THE world's tallest sand dunes, some half a kilometre high, survive in a windy desert because water cements them together. That's the conclusion of Ling Li from the University of Queensland in Australia and colleagues, who have studied the dunes of Badain Jaran desert in northern China.
The researchers were surprised to find moisture lurking just 20 centimetres beneath the surface. They suspect the water floods in through subterranean faults when snow melts on nearby mountains (
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