On January 10,1977, a lava lake at Nyiragongo, a stratovolcano in Zaire, drained in less than one hour. The lava erupted from fissures on the flank of the volcano and moved at speeds up to 40 miles per hour (60 km/hr).
https://volcanoworld.wordpress.com/2008/03/21/how-fast-does-lava-flow/...