Tenerife, a complex end member of basaltic oceanic island volcanoes, with explosive polygenetic phonolitic calderas, and phonolitic-basaltic stratovolcanoes

Tenerife, one of the active oceanic island volcanoes in the Canary Islands, located in the eastern Atlantic Ocean off northwest Africa, is the second largest intraplate oceanic island volcanic system after Hawai'i but is more complex and represents a different and more evolved end-member to Hawai'i in the spectrum of oceanic island volcanic systems. Tenerife began life as a mafic oceanic shield volcano at ~12 Ma, erupting (picro)basalt, basanite, hawaiite, mugearite, benmoreite series lavas of the Older Basaltic Series. These were derived from a spatially variable mantle plume source with varying degrees of magma-lithosphere interaction and fractional crystallisation. At ~3.05 Ma an evolved phonolitic magma system began to develop under the centre of the island. That led to the building of an initial summit effusive and explosive stratovolcano system (the Las Cañadas edifice) represented by the poorly understood Lower Group, followed by development of 3 cycles of explosive phonolitic caldera forming activity (Ucanca, Guajara, Diego Hernández) of the Upper Group, from ~1.66 Ma to ~0.175 Ma, each cycle separated by ~180 kyr (the recharge interval?). Phonolite genesis is complex, involving fractional crystallisation, partial melting of island crust including syenitic plutons, and recycling of crystal mushes. Three coalesced explosive calderas are preserved at the summit of Tenerife, constituting the Las Cañadas Caldera Complex. Since ~0.175 Ma two stratovolcanoes (Teide, Pico Viejo) have been growing along the northern rim of the caldera complex, becoming more phonolitic from basaltic beginnings and more explosive, perhaps heralding the beginning of a new explosive cycle. Simultaneously shield building basaltic volcanism has continued on the flanks to historic times through multiple monogenetic eruptions along the linear northwestern and northeastern rift zones, and a more diffuse southern volcanic zone. Volcanic eruption styles have included fissure fed basaltic shield sheet lava eruptions, monogenetic basaltic cone lava and scoria eruptions, highly explosive plinian phonolitic pumice and ash fallout, and pyroclastic flow forming eruptions. The volumes of the largest explosive eruptions likely caused a component of magma chamber roof block subsidence, with multiple, spaced eruptions during each caldera forming cycle producing incremental caldera collapse and polygenetic calderas. Major landslides coincide with some of the large explosive eruptions, raising the question of cause and effect.