Kaali
Key facts
- Country
- Estonia
- Diameter
- 110 m
- Age
- about 3,500 years
- Location
- 58.37° N, 22.67° E
A round, tree-ringed crater about 110 m across with a small lake at its bottom, and eight smaller craters scattered nearby on the island of Saaremaa.
Kaali, on the Estonian island of Saaremaa in the Baltic Sea, is one of the few meteorite craters that probably formed while people were living nearby. The impact happened in the Bronze Age, and it may have left a mark not only on the landscape but on local culture.
The impact. Around 3,500 years ago an iron meteorite entered the atmosphere and broke apart. The fragments struck the ground with great force, making a cluster of nine craters. The largest, the main Kaali crater, is about 110 m across and about 22 m deep from rim to bottom. It contains a small, round lake surrounded by trees. The eight smaller craters, scattered within about a kilometre, range from a dozen metres to a few tens of metres across.
The total energy of the main impact has been compared to a small nuclear explosion. People living on Saaremaa at the time would have seen a blinding fireball and felt the blast, and nearby forests may have been flattened and set alight.
Dating the impact. Estimates of Kaali's age have varied widely, from about 3,500 to more than 7,000 years. Recent work using radiocarbon dating of charcoal and of plant material buried by the ejecta points to an age of roughly 3,500 years, during the Bronze Age.
Proof of an impact. In the nineteenth century people debated whether the craters were volcanic, sinkholes or ancient fortifications. In 1937 the Estonian geologist Ivan Reinwald found small fragments of meteoritic iron, confirming the impact. The iron belongs to group IAB, one of the main families of iron meteorites. Fragments are small and rare.
Myths and memory. Kaali has inspired many suggestions linking the impact to ancient legends. Some scholars have proposed that stories in Finnish and Estonian folklore about the sun falling to Earth might preserve a memory of the event. These ideas are intriguing but impossible to prove. What is clear is that the site was important in later times: archaeologists have found evidence of a stone wall around the main crater and of offerings, including animal bones, suggesting it was used as a sacred place.
Visiting. Kaali is now a protected natural monument, with a visitor centre, museum and footpaths around the craters. A trail leads to several of the smaller craters. It is a peaceful, green place, and it is easy to imagine the moment, thousands of years ago, when it was anything but. Removing material from the protected site is not allowed.
Did you know?
Kaali's craters formed during the Bronze Age, when people already lived on Saaremaa.
The main crater holds a small lake surrounded by trees.
Iron meteorite fragments found in 1937 proved the craters were made by an impact.