On January 10, 1977, the summit crater walls of Mount Nyiragongo in the Democratic Republic of the Congo fractured, unleashing one of the most hazardous volcanic events in recorded history. The volcano contained a massive liquid lava lake that had been building pressure for decades. Within less than an hour, the entire lake drained through vertical fissures, spilling tens of millions of cubic meters of molten rock down the flanks toward the city of Goma.
What made this disaster unique was the extreme fluid dynamics of the lava itself. Unlike typical basaltic or silica-rich lavas that ooze slowly, Nyiragongo erupts ultra-alkaline, silica-poor foidite lava (specifically melilite-nephelinite). The unusually low silica content—around 38 to 40 percent—prevents the formation of complex silicate polymer chains that normally give magma high viscosity.
Combined with high dissolved volatile content and extreme eruption temperatures exceeding 1,200 degrees Celsius, the lava behaved like liquid water rather than molasses. Surging downhill at reported speeds between 40 and 60 miles per hour (60 to 100 km/h), the hyper-fluid lava inundated surrounding villages before residents could escape, forever changing volcanologists' understanding of lava flow hazards.