The Sinabung volcano erupted strongly in Indonesia on November 1, 2016.
And during the explosion some tornado-like vortices formed and amazed many witnesses and photographers.
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.
In this case, though, the phenomena are built from the ground up. The pyroclastic flow heats the air over the ground, causing it to rise. Air from the sides then rushes in to fill the partial vacuum. This creates swirls, which can get amplified into the vortices. This makes these events more like a dust devil than proper tornadoes. Or, I suppose, an ash devil.
Remember, that’s not just smoke you’re seeing; it’s vaporized rock, millions of tons of it! And it’s superheated to glowing, which can then flow downhill at hundreds of kilometers per hour, laying waste to whatever it touches.
Like I said, terrifying. Amazingly, though, volcanologists are getting better at predicting these. Magma moving underground can cause tremors that indicate an explosive eruption is imminent, allowing people to be evacuated… Sometimes.
There is a terrible beauty to volcano eruptions (much like hurricanes seen from space) that belies their destructive power. This video features a pyroclastic flow and ash devils at Sinabung in February 2014:
Mount Sinabung on Sumatra island erupts again. The volcano roared back to life in 2010 for the first time in 400 years and erupted once more in 2013, it has remained highly active since.