An industrial anomaly
On Mount Baigong in the remote Qinghai Province of China, dozens of pipe-like structures cut through the rock. They are found inside three triangular caves and on the shore of nearby Lake Toson, a saltwater lake. The objects look like a network of metallic pipes; some are as large as 40 centimeters in diameter, while others are the size of a toothpick. They are reddish-brown and appear embedded in the mountain's floor and walls, suggesting they are old.
The site is located about 40 kilometers from the city of Delingha in an inhospitable region where modern industry is absent. Human activity in this part of the Qaidam Basin dates back about 30,000 years, but historical inhabitants were nomads who left behind no complex industrial structures. This raises a question: if these are artificial pipes, who made them? Initial speculation, fueled by their unusual appearance, led to theories of a prehistoric high-tech civilization or even an extraterrestrial base. A local monument with a satellite dish on top now points tourists toward the "alien ruins".
Early analysis of the pipe material added to the confusion. A local smeltery reported the composition as mainly ferric oxide, silicon dioxide, and calcium oxide. However, about 8% of the material was of unknown composition. Later, thermoluminescence dating performed by the Beijing Institute of Geology on the surrounding rock suggested an age of around 150,000 years, adding to the mystery.
A case of mistaken identity
Geologists who visited the site in 2001 offered a less sensational but more evidence-based explanation. The "pipes" are a natural geological formation, not a manufactured product. The leading scientific theory is that they are fossilized casts of tree roots. According to a 2003 report, scientists found organic plant matter inside the pipe material. Cross-sections of some samples even revealed structures that look like tree rings.
The geological process that likely formed the pipes is known as diagenesis. In the distant past, the now-arid Qaidam Basin was a much wetter, subtropical area with abundant vegetation. When trees died, their roots became buried in sediment. Over long periods, mineral-rich groundwater seeped through the soil. As the organic root material decayed, minerals such as pyrite or hematite (iron oxides) precipitated in the voids, creating a perfect cast of the original root structure. This process, a form of fossilization, created the hard, hollow, pipe-like cylinders seen today. Similar iron-rich root casts have been documented by researchers in other parts of the world, such as southern Louisiana. The iron-rich sediments of the Tibetan Plateau provided the necessary ingredients for these specific formations.