful island to visit, rich in landscapes, culture and excellent cuisine. I will certainly be back. Let me know if you’d like to go; I would be happy to tag along!
James Day is a professor in the Geosciences Research Division at Scripps Institution of Oceanography at UC San Diego. He is a geologist and geochemist whose research focuses on volcanism and what the mineralogy and composition of rocks can tell about how the planets formed and evolved to their present-day states.
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