HR: 1330h
AN: V23A-07    [Abstracts]
TI: A Ground Deformation Monitoring Approach to Understanding Magma Chamber Systems and Eruptive Cycles of Mount Cameroon
AU: * Riley, S
EM: sdriley@asu.edu
AF: Arizona State University, Department of Geological Sciences, Tempe, AZ 85287 United States
AU: Clarke, A
AF: Arizona State University, Department of Geological Sciences, Tempe, AZ 85287 United States
AB: Mount Cameroon is a 13,400ft basanite volcano on the passive margin of West Africa. It has erupted seven times in the past century making it one of the most active volcanoes in Africa. Most recently Mount Cameroon erupted in 1999 and 2000 first issuing strombolian explosions from vents near the summit, and later erupting effusively from a fissure running southwest from the summit (Suh et al., 2003). Prior to 2004, the only monitoring equipment on Mount Cameroon was a small seismometer network installed following the 1982 eruption. By 1999 only a single seismometer in the network was functional. Seismic activity did not rise above background levels until the few days immediately preceding the eruption. In an effort to raise awareness of the volcano's condition and provide a more efficient warning of impending eruptions we have begun constructing a ground deformation network on Mount Cameroon. The new network currently consists of two Applied Geomechanics 711-2A(4X) biaxial tiltmeters capable of resolving 0.1 microradians of tilt. One station is located approximately 500 m from the 2000 summit vent, and the other is approximately 1km away from the central fissure approximately 5km southwest of the 2000 summit vent. Three primary processes could precede eruptions at Mt. Cameroon, offering the opportunity for detection and prediction by our network. These processes are magma chamber pressurization, magma ascent via a central conduit, and/or propagation of magma along the central fissure. Magma chamber location, if a significant chamber exists, is poorly constrained, however, previous petrologic studies on Mount Cameroon (Suh et al., 2003; Fitton et al., 1983) suggest Mount Cameroon magmas originate at a depth less than 40km. Published seismic data (Ambeh, 1989) contains evidence of magmatic activity and possible chambers at depths ranging from 10km to 70km. Preliminary calculations using a simple Mogi model suggest deformation caused by pressurization of a large (greater than 2km radius) chamber near 40km deep could be detectable with proper instrument placement. Similar models involving small (500m-1km radius) chambers at 10km depth indicate the current network will be effective at detecting pressurization to 10 MPa or more. Our calculations also suggest the current network is capable of detecting magma ascending a 50m radius conduit at depths of 500 m or shallower. Using mean extrusion rates calculated during the 1999 and 2000 eruptions to estimate maximum magma ascent time (Suh et al., 2003), our current network could provide up to a week of warning prior to eruption. These preliminary calculations will be used in conjunction with future finite difference modeling and tiltmeter data from existing stations to place additional instruments in the network. References: Suh, C.E., Sparks, R.S.J., Fitton, J.G., Ayonghe, S.N., Annen, C., Nana, R., and Luckman, A. The 1999 and 2000 eruptions of Mount Cameroon: eruption behaviour and petrochemistry of lava (2003). Bulletin of Volcanology. Fitton, J.G., Kilburn, C.R.J., Thirlwall, M.F., and Hughes, D.J. 1982 eruption of Mount Cameroon, West Africa (1983). Nature Vol. 306 p. 327-332. Ambeh, William Bah. Seismicity and Seismological Studies of Mount Cameroon, Cameroon, West Africa (1989). PhD Dissertation Department of Earth Sciences, The University of Leeds. Leeds, LS 2 9JT. July 1989.
DE: 0830 Teacher training
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2005 Joint Assembly