HR: 0800h
AN: V21D-0653    [Abstracts]
TI: Investigating Mount Cameroon^'s Magma Chamber System
AU: * Riley, S D
EM: xlaziox@yahoo.com
AF: Department of Geological Sciences, Arizona State University, Box 871404 , Tempe, AZ 85287-1404 United States
AU: Clarke, A
EM: amanda.clarke@asu.edu
AF: Department of Geological Sciences, Arizona State University, Box 871404 , Tempe, AZ 85287-1404 United States
AU: Watts, R
EM: rwatts@cas.usf.edu
AF: Department of Geology, University of Puerto Rico, University of Puerto Rico, Mayaguez, 00708 Puerto Rico
AU: Suh, C E
EM: chuhma@yahoo.com
AF: Department of Geology and Environmental Sciences, University of Buea, PO BOX 63, Buea, SW 0000 Cameroon
AB: Mount Cameroon, located in the middle of the Cameroon Volcanic Line (CVL) on the passive western margin of Cameroon, is one of Africa^'s most active volcanoes with seven eruptions in the past century. Many population centers are in lava flow hazard zones, making monitoring imperative. Despite its high activity level, monitoring is limited to a small network of seismometers, and only one instrument was functional immediately before the 1999 eruption. Seismic activity rose above background level only a few days prior to the eruption (Suh, et al.,2003, Bull. Volcanol., 65:267-281). In order to improve spatial coverage and potential warning time, we are designing a ground deformation monitoring network. Using existing seismic, petrologic, and historical eruption data (Ambeh,1989, PhD thesis, Leeds U., UK; Suh et al. 2003) along with corresponding models of subsurface magma storage, we apply simple elastic half-space models (Mogi, 1958; Pinel and Jaupart, 2000) to explore the nature of the volcano^'s plumbing system. We first assumed a closed-system and a 12km deep chamber (Ambeh, 1989), with sufficient overpressure to initiate the 1999 eruption. Given the total erupted volume of 8 x 10⁸ m³ and the required pressure, the chamber must be ~1.2 km in diameter. Overpressure in this chamber immediately prior to eruption causes maximum surface tilt of ~0.3 microradians at 6km from the center. This small amount of deformation is not detectable by surface mounted tiltmeters, however it is detectable by borehole strainmeters. Following conduit initiation, at an average extrusion rate of 40m³ s^-1 recorded for the 1999 eruption (Suh et al., 2003) and assuming a 10m radius conduit, magma would erupt roughly one full day after conduit initiation. However, if the system fills a shallow chamber at ~3km depth prior to eruption, as is the case in Hawaiian volcanoes (Dvorak & Okamura, 1987), then maximum surface tilt of ~17 microradians occurs at 1.5km from the center, making eruption prediction with tiltmeters feasible. At a 40m³ s^-1 chamber filling rate, the shallow chamber would take nearly a month to reach an eruptible pressure, providing two weeks of warning with tiltmeters.
DE: 8419 Volcano monitoring (7280)
DE: 8425 Effusive volcanism
DE: 8488 Volcanic hazards and risks
DE: 8494 Instruments and techniques
DE: 9305 Africa
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005