Sulfur dioxide (SO2) emissions from non-arc volcanoes constitute a significant component of the global volcanic sulfur budget, and have been assumed to scale directly with erupted lava volume (i.e. that there is no excess sulfur). However, to date there have been very few efforts to prove this, particularly for alkaline volcanoes. This project will merge remote sensing and petrological analysis to investigate the origins and dynamics of SO2 emissions from Nyamuragira and Nyiragongo, the active, alkaline volcanoes in the Virunga region of the western arm of the East African Rift in DR Congo. Both Nyamuragira and Nyiragongo are prodigious sulfur emitters, the former during its frequent effusive eruptions and the latter via persistent passive degassing since 2002. To date there has been no concerted attempt to link these SO2 emissions with magma production, or to investigate the origin of the exceptional SO2 output.
The main components of the VISOR project are: (1) Analysis of satellite data collected by several instruments since 1978 to develop a complete record of recent SO2 emissions from the Virunga volcanoes. An up-to-date map of recent lava flows will also be constructed; (2) Fieldwork in DR Congo to collaborate with Congolese scientists at the Goma Volcano Observatory (GVO) on ground-based SO2 monitoring at Nyiragongo, including measurement of SO2 emissions and interpretation of the data alongside other volcanological datasets collected by GVO and collaborators. Validation of satellite measurements will be achieved by comparing coincident field- and satellite-based SO2 measurements; (3) Petrological analyses of volatile concentrations and speciations in historical eruptive products of Nyamuragira and Nyiragongo to determine the extent of magma degassing during eruptions. These data will be combined with the remotely sensed SO2 measurements to assess the relationship between melt sulfur loss and measured SO2 production for a series of eruptive events; thus shedding new light on the incidence of excess sulfur emissions at non-arc, alkaline volcanoes, and into the behavior of sulfur and other volatiles in alkali-basaltic magmas. Broader impacts of this study include: strengthening of international collaborative links between groups in the USA, Africa, and Europe; training of a female graduate student in remote sensing, petrological techniques and fieldwork; a valuable infusion of expertise and collaborative activity for African scientists at GVO, which has suffered many years of neglect and civil unrest; outreach projects in Goma using satellite data acquired for the project; and the addition of exotic volcanic rock compositions to the National Rock Collection archive at the Smithsonian Institution, for future research efforts.
