A hike to the mysterious rock balls called Piedras Bola

A rock sphere perches on a pillar of volcanic tufa. Piedras Bola ("Ball Rocks") is a protected area deep in the mountains overlooking Ameca, in the Mexican state of Jalisco. The area is famous for the large stone balls found there, some of them almost perfectly spherical. They can be found lying on the ground or, in some cases, perched on rock pillars. A few months ago, I visited Piedras Bola, along with several carloads of expat hikers. We were led by my good friend Jim Boles, one of the more adventurous of my fellow hikers.


Overview

Google map showing the area between Lake Chapala and Piedras Bola. The protected area is identified by the red marker in the upper left of the photo. My hiking friends and I all live on the northwestern shore of Lake Chapala, between Chapala and Jocotopec. The drive from Chapala to the protected area is about 113km (70mi) and takes about 2 hours.

Upon arriving at the park entrance, you can leave your car by the highway and hike in on a forest road. However, it's a pretty fair distance and all up hill. If you try it, make sure you have plenty of time, water, and are in good shape.

Alternatively, you can drive in, but a high-clearance vehicle is necessary. Four-wheel-drive is not normally required, but there were some spots where I found it tough going in my two-wheel drive Toyota RAV-4. I guess it all depends on your sense of adventure and how many people are available to push if you get stuck.

Flower of the Leonotus leonurus. I took this shot at the parking area on the highway next to the Piedras Bola entrance road. This plant is native to southern Africa, according to Ron Parsons, my expert on Mexican flowers. How it got to this remote spot is a puzzle, but Ron says that it naturalizes easily. I guess it is just another sign of how small our world is. Ron is a wonderful resource and his work can be accessed through Wildflowers and Plants of Western Mexico or on his Flikr site: https://www.flickr.com/people/95453157@N02/?ytcheck=1&new_session=1

An almost perfectly conical mountain rises in the distance. There were numerous spectacular views on our drive up into the mountains, as well as along the trail. The conical mountain is almost certainly an extinct volcano, of which there are many in Jalisco. I have climbed several volcanos in the area, including Nevado de Colima and Volcán Tequila.

The forest through which we hiked was open and park-like. High altitude forests in Jalisco tend to have very little underbrush, giving them a pleasantly open feel. By contrast, the mountains around Lake Chapala, where I usually hike, are much lower and covered with dense, jungle-like foliage.


The hike in

Three expats hiker along the park's access road. The man on the left is Beto, a Mexican-American who moved down to live full-time in Mexico. The two others are Marilyn and Peter. All three are great people to hike with.

Not far along the trail, we encountered a small lake. For reasons not clear to me, the shoreline was bordered with dead trees. Perhaps it has something to do with the water. Whatever the water's quality, the setting was lovely.

A little further on, we reached this small, rather odd cottage. Notice the sofa sitting on the edge of the roof on the right. It seemed a strange place to store furniture. There was no one around, so we couldn't ask about it.

A tall mirador, or lookout point, was attached to the cottage in back. When we followed the trail behind the cottage, we noticed that the cream-colored mirador had a door at the bottom. Since it was standing wide-open, we decided to take a peek.

A spiral staircase led up to the viewing platform. This was too much to resist, so several of us climbed up to take a look. When we got to the top, we saw that the rooftop of the house was flat concrete. The sofa was apparently placed there so that the cottage's occupants could enjoy the view in comfort. The only thing missing was a cooler for the beer.

Penny, Beto, and Brian were surprised to find us on top of the house. By this point, the warm weather had persuaded Beto to strip off his long-sleeve shirt and zip off the leg bottoms of his hiking pants. After checking out the view, we descended the spiral stairway. The cottage is apparently a public building used in administering the park. We never did encounter the people who use it.

Near the cottage are a couple of very rickety footbridges. Brian and Beto's wife Shari decided to give one of them a try. The rest of us looked it over and took another route. As they say, discretion is the better part of valor.

Not far from the bridge and cottage was a large stone amphitheater. Perched around the amphitheater you can see several of the smaller piedras bola. The cottage, bridge, and amphitheater are all apparently part of the park's infrastructure.

Piedras Bola formations

Beto and Shari lean against two of the rock balls during a break. Many of the balls sit on the surface or are partly submerged in the tufa (volcanic ash). There are a number of theories about the composition of the rocks, why they are round, and how they got here. As usual, some are convinced that they were crafted and placed here by space aliens. Skeptical of such claims, I decided to investigate a bit further.

Other rock balls sit on top of eroded pillars of tufa. Another theory proposed that the balls were carved by pre-hispanic people. This sounded somewhat more plausible than space aliens. However, while pre-hispanic folks did a great deal of stone carving, there is no evidence that they created these megaspherulites, as the scientists call them. While Mexico's native people have probably been aware of the piedras bola for millennia, scientists did not take note of the rock balls until the 20th century.

Tufa pillar with a partially round ball on top. Actually the first person to take official notice was not a scientist but a silver mine manager named Robert Gordon. Beside the entrance to his mine sat a huge piedras bola, which gave the mine its name. In 1967, following his retirement, Gordon decided to contact an archeologist named Matthew Williams Stirling. The archeologist agreed to look into the matter and quickly discovered an additional 17 rock balls in the area. Stirling theorized that the balls were man-made. However, this was based on very little except Stirling's previous experience in other areas where stone balls were crafted by humans.

Anthony enjoys a view of the mountains from a cliff top. In addition to being an enthusiastic hiker, Anthony is a yoga instructor who, with his lovely wife Katherine, has lived full-time in Mexico for a number of years. Word about the strange rock balls spread and, in 1968, a team from the US Geological Survey, National Geographic magazine, and the Smithsonian Institute arrived to take a look. In an article that appeared in the August, 1969 issue of National Geographic, they disputed the archeological theory because of a lack of evidence. (Being scientists, I doubt they gave the space alien theory a moment's thought).

Jim Boles, at the base of a vertical cliff. I asked him to pose here to provide some scale to this photograph. When I walked around the back side of the cliff, I was astounded to find that it was part of a single huge rock. One half of the rock apparently sheered away sometime in the distant past. The leader of the scientists was Robert L. Smith, of the US Geological Survey. Smith and the others determined that the balls are made of rhyolite, a rock that is formed from volcanic lava.

Remains of a wasps' nest formed an interesting pattern on a tufa formation. The National Geographic article postulated that the piedras bola began to form when a volcano in the area erupted 10-12 million years ago. Fragments of molten lava and ash shot into the sky, along with superheated gases. When they landed in the valley below, they were covered by layers of tufa ash. The glassy fragments began to cool, forming the nucleus around which surrounding material began to crystalize into spheres. The size of the ball depended upon how slowly the crystalization occurred. The slower it went, the larger the ball.

Anthony leads a group of hikers up from an arroyo. In 1998, a scientist at the University of Guadalajara proposed still another theory. Arturo Curiel Ballesteros agreed with the volcanic origin of the piedras bola. However, he asserted that the spheres were formed while still hurtling through the air and retained their shape when they landed in the soft tufa. This seemed unlikely to some of his fellow scientists (as it did to me) at the University of Guadalajara. Six of them got together and, in 2007, published a 266-page book on the subject, known as "the Bola Book."

Jim Boles passes by a large and partially fractured rock ball, on his way out of the park. The Bola Book agrees on the volcanic origin and chemical make-up of the rocks, but differs on how they came to be spherical. The authors assert that the piedras bola were the result of a pyroclastic flow--basically a hot, gaseous, avalanche full of lava and debris. As the incandescent lava bombs inside the flow were pushed along, their rotation caused them to form spherical shapes which they retained when their motion stopped. They were then covered with falling ash and remained entombed for millions of years. Natural processes of erosion wore away the tufa, leaving the rock balls fully or partially exposed.

Tasty tostadas from the restaurant where we lunched after our hike. One of the most enjoyable aspects of these hikes is the aftermath. Sitting around with good friends, comparing our hiking experiences, while enjoying a feast like this, makes all the effort worth while. So, which theory to believe? I'll leave it to you. Meanwhile, Scientists believe that there may be many more piedras bola deep under the surface. And, there may yet be other theories in the works about their origin. Stay tuned...

This completes my posting on the Piedras Bola. I hope you enjoyed it. If you did, and would like to make a comment or ask a question, please do so in the Comments section below or email me directly.

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Hasta luego, Jim