Searing gas and ash rapidly melted the summit of Nevado del Huila on the night of Nov. 20, sending a flow of volcanic material cascading down the mountain’s slopes.
Authorities said the surge of water and debris also trapped 150 people in a downstream canyon of the Paez River.
Roads were blocked by the turbulent flow, which also destroyed bridges and about 20 homes.
The volcano roared to life again in 2007 after lying dormant for more than 500 years.
The latest eruption formed a crater approximately 1,300 feet in diameter in a region where the borders of Huila, Tolima and Cauca provinces merge.
CNN reports that the disaster struck as thousands of indigenous Colombians, many from the volcanic disaster zone, marched into the capital of Bogota to protest for land rights and a halt to economic policies they say are keeping them impoverished.