[1] We report on 4 years of airborne measurements of CO 2 , SO 2 , and H 2 S emission rates during a quiescent period at White Island volcano, New Zealand, beginning in 2003. During this time a significant crater lake emerged, allowing scrubbing processes to be investigated. CO 2 emissions varied from a baseline of 250 to >2000 t d À1 and demonstrated clear annual cycling that was consistent with numbers of earthquake detections and annual changes in sea level. The annual variability was found to be most likely related to increases in the strain on the volcano during sea level highs, temporarily causing fractures to reduce in size in the upper conduit. SO 2 emissions varied from 0 to >400 t d À1 and were clearly affected by scrubbing processes within the first year of lake development. Scrubbing caused increases of SO 4 2À and Cl À in lake waters, and the ratio of carbon to total sulphur suggested that elemental sulphur deposition was also significant in the lake during the first year. Careful measurements of the lake level and chemistry allowed estimates of the rate of H 2 O (g) and HCl (g) input into the lake and suggested that the molar abundances of major gas species (H 2 O, CO 2 , SO 2 , and HCl) during this quiescent phase were similar to fumarolic ratios observed between earlier eruptive periods. The volume of magma estimated from CO 2 emissions (0.015-0.04 km 3 ) was validated by Cl À increases in the lake, suggesting that the gas and magma are transported from deep to shallow depths as a closed system and likely become open in the upper conduit region. The absence of surface deformation further leads to a necessity of magma convection to supply and remove magma from the degassing depths. Two models of convection configurations are discussed.
a b s t r a c tRecent eruptions from Mt. Ruapehu have been difficult to predict, despite the presence of a multi-parametric monitoring network. As a result, it is necessary to assess precursory signals prior to an eruption and align those to magmatic processes at depth. Fortuitously, scoria from all historical Ruapehu eruptions contains pyroxene crystals that are strongly reversely zoned in the form of a thin (2 to 3 μm), outermost rim. These crystals therefore preserved changes in the magmatic system soon before their eruption. We used experimentally determined diffusion coefficients to assess the timescales of magma-magma interaction, and compared those to the monitoring record. Four of the five eruptions analysed (1969, 1971, 1977, 1995) gave diffusion timescales 3 to 5 months before their eruption, with an increased number of crystals recording timescales within 1 month of eruption. Pyroxene crystals from the 1996 eruption record events that occurred prior to and during the 1995 eruption suggesting that the bulk of the 1996 crystals was derived from the 1995 magma. These diffusion timescales do not compare well to a change in any monitoring signal before historical eruptions. However, an examination of recent seismicity (2005-2013) since a significant upgrade (both in number of stations and type of seismometers) showed that two phreatic eruptions in 2006 and 2007 were preceded by a seismic swarm from 5 to 15 km depth,~3 to 5 months before each eruption -consistent with the diffusion timescales. Based on this correlation, deep seismic swarms likely indicate a period of pressurisation in the magmatic system, which may lead to gas-rich, phreatic eruptions.
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