2023-06-05 14:45:15
A multidisciplinary team has examined galleries of great importance in the Cumbre Vieja volcano, on the island of La Palma, in the Spanish archipelago of the Canary Islands. The inspection has already confirmed the presence of another chasm on the north face of the volcano. The works include obtaining laser point clouds, temperature measurements and microbiological studies.
For almost a year, the collaboration established between the Volcanic Speleology Team, the Geological and Mining Institute of Spain (IGME, dependent on the Higher Council for Scientific Research (CSIC), the Department of Land Engineering and Morphology (ETSI of Roads, Canals and Ports at the Polytechnic University of Madrid (UPM)), the company Geoavance SL (official distributor of Leica Geosystems in the Canary Islands) and the Institute of Natural Resources and Agrobiology of Seville (IRNAS, of the CSIC), have allowed joining efforts to investigate in situ the magnitude of the new system of lava tubes forged by the intense volcanic activity that developed in the area. This exploration will surely last for years, but it may allow us to definitively answer the question: has the largest volcanic tube in the Canary Islands formed on La Palma?
As a result of these walks through the lava fields within the framework of the GEOPALMA project, it has been possible to confirm the rapid cooling of the tubes formed in more superficial lava flows, although only a tiny number of the mouths observed from the air have been reached. Being closer to the outside, and also aided by its location at high altitude or by the characteristics of its mouth, these shallow tubes can surprisingly become completely cold, even if the lava on their sides is not completely cold. It is not surprising: a volcanic tube, which represents the now empty arteries of the lava flow, will cool before the core of the rock, because where lava flowed before, now air does and the conduit acts as a cooling circuit.
A Volcanic Caving technician descending the new chasm to map the lower levels using a portable laser scanner with SLAM technology. (Photo: David Sanz / IGME / CSIC)
The pipes of the main system, deeper and with larger internal galleries, are still at temperatures that do not even allow them to come close to the mouths, most of them ranging between 200 and 400 degrees Celsius. But once again, the peculiar characteristics and arrangement of the entrances in one of these main tubes have allowed speleologists to find a series of refuge areas in which to move for significant distances, between 60 and 80 meters.
The so-called “Red Tube”, a branch of one of the labyrinthine systems that in November 2021 flowed towards where the town of Todoque was located, presents surprising internal characteristics, not only because of the peculiar red color that gives it its name, but also because of the profusion of lava stalactites and, above all, for its special ventilation characteristics: in this place it is possible to be inside a branch between 40 and 60 degrees Celsius, observing another at more than 200 degrees a few meters away.
The fact of being able to access these extreme temperature conditions represents an opportunity for speleologists and geologists to improve the understanding of the cooling of these structures, for which there are no clear figures regarding the time that must elapse for them to reach the outside ambient temperature. . After the observations made in other volcanic areas such as Hawaii, it can be said that from two years after their formation they are normally accessible in various sections, and that in general these cavities cool before the rock that surrounds them. La Palma is currently a new laboratory in which to improve general knowledge about the formation of volcanic tubes, and also has the ideal showcase to present the results as it has the Caños de Fuego Volcanic Cavities Interpretation Center very close to these localities.
As part of the exploration, the first tests of topographical surveys of the new cavities are being carried out, seeking the highest resolution and versatility that allows obtaining clouds of laser points quickly and with little restriction for explorers. It is here where the collaboration between Volcanic Speleology, the Department of Engineering and Terrain Morphology (Caminos – UPM), Geoavance SL and IGME has managed to show the first results obtained using portable laser scanners with SLAM technology, with which it is intended to map the thickness of the new volcanic tubes and chasms as its temperature allows it.
The prior knowledge of the cavities of La Palma by the IRNAS staff, who since 2012 have been studying the microbiology of the subsoil of La Palma in collaboration with local speleologists, provided the necessary impetus to obtain the financing that allows today to carry out the first samplings of bacterial fauna in the new tubes and continue the laser scans after the initial tests, within the framework of the MICROLAVA project.
Precisely one of the first samples of microbiota and laser clouds have been obtained in a new volcanic chasm, small but geomorphologically complex, which has been located on the north face of the cone and which is linked to the emitting centers that developed there at the end of November 2021. This small cavity, which has already been partially explored and studied, turns out to be a fissure-type chasm; that is to say, one of the multiple dykes that conducted lava inside the cone, which, when it reached the outside, was emptied and allowed speleologists to enter. Who knows if when the temperature drops it will also allow us to delve into the secrets of this colossus that has changed the face of the Aridane Valley on the surface and left behind a vast legacy of volcanic cavities. (Source: UPM)
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