Wits team shows how lightning shapes mountains


10 January 2014

Scientists at Wits University in Johannesburg have made a “shocking” discovery – lightning rather than ice or heat is the main force shattering rocks on Drakensberg summits.

National Geographic reports on research published in the journal Geomorphology on 1 January 2014. The evidence gathered by geomorphologist Stefan Grab and geologist Jasper Knight has apparently changed their own conventional notions about the forces that shape mountain peaks.

For their research, the pair surveyed almost half a kilometre of the Drakensberg in Lesotho, where they found 90 sites where lightning strikes had blasted apart the basalt rock face, the website reports.

While frost alters the shape of rocks over thousands of years, lightning – at temperatures of up to almost 30 000°C – can shatter rocks milliseconds, the researchers say.

Lightning “basically causes a bomb to explode on the rock surface”, Knight told National Geographic.

The fact that a lightning strike will partially melt basalt in an instant meant the researchers were able to develop a diagnostic “tool kit” to distinguish the sites of lightning strikes from other rock fragments affected by heat or ice.

Lightning is “part of the much bigger jigsaw,” a puzzle piece that had been “passed over by geoscientists for decades”, Grab is quoted as saying.

The two researchers told National Geographic that further exploration would reveal other examples of mountain ranges shaped in large part by lightning – especially in warmer regions of Australia, Africa, and Asia that were mostly passed over by the Ice Age.

SAinfo reporter and National Geographic