Many of the textbooks, encyclopedias and tourist guides indicate that the most recent volcanic activity in the Iberian Peninsula occurred around 13,000 years ago in the vicinity of Olot (region of La Garrotxa, Catalonia). The location is quite accurate but the calendar is far from reality, according to the results of a study whose results have been published this May in The Holocene and Scientific Reports magazines.
The main novelty of this research is the determination that the most recent volcanic activity on the peninsula occurred in the area currently known as Pla de les Preses, in Vall d'en Bas, La Garrotxa, 8,300 years ago. The double-published study was carried out by experts from IPHES-CERCA, the Rovira i Virgili University, the University of Burgos, IDAEA-CSIC, the Autonomous University of Barcelona, the University of Valencia and the University of Montpellier (France).
One of the main bases of the new study are the surveys carried out up to 14 meters deep in the Vall d'en Bas, which have made it possible to obtain "very interesting and unpublished data on the paleoclimatic and paleoenvironmental evolution of the La Garrotxa Volcanic Field (GVF, Girona) and discovered that its volcanic activity lasted until just 8,300 years ago (until now it was thought that volcanism ceased about 13,000 years ago), which constitutes the most recent volcanism in the entire Iberian Peninsula", the IPHES summarizes in a note information about the results of this project.
The most recent volcanic activity known now caused several lava flows to fill up or block the valley of the Fluvià river near Olot with materials and to form a large lake on the plain known today as Pla de les Preses.
The sediments that were deposited in this ancient lake surrounded by volcanoes, which include numerous layers of volcanic ash and lapilli (small fragments of lava), have been studied by different specialists, analyzing different sedimentary, paleoclimatic and biological indicators such as chronostratigraphy, sedimentology, pollen, ostracods (small crustaceans), lake algae, diatoms...
The research has made it possible to "reconstruct the paleoclimatic evolution of the last 13,000 years in the NE of the Iberian Peninsula, the volcanism of La Garrotxa, and the impact of these eruptions on the plant and lake ecosystems and on the Mesolithic human populations of the area", highlights the IPHES.
The sedimentary sequence of the studied borehole records local and regional signals related to the geomorphological, paleoclimatological and volcanic dynamics of the La Garrotxa volcanic field. The analyzed geological and biological indicators, aquatic organisms, pollen record, sedimentology and geochemistry report mainly local hydrological variations, which have been related to the main Holocene and late Pleistocene climate trends, including several abrupt climate changes that offer clues about the processes that could be triggered in the context of the current global warming.
The authors of the research highlight that, in the area closest to the area of volcanic activity (up to 50 km) and during volcanic eruption events, different processes (such as lava flows, deposit of volcanic materials, ash rain, emanation of gases, aerosols, pyroclastic flows and earthquakes), affected flora and fauna, as well as air and water quality, and constituted a danger to human populations.
In this sense, and based on the study of nearby archaeological sites, it can be seen that the closest hunter-gatherer populations left the area temporarily during periods of high volcanic activity, to later return in quiet times, demonstrating a high capacity for reorganization. and adaptation.
The published works show, in great detail, the paleoenvironmental evolution of the NE of the Iberian Peninsula and the socio-ecological impact of the volcanism that occurred in La Garrotxa. In addition, they show the interest in developing interdisciplinary paleoecological research, which analyzes all the processes involved in the transformations of the landscape caused by volcanism and allows a correct understanding and knowledge of its repercussions.
Scientific articles in which the results of this research are presented:
-Iriarte, E., Revelles, J., Finsinger, W., Mesquita-Joanes, F., Rodrigo, M.A., Burjachs, F., Expósito, I., Marti-Molist, J., Planagumà, Ll., Alcalde , G., Sana, M. (2023). Youngest Iberian Holocene volcanic eruptions and paleoenvironmental evolution of a barrier-paleolake in the Garrotxa Volcanic Field (NE Spain). The Holocene. https://journals.sagepub.com/doi/10.1177/09596836231169989
- Revelles, J., Marti-Molist, J., Burjachs, F., Finsinger, W., Iriarte, E., Mesquita-Joanes, F., Pla-Rabes, S., Rodrigo, M.A., Alcalde, G. , Sana, M. (2023). Socio-ecological impact of monogenetic volcanism in the La Garrotxa Volcanic Field (NE Iberia). Scientific Reports.
https://www.nature.com/articles/s41598-023-35072-0
