Geologists reveal the ‘master sculptor’ behind the world’s dramatic sandstone formations
Arches 'carved' from sandstone are found all over the world
It’s long been thought that the arches, columns and bridges of natural sandstone formations were created by years of erosion from wind and rain, but new research suggests that these fantastic shapes are actually the product of gravity instead.
Scientists from the Charles University of Prague explain that it’s not that erosion doesn’t play its part, but that it is the rock’s “internal stress fields” – the different areas of pressure caused by weight and gravity - that dictate the final form.
“Erosion gets material out, but doesn’t make the shape,” explains Jiri Bruthans, a hydrogeologist who led the research. Instead, he says, the wind and the rain are merely the “tools” that reveal the shape that is latent in the rock.
Dr Bruthans began his research after visiting the Stralec Quarry in the Czech Republic and observing the unusual properties of a type of sandstone known as “rock sand”. Bruthans noticed that although the miners had to use dynamite to break the rock walls apart, once they had the material itself just crumbled apart - often leaving behind the arches and bridges seen in natural sandstone formations.
The team from Prague took away blocks of rock sand from the quarry to conduct their own experiments, exposing the samples to cycles of heat, cold and salt to simulate natural erosion, and even leaving one block out in the rain for 15 months to see if it would form a natural arch.
They found that by placing weights and pressures on the material they could accurately predict how arches, alcoves and other features would form, baking cubes of the rock sand in the oven to harden it then dunking it under water to watch erosion take place.
One of the rock sand cubes and the arch it formed after being squeezed by weights and submerged underwater. Image credit: Marek Janac
"You can control it completely," Dr Bruthans told the BBC. "You select the pillar direction, by choosing the points where you apply the compression. It's just the stress which controls the shape - nothing else."
In an article written to accompany the research in Nature Geoscience, Professor Chris Paola of the University of Minnesota described the discovery as "a lovely and elegant formative mechanism for a lovely and elegant kind of landform".
"These natural sculptures have delighted countless visitors, some of whom must have paused to wonder where they come from," said Professor Paola. "Here is an answer."
- 3 The enemy within: People who hear voices in their heads are being encouraged to talk back
- 4 British grandmother Lindsay Sandiford faces execution by firing squad in Indonesia
Paris attacks: Do not call Charlie Hebdo killers 'terrorists', BBC says
UK weather: Snow to fall in the coming week with sub-zero temperatures to last until early February
Asteroid narrowly scrapes past Earth: how to watch the closest space rock for decades as it flies by
Saudi preacher who 'raped and tortured' his five -year-old daughter to death is released after paying 'blood money'
Prince Philip set to be knighted by Australia: Celebrate by reading his greatest gaffes
'We would evict Queen from Buckingham Palace and allocate her council house,' say Greens
French court convicts three over homophobic tweets, in case hailed as a 'significant victory' by LGBT rights campaigners
Greece elections: Syriza and EU on collision course after election win for left-wing party
British Muslim school children suffering a backlash of abuse following Paris attacks
Islamic history is full of free thinkers - but recent attempts to suppress critical thought are verging on the absurd
30,000 reasons why the rhetoric on immigrants claiming benefits can stop now
£38000 - £42000 per annum: Recruitment Genius: One of the UK's best performing...
£35000 - £43000 per annum: Recruitment Genius: Our award-winning client is one...
£15000 - £21000 per annum: Recruitment Genius: This leading provider of Atlas ...
£18000 - £20000 per annum: Recruitment Genius: Opportunity to join established...