HR: 1340h
AN: V53C-1422    [Abstracts]
TI: Inflation of Sierra Negra Volcano Since the 2005 Eruption
AU: * Ruiz, A
EM: gorkiruiz@hotmail.com
AF: University of Idaho, Box 3022, Moscow, ID 83844, United States
AU: Geist, D
EM: dgeist@uidaho.edu
AF: University of Idaho, Box 3022, Moscow, ID 83844, United States
AU: Chadwick, W
EM: William.W.Chadwick@noaa.gov
AF: NOAA/OSU, 2115 SE OSU Drive, Newport, OR 97365, United States
AB: Sierra Negra volcano, an active volcano in the western Galapagos Islands, erupted in Oct. 2005, following prolonged and rapid uplift of the caldera floor and several episodes of trapdoor faulting. Deformation data indicate that a shallow (~ 2 km) sill underlies the caldera floor, and the pre-eruptive intrusion rate between the trapdoor faulting and the eruption has been calculated to be 64 x 106 m3/y. Immediately after the eruption, the inflation rate was very fast, averaging ~ 212 cm/y during November, 2005 to February 2006. Since then, inflation of the caldera center has decelerated to a rate of 73 cm/y in 2006 and 44 cm/y 2007. The caldera rim is inflating at only 1.8 cm/y, indicating that the pressure source continues to be very shallow. We interpret the decelerating inflation as being caused by a decreased pressure gradient between the deep magma source and the shallow subcaldera magma chamber; this was driven mostly by depressurization of the shallow body during the 2005 eruption and continuous repressurization as the shallow magma body refills. Seismic activity in February, 2007 coincided with a change to deflation at a rate of 22 cm/y in the southwestern part of the caldera area, near an active geothermal area. This deflation is likely related to the depressurization of the geothermal system, but it is unclear how that is related to the measured earthquake. More recently, the southwestern caldera floor has renewed inflation at 14 to 18 cm/y.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 8419 Volcano monitoring (7280)
DE: 8439 Physics and chemistry of magma bodies
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting