Evolution of the eruption of the Ubinas Volcano (Peru) 2006

Abstract

[Abstract] The gases emanations of Ubinas volcano (16º 22' S, 70º 54' O; 5672 altitude. ), was increased lightly during July of 2005, after these was almost void since 2001. The emitted gases came up to 200 - 300 m of height during the month of December of the same year, in March 27 2006 was produced the first emissions of ashes, that came up to 4 km of distance. Since April 12 starting to produce small explosions and in April 19 was caught sight of for the first time a lava body in the bottom of the volcano’s crater, that had approximately 60 m of diameter. The later activity of the volcano was characterized for occasional explosions as well as for moderated emissions of ashes. T he ballistic projections constituted by young and accidental lavas emitted during the activity, came up to 1,8 km of the crater, and the columns of gases and ashes reached up to 2,5 - 3,5 km of height above the volcano boiler and the ash falls affected mainly a ratio of 12 km around the volcano. The ashes emitted during the first weeks contain a high percentage of hydrothermal components and fragmented crystals of plagioclase, pyronenes and Fe Ti oxides however the ashes emittedsince the end of April contain mainly young components (magmatics). This suggests an initial activity purely phreatic and later magmátic (vulcanian). The Ballistic projecctions are glassy and schorl, they have a andesitic composition (55 to 57 % of SiO2 ), it contain phenocrytals of plagioclase (some zoning), clynopyroxene, ortopyroxene, olivine, black mica and oxides. The greater volcanic activity got registered during the months of April, May, June, July and August. It diminished drastically as from of September. The emitted ashes have 1,5 cm of thickness to 4 km of the crater, 0,5 to 0, 8 cm of thickness to 7 km of the crater and less than 0, 1 cm to 16 km of the crater. It is estimated that the eruption had a Volcanic Explosivity Index (VEI) between 1 and 2. --- [Resumen] Se describe la evolución de las emanaciones de gases del Volcán Ubinas (16 º 22 'S, 70 º 54' O;. 5672 de altitud) de Julio de 2005, ubicado al sur del Perú. Se explican las pequeñas explosiones del 19 de Abril de 2006 con la presencia de lava en el fondo del cráter del volcán y emisiones de cenizas. Esto sugiere una primera actividad puramente freática y posteriormente magmática.