The death toll from last Saturday’s eruption climbed to at least 39 dead, while dozens of people are still missing and many are in critical conditions mostly from burns. Several thousand houses are damaged or destroyed as they were covered in ash or mud.
While nothing suggests that the volcano is in a more or less active state as during the past weeks and months, but continues with slow effusion of viscous lava and intermittent mostly mild explosions, it becomes more and more evident that heavy rain was likely one of if not the main ingredient that triggered the catastrophic landslides that devastated the area. During the landslide, which both created a hot turbulent pyroclastic flow as well as a hot mud flow, a part of the lava dome in the summit crater was removed, but probably more significant, much of the lava flow and other older loose debris was removed from the Koboan ravine on the southeast side of the cone.
The ravine starts at the crater and extends all the way to the feet of the massive stratovolcano. When comparing radar images from before and after the eruption, one can not only recognize the vast areas covered by the resulting ash and mud flows downslope towards the SE along the Koboan river in to up to 15-20 km distance (darker layers in image), but also see that the ravine is now much deeper along the steep slope of the main cone of the volcano: whatever deposits had filled it – the lava flow along with lots of loose material – has been excavated during Saturday’s event. It is assumed that the large amounts of rain had infiltrated and eroded the base between the lava flow and the bed of the ravine, until it all gave way: