Geologists first documented the moving rocks in 1915, but serious study began in the 1940s. The rocks - granite and dolomite boulders ranging from pebbles to 700-pound monsters - leave tracks in the playa's dried mud. The tracks are sometimes straight, sometimes curved, sometimes with abrupt turns. Different rocks leave different paths, ruling out a single wind event. The rocks clearly move, but no one could explain how. Theories multiplied: wind alone (but rocks this heavy?), ice sheets (but the playa rarely freezes), dust devils (but the paths were too organized), floods (but the tracks showed no water flow).

In 2011, scientists Richard Norris and James Norris began a monitoring project using GPS units attached to rocks and time-lapse cameras. In December 2013, they witnessed the phenomenon directly. Their observations confirmed the ice-sheet theory: when the playa has a shallow layer of water that freezes overnight, thin ice sheets form that can be pushed by light winds. Rocks become embedded in these ice rafts. When wind blows, the ice moves, taking the rocks with it. Temperatures must be cold enough to freeze water but warm enough to melt the ice by afternoon, leaving tracks in the exposed mud.

Rock movement requires a precise combination of conditions: enough rainfall to create a shallow lake, cold enough nights for ice to form, warm enough days for ice to melt, wind at the right time to push the ice, and mud of the right consistency to record tracks. This combination occurs rarely - perhaps once or twice per decade. Rocks may not move for years, then move multiple times in one season. The tracks persist for years, slowly eroding, so the playa always shows evidence of past movement even when conditions aren't right for current events.

The Racetrack itself is a remarkably flat, 2.8-mile-long dry lake bed at 3,700 feet elevation in the northern mountains of Death Valley. The rocks originate from a dolomite outcrop at the playa's southern end and from granite slopes to the south. They're scattered across the playa, each with its track trailing behind. Grandstand Island, an outcrop of dark rock, rises from the playa's northern end. The setting is desolate: no water, minimal vegetation, surrounded by bare mountains. The silence is profound.

Racetrack Playa is one of Death Valley's most remote attractions. The 28-mile road from Ubehebe Crater is unpaved, rough, and potentially impassable - high-clearance vehicles are essential, and 4WD is recommended. The road takes 2-3 hours each way. There are no services; bring everything you need. Cell service doesn't exist. The playa is best visited in morning or evening light when the rocks cast long shadows. Walking on the playa when wet damages the surface and is prohibited. Never move or disturb the rocks - doing so destroys the tracks and is illegal in the national park. The journey is demanding, but finding the moving rocks and their tracks is otherworldly.