The first well-documented surge occurred on July 3, 1902, in the midst of an unusually hot summer, when the mean temperature was 2.7 °С higher than normal.
A series of heavy rains occurred in June and early July, filling the river basins with rain and melt water and by the middle of June, a tongue of the Kolka glacier was on the move.
Loud crackling was heard in the nearby settlements and, at times, the Genaldon river was turned into a stream of black mud.
By the end of June, the heavily cracked glacier tongue was seen in a narrow gorge next to the Maili glacier.
The tongue then partially collapsed, temporarily damming the river.
A pulp of ice, water and morainal material then formed a mudflow which streamed down the river's course, stopping near the Tmenikau aul high on the valley slope.
The glacier, which was still on the move, then blocked the gorge causing it to fill up with meltwater.

A second mudflow surge occurred on July 6 when a 9 km stretch of the valley floor was buried underneath a mass of ice and rocks.
Its thickness at times approached 50 m, the scouring of the valley slopes reaching a height of 100 m. The estimated volume of ice that was ejected into the valley, obstructing the gorge, was in excess of 100 million m³. The mudflow speed averaged 60–70 km/h, peaking at 100 km/h.
At least 32 people were killed.
The first well-documented surge occurred on July 3, 1902, in the midst of an unusually hot summer, when the mean temperature was 2.7 °С higher than normal. A series of heavy rains occurred in June and early July, filling the river basins with rain and melt water and by the middle of June, a tongue of the Kolka glacier was on the move. Loud crackling was heard in the nearby settlements and, at times, the Genaldon river was turned into a stream of black mud. By the end of June, the heavily cracked glacier tongue was seen in a narrow gorge next to the Maili glacier. The tongue then partially collapsed, temporarily damming the river. A pulp of ice, water and morainal material then formed a mudflow which streamed down the river's course, stopping near the Tmenikau aul high on the valley slope. The glacier, which was still on the move, then blocked the gorge causing it to fill up with meltwater.
A second mudflow surge occurred on July 6 when a 9 km stretch of the valley floor was buried underneath a mass of ice and rocks. Its thickness at times approached 50 m, the scouring of the valley slopes reaching a height of 100 m. The estimated volume of ice that was ejected into the valley, obstructing the gorge, was in excess of 100 million m³. The mudflow speed averaged 60–70 km/h, peaking at 100 km/h. At least 32 people were killed.
Kolka Glacier