Turrialba volcano (Costa Rica): activity updates and eruption news

Turrialba volcano (Costa Rica), activity update: increased fumarolic activity

Volcanic unrest at Turrialba volcano continues. Signs of an ongoing slow intrusion of magma at shallow depths indicating a possible eruption in the near-medium term future increase.
The following report sent to the volcano list by Eliecer Duarte from the volcano observatory summarizes the changes and activity at Turrialba during the past 2 months:

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Wednesday, August 8, 2007 TURRIALBA VOLCANO, COSTA RICA: enhanced fumarolic activity accompanied by fractures at the summit.

Within the recent past 2 months several changes have occurred about Turrialba´s activity. Spreading of fumaroles, fracture openings, temperature increase and acute impact of gases on vegetation are among them.

Recent observations: Wide spreading of fumaroles (Temp around 90°C) on the upper edifice correlate with enhanced levels of microseismicity (last swarm in mid July near 2000 a day). The main fumarole at the bottom of W crater reached 138°C producing a distinctive sound of high pressure valve that may be heard as far as 500m. Such fumarole is melting discrete mounts of sulphur, phenomenon never seen in more than 25 years of continuous monitoring by OVSICORIs team. Moreover, its jet spray dispersed by erratic winds is coloring most of the inner crater walls with a fine yellowish film, giving a new appearance to the dark old colors. Besides the multiple cracks associated to the expansion of the fumarolic areas around crater W, two main ones were documented recently. Such cracks (longer than 100m) departing radially from the W and NW borders of the volcano indicates a significative degree of physical instability at least on top of the summit. A wide fumarolic field between these 2 fractures along with the large number of vapor and gas spots on the outer walls of the volcano also indicates the degree of permeability in that area.
Needless to mention the effect of gases on surrounding vegetation (in a radius reaching 4km) expanding to flanks not traditionally affected due to the prevailing winds. Acute burning of important patches of natural forest is visible from several km beyond the volcano. Vegetated flanks to the NW, W and SW look yellowish to dark brown. Some of the effects are already reaching areas of commercial interest used for potato fields and dairy pasture.
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