A Structure Out of Place
In 1949, geologist Vadim Kolpakov was surveying the remote taiga of southeastern Siberia when he encountered a bizarre geological feature. Rising from the forested slopes of the Patom Highlands was a massive cone of shattered, whitish limestone blocks. The structure, now known as the Patomskiy Crater, is approximately 40 meters (130 feet) high and has a base diameter of about 160 meters (520 feet). Its total volume is estimated to be between 230,000 and 250,000 cubic meters, weighing over a million tons.
The cone is a near-perfect ring, but its top is not a simple depression. Instead, it features a circular trench and a central mound that rises about 12 meters (39 feet) high. The entire formation is composed of broken limestone and smaller amounts of sandstone and schist, all from the local Proterozoic-era bedrock. Kolpakov initially considered an archaeological origin, but the scale of the structure made that impossible. The local Yakut and Evenki people knew of the site, calling it the "Fire Eagle Nest," and they consider it an evil place that animals avoid and where people can fall ill or disappear.
Searching for an Origin
Dendrochronology, the study of tree rings, has been a primary tool for dating the crater. Analysis of trees growing on and around the structure suggests it formed between 300 and 500 years ago. This relatively young geological age rules out any connection to the 1908 Tunguska event. The trees also present their own anomaly; for a period after the crater's formation, their growth accelerated rapidly, a phenomenon also seen in trees near Chernobyl.
Obvious explanations have failed to hold up. A meteorite impact is unlikely because there are no impact fragments, no trace of meteoritic elements like iron or nickel in the rock, and no significant magnetic anomaly under the cone. A standard volcanic eruption is also improbable, as the region is not volcanically active and the cone contains no igneous or melted material.
Leading theories point to endogenous, or internal, geological processes. One strong hypothesis is a phreatic explosion, where deep magmatic heat instantly vaporized groundwater, causing a massive steam-driven blast that shattered the overlying limestone from below. Isotopic analysis of the limestone shows it interacted with hot water exceeding 100°C. Another theory involves the explosive release of a deep pocket of gas, like methane or hydrogen. These scenarios would explain the explosive formation and the lack of foreign materials, but the precise mechanism remains unconfirmed.