The video about the strange phenomenon attracted nearly 20 million views when So Fain posted it on social networks, Newsweek reported on October 22. It’s possible for a fire to start in the trunk of a tree even though the outside isn’t completely burned, according to the University of California Cooperative Extension.

“The video records a rare and interesting phenomenon that has been studied by scientists. Maybe after lightning strikes, the smoldering fire gradually hollows out the tree and rises upward. This process creates a chimney naturally inside the body, then the fire flares up and burns faster,” explained Professor Guillermo Rein, an expert in fire science at the Royal Academy of London.

Burning tree trunks is also likely linked to honey fungus, or Armillaria, according to Scott Stephens, a professor of fire science at the University of California, Berkeley. This is a parasitic species that eats trees, causing the trunk to be hollow on the inside and dry and brittle on the outside.

This makes the tree vulnerable to flames formed by forest fires, lightning strikes or human activities. If fire enters the cavity, the tree could burn for several days before eventually collapsing, Stephens said.

In May, the Millbury, Massachusetts fire department posted on social networks an image of a large tree with a hollow cavity on fire due to lightning. In 2017, people also caught fire licking inside a tree trunk after a forest fire in Sonoma County, California.