Measuring the Ash Layer after the Eruption of the Tajogaite Volcano

January 2024
5 min

Measuring the Ash Layer after the Eruption of the Tajogaite Volcano on La Palma, Canary Islands, Spain

written by Christopher Shatto

In the tumultuous year of 2021, the picturesque island of La Palma in the Canary Islands, Spain, witnessed a catastrophic event—the eruption of the Tajogaite Volcano. Beyond the immediate chaos and devastation caused by volcanic eruptions, this natural disaster left a lasting imprint on both human settlements and the island's diverse ecosystems. In the aftermath, researchers embark on a mission to quantify and understand the far-reaching consequences of the eruption, particularly on the unique flora of La Palma.

The eruption of Tajogaite Volcano, characterized by its explosivity and lava flows, resulted in the destruction of hundreds of buildings, houses, and roads. The island was submerged under a staggering 23,000,000 m3 of ash and tephra, leaving a haunting landscape in its wake. Even today, the pine forest surrounding the eruption crater reveals only the tips of tree canopies, with the understory vegetation concealed beneath meters of ash and tephra—a somber reminder of the enduring impact on the island's ecology.

Figure 1. Photo of the ash fallout blanketing the island, submerging large portions of the Canary pine forest in the process. In some areas, only the tree canopies are visible while the remaining trees were exposed to sulfur dioxide emissions during the eruption, which explains the intense browning of the pine trees. Photo taken by Dr. Frank Weiser.

La Palma, renowned for its great endemic diversity, harbors species found exclusively on the island or within the Canary Islands. Notable among them is the genera Erica, known as heath or heather, which grows remarkably taller and tree-like compared to its counterparts in other regions. Similar trends are observed in various plant varieties, with non-native species displaying a woodier and taller stature on the island. The intriguing question arises: Why do these evolutionary trends manifest on islands? Numerous theories attempt to unravel the mysteries behind the distinctive evolutionary trends observed in island ecosystems. The aftermath of the Tajogaite eruption offers a unique opportunity for researchers to delve into the ecological nuances of La Palma's flora and investigate the impact of the volcanic event on the island's biodiversity.

Figure 2. Dr. Frank Weiser seen digging a hole (left) to measure the depth of the ash layer near the crater (right). Permits were required to access the hazardous vicinity of the crater since the land surface is unpredictable and the sulfur dioxide emissions are toxic to breathe. In addition, holes were only dug to a maximum of 150 cm for safety precautions. The ash layer in this area was too deep to measure accurately through digging. Photos taken by Dr. Anna Walentowitz and Dr. Frank Weiser.

To comprehensively understand the ash fallout from the eruption, researchers undertook a meticulous task—measuring ash depth across the entire island. Dr. Frank Weiser and Dr. Anna Walentowitz played pivotal roles in this endeavor, contributing significantly to the creation of a freely available dataset for scientific research. This task was much harder than it sounds since digging holes can be dangerous, especially in proximity of the crater where ash is the deepest. Stringent safety precautions were untaken and for that reason holes were dug to a maximum of 150 cm. For locations that could not be measured accurately in the field (i.e., too deep), we supplemented those values for values recorded by a lidar-based drone.

Figure 3. Resulting product from the spatial interpolation of field- and drone-based measurements. The location of La Palma within the Canary Islands and in relation to continental Europe can be seen in Box A, the distribution of the ash measurements used in the spatial interpolation in Box B, and finally, the visualization of the ash layer in Box C. Figures can be viewed in the publication by Shatto et al. 2023.

The team utilized a spatial interpolation technique called Inverse Distance Weighting (IDW) to estimate ash depth at locations across the rest of the island. The resulting raster image, with 2-meter pixels representing ash layer depth, boasts an impressive accuracy of 0.34 cm. This invaluable dataset, accessible from the Zenodo repository, has become a cornerstone for scientific investigations into the Tajogaite eruption's repercussions on vegetation, local biodiversity, and serves as a comparative tool for volcanic events globally.

The aftermath of the Tajogaite Volcano eruption on La Palma transcends the immediate destruction, inviting scientists to explore the intricate relationship between geological events and evolutionary patterns in island ecosystems. The ash layer dataset stands as a testament to the collaborative efforts of researchers and offers a wealth of information for ongoing and future studies, furthering our understanding of the enduring ecological impact of volcanic eruptions.


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.

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.

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