HR: 0800h
AN: V11B-1423    [Abstracts]
TI: A Volcano Reawakens: Multiparameter Observations of Activity Transition at Galeras Volcano (Colombia)
AU: Gomez, D
EM: dgomez@ingeomin.gov.co
AF: Observatorio Vulcanol\'ogico de Pasto, INGEOMINAS Carrera 31 \# 18-07, Pasto, 00000 Colombia
AU: * Hellweg, M
EM: peggy@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, UC Berkeley 215 McCone Hall \# 4760, Berkeley, CA 94720-4760 United States
AU: Buttkus, B
AF: Bundesanstalt f\"ur Geowissenschaften und Rohstoffe (BGR), Alfred-Bentz-Haus Stilleweg 2, Hannover, D-30655 Germany
AU: B\"oker, F
AF: Bundesanstalt f\"ur Geowissenschaften und Rohstoffe (BGR), Alfred-Bentz-Haus Stilleweg 2, Hannover, D-30655 Germany
AU: Calvache, M L
AF: Instituto Colombiano de Geolog\'ia y Miner\'ia, (INGEOMINAS) Diagonal 53 \#34-53, Santa Fe de Bogot\'a, DC 00000 Colombia
AU: Cort\'es, G
AF: Observatorio Vulcanol\'ogico de Manizales, INGEOMINAS Avenida 12 de Octubre \#15-47, Manizales, 00000 Colombia
AU: Faber, E
AF: Bundesanstalt f\"ur Geowissenschaften und Rohstoffe (BGR), Alfred-Bentz-Haus Stilleweg 2, Hannover, D-30655 Germany
AU: Gil Cruz, F
AF: Observatorio Vulcanol\'ogico de Manizales, INGEOMINAS Avenida 12 de Octubre \#15-47, Manizales, 00000 Colombia
AU: Greinwald, S
AF: Bundesanstalt f\"ur Geowissenschaften und Rohstoffe (BGR), Alfred-Bentz-Haus Stilleweg 2, Hannover, D-30655 Germany
AU: Laverde, C
AF: Observatorio Vulcanol\'ogico de Pasto, INGEOMINAS Carrera 31 \# 18-07, Pasto, 00000 Colombia
AU: Narv\'aez, L
AF: Observatorio Vulcanol\'ogico de Pasto, INGEOMINAS Carrera 31 \# 18-07, Pasto, 00000 Colombia
AU: Ortega, A
AF: Observatorio Vulcanol\'ogico de Pasto, INGEOMINAS Carrera 31 \# 18-07, Pasto, 00000 Colombia
AU: Rademacher, H
AF: Geo Enterprises Orinda, 112 Southwood Dr., Orinda, CA 94563 United States
AU: Sandmann, G
AF: Bundesanstalt f\"ur Geowissenschaften und Rohstoffe (BGR), Alfred-Bentz-Haus Stilleweg 2, Hannover, D-30655 Germany
AU: Seidl, D
AF: Bundesanstalt f\"ur Geowissenschaften und Rohstoffe (BGR), Alfred-Bentz-Haus Stilleweg 2, Hannover, D-30655 Germany
AU: Silva, B
AF: Observatorio Vulcanol\'ogico de Pasto, INGEOMINAS Carrera 31 \# 18-07, Pasto, 00000 Colombia
AU: Torres, R
AF: Observatorio Vulcanol\'ogico de Pasto, INGEOMINAS Carrera 31 \# 18-07, Pasto, 00000 Colombia
AB: Following 11 years of relatively low activity, Galeras Volcano (Colombia) produced a sequence of ash eruptions in July and August, 2004. Starting in March 1996, a multiparameter real-time monitoring system was installed at Galeras, as a part of a cooperative program between INGEOMINAS (Colombia) and the BGR (Germany). Broadband seismometers were installed first, with electromagnetic (EM) sensors, sensors for the chemistry and physics of the fumarole gases and a weather station following later. The data from these instruments augment the short-period seismic network and tiltmeters of Observatorio Vulcanol\'ogico de Pasto (OVP). Additional spot measurements are made using visual inspection from the ground or helicopter, a thermal camera and regular geological forays onto Galeras' slopes. Initial evidence of the activity transition appeared in the gas measurements in early June, followed by a strong increase in the shallow seismic activity below the active cone on June 27. As in many cases at other volcanoes, the most clear evidence for the transition came in the form of seismic swarms and tremor. The current activity has culminated in two brief episodes of ash emission, on July 16 and July 21, followed by two longer episodes, July 27 - August 8, and August 11 - 19. This last episode began with a large explosion and released more ash than any individual episode from 1989 to 1993. Sudden deformation, as well as changes in the electric and magnetic fields at the crater EM station, and the gas parameters such as CO$_2$ concentration and fumarole temperature accompanied the ash emissions on July 16 and July 21. Unfortunately, the EM and gas instruments were lost to ashfall shortly afterward. As of the writing of this abstract, the ash emissions continue intermittantly.
DE: 8404 Ash deposits
DE: 8419 Eruption monitoring (7280)
DE: 8494 Instruments and techniques
DE: 8499 General or miscellaneous
DE: 7280 Volcano seismology (8419)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting