Mount Slamet headed towards a major eruption?

Mt. Slamet, Indonesia, with agricultural fields in the foreground.

I’ll be brief, mostly because I’m still lost in a haze of jetlag and allergies, but …

Mt. Slamet on the island of Java in Indonesia is showing signs of a “major eruption”. Preparations have begun by the Indonesian government to evacuate people in the event that the volcano erupts, however, it is unclear when that might be. Agus Budianto, head of the volcanology unit at the Bandung, West Java-based Volcanology and Disaster Mitigation Agency, said this about the current activity at the volcano:

“Even though the earthquake activity is increasing, we have not yet decided to raise Slamet to the highest alert level, or awas status, as we think the danger level will continue to fluctuate.”

It seems that Indonesian officials are playing it cautiously, especially considering that the volcano has already “sprayed molten lava up to 600 meters into the air and we have recorded bursts of volcanic ash up to 112 times within a six-hours period.” Now, that sounds like a volcano in full eruption to me, so I have no idea what it takes to get to the highest level of alert in Indonesia. People have been told to stay out of a 2-km exclusion zone and the area in most peril if the eruption gets larger are Purbalingga, Bayumas, Pemalang, Tegal and Brebes districts in Central Java Province – they remain on 24-hour alert to evacuate. However, it never seems promising when the report mentions things like “hundreds of residents living at the base of the mountain had said they would not evacuate until the mountain was put on the highest level of alert.” That is a recipe for a disaster.

Mt. Slamet last erupted in 1999 and produces eruptions similar to most Indonesia volcanoes: central vent explosions and lava flows, all in the VEI 1-2 range. Slamet has erupted frequently over the last 100 years.