HR: 1340h
AN: V53B-1551    [Abstracts]
TI: Holocene Eruptions of Machin Volcano: Stratigraphy and Eruptive Dynamics
AU: * Rueda, H
EM: hrueda@geofisica.unam.mx
AF: Instituto de Geofisica - Dpto de Vulcanologia, Ciudad Universitaria-Unam Coyoacan, Mexico, DF 04510 Mexico
AU: Macias, J
EM: macias@geofisica.unam.mx
AF: Instituto de Geofisica - Dpto de Vulcanologia, Ciudad Universitaria-Unam Coyoacan, Mexico, DF 04510 Mexico
AU: Siebe, C
EM: csiebe@geofisica.unam.mx
AF: Instituto de Geofisica - Dpto de Vulcanologia, Ciudad Universitaria-Unam Coyoacan, Mexico, DF 04510 Mexico
AU: Cepeda, H
EM: mapuchito@yahoo.com
AF: INGEOMINAS, Cede Central -Bogota, Bogota, Cun 90122 Colombia
AU: Mendez, R
EM: rmendez@ingeomin.gov.co
AF: INGEOMINAS, Observatorio Vulcanologico y Sismologico- UOP -Manizales, Manizales, Cds 58 Colombia
AU: Cortes, G
EM: gpcortes@ingeomin.gov.co
AF: INGEOMINAS, Observatorio Vulcanologico y Sismologico- UOP -Manizales, Manizales, Cds 58 Colombia
AB: Cerro Machin (2,750 m a.s.l.) is a Quaternary dacitic volcano located in the Central Cordillera of the Andes in Colombia. It is a 2.4-km wide tuff ring that hosts three domes with fumarolic activity. The volcano's origin is linked to the development of a pull apart basin bounded by the Machin and Cajamarca faults. Detailed stratigraphy and radiocarbon dating indicate that six eruptions have taken place during the Holocene. Each eruptive event established a Plinian column that deposited pumice fall deposits followed by the collapse of the column ensuing pumiceous pyroclastic flows, surges and secondary lahars. These eruptive events are dubbed and dated (average age) as the Espartillal (5000 yr.), P0 (4600 yr.), P1 (3600 yr.), Guaico (2600 yr.), P2 (1200 yr.), and Anillo (900 yr.). The pyroclastic fall deposits have dispersal axes to the NW, they are exposed up to 60 km from the crater and cover a total approximated area of 2000 km2 and have a total volume of 4.9 km3. Calculated column heights oscillate between 19 and 32 km. The collapse of these columns generated pyroclastic flow deposits that traveled up to 15 km around the volcano infilling the Coello valley. Some pyroclastic flows were able to surmmount 200-m high topographic barriers. Remobilization by water of this unconsolidated material generated lahars that followed the Coello and Magdalena Rivers and traveled up to 115 km from the volcano covering and area of 1000 km2. The deposits of all these eruptions have affected large areas where the modern important cities of Colombia are now located, as well as routes of great economic importance. Although the volcano is in a quiescent state it must be closely monitored since it has produced cataclysmic eruptions ca. every 1000 yrs.
DE: 8428 Explosive volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005