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Sandstone structures form without cement

Weighed-down sand interlocks into rock-hard arrangement, allowing spectacular formations

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1:18pm, July 21, 2014

SAND SCULPTURE  Sandstone arches such as the 22-meter-long Double O Arch in Utah’s Arches National Park form without chemical glue. Instead, downward forces cause sand grains to interlock.

Gravity, not glue, allows towering sandstone pillars and arches to withstand howling wind and pouring rain, researchers propose July 20 in Nature Geoscience.

Sandstone forms when tiny sand grains bind together into a solid mass. The edges of sandstone slabs wear away when exposed to the elements, leaving behind spectacular structures such as arches, columns and alcoves that resist further erosion.

Geologist Jiří Bruthans of Charles University in Prague was touring a sandstone quarry when he noticed something odd: The workers had to use explosives to break apart the solid sandstone walls, but rocks that broke free often quickly crumbled apart. Bruthans says this behavior seemed to contradict the conventional explanation that chemical cement glues sandstone structures together. Thinking another overarching force was responsible, Bruthans decided to play in the sand.

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