Eruption Increases, Large Pyroclastic Flows At Sinabung Volcano, Sumatra
After a few days of deceiving calm, the eruption of the volcano intensified again today and produced the so-far largest pyroclastic flows, reaching probably more than 5-6 km in length, and associated ash plumes that rose to approx. 25,000 ft (8 km) altitude.
It seems that the previous dome which grew at the summit of Sinabung, collapsed a few days ago, leaving a large crater breached on the side where the earlier pyroclastic flows had gone down. The temporary absence of a lava dome in the past days led to the cessation of pyroclastic flows. Now, the new dome has again surpassed the boundary of the breach and sheds pyroclastic flows into the deep ravine below. (Thanks to B. Behncke for the comment)
On the other hand, a strong increase in SO2 emissions and hybrid earthquakes indicate that a larger new batch of new magma has risen, which also explains the new more vigorous activity.