While battling a blaze on the slopes of Mauna Kea in August, a Hawaii firefighter captured rare footage of a fire tornado. The flaming whirls can spew embers thousands of feet, helping wildfires spread.

© 2010 National Geographic; video courtesy Hawaii Dept. of Land and Natural Resources

They’re called fire tornadoes. Or fire whirls. Or fire devils.

They’re a rarely-seen phenomenon that can be catastrophic.

This fire tornado was recorded in late August by a firefighter with the Hawaii Department of Land and Natural Resources.

Fire tornadoes occur when intense heat causes air to rise and combine with whirling eddies of air. It consists of a core, and an invisible pocket of rotating air.

Because of the intense heat, the rotating air, mixed with gases from