A new scientific study reveals more recent volcanic activity, dating back 20,000 years, in the volcanic area of La Garrotxa

CST
Jan 21
4 min read

Schematic Summary of the Temporal Evolution of Eruptive Activity in the La Garrotxa Volcanic Field Integrating new and previous ages, locations ordered from most recent to oldest

(Martí et al., 2025)

Researchers Dr. Llorenç Planagumà (Geonat SL and CST) and Dr. Joan Martí Molist (IDAEA-CSIC) have been part of a research1 team tasked with reviewing the stratigraphy2 and ages of eruptions in the volcanic field of La Garrotxa (Martí et al., 2025). In January 2025, their findings were accepted for publication as a scientific article in Quaternary Science Advances. Both Dr. Planagumà and Dr. Martí are part of the GarMultiRisk project at CST, and their new results provide valuable information for analyzing the hazards associated with volcanic activity in La Garrotxa.

The study was conducted using 14 samples from different volcanic cones and lava flows. These samples yielded unprecedented data, allowing researchers to refine the eruption ages previously available, thanks to more advanced technology. The most surprising findings include:

The lava flow from Molí Fondo in Sant Joan les Fonts, corresponding to the area's first eruption, was dated to 248,000 years ago.
Montsacopa volcano (Olot) erupted just 20,000 years ago.
The lava flow at La Moixina (Olot) dates back 26,000 years.
The Croscat volcano (Santa Pau) erupted between 13,000 and 15,000 years ago.
The lava flow at Bosc de Tosca was emplaced 17,000 years ago.

The dating technique used was radiometric analysis, which determines the exact age of rocks by analyzing their chemical elements, such as the ratio of isotopes 40Argon/36Argon present in the rock. The analyses were performed at the Geochronology Research Laboratory at New Mexico Tech University (Socorro, USA), which has extensive experience in radiometric dating of young basaltic volcanic rocks.

The investigation concludes that obtaining this data represents a significant improvement in understanding the volcanic field of La Garrotxa. It provides new information on the stratigraphy of the volcanic units in the area and shows that eruptions were more frequent and more recent than previously believed.

The study also argues that the shape and conservation state of volcanoes are not definitive indicators for determining their relative age, as urbanization and other erosion factors may have altered them, leading to potential errors.

This research represents the second phase of a broader study on the ages and evolution of volcanism in the region. The first phase focused on data collection from volcanic ash in the ancient lake (paleolake) that once occupied the Vall d'en Bas. The results were published in the scientific journals Scientific Reports-Nature and The Holocene (Iriarte et al., 2023; Revelles et al., 2023).

A third phase, currently underway, will include new datings to complete the evolutionary framework of volcanic activity and eruption frequency in the La Garrotxa volcanic field. The ultimate goal is to establish a precise model of the functioning and associated risks of this type of volcanic zones, which are the most abundant on our planet.

Finally, the study highlights the need for more detailed geological and geochronological research to better understand these volcanic fields and, consequently, the European Rift System. This geological structure stretches across parts of Europe and consists of cracks and fractures in the Earth's crust, including the La Garrotxa volcanoes. Given the Rift System's relative youth and its current manifestations of activity (earthquakes, fumaroles, etc.), it should be monitored more effectively to address future challenges in mitigating volcanic risks.

Studying volcanic activity in La Garrotxa not only advances basic science but also provides useful data for multi-hazard assessment projects in the region, such as the GarMultiRisk project. Although volcanoes fall outside the 123-year temporal period considered in the project for collecting data on natural hazards in the area, they remain an important factor to consider as a natural risk element. For more information, we encourage you to read the interview with Arnau Lagresa, where the creation of the project’s database is explained in greater detail.

If you have any questions or would like to know more about the project or the study, please do not hesitate to contact us directly at centresostenibilitat@gmail.com or reach out to the principal investigators (Dr. Llorenç Planagumà: llplanaguma@gmail.com; Dr. Joan Martí Molist: joanmartimolist@gmail.com).

References:

Martí, J., Ricci, J., Planagumà, L., & Aguirre Díaz, G. J. (2025). The Quaternary La Garrotxa Volcanic Field (NE of Iberia): A geochronological approach. Quaternary Science Advances, 100267. https://doi.org/10.1016/j.qsa.2025.100267

Iriarte, E., Revelles, J., Finsinger, W., Mesquita-Joanes, F., Rodrigo, M.A., Burjachs, F., Expósito, I., Martí-Molist, J., Planagumà, Ll., Alcalde, G., Saña, M. (2023). Youngest Iberian Holocene volcanic eruptions and paleoenvironmental evolution of a barrier-paleolake in the Garrotxa Volcanic Field (NE Spain). Holocene, 33(8), 939-959. https://doi.org/10.1177/09596836231169989

Revelles, J., Martí-Molist, J., Burjachs, F., Finsinger, W., Iriarte, E., Mesquita-Joanes, F., Pla-Rabes, S., Rodrigo, M.A., Alcalde, G., Saña, M. (2023). Socioecological impact of monogenetic volcanism in the La Garrotxa Volcanic Field (NE Iberia). Scientific Reports, 13, Article 8168. https://doi.org/10.1038/s41598-023-35072-0

Authorship of the text:

Llorenç Planagumà Guàrdia, with review by Joan Martí Molist and Iris Schneider Pérez.

1 New Mexico Tech University (USA) and Universidad Nacional Autónoma de México (Mexico).

2 Stratigraphy: A field of geology that studies rock layers to understand how they formed and in what order over time.

These datings have been made possible, in part, thanks to the funding received from the GarMultiRisk project, which is supported by the Fundación Biodiversidad of the Ministry for Ecological Transition and Demographic Challenge, through the Call for Grants for the Implementation of Projects Contributing to the National Plan for Adaptation to Climate Change (2021-2030).

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