The materials in this period may be considered the frame of the island, and represent its period of highest subaerial growth (Ancochea et al, 1993), with the highest eruptive rates of the construction of the island’s block, 0.01-0.02 km3/ka (Coello et al., 1992). The constructions in this period originated from a complex tabular sequence of basaltic lava and tephra mainly and softly heading towards the southeast and east southeast, with some outcrop of well-differentiated trachybasalt and trachytic.
Recent volcanic formations
The second subaerial period comprises the recent activity on the island during the Pleistocene Holocene. It is characterised by the generation of vast lava fields that cover the materials from the previous period and for having most of the emission centres aligned northeast southwest. This period started around 2 Ma and lasted the whole Quaternary to the present day. The eruptions during this period took place throughout the territory, affecting ancient massifs as well as the central sector of the island, although different to the materials from the first subaerial period, and following the well-defined spatial organisation guidelines, orientated northeast southwest, east northeast and west southwest.
The islets of the Chinijo Islands originated during the Pleistocene and are mainly formed by basalts and basanites generated by hydromagmatic eruptions (De la Nuez et al., 1997).
This second cycle had a generally continuous volcanic activity from the end of the Pliocene until the present day, with eruptive rates that are much lower than those during the previous period, 0.013-0.027 km3/ka. The emission of alkaline rocks that later evolved into basaltic magma, with a decrease in alkalinity ending up emitting tholeiitic olivinic basalt, mark this period of formation (Armienti et al., 1989; Carracedo and Badiola, 1993).
During the initial stages of this second subaerial cycle, the volcanic activity seemed to be limited to the interior or periphery of the two large volcanic massifs, with numerous volcanic formations in Ajaches, in Famara and the area surrounding the massif in the south and southeast near Teguise. Subsequent volcanic activity brought about the formation of less significant volcanic alignment of monogenic constructions, more or less parallel to each other and with preferential orientations northeast and east northeast (Coello et al., 1992).
During this period, there are two significant historic eruptions: the Timanfaya eruption that took place from 1730 to 1736, and the treble 1824 eruption that led to the formation of the Tao, Nuevo del Fuego and Tinguatón volcanoes (fig. 3). Both are fissured multiple events, which in Timanfaya’s case led to a complex set of eruptions resulting from multiple simple volcanic constructions throughout a largely developed longitudinal fracture; during the 1824 eruption, a linear eruptive system was put in place, with three separate eruptive formations, of very modest dimensions.