High in the Andes, on the border between Chile and Argentina, lie some mysterious dunes. The Salar de Gorbea, as the dunes are known, contain huge needle-shaped crystals, up to 27cm long. No ordinary wind could have lifted these giant grains into this high-level basin, so how were the dunes created?
Kathleen Benison, a geologist from West Virginia University, in the US, thinks they may be the handiwork of the largest and strongest whirlwinds on Earth.
When she visited the region in 2007, Benison established that the dune crystals had been transported from a salt pan 5km away. She thinks that, when the salt pans are dry, the crystals are sometimes spun up to the Salar de Gorbea by incredibly powerful “dust devils”. Until now, the maximum speed had been thought to be about 70kph (equivalent to an F0 tornado). But winds of 70kph would not be capable of lifting gravel into the air.
Writing in the journal Geology, Benison concludes that the dust devils that made the Salar de Gorbea dunes must be significantly faster and stronger. The low air pressure and the elongated shape of the crystals may also help them become airborne and stay aloft.
Giant whirlwinds (up to 500m wide) have been seen in the region, but as yet no-one has seen one strong enough to explain the presence of the massive crystals in the dunes. However, for anyone willing to stand there for long enough, it appears that the Salar de Gorbea is a prime location to spot one of the largest dust devils our planet can produce.
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