Sources used for this story include: “Raising Heaven: Where Rocks Go Wandering,” by Tim Cahill (National Geographic).
The world still holds many wonders that science—so far— cannot explain. As you learn about the three mysteries described, see if you can hypothesize any scientific explanations for them.
1. Ball Lightning
Too many public sightings of ball lightning have been reported to write it off as fictitious. It is literally a blazing ball of lightning that usually appears during a thunderstorm. What makes it incredibly intriguing is that these burning spheres are actually mobile, with seemingly unexplainable powers. People have seen ball lightning pass through blocks of metal, wood, and even buildings. They are accompanied by strong sulfurous odor, and have a lifespan ranging from one second to a minute.
Ball lightning can cause major damage, such as burning objects in its path. So far, the most popular scientific explanation says that lightning balls are made of vaporized silicon. In 2012, scientists in China captured video and spectrographic images of ball lightning for the first time. The images have allowed scientists to determine what these balls of fire are made of, so, we may be close to an explanation.
2. Earthquake Lights
Sometimes before, during, or after a large earthquake, mysterious, flashing lights are seen in the sky. People have described them as blue, white, multicolored, or sometimes every color in the spectrum. These earthquake lights usually last only a few seconds, though some have been observed for as long as a minute.
Earthquake lights have been observed throughout history, with the earliest report dating back to 373 BCE. The 20th century provides the majority of reports. After the 1930 earthquake at Japan’s Idu Peninsula, more than 1,500 people told researchers they had seen mysterious lights. After the 1976 Tangshan earthquake in China, people reported a "colorful, flashing light display [that] was seen in the sky 200 miles away."
Scientists began to take earthquake lights seriously in the 1960s, when they were first photographed. More recently, people have captured earthquake lights on video. Many wonder whether earthquake lights can be taken as a warning that an earthquake is about to happen.
In 2010, Chilean journalist Cecilia Lagos witnessed earthquake lights. Later, she said:
I saw through my window, while I was still in bed, I saw the sky changing colors, it was absolutely surreal. I really thought it was the end of the world...I don't know I hope you understand me because I'm not exaggerating really because I saw it through my window like that.
That was the most terrifying thing seeing the sky changing colors with the terribly, amazingly strong movement of the earth, I thought, ok...this is mother earth.
An old, Japanese haiku poem (author unknown) hints at the connection of these lights to movement under the earth’s surface:
The earth speaks softly
To the mountain
And lights the sky.
Some think that certain types of rock grinding against one another may generate electrical charges that make the sky glow. But, science does not yet know with certainty the cause of earthquake lights.
3. Sliding Rocks
Another geological mystery is sliding rocks, also called sailing stones or moving rocks. These are large, heavy rocks that appear to move, apparently on their own, along the smooth ground of a valley. No one has seen the rocks move. We know they have moved because of the long tracks they leave in the ground.
In Death Valley, Arizona, a large, flat area known as Racetrack Playa has many of these moving rocks. A writer in National Geographic magazine said:
I am thinking specially of an area in the northwest section of Death Valley called the Racetrack, where, inexplicably, …rocks as big as microwave ovens go zipping across the desiccated mud for distances of more than half a mile (880 m). The evidence is all there: deep tracks in the surface, with a rock at the end. One concludes, reluctantly, that the rocks somehow traveled a couple of hundred yards, leaving a telltale trail behind. There are over 150 of these roving rocks. But no one has ever seen them move.
No one has seen the rocks move, nor is there evidence that an animal or human moves them—so, how and why do the rocks move?
At Racetrack Playa, many curious visitors have observed the stones and the tracks they leave. The tracks can be hundreds of feet long and are typically less than an inch deep. The stones appear to move every two or three years and most tracks develop over three or four years. Rocks with rough bottoms leave straight tracks, while those with smooth bottoms seem to wander. Rocks sometimes turn over, exposing another edge to the ground and making a different-looking track.
Sometimes two rocks seem to have started together, traveling side by side, until one abruptly took another direction, to the left, to the right, or even backward. Because no one has witnessed the rocks moving, the speed the rocks travel at are not known.
One theory suggests that the rocks are so porous that there is air inside them. On a sub-zero night, the air inside a rock will compress. The next day, the intense desert heat causes the air inside to once again expand, which pushes the rocks along their paths.
Gravity is not the cause. Sliding rock trails go in a variety of different directions, often uphill. Many people believe that strong winds move the rocks when the weather is wet. The dried mud at Racetrack Playa, becomes slippery when wet and can sometimes freeze overnight into sheets of ice. But some of the rocks weigh as much as a human, which some researchers feel is too heavy for the area's wind to move, even across a very slippery playa. People have tried to move the rocks when the ground is slippery, using ropes, and have failed.