HR: 0800h
AN: V21E-0665    [Abstracts]
TI: Monitoring Emissions at White Island Volcano, New Zealand; Evidence of Sustained Magmatic Degassing during Crater Lake Growth
AU: * Werner, C A
EM: c.werner@gns.cri.nz
AF: Geological and Nuclear Sciences, Private Bag 2000, Taupo, 2730 New Zealand
AU: Christenson, B W
EM: b.christenson@gns.cri.nz
AF: Geological and Nuclear Sciences, P.O. Box 31-312, Lower Hutt, 6315 New Zealand
AU: Hurst, T
EM: t.hurst@gns.cri.nz
AF: Geological and Nuclear Sciences, P.O. Box 31-312, Lower Hutt, 6315 New Zealand
AU: Scott, B J
EM: b.scott@gns.cri.nz
AF: Geological and Nuclear Sciences, Private Bag 2000, Taupo, 2730 New Zealand
AU: Britten, K
EM: k.britten@gns.cri.nz
AF: Geological and Nuclear Sciences, Private Bag 2000, Taupo, 2730 New Zealand
AB: The commencement of routine monitoring of CO₂ and SO₂ emissions at White Island volcano in March 2003 indicated that degassing was at quiescent levels (880 and 225 td^-1, respectively) similar to previous estimates of long-term (20-yr) emissions. Following an abrupt decrease in prolonged 2-5 Hz volcanic tremor in February, 2003, emissions decreased dramatically to ~250 and 0 td^-1 CO₂ and SO₂, respectively. These decreases were coincident with the formation of a significant crater lake at the volcano. Since this time, however, CO₂ emissions have increased and decreased by as much as an order of magnitude over periods of months with ~10 and 12 months between the lowest measured values. SO₂ emissions also displayed similar variability, but changes were superimposed on a long term trend of increasing emissions. Likewise, SO₄ concentrations in the crater lake increased steadily and also showed small deviations during periods of increased degassing. Crater lake temperatures varied primarily between 48 and 58 ^oC, but also displayed short-lived increases to 63 and 68 ^oC during periods of higher degassing. Similarly, modelled estimates of steam input to the lake, while varying, have remained relatively unchanged over the monitored period. Such changes suggest that a decrease in the magmatic mass and heat output from the volcano allowed the crater lake to form, but that overall, the mass and heat output have fluctuated about quiescent levels since the formation of the crater lake. White Island last erupted in 2000 marking the end of 25 years of episodic eruptions. We suggest that the variability of volatile output over timescales of months is related either to magma convection deep within the volcanic edifice or to changes in shallow permeability due to conduit saturation or mineral precipitation.
DE: 8419 Volcano monitoring (7280)
DE: 8430 Volcanic gases
DE: 8485 Remote sensing of volcanoes
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005