An intense Arctic cold wave has covered nearly two-thirds of the U.S. over the past week, bringing temperatures as low as minus 30 degrees Celsius in some areas and snowfall measuring dozens of centimeters.
The severe weather has caused widespread damage to people and property, while also triggering an unusual event that has drawn widespread attention online.
Trees explode during winter storm
(Video: Social media)
The phenomenon, commonly referred to as frost cracks, occurs when rapid and extreme temperature changes cause tree trunks and bark to split. These cracks weaken the trees’ structure, making them more vulnerable and prone to sudden breakage. As a result, branches can snap abruptly and crash to the ground, creating what has been dubbed the “exploding trees” effect.
“A sudden drop in temperature can cause branches to fall off,” Bill McNee, a forest health specialist with the Wisconsin Department of Natural Resources, told the Milwaukee Journal Sentinel, part of the USA Today network. "Rapid temperature changes cause uneven contraction and expansion, putting tremendous pressure on the inside of the tree, leading to this unusual phenomenon.”
According to the Wisconsin Department of Natural Resources, longitudinal frost cracks can run the entire length of a tree trunk and are often accompanied by a loud booming sound. McNee said frost cracks typically occur when temperatures plunge so quickly that trees do not have time to adjust, causing sap or water inside the wood to begin freezing.
“That water expands as it freezes, and it can happen usually under very, very drastic drops in temperature,” said Dr. Doug Aubrey, a professor at the University of Georgia’s Warnell School of Forestry and Natural Resources, in an interview with CNN.
The internal expansion places intense pressure on the bark and trunk, sometimes causing them to split in a way that sounds like an explosion, as heard in several of the viral videos. In some cases, the cracking noise resembles a gunshot.
"When internal freezing happens inside a tree, it's similar to ice forming in a drink placed in a freezer. It creates a lot of physical pressure that can lead to the frost cracking appearing suddenly, branches can fall off, and people hear this really loud crack from their tree, almost like it's a gunshot", said McNee.
Forecasters say the extreme winter weather is expected to continue into the weekend, with parts of the East Coast likely to see additional winter precipitation. Dr. Aubrey warned that "during the storm, there is higher risk of heavy branches falling from trees due to the weight of ice or snow. A heavy tree branch could harm a home, a vehicle or even a person."