Iso-Naakkima

Iso-Naakkima is a lake in Southern Savonia, Finland, about 10 km south of the town of Pieksämäki. It is notable for having an eroded impact crater under the northwestern part of the lake. It is one of the oldest known, about 1200 million years old (900–1200 Ma, Mesoproterozoic). Of the known craters older than a billion years old, it is also one of the smallest being only 3 km in diameter.[3]

  • Iso-Naakkima in the impact crater area
Iso-Naakkima
Iso-Naakkima
Lake Iso-Naakkima with the impact structure area in grey.
LocationSouthern Savonia
Coordinates62°11′N 27°9′E
Primary outflowsSahinjoki
Basin countriesFinland
Max. length4.9 km (3.0 mi)
Max. width3.3 km (2.1 mi)
Surface area11.14 km2 (4.30 sq mi)[1]
Surface elevation111.2 m (365 ft)[2]
References[1][2]

At the time of the impact event, the continent of Baltica (modern northeastern Europe) was located near the equator. The crater is filled by recent (Quaternary) sediments and is not visible to the surface. Its existence was revealed by strikingly circular geophysical anomalies which are concentrated in a region 3 km in diameter; the actual remnant is about 2 km wide and 160 m deep. Its existence was later confirmed by drilling results. The discovery was made in 1989 and therefore Iso-Naakkima is the fourth known impact structure in Finland.[3]

See also

References
  1. www.ymparisto.fi - Iso-Naakkima Archived 2007-09-30 at the Wayback Machine
  2. Citizen´s MapSite
  3. "Iso-Naakkima". Earth Impact Database. Planetary and Space Science Centre University of New Brunswick Fredericton. Retrieved 2015-12-30.
  • Pesonen, L. J., Järvelä, J., Sarapää, O., & Pietarinen, H. (1996). "The Iso-Naakkima Meteorite Impact Structure: Physical Properties and Paleomagnetism of a Drill Core". Meteoritics & Planetary Science. 31: A105–A106. Bibcode:1996M&PSA..31S.105P. doi:10.1111/j.1945-5100.1996.tb02098.x.CS1 maint: multiple names: authors list (link)
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