The Sociedad Democracia de Arrecife has hosted another day of commemorative events for the X Anniversary of the Mercedes Medina Díaz Association, with the conference this Monday by the Doctor in Geography from the University of Las Palmas de Gran Canaria, Alex Hansesn Machín, entitled "The eruption of the Cumbre Vieja volcano on September 19, 2021 within the framework of recent and historical volcanism in the Canary Islands"
The conference covers "the different eruptions in historical and recent times", a term which sometimes leads to error, since it really "is a geological period, which refers to the current stage of the Holocene, at the end of the last glacial period Würm 11,700 years ago, when the glaciers abandoned us and the islands were configured with their current outline". He begins his presentation by referring to the current situation in La Palma: "we are witnessing a marvel of modernity, since it is not only a phenomenon observable by the people who suffer it, but the entire archipelago is attentive from land, sea and air in real time, being covered with great care by TV Canaria from its very beginning, possible thanks to the network of seismographs and the constant monitoring of them, which had already warned about it".
For the speaker, of all the islands, "the eruptive activity of Tenerife stands out in recent and historical times," with El Teide being a volcanic massif that, at around 180,000 years old, "we can consider young", considering the 10-11 Ma of the oldest part that makes up the Teno massif. This island has seen "23 eruptive processes in the last 1000 years", including the one that Christopher Columbus would see when he docked in San Sebastián de La Gomera. But the most devastating effect on the socio-economic level occurred at the beginning of the 18th century, the lower island of Garachico, or fajana as it is said in La Palma, had in its cove "the most important port in the entire archipelago, which was completely buried with the eruption of 1706", thus ceding its importance to the Port of La Orotava, current Puerto de la Cruz. Coming from another geological event such as a large landslide of more than 300 km³ the Orotava itself, whose remains we find on the ocean floor.
The speaker continued detailing chronologically: "in 1909 we have the case of Chinyero", which is distinguished from the others not by its strength, nor by its effects on the territory, but because "it could be photographed and posters were even printed and disseminated to promote tourism", which already in those years was beginning to originate in the north of the island. The eruption was located again on the Abeque ridge (NW of Tenerife).
The 18th century would be "very inclement for the islands, with another eruption that seriously affected Lanzarote" being the longest in history with a duration "of 6 discontinuous years", extending 200 km² of surface on an island of 700 km², with what that meant, "burying some of the most fertile plains of the island, about twenty population entities of different sizes, maretas and even chapels such as Candelaria, representing a hard economic and population blow for the island". Being exceptional in itself for different reasons, since in historical times the area of greatest activity has always been located in the western part of the islands, in addition to its great extension since the magma emitting sources migrated "during those years up to 13 km, even changing direction, something unprecedented in the Canary Islands".
With the particularity for the geological study of the good state of conservation for the geological study due to the unique climate, which leads to the malpaís having barely been colonized by lichens.
"Our scientific teams had never had the opportunity to carry out such an exhaustive monitoring until the Tagoro volcano in El Hierro in 2011 that erupted in the sea, in one of the three ridges that make up the newest of the islands with 1 Ma, a baby at a geological level if we compare it with the 20 Ma of Fuerteventura that make it the grandmother of the insular family. Sometimes it seems small to us, however we must remember that it has 1500 m.a.s.l., but 4000 under the sea, which makes it a colossal mountain", explains the Doctor, who adds that as an example "we can observe the Hawaiian case, in which its largest island is composed in the same way by a triangular ridge".
Taking a tour of the eruptions that have affected the island of La Palma, the speaker notes that there are "two well-differentiated parts, one more calm, or inactive to the north, and a southern part composed of a mountain range that goes from Cumbre Nueva to Fuencaliente, which is really a stratovolcano of 20 km, where most of the recent volcanoes are concentrated, which is presented to us as if we were reading an open book to which we add more and more pages in its central part and it grows with each eruption, having been built all in the last 150,000 years".
Unlike 1949, when San Juan erupted, with Teneguía in 1971 "the NO-DO came", for scientific observation, taking measurements, a film was made and the team of volcanologists led by J. M. Fúster was present for the first time.
To characterize the eruptive style of Canarian volcanism, we talk about the Teneguía model. "It also left in La Palma the idea of a "good" volcano, benefactor because it occurred at a low altitude and without many consequences". Another consequence it had was "the implementation of a geodetic and seismographic network that has been densifying, which was boosted with the eruption of Tagoro in El Hierro especially after 2011".
Alex Hansen closed the presentation with a consideration to take into account, and that is that "investment in Science is our greatest ally in situations like the current one". "Although the tremors lasted much less than on previous occasions, Civil Protection and society were alerted, so much so that the media were present in the area when the first fumarole appeared and this is due to scientific activity, to said network of seismographs and the scientists who are always watching", the speaker concluded.
His thesis addressed the Volcanology and geomorphology of the Pliocene-Pleistocene rejuvenation stage of Gran Canaria. Hansel worked for 13 years at the University School of Teacher Training of Las Palmas de Gran Canaria as a member of the Department of Geography of the University of La Laguna, moving to the Faculty of Geography of the ULPGC in 1993, joining as a professor and researcher of the Department of Art, City and Territory and later, of the Department of Geography, in the area of Physical Geography. In addition, he was a member, representing the University of Las Palmas, of the Board of Natural Spaces of Gran Canaria, of the Board of Natural Spaces of La Palma and of the Timanfaya National Park. Author of more than 70 scientific publications, he has published several geomorphological maps such as that of Gran Canaria (1990) and that of Lanzarote (1999) and is the author of eight books.
