Paasselkä
Key facts
- Country
- Finland
- Diameter
- 10 km
- Age
- about 231 million years
- Location
- 62.15° N, 29.42° E
A round basin of the lake Paasivesi in eastern Finland, part of the great Saimaa lake system, about 10 km across.
Paasselkä is an impact structure about 10 km across in eastern Finland, filled by a round basin of the lake Paasivesi, part of the Saimaa lake system.
Discovery. The round shape of the lake basin, and an unusual pattern in magnetic surveys, drew attention. In 1999 geologists confirmed an impact when they found shatter cones, cone-shaped fractures produced only by shock, and quartz with planar deformation features in boulders and drill cores from the area.
What it hit. The impactor struck ancient crystalline rocks of the Baltic Shield, mainly gneiss and granite nearly 2 billion years old.
Age. For years the age was poorly known. More recent argon dating of impact melt rock gives about 231 million years, in the Late Triassic.
Why it matters. Paasselkä is one of the larger impact structures in Finland. The impactor is unknown.
Visiting. The lake is a popular area for boating and holiday cottages.
Did you know?
Paasselkä is part of the great Saimaa lake system of eastern Finland.
Its impact origin was confirmed in 1999.
It formed in the Late Triassic, when the first dinosaurs were spreading.