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 | |
.png) The lake with the impact structure area in grey. | |
| Location | Petäjävesi |
| Coordinates | 62°13′N 25°15′E / 62.217°N 25.250°E |
| Type | Impact crater lake |
| Primary inflows | Könkköjoki |
| Primary outflows | Autionsalmi |
| Basin countries | Finland |
| Max. depth | 26 m (85 ft)[1] |
| Surface elevation | 111.1 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
edit
References
edit- ^ a b c Citizen's MapSite
- ^ a b Moilanen, Jarmo. "Karikkoselkä impact structure". Impact structures in Finland. Archived from the original on September 27, 2007. Retrieved 2006-05-08.
- ^ 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.
- ^ "Karikkoselkä". Earth Impact Database. Planetary and Space Science Centre University of New Brunswick Fredericton. Retrieved 2009-08-19.
- ^ "Karikkoselkä". Earth Impact Database. Retrieved 2006-05-08.
- ^ "Petäjäveden kulttuuriympäristö". 2006-06-22. Archived from the original on 2007-09-30. Retrieved 2007-08-30.