A ring of broken limestone 160 metres across and 40 metres tall standing in Siberian forest, with a smaller mound about 12 metres high sitting in the middle of it, roughly 350 km from Bodaibo. The Evenki knew it and avoided it, calling it the Fire Eagle Nest. Vadim Kolpakov, a Russian geologist, walked into it in 1949 and described it for science, and for sixty years it was one of the better arguments in Russian geology: meteorite, volcano, or gas. Tree rings settled the timing, which is the part that keeps it interesting, because the mound is only about 300 years old and holds 230,000 to 250,000 cubic metres of rock, so something pushed all that up in recent history. The Patom Crater Conference in 2010 came down on gas: a fast outflow of deep gases and fluids, with no evidence for an impact and the chemistry against it. Irkutsk Oblast.
Irkutsk Oblast, Russia
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