The Kaali crater

A real Bronze Age impact crater, possibly remembered in folklore

A meteorite hit a populated island, and people watched it happen. That is rare enough that Kaali is grouped with only a couple of comparable events, the Henbury craters in Australia and Carancas in Peru.

The incoming body was travelling somewhere between 10 and 20 kilometres a second with a total mass of twenty to eighty tonnes. It broke apart five to ten kilometres up, and the pieces came down across the Estonian island of Saaremaa as nine separate craters. The largest is 110 metres across and 22 metres deep, and holds Lake Kaali. The explosion threw out around 81,000 cubic metres of dolomite and other rock and produced a column of extremely hot gas several kilometres high. Vegetation burned up to six kilometres away. A local heritage account puts the devastation on an already densely populated island in the range of a small nuclear weapon, and suggests survivors may have read it as the death of the sun, with dust darkening the daylight for days.

When it happened is genuinely unsettled. Published estimates range from about 6,400 BCE to about 400 BCE depending on method: silicate spherules in Estonian bogs point to roughly 7,600 years ago, an iridium signal in a nearby bog to the fourth century BC, and recent work to shortly after 1530 to 1450 BC. The heritage account favours the second half of the Bronze Age, around 1600 to 1800 BC.

There is a second correction worth knowing. The lake is widely treated today as an ancient holy site, but the same account says it was not known that way in local folklore until the early nineteenth century, when Baltic German scholars proposed the idea and it spread from their writing back into the population as secondary folklore. It adds, fairly, that this does not prove the lake was never sacred.