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article imageStress, not weather erosion, architect of sandstone formations

By Greta McClain     Jul 22, 2014 in Science
Prague - A new study by Czechoslovakian researchers has "convincingly" shown how mother nature creates the intricate carvings in sandstone formations.
Czech scientist Jiri Bruthans, a hydrogeologist at Charles University in Prague, recently led a research team in a study to determine exactly how massive sandstone arches are formed. For years, scientists believed that wind and rain eroded sandstone, creating the intriguing natural sculptures seen throughout the world. Although the new study shows that erosion does play a part in the process, Bruthans' research points to gravity and stress as being the key to how arches and other formations are created.
In the study published in Nature Geoscience, Bruthans shows that increased stress actually reduces the amount of weather erosion on sandstone, causing the appearance of arches, alcoves and multiple pillars.
The revelation came when Bruthans was visiting the Stralec Quarry in the Czech Republic. During his visit, he noticed that the sandstone that had recently been blasted quickly formed arches and other shapes. He took sample blocks of sandstone to his laboratory and exposed the blocks to accelerated erosion. The result was that the blocks simply crumbled into piles of sand. Bruthans and his research team then added weight to the top of the sample blocks. The weight triggered a locking mechanism within the sandstone. The studies co-author, Alan Mayo, a hydrogeologist at Brigham Young University in Provo, Utah, told that once criticle pressure was reached, the sand grains lock together and become “incredibly stable”.
By shifting the direction of the pressure and adding faults and distortions to the sample cubes, researchers were able to replicate various shapes seen in natural sandstone landforms. Bruthans told the BBC:
"You can control it completely. 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."
Other scientists agree that the research study finally shows a definitive answer as to how the natural rock formations are created, with University of Minnesota sedimentologist Chris Paola saying:
"These natural sculptures have delighted countless visitors, some of whom must have paused to wonder where they come from. Here is an answer."
University of Edinburgh professor, Dr Simon Mudd, agrees, telling the BBC:
"They've really demonstrated convincingly that as you erode this material, it begins to concentrate stress."
More about sandstone, Gravity, rock formations, Stress
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