After a long period of subaerial fissure-fed extrusions of basaltic magmas (∼ 12 to > 3 Ma) volcanic activity was then concentrated in the central part of Tenerife. Phonolitic magma chambers formed and a central volcanic complex was constructed (the Las Canadas edifice). The formation of a large depression (the Las Canadas caldera) truncated the top of the edifice. The active twin strato-cones Teide—Pico Viejo are sited in this depression. The history of the Las Canadas caldera and edifice are established from stratigraphy, geochronology (K—Ar dates) and volcanological studies. Two different groups are recognized, separated by a major unconformity. The Lower Group is dated at 2 to 3 Ma and includes the products of several volcanic centres, which together represent several cycles. The Upper Group ranges from 1.56 to 0.17 Ma and includes three different formations representing three long-term (∼ 100 to 300 Ka) volcanic cycles. The periods of dormancy between each formation were of ∼ 120 to 250 Ka duration. The Las Canadas caldera is a multicyclic caldera which formed over the period 1.18–0.17 Ma. Each cycle of activity represented by a formation culminated in caldera collapse which affected different sectors of the Las Canadas edifice. Geological observation and geochronology support an origin by collapse into a magma chamber. The minimum volume of pyroclastic ejecta is substantially greater than the present caldera depression volume (45 km3), but approaches the inferred volume of the original caldera depression (> 140 km3). After the formation of the caldera, sector collapses could also occur at the northern flank of the volcano causing the disappearance of the northern side of the caldera wall.

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The Las Canadas Caldera corresponds to a volcanic caldera formed after a long period of explosive activity. The structural and lithological variations which can be observed in the caldera wall make clear the complexity of the original Las Canadas Edifice in which different eruptive centres existed. The stratigraphic and structural reconstruction of the Las Canadas Caldera indicates that the Diego Hernández wall, located at the eastern side of the caldera wall, comprises the youngest pre‐caldera deposits. Determination of their K‐Ar ages has provided the maximum age for the formation of the Las Canadas caldera. The results are internally consistent with stratigraphic relationships and allow two pre‐caldera volcanic cycles in the Diego Hernández wall to be differentiated in accordance with geological evidence. The first cycle shows imprecise age limits. The second cycle ranges from 0.35 to 0.17 Ma. This upper pre‐caldera age suggests that the Las Canadas caldera and the Teide‐Pico Viejo were formed more recently than was previously assumed.

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