HR: 10:35h
AN: V42A-02 INVITED     [Abstracts]
TI: Magma plumbing processes for persistent activity at Poas Volcano, Costa Rica
AU: * Rymer, H
EM: h.rymer@open.ac.uk
AF: The Open University, Walton Hall, Milton Keynes, Buc MK7 6AA, United Kingdom
AU: Locke, C A
EM: c.locke@auckland.ac.nz
AF: University of Auckland, Private Bag 92019, Auckland, New Zealand
AU: Brenes, J
EM: jbrenes@una.ac.cr
AF: cObservatorio Vulcanologico OVISCORI-UNA, Apartado 86-3000, Heredia, Costa Rica
AU: Williams-Jones, G
EM: glynwj@sfu.ca
AF: Simon Fraser University, 8888 University Drive, Burnaby, V5A 1S6, Canada
AB: Microgravity data from the active crater of Poas volcano, Costa Rica, collected between 1986 and 2004 extends the existing dataset to provide a unique time series. These data show that gravity has decreased monotonically in the north and east of the crater over the last 5 years, whilst it has increased to the west and remained approximately constant in the south. These changes are interpreted in terms of convective recharge within dendritic intrusions beneath the crater, with overall down-welling in the north and up-welling in the west. The data reveal a 5-10 year periodicity in sub-crater mass movement, but overall, the upper part of the conduit system appears to have maintained a state of mass equilibrium. The intrusion episodes in 1953-4 and the 1980s at Poas have resulted in considerable local environmental destruction and hazard to the population. Here we present data which suggest that a further intrusive episode may be occurring in the west of the lake whilst magma withdrawal is ongoing to the northeast.
DE: 7280 Volcano seismology (8419)
DE: 8419 Volcano monitoring (7280)
SC: Volcanology, Geochemistry, and Petrology [V]
MN: 2007 Joint Assembly