Evaluation of the slopes stability in the lava field of the 2021 Tajogaite eruption (La Palma, Canary Islands) in order to recover the territory for the development of new infrastructures

The Tajogaite volcanic eruption took place at the west side of La Palma (Canary Archipelago) from september 19 to december 13 of 2021. Around 200 million cubic meters of lava emitted by the volcano ended up burying an area of 12.2 km2, destroying around 1,700 buildings and causing the displacement of roughly 7,000 people. In order to promote the recovery of the affected territory, the regional authorities commissioned to the Volcanological Institute of the Canary Islands (INVOLCAN), a report consisting on a Evaluation of the slopes stability in the new lava field and nearby areas which is summarized in this work. The results were applied to a three selected areas called reconstruction sectors with the following names: 1) La Laguna, 2) La Asomada and 3) Las Norias-La Majada. These sectors were divided into 250 x 250 m grids on which a susceptibility estimation was carried out.

The field reconnaissance and aerial photography, allowed the identification of a series of surfaces and slopes within those sectors whose stability was valued based on the Slope Susceptibility Index in Volcanic Terrains (ISTV). The stability was scaled into four main categories according to the ISTV value: very high (ISTV ≥80); high (ISTV 60-79); moderate (ISTV 35-59) and low (ISTV <35).

In La Laguna sector, of four study points, two of them were classified as moderate, one as low and another one as high. In La Asomada sector, only one study point could have been evaluated as high and finally, in Las Norias-La Majada sector, of twelve study points, eight of them were classified as moderate, two as low, one as high and another one as very high, being the moderate ISTV the most dominant in this sector.