TY - JOUR
T1 - 14C ages and activity for the past 50 ka at Volcán Galeras, Colombia
AU - Banks, N. G.
AU - Calvache V., M. L.
AU - Williams, Stanley
N1 - Funding Information:
Our studies were a cooperative,m ultinational effort augmentedb y the observations and experience of Alicia Sandvinetti (Argentina); Eduardo Soria (Bolivia); Pablo Acevedo, Jorge Ardila, Arturo Al-varado, Hector Cepeda, Gloria Hincapie, Manuel Moreno, Jose Daniel Pabon, and Bernard0 Pulgarin (Colombia); Minard Hall, Patti Mothes, Juan Figueroa, and Eduardo Fernando (Ecuador); Isabel Leon and Guido Salas (Peru); and Richard Janda and Barry Voight (USA). Jose Daniel Pabon compiled the referencedm eteorologicald ata. Our successw as due in part to support by a number of Colombian agenciesi ncluding COLCIENCIAS, INGEOMINAS, and to the city of Pasto and state of Nariilo (Colombia). Support also came from the parental agencies and countries of the participantsa s well as from UNESCO (United Nations), Arizona State University, Louisiana StateU niversity, the National Science Foundation, the Geological Society of America, the U.S. Geological Survey and U.S. Department of State’s Office of Foreign Disaster Assistance. Helpful reviews were provided by Jamie N. Gardner, Richard B. Moore, Donald Swanson, and an anonymous reviewer.
PY - 1997/5
Y1 - 1997/5
N2 - Volcán Galeras is the southernmost Colombian volcano with well-recorded historic activity. The volcano is part of a large and complex volcanic center upon which 400,000 people live. Historic activity has centered on a small-volume cone inside the youngest of several large amphitheaters that breach the west flank of the volcano, away from the city of Pasto (population 300,000). Lava flows (SiO2 between 54.6 and 64.7 wt.%) have dominated activity for more than 1 Ma, but explosive events have also occurred. Joint studies by volcanologists from Colombia, Ecuador, Peru, Bolivia, Argentina, and the United States produced 24 new 14C ages and more than 100 stratigraphic sections to interpret the past 50 ka of activity at Galeras, including sector collapse events. The youngest collapse event truncated 12.8 ka lava flows and may have occurred as recently as 8 to 10 ka. Tephra-fall material rapidly thins and becomes finer away from the vent area. The only widespread marker in the < 10 ka section is a biotite-bearing tephra deposited between 4.1 and 4.5 ka from a source south of Galeras. It separates cryoturbated from largely undisturbed layers on Galeras, and thus dates a stratigraphic horizon which is useful in the interpretation of other volcanoes and geotectonics in the equatorial Andes. Pyroclastic flows during the past 50 ka have been small to moderate in volume, but they have left numerous thin deposits on the north and east flanks where lava flows have been impeded by crater and amphitheater walls. Many of the pyroclastic-flow deposits are lithic rich, with fines and clasts so strongly altered by hydrothermal action before eruption that they, as well as the sector collapse deposits, resemble waste dumps of leached cappings from disseminated sulfide deposits more than volcanogenic deposits. This evidence of a long-lived hydrothermal system indicates susceptibility to mass failure and explosive events higher than expected for a volcano built largely by lava flows and modest Vulcanian eruptions. Photographs, written accounts, and our study document historic north and east flank pyroclastic flows as far as 10 km from the summit; however, none have left recognizable deposits in Pasto for more than 40 ka.
AB - Volcán Galeras is the southernmost Colombian volcano with well-recorded historic activity. The volcano is part of a large and complex volcanic center upon which 400,000 people live. Historic activity has centered on a small-volume cone inside the youngest of several large amphitheaters that breach the west flank of the volcano, away from the city of Pasto (population 300,000). Lava flows (SiO2 between 54.6 and 64.7 wt.%) have dominated activity for more than 1 Ma, but explosive events have also occurred. Joint studies by volcanologists from Colombia, Ecuador, Peru, Bolivia, Argentina, and the United States produced 24 new 14C ages and more than 100 stratigraphic sections to interpret the past 50 ka of activity at Galeras, including sector collapse events. The youngest collapse event truncated 12.8 ka lava flows and may have occurred as recently as 8 to 10 ka. Tephra-fall material rapidly thins and becomes finer away from the vent area. The only widespread marker in the < 10 ka section is a biotite-bearing tephra deposited between 4.1 and 4.5 ka from a source south of Galeras. It separates cryoturbated from largely undisturbed layers on Galeras, and thus dates a stratigraphic horizon which is useful in the interpretation of other volcanoes and geotectonics in the equatorial Andes. Pyroclastic flows during the past 50 ka have been small to moderate in volume, but they have left numerous thin deposits on the north and east flanks where lava flows have been impeded by crater and amphitheater walls. Many of the pyroclastic-flow deposits are lithic rich, with fines and clasts so strongly altered by hydrothermal action before eruption that they, as well as the sector collapse deposits, resemble waste dumps of leached cappings from disseminated sulfide deposits more than volcanogenic deposits. This evidence of a long-lived hydrothermal system indicates susceptibility to mass failure and explosive events higher than expected for a volcano built largely by lava flows and modest Vulcanian eruptions. Photographs, written accounts, and our study document historic north and east flank pyroclastic flows as far as 10 km from the summit; however, none have left recognizable deposits in Pasto for more than 40 ka.
KW - C age
KW - Colombia
KW - Eruption
KW - Galeras Volcano
KW - Pyroclastic flow
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U2 - 10.1016/S0377-0273(96)00085-6
DO - 10.1016/S0377-0273(96)00085-6
M3 - Article
AN - SCOPUS:0030796545
SN - 0377-0273
VL - 77
SP - 39
EP - 55
JO - Journal of Volcanology and Geothermal Research
JF - Journal of Volcanology and Geothermal Research
IS - 1-4
ER -