Summasjärvi

Lake Summanen (Finnish: Summasjärvi, Summanen) is a medium-sized lake of Finland. It is located in Saarijärvi, in the region of Keski-Suomi. There is a Stone Age Museum in the island of Summassaari.

Summasjärvi
Summasjärvi
Coordinates62°39′N 25°24′E
TypeLake
Catchment areaKymijoki
Basin countriesFinland
Surface area21.9 km2 (8.5 sq mi)
Average depth6.73 m (22.1 ft)
Max. depth41 m (135 ft)
Water volume0.147 km3 (119,000 acre⋅ft)
Shore length150.15 km (31.16 mi)
IslandsSummassaari, Lamposaari
1 Shore length is not a well-defined measure.

The Summanen crater

The 12th impact crater identified in Finland is located at the center of the lake.[1][2] The crater is 2.6 kilometers wide, ~200 meters deep, and mostly buried under later sediments. The age of the crater is not known. It formed before the Quaternary glaciation, but on the other hand after the host rock which formed in the Svecofennian orogeny 1910 million years ago. (Plado et al. assume the impact was Phanerozoic, but give no evidence to support this.[1])

The otherwise shallow lake (depth <10 m) has a 41 m central deep or trench at the crater site. The location is also occupied by a significant, circular electromagnetic anomaly (with more conductive materials at the site).[3] The anomaly is supposedly the result of a 100 to 200 m thick subsurface lens, presumably formed of fractured rock with saline liquids.[2][3] The impact origin was inferred from the anomaly and the deep, and proven by identifying shatter cones and planar deformation features in glacial erratics adjacent to the crater.

See also

References
  1. Plado, Jüri; Hietala, Satu; Kreitsmann, Timmu; Lerssi, Jouni; Nenonen, Jari; Pesonen, Lauri (25 June 2018). "Summanen, a new meteorite impact structure in Central Finland". Meteoritics & Planetary Science. 53 (11): 2413–2426. Bibcode:2018M&PS...53.2413P. doi:10.1111/maps.13134. hdl:10138/321414.
  2. Korteniemi, Jarmo (26 June 2018). "Saarijärveltä Keski-Suomesta löytyi uusi törmäyskraatteri". Tiedetuubi. Retrieved 26 June 2018.
  3. Lerssi, Jouni; Mursu, Juha; Niskanen, Matti; Pajunen, Hannu (2007). Summasenjärven johtavuusanomalian tutkimukset vuosina 2005 ja 2006 (PDF). Geological Survey of Finland.
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