On 19 September 2021, a new monogenetic volcano (Tajogaite) erupted on the island of La Palma (Canary Islands, Spain). After 86 days of strombolian eruption, with emissions of volcanic material, a pyroclastic cone 200 m high and 800 m in diameter was formed. Successive lava flows descended the western slopes and reached the sea on 29 September. On descending the coastal cliffs and entering the sea, the lava flows formed two lava deltas of 75 and 5 ha, on the submarine island shelf, backed by fossilized coastal cliffs. This work presents an approach, using comparative and numerical methods, to estimate the geoheritage value and support the conservation of a new volcanic landscape in an island territory with high anthropic pressure on land uses. In a first phase, a cartographic inventory was made of all the volcanic formations similar to the new volcano in the geological domain of the Canary Islands. In a second phase, their representativeness (A), rarity (R), diversity (D), integrity (I) and observability (O) was quantitatively measured by means of dimensional estimators. The results obtained show that the new volcano presents a geological value of the first order in the context of the Canary Islands, which is one of the most prominent hot-spot archipelago worldwide. Its value is based above all on its high conservation state with respect to the similar volcanoes in the Canary Islands. The high mismatch found between the intrinsic geological value and the environmental protection of this area, justifies the development and application of urgent basic guidelines for its protection, as well as the promotion of geotourism as opposed to alternative land uses.

Historical volcanic eruptions in Canary Islands have traditionally been considered as quiet eruptions, mostly effusive and with scant explosions (VEI 1-2), attending to the general characteristics of this volcanism. Nevertheless, the geological record of these eruptions shows abundant signs of moderately explosive activity with PDC desposits and bombs and blocks of considerable size outcropping in the islands. Scientific studies of Canarian historical volcanism have been focused on the analysis of the volcanic processes and the assessment of related hazards, paying special attention to the monitoring of volcanic activity in the last few years. However, there is hardly any data of their effects on the population, like number of victims, affected people, displaced, emigrated, damage to the crops, lands, animals, etc. In general, there is also no accurate information on the actions of authorities or on the crises management. The knowledge of the impacts caused by volcanic eruptions provides very significant information to be prepared for future eruptions, and can be found in documentary sources, both handwritten and printed and graphic, in official or private documentation. The analysis of these historical chronicles has shed light on these aspects not previously considered neither by the authorities nor the scientist or general public. The results of this research examining the historical chronicles shows that, contrary to what is generally believed, historical eruptions in Canary Islands did cause several impacts both on the population (dead, injured or missing, displaced and evacuated), and on the economy (damage to crops, livestock, buildings, roads and various infrastructures). The historical documents also highlight that there was indeed crisis management, both from the political and scientific authorities in most of the eruptions. From all these we can conclude that no social interpretation has been made about the legacy of historical eruptions in Canary Islands nor about the impact they had. We should implement this knowledge in the prevention and emergency plans made by the authorities for a better management of future eruptions, considering the population increase in the Canary Islands from ca. 360000 inhabitants in 1900 up to ca. 2.13 millions in 2018, plus some millions of tourists (15.5 in 2018).

Canary Islands constitute an active volcanic archipelago. From the time immediately before the Castilian conquest of the islands, 17 volcanic eruptions have occurred: 2 prehispanic and 15 historical, some of them with multiple eruptive vents, affecting the islands of Lanzarote, Tenerife, La Palma and El Hierro. In order to carry out the inventory of geosites for the Canary Islands at a regional scale, it has been applied a methodology consisting of two sequential phases: the first one address the selection of geosites that will be part of the inventory, and the second one deals with the characterization and assessment of the selected geosites. In this methodology, geosites are selected within geological frameworks previously established given their regional significance for Canary Islands. With this aim, 12 geological frameworks representative of the geodiversity of Canary Islands have been identified, which include the essential elements, processes and morphologies of the Canarian geology, covering all stages of construction of the islands as well their geological evolution, including processes, morphologies, fossils and deposits associated both to the volcanism and the external geological agents. The selection of geosites is then constrained and facilitated by its representativeness within each geological framework. One of these 12 geological frameworks corresponds to “Historical and prehistorical volcanism”. The scarce number of volcanic eruptions, their low frequency and their general characteristics –fissure mafic eruptions, low VEI and strombolian eruptive styles- determine an apparent geological homogeneity. Nevertheless, the high variety of processes, morphologies and deposits associated to this framework, their good conservation status, as well as the information from the historical chronicles, have permitted to identify 19 geosites of high scientific value. They highlight the existence of eruptive styles ranging from hawaian to vulcanian, with short phases of water-magma contact, quiet emissions of water or in geysers, phreatomagmatic explosions, etc. These geosites constitute a unique and representative record of the volcanology, geomorphology, tectonics and petrology characterizing the most recent mafic volcanism of the Canarian archipelago.