South Africa's Mountains Were Shaped By Lightning Strikes

New research done on mountains in South Africa debunks previous suggestions that cold temperatures played a dominate role in mountain formation and also suggests that the rocky mounds are not as stable as we think, according to new research published in the journal Geomorphology.

For the first time, researchers have shown that lightning strikes play a role in shaping mountain landscapes.

The researchers say their find has vast implications in a world where mountains are crucial to food security and water supply.

The team used a simple compass to prove -- for the first time ever -- that lightning strikes are responsible for some of the angular rock formation in the Drakensburg, South Africa's highest mountain range.

"A compass needle always points to magnetic north. But when you pass a compass over a land's surface, if the minerals in the rock have a strong enough magnetic field, the compass will read the magnetic field of the rock, which corresponds to when it was formed. In the Drakensburg, there are a lot of basalt rocks which contain a lot of magnetic minerals, so they've got a very strong magnetic signal," said Jasper Knight of the School of Geography, Archaeology and Environmental Studies at Wits University.

If the compass needle passes over an area where there was a lightning strike, it starts to spin around.

"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," said Knight.

Knight said that because of the movement of continents, magnetic north for the newly formed rock will be different from that of the older rock around it. "You have two superimposed geomagnetic signatures," he said. "It's a very useful indicator for identifying the precise location of where the lightning struck."

By taking measurement of these geomagnetic signatures, Knight and his team learned that the mountain peaks were shaped significantly by lightning strikes. This suggests that the old theory of changes in pre-glacial environments as the source of mountain shaping is wrong.

"Many people have considered mountains to be pretty passive agents, just sitting there to be affected by cold climates over these long periods of time," Knight said.

"This evidence suggests that that is completely wrong. African mountain landscapes sometimes evolve very quickly and very dramatically over short periods of time. These are actually very sensitive environments and we need to know more about them."