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The only known substantial post-caldera explosive eruption occurred about 2000 years ago from satellite vents at Monta Blanca, to the east of Teide and at Pico Viejo. Both eruptions have been reconstructed and described in detail by Ablay et al. (1995). They suggest that the Monta Blanca eruption began with extrusion of ~ 0.022km3 of phonolite lava from a fissure system. The eruption then entered an explosive subplinian phase in which, over a 7-11 hour period, 0.25km3 of phonolitic lapilli grade pumice was deposited from a 15km high subplinian column, dispersed to the NE by 10m/s winds. Analyses of glass inclusions from phenocrysts show that the pumice was derived from the water-saturated roof zone of a chamber containing 3.0-4.5 wt.% H2O and abundant halogens (Fluorine c. 0.35 wt.%). Although highly evolved materials such as phonolites have been the dominant product of the youngest activity of the Teide-Pico Viejo system there have been no eruptions of phonolitic composition for at least 500 years from Teide itself and for c. 2000 years from Pico Viejo system. Ablay et al. (ibid). suggest that there may, therefore, be a large volume of highly evolved, volatile magma accumulating in these systems. An eruption of fluorine-rich magma comparable with Monta Blanca would have major damaging effects on the island.
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