The forgotten eruption: The basaltic scoria cone of Montana Grande, Tenerife

摘要

We report on the Strombolian to Violent Strombolian eruption of Montana Grande which occurred between 789 and 725 BCE in the Guimar Valley on the NE flank of Tenerife island. The eruption produced a ca. 180 m-high scoria cone, a thick fallout deposit mostly dispersed southwest and avast lava flow field that extends east of the cone, towards the coast, for 33 x 22 km. The eruption occurred in an unusual geodynamic context, outside the North West Rift and North East Rift zones and out of Las Canadas caldera which are the main geological structures of Tenerife, where the volcanic activity concentrated during the Holocene. The tephra and lava have a trachybasalt composition similar to products of the recent activity of Tenerife but characterized by a distinct trace element pattern (Ta depletion relative to Nb), that points to a distinct source for the magma feeding the eruption and an ascent history along the whole crust which is independent and different from the central feeding system of the Teide-Pico Viejo volcanic complex. The study of this eruption, which until now had been completely neglected, adds new significant data for the correct definition of volcanic risk in Tenerife. (C) 2020 Elsevier B.V. All rights reserved.