Ash Devils

by Phil Plait



The Indonesian volcano Sinabung was dormant until pretty recently. In 2010 it kicked into action, but in January 2014, it switched to high gear, blasting out massive amounts of ash high into the atmosphere (see picture below). Then a lava dome collapse on Feb. 1 created a pyroclastic flow, a rapid wave of hot gas and rock that thundered downslope.

These flows are incredibly dangerous (15 people were killed by Sinabung’s flows when they ventured inside the 5-kilometer exclusion zone) and are for my money one of the most terrifying events on Earth.

And now I find out they can create tornado-like vortices! And they’ve been caught on camera. Here is some video of the flow, which cuts to the towering funnels about a minute in:

Now technically these aren’t tornadoes, even if they look like it. Tornadoes are when a funnel cloud is connected to the ground at its bottom and the base of a cumulonimbus cloud at its top. They form from the top down, dropping from the cloud base.

more

http://www.slate.com/blogs/bad_astronomy/2014/02/07/volcano_twisters_ash_devils_spawned_from_sinabung.html