These were thought to only form in nuclear tests and meteor impact craters

This creates distinct structures known as shock lamella, or shocked quartz

Lightning melts the rock surface but an intense pressure wave goes deeper

It is one of the most elemental forces of nature, but it seems lightning bolts are so powerful they can reshape the atomic structure of rocks they strike.

Researchers have uncovered evidence that lightning can not only melt the surface of rock but also alter the crystals beneath in ways only thought to occur in the extreme pressures of meteor impacts.

Geologists found the lightning strikes turned the rock into a material known as shocked quartz, which only forms under extreme pressure.

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Lighting bolts (like above) strike with a force equivalent to meteor impacts, geologists have discovered. This is powerful enough to reshape the atomic structure of rock, creating a material known as shocked quartz, which has previously only ever been found in meteor impact craters and at underground nuclear bomb test sites

They estimate it would require pressures of at least 10 gigapascals to form the structures – about 20 million times greater than a boxer's punch.

The findings could also give clues for how lightning strikes can damage buildings and monuments like statue of Christ the Redeemer in Rio de Janeiro, Brazil, which is regularly hit in thunderstorms.

COSMIC RAYS TRIGGER LIGHTNING The mystery of how lightning begins in clouds may have been solved, scientists have claimed. Research has shown the interaction of hail and cosmic rays from elsewhere in the universe could be causing the huge bolts. The model also suggests that lightning is less likely to form at high altitudes. Scientists say it begins with large ice particles, or hydrometeors, forming in clouds. These are caused by hailstones moving up and down in the turbulent air inside thunderclouds When these ice particles grow in an elongated shape, about 2.4 inches (6cm) long, it focuses electric fields inside the cloud towards their tips. This creates what is known as a ‘conductive tube’. Normally, there are too few free electrons in the surrounding air for anything to short-circuit these tubes and create lightning. However, high-energy cosmic rays from supernovae, black holes and so on can generate large showers of free electrons. Advertisement

Professor Reto Gieré, a geologist at the University of Pennsylvania who was one of the authors of the new study, said: 'I think the most exciting thing about this study is just to see what lightning can do.

'To see that lightning literally melts the surface of a rock and changes crystal structures, to me, is fascinating.'

Lightning is well known to cause rapid heating and melting on the surface of rocks and sediments. When it strikes sand, the grains can fuse together to form glass tubes known as fulgurites.

Similar structures can also form on rocks, leaving a distinctive black glaze on the surface of the rock.

However, Professor Gieré and his colleagues, whose work is published in the journal American Mineralogist, examined thin sections of rock fulgurite found near Les Pradals, France, that had been struck by lightning and found this outer black layer could also be porous, like a foam.

This was a result of the heat from the lightning bolt vaporising the rock's surface.

However, deeper inside the rock beneath this layer the researchers discovered an unusual set of quartz crystals arranged in straight parallel lines.

These shock lamella, or shocked quartz, is known to occur when a vast wave of pressure pushes through the rock.

It has only been found before at meteorite impact sites and the sites of underground nuclear bomb tests.

Lightning strikes can cause a distinctive melting and blackening as it passes through rock (shown left). Geologists discovered strange structures deeper in the rock where intense pressure waves from the strike reshaped the atomic structure into parallel lines known as shock lamella (shown in the micrograph right)

Professor Gieré said: 'It's like if someone pushes you, you rearrange your body to be comfortable. The mineral does the same thing.'

He said he hoped to do further work to study the physical and chemical effects of lightning bolts in more detail.

He said the scars left by lightning strikes on rocks could act as a warning sign to help climbers and hikers spot sites that are prone to being hit during storms.

Lightning strikes in sand can cause the grains to fuse together to create distinctive fulgurites (shown above)

Stone monuments such as Christ the Redeemer in Rio de Janeiro, Brazil, are often struck with lightning (as shown above), requiring regular work to repair the damage left by these powerful impacts

Lightning strikes have chipped the fingers and head of Christ the Redeemer. Workers regularly have to examine the statue and place lightning rods to protect the stone from damage (shown above)

He said the tell-tale shiny black glaze left by a strike could allow them to avoid those areas.

He said: 'Once it was pointed out to me, I started seeing it again and again.