******************************************************** From: Eliecer Duarte <eduarte@xxxxxxxxx> ******************************************************** Observatorio Vulcanológico y Sismológico de Costa Rica. OVSICORI-UNA Turrialba Volcano: Tall gas and vapor columns correlate with acute external changes. (Fieldwork report, December 05, 2007) An early alert was raised by media and neighbours of Turrialba volcano at early hours of December 5th, 2007. A tall column ( taller than 2kms above the summit) was observed from different areas in the Central Valley (Fig 1). Despite several reports about the dark color of such column, it was determined that this was due to an optical effect given the sunlight and the position of observers. Color was white typical of an impulsive discharge of gases and vapor. A team from OVSICORI-UNA conveyed to the area to confirm several facts. Neighbours were preoccupied due to the vigorosity and height of the plume. Nonetheless there was no ash or dust involved in the incident. An abnormal output of gas along the south outer wall of the volcano was confirmed. Several well defined fumaroles, located on the outer south wall, grow above the summit rim provoking an acute effect on the perception of park rangers, settlers and visitors (Fig 5). Areas burned by acute acidification have extended in the last month. (Fig 2). Sectors towards the south and southeast show deep impact on pasture, native and exotic trees. Birch patches along most drainages have been completely defoliated. The yellowish appearance of pasture land increases as the areas get closer to the upper areas (Fig 4). Towards the southwest, effects on native vegetation, pasture, and potato fields have extended dramatically to lowerlands.(Fig 3). A rapid inspection of changes intra caldera gives some elements that correlate with the tall columns observed. Temperature of some fumaroles inside crater W have reached 280ºC, some of them make a sharp noise of high pressure valve. Melting native sulphur is still an undergoing process. Finally, toward the east of the caldera the decaying impact of acidification is evident (Fig 6). Here most species have died due to rapid burning occurring, even under rainy conditions. It is to be expected greater effects in the coming months due to the strengthening of trade winds and reduction of rain. Details and photos can be found at: http://www.ovsicori.una.ac.cr/pdf/2007/FieldreportTurri51207.pdf or http://www.ovsicori.una.ac.cr/vulcanologia/Volcan_Turrialba.htm# Report and fieldwork: E. Duarte, E. Fernández, A. Tellez y Francois Robichaud. (OVSICORI-UNA). ============================================================== To unsubscribe from the volcano list, send the message: signoff volcano to: listserv@xxxxxxx, or write to: volcano-request@xxxxxxxx To contribute to the volcano list, send your message to: volcano@xxxxxxxx Please do not send attachments. ==============================================================
