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Cool Discovery: Mountains Moved by Lightning

Growing up in the Midwest instilled in me a fascination with thunder and lightning. Summer storms would light up the sky with brilliant flashes, filling the air with deafening thunderclaps. While others would seek refuge, I would search for the best vantage point to witness the spectacular show. One time, lightning struck a tree about 40 feet away from where I stood (in full disclosure, I was inside the house and not in danger of being struck)!

Lightning, as fleeting as it may be, shapes the land around us. Although many processes weather the landscape, a recent paper published in the journal Geomorphology demonstrates that rock formations of a particular shape and signature were thought to result dominantly from cold temperatures. However, studies of such rock formations in Lesotho, South Africa show that lightning strikes also play a major role.

The magnetic fields contained in the rocks distinguish the role of lightning in rock formation compared to that of cold weather. When rocks cool, they record the magnetic field of Earth in the location where they formed. However, lightning can reorient this field because of the high temperatures reached during a strike. Scientists found the magnetic signature expected from a lightning strike in rock formations usually attributed to cold weather processes.1

This research confirms my intuition that we should pay attention to lightning whenever possible. Not only does it produce dramatic displays across the sky, it also significantly affects how quickly mountains change.

  1. Jasper Knight and Stefan W. Grab, “Lightning as a Geomorphic Agent on Mountain Summits: Evidence from Southern Africa,” Geomorphology (2013): in press, corrected proof,