ERT characterisation of la calderilla volcanic caldera (Gran Canaria Island, Spain)

Abstract

Maar are a singular type of volcanic structure generated by explosive phreatomagmatic eruptions as a result of interaction between rising magma and groundwater. This kind of structures are characterised by circular craters, often filled with water and/or lacustrine sediments and surrounded by a ring of pyroclastic deposits. The whole of the volcano, including the pyroclastic ring surrounding the crater maar is called maar-diatreme. Recently borehole was drilled at the bottom of the volcanic crater which penetrated about 8.7 m in its sedimentary sequence and the paleobotanical study has supplied the first evidence of paleoenvironmental evolution during the Holocene on the Gran Canaria Island. The possibility of its sedimentary fill extends beyond of the Holocene is extremely attractive, since, for example, and there are few paleoenvironmental data regarding how much the last glaciation that affected the Canary Islands. In these circumstances, the knowledge of the total thickness of the lacustrine sediments is crucial to design a deeper borehole in the next future. Therefore, the subsurface characterisation provided by geophysics is essential for determining thickness and geometry of the sedimentary filling.