Mountains not as stable, Wits researchers prove

2013-10-15 11:37
Mountains are not as stable as previously thought, researchers have found. (Duncan Alfreds, News24)

Mountains are not as stable as previously thought, researchers have found. (Duncan Alfreds, News24)

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Johannesburg - New evidence by South African researchers has shown that mountains are not as stable as previously thought.

Lightning strikes causing rocks to explode have for the first time been shown to play a huge role in shaping mountain landscapes in southern Africa, debunking previous assumptions that angular rock formations were necessarily caused by cold temperatures

Professors Jasper Knight and Stefan Grab from the School of Geography, Archaeology and Environmental Studies at Wits University used a compass to prove that lightning is responsible for some of the angular rock formations in the Drakensburg.

"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," said Knight.

"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."

Slow change

He added that readings showed a dramatic shift in the polarity of rocks where lighting was known to have struck. This indicates that the phenomenon had the ability to melt the rock and which took on the polarity of the Earth when it cooled again.

"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.

Because of the movement of continents, magnetic north for the newly formed rock will be different from that of the older rock around it.

The researchers challenge the assumption that mountains are passive and that change occurs very slowly over long periods of time.

"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.

"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," said Knight.

The research was published in the Geomorphology journal and may hold important clues for the people living in the valleys below mountain ranges.
- SAPA
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