Abstract

AGUILAR, Irene L.  and  ALVARADO, Guillermo E.. The relevant eruptions of Rincón de la Vieja in the last 6000 years based on tephrostratigraphy on his SW slope. Rev. Geol. Amér. Central [online]. 2020, n.63, pp.1-19. ISSN 0256-7024.  http://dx.doi.org/10.15517/rgac.v63i0.43403.

The Rincón de la Vieja volcano the only volcano in the Guanacaste mountain range that has historical activity and is one of the few in the World that has a hot and acid lake in its crater. The present work shows new radiometric dates from the Middle Holocene to the Upper Holocene (last 6000 years), fundamental information for volcanic hazards studies. Its prehistoric activity was significantly more violet, with Plinian, Sub-Plinian, Vulcanian and Strombolian eruptions. During its historical activity (1700-2020), Rincón de la Vieja volcano has presented freatosurtseyan and phreatomagmatic events, with tefra fall,acid rain and generation of hot lahars. The deposits 10 km away from the active crater on the SSW flank are ash and pumice (Sub-Plinian and Plinian) and piroclastic surge deposits (3650 a. C., 1130 a. C., 460 A. D., 1040 A. D., 1650 A. D.) and, within them, the Plinian Río Blanco layer (450 A. D.), was dated at a younger age than previously reported in the literature. The volume of the deposit associated with the eruption of Río Blanco (pumice fall and pyroclastic density currents deposits) has been recalculated to 1.21 km3, and the height of the eruptive column to 30 km with a VEI 5. For the last 2 ka, the periods of recurrence of large eruptive events (VEI > 4) could be about 600 years, while minor events (VEI 3) could occur before the end of this century.

Keywords : Rincon de la Vieja; Rio Blanco plinian deposit; eruptive frequency; Middle Holocene; Upper Holocene; historical eruptive activity.

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