Geologists have discovered the secret that gives dramatic natural sandstone monuments their shape: gravity.
By studying cubes of sand in the lab, they showed that areas squeezed by vertical stress are protected from erosion, while others wash away.
The process had proved difficult to study, because natural slabs of sandstone erode over millions of years.
The key to the experiments, published in Nature Geoscience, was an unusual “locked sand” dug from a Czech quarry.
The study’s first author, Dr Jiri Bruthans from Charles University in Prague, said the new study revealed the “Michelangelo” behind some of the world’s most famous rocky landmarks.
“The stress field is the master sculptor – it tells the weather where to pick,” he said.
Erosion by wind and water, it seems, is merely the sharp instrument. The remarkable shapes are controlled by internal stresses and strains within the rock, applied by the pull of gravity.
