Karikkoselkä is a lake formed in an impact crater in Petäjävesi, Finland. Karikkoselkä is located in Central Finland approximately 30 km east from the centre of Keurusselkä, a much older and larger impact crater.[2] Most lakes in the region are elongated in northwest–southeast direction due to glaciation, but Karikkoselkä is strikingly round.

Karikkoselkä
Landsat 7 image of Karikkoselkä.
Karikkoselkä is located in Finland
Karikkoselkä
Karikkoselkä
The lake with the impact structure area in grey.
LocationPetäjävesi
Coordinates62°13′N 25°15′E / 62.217°N 25.250°E / 62.217; 25.250
TypeImpact crater lake
Primary inflowsKönkköjoki
Primary outflowsAutionsalmi
Basin countriesFinland
Max. depth26 m (85 ft)[1]
Surface elevation111.1 m (365 ft)[1]
References[1]

Many shatter cones, rock formations that form under the extreme pressures of impact, have been found around the lake. Further evidence comes from aeromagnetic maps, which show a clear magnetic anomaly in the impact crater area.[3] In addition, samples collected from deep drillings into the lake bottom confirm the impact origin of the structure.

The crater is the smallest identified in Finland, 1.4 km diameter and 150 m deep. Due to sediments the lake has a maximum depth of 26m which is unusually deep for a lake in the region. Karikkoselkä is estimated to be between 230 Ma and 450 Ma (million years old), most likely near 240 Ma (Triassic or earlier).[3] Some sources give an unreasonably young age of 1.88 Ma,[4][5] which is likely a misquotation – the discovery paper mentions that the bedrock in the region (known as the Central Finland Granite Complex) formed about 1.88 Ga (thousand million years ago), in the late Paleoproterozoic era.[2][3]

There is evidence of a neolithic settlement on the southern shore of the lake.[6] According to a plate erected there, no excavations have yet been conducted and the age of the settlement remains unknown.

See also

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References

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  1. ^ a b c Citizen's MapSite
  2. ^ a b Moilanen, Jarmo. "Karikkoselkä impact structure". Impact structures in Finland. Archived from the original on September 27, 2007. Retrieved 2006-05-08.
  3. ^ a b c Lehtinen, M.; Pesonen, L. J.; Puranen, R.; Deutsch, A. (1996). "Karikkoselkä - A new impact structure in Finland". Lunar and Planetary Science. 27 (3): 739–740. Bibcode:1996LPI....27..739L.
  4. ^ "Karikkoselkä". Earth Impact Database. Planetary and Space Science Centre University of New Brunswick Fredericton. Retrieved 2009-08-19.
  5. ^ "Karikkoselkä". Earth Impact Database. Retrieved 2006-05-08.
  6. ^ "Petäjäveden kulttuuriympäristö". 2006-06-22. Archived from the original on 2007-09-30. Retrieved 2007-08-30.
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