Kaluga
Key facts
- Country
- Russia
- Diameter
- 15 km
- Age
- about 380 ± 5 million years
- Location
- 54.50° N, 36.20° E
Nothing: the crater lies buried about 700 m beneath the city of Kaluga, south-west of Moscow.
Kaluga is a buried impact crater about 15 km across beneath the city of Kaluga, about 160 km south-west of Moscow, in Russia.
Discovery. Boreholes drilled beneath the city met thick, unusual breccia where flat layers were expected. For a time the cause was debated, and some geologists favoured a volcanic explosion, until study of the cores found shock features in quartz and other minerals, proving an impact.
What it hit. The impactor struck a sequence of Palaeozoic sedimentary rocks lying on crystalline basement. The crater was soon covered by the sea and filled with Devonian sediments, and it now lies about 700 m below the surface.
Age. Fossils in the sediments that filled the crater, and dating of impact rocks, give an age of about 380 million years, in the Middle to Late Devonian, with an uncertainty of about 5 million years.
Why it matters. Kaluga is one of the best-studied buried craters in Russia, with many boreholes through it. The impactor is unknown.
Did you know?
The city of Kaluga is built above a buried impact crater.
It was once thought to have been made by a volcanic explosion.
The crater lies about 700 m underground.