Origin and evolution of an inflated lava tube between the Mio-Pliocene volcanic complex of Famara and the Quaternary lava flows of La Corona in Lanzarote (Canary Islands)

The island of Lanzarote (Canary Islands) has a volcanic origin and among the volcanic landforms existing in Lanzarote, some of them are peculiar both of Earth and Mars, such as shield-volcanoes, cinder cones, tuff rings and lava tubes, making Lanzarote a good Martian analogous. In particular, the study of lava tubes has covered great importance in the space research in the last years because they represent the ideal environment to host life-forms on Mars and an important factor for the habitability not only of Mars but also of the Moon. The northern part of the island has been affected by two periods of volcanic activity: the first one, long-lasting that built up the Famara complex among the Miocene and Pliocene and the second, short-lived but intense that formed the NE-SW alignment of volcanic cones of Los Helechos – La Corona – La Quemada during the Quaternary. The Famara complex is the remnant of a shield-volcano rose up in three different stages, separated by periods of inactivity or erosional gaps. The lower unit (10.2-8.3 Ma) is made of essentially basaltic lava flows, the intermediate unit (6.7-5.3 Ma) is represented by pyroclastic deposits, both scoria cones and fallout material and the upper unit (3.8-3.9 Ma) is formed of basaltic lava flows filling in the ravines gouged out in the period of quiescence between the intermediate and the upper unit. These three units are separated from each other by soils and/or sedimentary beds formed during the gap periods between the different phases of activity but we have been able to recognize and describe other six soils interlayered among the lava flows of the third unit. The Quaternary volcanism occurred with fissure eruptions giving rise to three volcanic edifices that, with their basaltic lava flows, buried the reshaped and partially eroded massif of Famara, covering the central and eastern portions on an area of almost 50 km2. The most interesting feature of this part of Lanzarote is the presence of the 7.6 km long lava tube of La Corona and we have suggested that it has formed between the Famara complex and La Corona lava flows. These lava flows, through the inflation mechanism, have formed the lava tube by exploiting a discontinuity provided by a widespread level of dark lapilli, since it has provided a weakening zone that eased the placement of the lava tube.