Racetrack Playa
Interesting facts
- The playa is almost perfectly level: its northern end stands only about 4 cm higher than its southern end, nearly three miles away.
- The earliest known account of the moving rocks dates to 1915, when a prospector named Joseph Crook from Fallon, Nevada, visited the playa.
- In a study begun in 1968, geologists gave 30 stones names; the smallest, Nancy, only about 6 cm across, travelled the farthest, some 260 metres in total.
- A dolomite block of about 320 kg nicknamed Karen vanished before 1994 with no sign of vehicles on the playa, and was found again by geologist Paula Messina in 1996.
- Most of the travelling stones are dolomite or syenite, the dark dolomite breaking off a steep promontory along the eastern shore near the south end.
- The dried surface cracks into polygons typically 8 to 10 cm across, formed where three cracks meet at angles of 120 degrees.
- A few days after rain, small curls of drying mud nicknamed corn flakes appear on the surface of the playa.
- Scientists have compared the shape of Ontario Lacus, a shallow hydrocarbon lake on Saturn's moon Titan, to that of Racetrack Playa.
- The basin receives only about 3 inches of rain a year and stays dry and bare of vegetation for almost the whole year.
Why it is worth it
Racetrack Playa is a dry lakebed high in a remote valley of Death Valley National Park, about 3 miles long and just over a mile wide, at 3,708 feet above sea level. Its surface is a perfectly flat mosaic of cracked clay polygons, pale as bone and ringed by dark mountains. Scattered across it lie rocks of all sizes, from pebbles to sizeable boulders, and behind each one runs a long, shallow groove: a trail showing that the stone has travelled across the mud, sometimes in straight lines, sometimes in curves and zigzags, and occasionally in parallel with a neighbour.
For decades the "sailing stones" were a genuine scientific puzzle, because no one had seen them move. The answer came in 2014, when researchers who had fitted rocks with GPS units recorded the motion directly. On rare winter days, a shallow layer of rainwater on the playa freezes overnight into thin panes of ice; as the sun breaks them up, light winds of only a few metres per second push the floating ice sheets, which shove the rocks along the soft mud at up to about five metres a minute. A single move can last a quarter of an hour; on a single December day in 2013 more than sixty rocks moved, some travelling over 200 metres that winter, and the tracks they leave may survive for years.
At the north end of the playa, the Grandstand, a 73-foot island of dark quartz monzonite, rises abruptly from the white floor and makes a natural lookout. The moving rocks are found mostly toward the southern end, about two miles beyond it, below the slopes that shed them. The best light for the patterned surface and the long trails is early and late in the day. The playa is extremely fragile: footprints and tyre tracks in damp mud last for years, and rocks must never be moved or taken.
Getting there
The Racetrack lies in the northwest of Death Valley National Park in Inyo County, California. It is reached by a rough, washboarded gravel road of about 26 miles running southwest from Ubehebe Crater, past Teakettle Junction, to the Grandstand parking area; the park advises high clearance, heavy-duty tyres and usually four-wheel drive, and the drive from Furnace Creek takes at least three and a half hours each way. The nearest town is Ridgecrest, about 118 km away in a straight line, and the nearest airport is Eastern Sierra Regional Airport (BIH) in Bishop, about 105 km away; many visitors arrive instead via Las Vegas.
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From the encyclopaedia
The Racetrack Playa, or The Racetrack, is a dry lake feature with sailing stones that inscribe linear "racetrack" imprints. It is located above the northwestern side of Death Valley, in Death Valley National Park, Inyo County, California, U.S.
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