Summasjärvi
| Summasjärvi | |
|---|---|
 | |
| Coordinates | 62°39′N 25°24′E / 62.650°N 25.400°E |
| Type | Lake |
| Catchment area | Kymijoki |
| Basin countries | Finland |
| Surface area | 21.9 km2 (8.5 sq mi) |
| Average depth | 6.73 m (22.1 ft) |
| Max. depth | 41 m (135 ft) |
| Water volume | 0.147 km3 (119,000 acre⋅ft) |
| Shore length1 | 50.15 km (31.16 mi) |
| Islands | Summassaari, Lamposaari |
| 1 Shore length is not a well-defined measure. | |
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.
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 by 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
- ^ a b 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.
- ^ a b Korteniemi, Jarmo (26 June 2018). "Saarijärveltä Keski-Suomesta löytyi uusi törmäyskraatteri". Tiedetuubi. Retrieved 26 June 2018.
{{cite web}}: Cite has empty unknown parameter:|dead-url=(help) - ^ a b Lerssi, Jouni; Mursu, Juha; Niskanen, Matti; Pajunen, Hannu (2007). Summasenjärven johtavuusanomalian tutkimukset vuosina 2005 ja 2006 (PDF). Geological Survey of Finland.
- Finnish Environment Institute: Lakes in Finland
- Etelä-Savon ympäristökeskus: Saimaa, nimet ja rajaukset