Balancing rocks are truly stellar (and indeed interstellar) features that attract tourists, geologists, and increasingly, artists.
1. BALANCED ROCK // COLORADO, USA
A few hundred million years ago, Colorado was covered by a shallow inland sea that eventually turned into sandstone. As the area rose during the creation of the Rocky Mountains, the softer areas of sandstone eroded away, while the areas of the sandstone that were harder stayed put, giving us Colorado’s Garden of the Gods. Eventually, the erosion and weathering around the base will cause Balanced Rock (see photo above) to lose its balance and collapse.
2. BALANCING ROCKS // SEVERAL PLACES AROUND ZIMBABWE
As in Colorado, these features were originally surrounded by softer rock that eroded away. As the rocks warmed and cooled, they cracked into nice geometric patterns. When the surrounding rock and dirt disappeared, they fell onto each other, just like bricks would if you removed the mortar [PDF]. Zimbabwe so appreciates these features that they have the rare geologic distinction of being featured on the 100 trillion Zimbabwe dollar note.
3. BIG BALANCED ROCK // CHIRICAHUA NATIONAL MONUMENT, ARIZONA
Around 27 million years ago, the Turkey Creek volcano (now a caldera) erupted, covering areas of modern Arizona with over 1600 feet of ash and pumice that fused into a soft rock called welded tuff. But tuff isn’t very tough, and it began eroding away along the weaker areas at the rate of two thirds of an inch per thousand years [PDF]. Thankfully, the USGS says there is no risk to these rocks from erosion for the next several thousand years. A much bigger concern for the rocks is earthquakes, although they came through a recent 7.2 quake with only minor damage (nearby buildings weren't so fortunate).
4. PRECARIOUSLY BALANCED ROCKS // NEAR SAN ANDREAS FAULT, NEVADA AND CALIFORNIA
Nick Hinz // Nevada Bureau of Mines & Geology
If there's any place in the country where balancing rocks shouldn’t exist, it's near the San Andreas fault, where you'd think earthquakes would topple them like dominoes. Yet they are there, and have been for at least 10,000 years, through at least 50 large earthquakes. An attempt to address the mystery of how the rocks stay put was published in August, suggesting a theory that since the rocks are between the San Andreas and San Jacinto faults, there might be an interaction between the faults that protects the balanced rocks by lessening ground vibration in the area. This idea would fit into geologic theory—but would mean all our current models of the San Andreas fault are incomplete.
5. IDOL ROCK // YORKSHIRE, UNITED KINGDOM
The strange Brimham Rocks in Yorkshire, of which Idol Rock is the most famous, were formed around 400 million years ago when the area was under a river. During the last glacial maximum, the nearby mountains were covered in glaciers, and where there are glaciers, there are glacial winds. The winds blew sand across the rocks at great speed, carving them into their odd new look—think of it like a natural form of sandblasting.
6. KUMMAKIVI BALANCING ROCK // FINLAND
Wikimedia Commons // CC BY-SA 4.0
The name translates as “strange rock,” but in English we have our own name for these features: erratics. As glaciers advanced, they picked up boulders from the surrounding countryside, and carried them along—sometimes for hundreds of miles. But when the glacier began retreating, the rocks didn’t make the trip back, and instead were set down on the surrounding countryside—sometimes perfectly balanced on top of another rock.
7. BALANCING ROCK // HOLLISTON, MASSACHUSETTS
WikimediaCommons // Public Domain
What makes this rock interesting is less the rock (it's a standard glacial erratic) than who attempted to knock it over. According to local legend, George Washington was traveling through and tried to push the rock down. Obviously, he failed.
8. RUGGESTEINEN // NORWAY
Sometimes a rock is so perfectly balanced that it can be rocked with just a bit of effort. This is the case with Ruggesteinen in Norway, also known as the Rocking Stone. Despite being over 70 tons, a couple of people pushing can move it.
9. KRISHNA'S BUTTER BALL // MAHABALIPURAM, INDIA
Wikimedia Commons // CC BY-SA 3.0
This one is mysterious. It might be a glacial erratic, it might have been eroded out of the surrounding rock, or it may have been placed there by ancient Indians. According to legend, in 1908 the local British Governor decided that it was dangerous and needed to be removed. Seven elephants supposedly weren’t able to budge it. While the elephant story might be a myth, glaciers can transport extremely heavy rocks—there’s one in Canada that weighs 16,500 tons.
10. GOLDEN ROCK PAGODA // MYANMAR
Wikimedia Commons // Public Domain
This 25-foot-tall rock is also mysterious. Myanmar does have glaciers, so that is always a possibility, but according to Buddhist tradition, the rock was placed there to enshrine a hair from the Buddha’s head.
11. MANMADE BALANCING STONES // AROUND THE WORLD
Recently, rock balancing has become a popular art. Based on traditional cairns (stacks of rocks that are either memorials or landmarks) they can become extremely intricate. But the craze is not without its critics. The removal of the rocks for the balancing act can cause the underlying soil to erode faster, as well as destroy the homes of small animals. In addition, building them in areas where cairns are used as trail markers is a quick way to get a lot of people very lost. Because of this, modern rock balancers prefer to place their rocks back where they found them after they take a few photos.
12. 67P/CHURYUMOV-GERASIMENKO // OUT OF THIS WORLD
ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
In 2014, the European Space Agency landed on comet 67P/Churyumov-Gerasimenko. In the images sent back to Earth was a picture of what look like balancing rocks on the surface of the comet. Their origin is mysterious: it could be that as the comet neared the Sun, ice melted away around these more impervious objects, leaving them behind. It could be that various interactions cause these boulders to move. Or it might even be camera perspective, and better imaging will reveal nothing out of the ordinary. Until then, any tour of the best balancing stones will require a space suit.