LUMAJANG, INDONESIA — Rescue workers were continuing to dig for survivors of Saturday’s catastrophic eruption at Mount Semeru on the evening of Monday, December 6, with flows of deadly ash, lava and mud responsible for the deaths of 22 people so far, according to the Head of Data and Information for Indonesia's National Board for Disaster Management, cited by CNN.
Semeru, on the island of Java, is one of the most active volcanoes in Indonesia, with small strombolian explosions frequently occuring, according to the Volcan Discovery site.
These explosions may have led to the accumulation of material in the crater area, causing instability.
However, the head of the Indonesian Geological Agency said persistent rain eroded part of the solidified lava dome at Semeru’s summit, which led to its collapse, releasing an ash plume that reached 15 kilometers into the atmosphere.
At the same time, pyroclastic flows — clouds of solidified lava, ash and gas — and volcanic mudflows also streamed down the sides of the volcano at high speeds, according to The Conversation.
The Indonesian Geological Agency says from there, hot clouds of rocky material with a high temperature of between 800 and 900 degrees Celsius moved towards the southeastern slope of the volcano, as far as 4 kilometers from the peak, before entering the valley of the Kobokan River, interacting with river water and other materials, and forming mud flows along the river.