GO 2... http://www.nps.gov/deva/planyourvisit/the-racetrack.htm

The Racetrack Playa, or The Racetrack, is a scenic 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.

The sailing stones are a geological phenomenon found in the Racetrack.
Slabs of dolomite and syenite ranging from a few hundred grams to hundreds
of kilograms inscribe visible tracks as they slide across the playa surface,
without human or animal intervention.

The tracks have been observed and studied since the early 1900s,
yet until 2014 no one had ever seen the stones in motion.
Racetrack stones only move once every two or three years
and most tracks last for three or four years.
Stones with rough bottoms leave straight striated tracks
while those with smooth bottoms wander.