The pyroclastic flow deposits red-hot material on the slope of the volcano. After a few minutes, air heated by the deposit establishes a convective regime and due to the speed of the rising air a series of small tornados are formed.
During daylight it is difficult to imaging how hot the deposit is. Click here to see a pyroclastic flow deposit glowing at night from this same location.

Seth Dixon‘s insight:

Mount Sinabung recently erupted, killing at least 15 people and destroying tons on property on the island of Sumatra in Indonesia.  This footage is both awe-inspiring and terrifying.    

Tags: disasters, Indonesia, physical, SouthEastAsia.

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