View of Lake Kivu, from Kibuye, Rwanda.  On the horizon is Mt. Nyiragongo, one of Africa’s most active volcanoes, and which holds the world’s largest lava lake.  The plume from this volcano can be clearly seen here, and is one of the largest natural sources of SO2 to the atmosphere.   Nyiragongo’s alkaline lavas have low-viscosity, posing a natural hazard to surrounding communities, including the city of Goma, with a population of approximately 2 million.