Measurement of the ash layer after the eruption of the Tajogaite volcano on La Palma, Canary Islands, Spain

_{written by Christopher Shatto}

In the turbulent year of 2021, the picturesque island of La Palma in the Canary Islands, Spain, witnessed a catastrophic event - the eruption of the Tajogaite volcano. Aside from the immediate chaos and devastation that volcanic eruptions cause, this natural disaster left lasting marks on both human settlements and the island's diverse ecosystems. In the aftermath, researchers set out to quantify and understand the eruption's far-reaching consequences, especially on La Palma's unique flora.

The eruption of the Tajogaite volcano, characterized by its explosiveness and lava flows, resulted in the destruction of hundreds of buildings, houses and roads. The island was inundated by 23,000,000 m3 of ash and tephra, leaving a ghostly landscape. Even today, only the tips of the treetops of the pine forest surrounding the eruption crater can be seen, while the undergrowth vegetation is hidden under meters of ash and tephra - a grim reminder of the lasting impact on the island's ecology.

La Palma is known for its great endemic diversity, hosting species that are exclusive to the island or the Canary Islands. Of particular note is the genus Erica, also known as heather, which grows remarkably tall and tree-like compared to its counterparts in other regions. Similar tendencies are observed in various plant species, with the non-native species on the island exhibiting a more woody and taller habit. This raises an intriguing question: why do these evolutionary trends occur on islands? Numerous theories attempt to unravel the mysteries behind the distinct evolutionary trends in island ecosystems. The aftermath of the Tajogait eruption provides researchers with a unique opportunity to delve into the ecological nuances of La Palma's flora and study the impact of the volcanic event on the island's biodiversity.

To fully understand the ash fall of the eruption, the researchers undertook a meticulous job - measuring the ash depth across the entire island. Dr. Frank Weiser and Dr. Anna Walentowitz played a crucial role in this and contributed significantly to creating a freely available dataset for scientific research. This task was much harder than it sounds, as digging holes can be dangerous, especially near the crater where the ash is deepest. Strict safety precautions were taken and for this reason the holes were dug to a maximum depth of 150 cm. For places that could not be measured accurately on site (i.e. too deep), we supplemented these values ​​with values ​​recorded by a lidar drone.

The team used a spatial interpolation technique called inverse distance weighting (IDW) to estimate the ash depth at locations across the rest of the island. The resulting raster image, with 2-meter pixels representing the depth of the ash layer, has an impressive accuracy of 0.34 cm. This important dataset, accessible through the Zenodo repository, has become a cornerstone for scientific studies of the impact of the Tajogait eruption on vegetation and local biodiversity, and serves as a comparison tool for volcanic events worldwide.

The consequences of the eruption of the Tajogaite volcano on La Palma go beyond the immediate destruction and invite scientists to explore the intricate relationship between geological events and evolutionary patterns in the island's ecosystems. The ash layer dataset is a testament to the researchers' collaborative efforts and provides a wealth of information for ongoing and future studies that advance our understanding of the lasting ecological impacts of volcanic eruptions.

Sources

Shatto, C., Weiser, F., Walentowitz, A., Stahlmann, R., Shrestha, S., Guerrero-Campos, M., Medina, F., Nogales, M., Jentsch, A., & Beierkuhnlein, C. (2023). Volcanic tephra deposition dataset based on interpolated field measurements following the 2021 Tajogaite Eruption on La Palma, Canary Islands, Spain. Data in Brief, 52, 109949.   https://doi.org/10.1016/j.dib.2023.109949

Weiser, F., Walentowitz, A., Baumann, E., Shatto, C., Guerrero-Campos, M., Jentsch, A., Nogales, M., Medina, F. M., & Beierkuhnlein, C. Combining in-situ monitoring and remote sensing to detect spatial patterns of volcanic sulphur impact on pine needles. Forest Ecol. Manag. 549. https://doi.org/10.1016/j.foreco.2023.121468