Multi-year Satellite Observations of Sulfur Dioxide Gas Emissions and Lava Extrusion at Bagana Volcano, Papua New Guinea

Abstract

Bagana, arguably the most active volcano in Papua New Guinea, has been in a state of near-continuous eruption for over 150 years, with activity dominated by sluggish extrusion of thick blocky lava flows. If current extrusion rates are representative, the entire edifice may have been constructed in only 300-500 years. Bagana exhibits a remarkably high gas flux to the atmosphere, with persistent sulfur dioxide (SO 2) emissions of several thousand tons per day. This combination of apparent youth and high outgassing fluxes is considered unusual among persistently active volcanoes worldwide. We have used satellite observations of SO 2 emissions and thermal infrared radiant flux to explore the coupling of lava extrusion and gas emission at Bagana. The highest gas emissions (up to 10 kt/day) occur during co-extrusive intervals, suggesting a degree of coupling between lava and gas, but gas emissions remain relatively high (∼2,500 t/d) during inter-eruptive pauses. These passive emissions, which clearly persist for decades if not centuries, require a large volume of degassing but non-erupting magma beneath the volcano with a substantial exsolved volatile phase to feed the remarkable SO 2 outgassing: an additional ∼1.7-2 km 3 basaltic andesite would be required to supply the excess SO 2 emissions we observe in our study interval (2005 to present). That this volatile phase can ascend freely to the surface under most conditions is likely to be key to Bagana's largely effusive style of activity, in contrast with other persistently active silicic volcanoes where explosive and effusive eruptive styles alternate.

Open-vent volcanoes fuelled by depth-integrated magma degassing

“…4). Instead, the observed rates of degassing from 2005-2015 require around 5-6 times the observed magma flux when reasonable water and sulphur melt concentrations for arc magmas are assumed (McCormick Kilbride et al 2019).…”

“…Bagana Volcano (Papua New Guinea) has exhibited longlived and continuous degassing, perhaps over centuries (McCormick et al 2012;McCormick Kilbride et al 2019;Wadge et al 2018). Bagana's edifice is built of crystal-rich andesite lava flows and tephra (53-58 wt% SiO 2 ) and eruptive activity is characterised by the emplacement of steepsided lava flows, pyroclastic density currents and ash-rich explosions (Bultitude and Cooke 1981;Wadge et al 2018).…”

“…A recent global inventory of volcanic SO 2 emissions measured via satellitemounted UV sensor (ozone mapping instrument (OMI)) reported Bagana's mean SO 2 flux as 1380 t/day for the period 2005-2015 (Supplementary Material Table 1), placing it 3rd in the global ranking of sustained SO 2 fluxes (Carn et al 2017). The highest SO 2 fluxes occur during eruptive periods (up to 10,000 t/day) but gas emissions remain high (≤ 2500 t/day) during eruptive pauses (McCormick Kilbride et al 2019). These high gas emissions cannot be supplied by the erupted magma, which has a time-averaged eruption rate of 1 m 3 /s (Wadge et al 2018) (Fig.…”

The Evolution of Icelandic Volcano Emissions, as Observed From Space in the Era of NASA's Earth Observing System (EOS)

“…OMI observations are nearly coincident with those from the Aqua/MODIS. Similarities in the spectral absorption bands of ozone and key volcanic gases, particularly sulfur dioxide (SO 2 ) (Krotkov et al, 2006;Krueger, 1983) make it invaluable for identifying and tracking volcanic emissions (Carn et al, 2015(Carn et al, , 2016Krotkov et al, 2006;McCormick et al, 2013;McCormick Kilbride et al, 2019). At launch, OMI provided the highest spatial resolution available for near-global daily volcanic SO 2 measurements (13 × 24 km 2 at nadir).…”

Temporal Variability in Gas Emissions at Bagana Volcano Revealed by Aerial, Ground, and Satellite Observations

“…Bagana's characteristic activity comprises the alternation of extrusive eruptions persisting for several months and quiescent intervals dominated by voluminous passive degassing. Comprehensive reviews of Bagana's activity are provided by Bultitude (1976Bultitude ( , 1981, Bultitude and Cooke (1981) and, more recently, by Wadge et al (2018) and McCormick Kilbride et al (2019). The volume of the Bagana edifice is estimated to be 5.1-9.6 km 3 , depending on the (unknown) geometry of the underlying topography (Wadge et al, 2018).…”