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From: Eliecer Duarte G. <eduarte@xxxxxxxxx>
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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 amounts 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.
For additional information, background and images. (Spanish):
{http://www.ovsicori.una.ac.cr/vulcanologia/Volcan_Turrialba.htm";
}http://www.ovsicori.una.ac.cr/vulcanologia/Volcan_Turrialba.htm
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M.Sc. Eliecer Duarte G.
Observatorio Vulcanologico y Sismologico
de Costa Rica. OVSICORI-UNA.
fax (506) 2610303 tel (506) 5624015
email:eduarte@xxxxxxxxx
or eliduarte@xxxxxxxxxxxxxxxx
http://www.ovsicori.una.ac.cr
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