Is That Rock Alive?

Welcome to Death Valley. The very name of this place might fill some people with dread, but you’re not afraid. You’re just out enjoying the desert sunshine. Besides, there’s nothing much here except for some rocks.

Wait: Did that rock just . . . move? No that’s ridiculous. But seriously . . . did it?

Death Valley National Park is located in California and Nevada. It’s a place of such extremes that it can seem like another planet. There are deep canyons, towering peaks, and a collection of wildlife: rattlesnakes, scorpions, mountain lions, and spiders bigger than your hand. The heat, too, can seem otherworldly. Summer temperatures regularly climb to 120 degrees.

The strangest area of Death Valley can be found in Racetrack Playa [PLAHY-uh]. The playa is more than 80 miles from the nearest visitor’s center. It’s a shallow, 3-mile-long section of sunken earth. Scattered across it are hundreds of rocks ranging from stones the size of your fist to boulders weighing hundreds of pounds. And in the ground behind each rock is a mysterious trail, as if the rock had been pushed along in the dirt. Some of these trails are a few feet long. Others are nearly a half mile.

So who is moving the rocks? A ghost? An animal? Someone playing a trick?

Actually, nobody. The rocks appear to be moving by themselves, as if they were alive.

People have been trying to solve the mystery of the “sailing stones” for years. One explanation was that whirlwinds moved the stones. Other explanations have included animals, magnets, pranksters, and, of course, aliens. (What mystery hasn’t been blamed on aliens?)

In 2006, a scientist named Ralph Lorenz came up with a new theory. He suggested that in the winter, slabs of ice form around the rocks. When the ground begins to thaw, the rocks, wearing collars of ice, float out of the mud and sail along, leaving trails in the dirt behind them.

Lorenz put his theory to the test in his own kitchen. He dropped a rock into a plastic dish, added water, and stuck the dish in his freezer. Later, he popped the rocksicle out and placed it in a shallow tray of water with sand at the bottom. Sure enough, with a gentle breath, Lorenz was able to send the rock moving across the water, carving a trail in the sand as it moved.

It seemed Lorenz had solved the mystery of the sailing stones at last. Alas, no aliens were involved.