New lava lake at Nyamuragira volcano revealed by combined ASTER and OMI SO<sub>2</sub>measurements
We report recent satellite measurements of the SO2 emissions from the Virunga Volcanic Group (VVG), which comprises the very active Nyamuragira and Nyiragongo volcanoes. Combining high time resolution data from the UV-operating OMI (Ozone Monitoring Instrument) with high ground resolution data from the IR-operating ASTER (Advanced Spaceborne Thermal Emission and Reflection radiometer), we show that (1) the SO2 emissions from the VVG have increased severalfold since the end of the last eruption of Nyamuragira. (2) Nyamuragira, which used to have very low intereruptive emissions of SO2 before this eruption, is now contributing to 60 to 90% of the combined emissions measured by OMI. Considering the eruptive history of Nyamuragira, the evidence from previous research for the existence of a shallow magma chamber, and the detection of isolated thermal anomalies since April 2014, we conclude that a deep-seated lava lake has formed in the N pit of Nyamuragira's caldera.