That’s not something someone just made up, even if it’s a bit of an exaggeration. Extreme cold can cause trees to explode, and it’s likely to take many people by surprise when it happens.
“It can make you jump if you’re not expecting it,” said Shane Smith, former director of the Cheyenne Botanic Gardens. “It's pretty rare, but it does happen and could happen across a lot of the country as this Arctic front moves in.”
‘Exploding' Trees
The concept of an exploding tree conjures images of a tall tree spontaneously bursting with a massive cloud of wood chips and debris. The real phenomenon, called “frost cracking,” isn’t that dramatic, but has impressive results.
When temperatures drop rapidly, the outer part of a tree trunk will shrink faster than the inner part. That buildup of stress can lead to a sudden, explosive release of energy, resulting in an explosion. Smith added that trees or parts of trees can “explode” when the water and sap contained inside their cells rapidly freeze and expand. That can split the wood and bark with a “loud pop” reminiscent of a gunshot, he said.
"It's a function of how much water a tree carries in its vascular system,” he said. “Freezing water can form spontaneous cracks, just like it does when water’s frozen in a glass.” The sun can also trigger exploding trees. Even on days with high temperatures below zero, a tree’s bark can reach temperatures of 70 degrees if it’s in direct sunlight.
“We know how fast the temperature drops once the sun sets,” Smith said. “If you're in for an unusually cold or maybe even a normally cold night, that can cause a tree to crack.”
It’s rare for a tree, especially a large one, to completely explode under these circumstances. It’s more likely to happen to a branch, although Smith said that can be dangerous enough.
“It’s not going to turn a branch into a flying projectile, but a large branch could still drop onto a person, home, or vehicle,” he said. ....
“Tree explosions can happen, but it’s pretty rare,” Smith said. “But when it does, that'll scare the bejeebers out of you.”
Andrew Rossi can be reached at arossi@cowboystatedaily.com.