The moment lightning strikes a tree outside Wautoma High School in Wisconsin on April 8, 2021.
  • Lightning struck a tree outside a Wisconsin high school while students were taking a test.
  • A video of the incident shows a tree collapsing immediately after being struck by the lightning bolt.
  • The way in which the tree shattered is "unusual," a leading expert on tree biology told Insider.
  • Visit Business Insider's homepage for more stories.

Students were preparing for their ACT Aspire test in a small Wisconsin town when they heard the deafening roar of thunder.

"Initially, the students and staff were startled by the event," Wautoma High School's principal, Jennifer Johnson, told Insider. "However, after realizing what had just happened, they were fascinated by the rare incident that occurred just feet from them."

In the space of a few seconds, a lightning bolt struck a tree, and then it immediately crumbled.

In footage captured on the school's security cameras and later shared by the US National Weather Service, a slowed-down version of the dramatic weather event can be seen with total clarity.

Kim D. Coder, professor of tree biology at the University of Georgia, told Insider what is likely to have happened.

"The current enters near the treetop and generates a large explosive pressure on the tree," he said. "The tree shatters due to the explosive force of the current movement down the stem with large splinters and fractured wood throw around."

This tree sustained a ground strike connection and internalized some of the energy causing massive fractures along the stem at different locations," he said.

Its total obliteration was very "unusual," he added.

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