Lighting Strikes Identified As A Shaper Of Mountain Ranges
October 16, 2013 by UPI - United Press International, Inc.
WITWATERSTRAND, South Africa (UPI) — Lightning strikes exploding rocks helped shape mountain landscapes in southern Africa, proving mountains are a lot less stable than we think, scientists say.
The findings contradict previous assumption cold weather caused distinctive angular rock formations by freezing and cracking the rocks over millenia, the researchers said.
A study by the University of Witwaterstrand in Johannesburg used a compass to provide the first-ever proof that lightning is responsible for some of the angular rock formations in the Drakensburg, the highest mountain range in southern Africa.
Passing a compass over an area where a lightning strike occurred can cause the needle to suddenly swing through 360 degrees, the researchers found, affected by the magnetic field of the rock, which corresponds to when it was formed.
“The energy of the lightning hitting the land’s surface can, for a short time, partially melt the rock and when the rock cools down again, it takes on the magnetic imprint of today’s magnetic field, not the magnetic field of millions of years ago when the rock was originally formed,” geographer Jasper Knight said.
Mapping out the distribution of lightning strikes in the Drakensburg showed lightning significantly controls the evolution of the mountain landscapes, the researchers said, because it helps to shape the summit areas — the highest areas — with their blasting effect.
“African mountain landscapes sometimes evolve very quickly and very dramatically over short periods of time,” Knight and his colleague Stefan Grab said. “These are actually very sensitive environments and we need to know more about them.”