Morphological evolution of the 2021 Tajogaite cone (Cumbre Vieja, La Palma, Spain) between January 2022 and July 2024: a quantitative UAS study

Volcanic eruptions shape the landscape. While some events may locally cause mass loss (e.g., gravitational failure, explosive excavation, or collapse following magma withdrawal), constructive processes are dominant: volcanic deposits create new land, cover the landscape, and build new cones around vents. The 2021 Tajogaite eruption (La Palma, Spain) produced a cinder cone complex that was initially 187 m taller than the pre-eruption topography (January 2022). This new volcanic edifice presented an unparalleled chance to quantitatively track its post-eruptive morphological changes. To this end, we are using seven UAS surveys with optical cameras between January 2022 and July 2024. This unique dataset allows us to constrain these changes at high temporal and spatial resolution. Over the course of our observation period the cone "shrank" by more than 11 m in height and lost almost 0.85 x 10 ⁶ m ³ of volume. The rate of these changes was highest at the beginning (6.3 cm height loss/day between January and March 2022) and then decreased exponentially. Towards the end of the observation period (August 2023 to July 2024), the average rate was 0.5 cm/day. These quantifications show that surface processes (wind, rain) accounted for only approximately 10% of the volume loss, with ca. 63 x 10 ³ m ³ redeposited at the base of the cone. We attribute most of the observed shape change of the Tajogaite cone to local endogenous processes, either in the shallow plumbing system under the cone, such as 1) decrease of magmatic pressure, bubble collapse and magma drainage, 2) volume loss due to cooling, or within the cone itself, by, e.g., 3) compaction of tephra deposits.