The Indonesian volcano continues to experience explosions, which one last night (well, last night here in Ohio) that prompted an ash advisory for aircraft up to 6,100 m / 20,000 feet, although most reports I've seen pegged the ash column at closer to 2,000 m / ~6,500 feet. This definitely makes it seem that the vent is partially blocked and these explosions are helping "clear the throat" of the volcano (NOTE: this does NOT mean I think something big is going to happen, rather just that it seems to be the reasonable explanation for the bifurcation of the plume).
My hunch is that even now, very little "new" juvenile magma has been erupted from Sinabung, but that is pure speculation until there are any analyses of the ash shard morphology or composition. Evacuations have increased to over 21,000 people living near the volcano and some flights have been diverted due to the taller ash plume. The biggest threat right now is the ash fall from the explosions and as such, the government is providing face masks and moving people to sturdier shelter. The current death toll appears to be 8 (video), mostly from respiratory-related problems.
What comes next might be a guess for everyone at this point as the Surono, head of the Indonesian Center for Volcanology and Geological Disaster Mitigation admitted again "We don't know what set it off, how long it will continue or whether to expect pyroclastic flows or more powerful eruptions."
Eruptions readers were quick on the news about the new eruption at Sinabung in Indonesia. There isn't much known about the eruptive history of the volcano - checking out the Global Volcanism Program, the last activity at Sinabung might have been an explosive event in 1881 with persistent fumaroles up until 1912. However, most news sources are quoting 400 years as the last known eruption of the volcano, apparently information from the Indonesian government.
The eruption itself appears to be an ash-rich explosion with ash fall reported up to 30 km from the volcano although the ash column from the explosion was only 1.5 km (~5,000 feet) tall. The volcano had been showing signs of activity with smaller explosions and minor steam-and-ash plumes on Friday, but the explosion on Saturday was much larger than expected.
From the details I've read, [speculation] I wouldn't be surprised if there is no new magma (juvenile material) in this eruption, but rather just older material that was in the conduit. My hunch is that this explosion might be the start of more and the heat from the magma interacted with groundwater near the summit to cause the explosion - a very common precursor activity at a composite cone like Sinabung (think about the events leading to the eruption at Redoubt).
Thousands of people have needed to evacuate their homes around the volcano on Sumatra after this explosion - however, some have stayed behind to prevent the looting of their property. A 6-km exclusion zone has been set up around the volcano by the Center for Volcanology and Geological Disaster Mitigation as well.
