Paasselkä (earlier ''Paasivesi'', both names roughly mean 'Stone lake') is an oval-shaped lake formed in an eroded

impact crater An impact crater is a depression (geology), depression in the surface of a solid astronomical body formed by the hypervelocity impact event, impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal c ...

Southern Savonia South Savo (or Southern Savonia; ; ) is a Regions of Finland, region in the south-east of Finland. It borders the regions of North Savo, North Karelia, South Karelia, Kymenlaakso, Päijät-Häme, and Central Finland. The total area of South Savo ...

Finland Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, ...

. The lake, which is a part of

Orivesi Orivesi () is a town in Finland, located in the Pirkanmaa region. It lies to the northeast of the regional capital, Tampere. The population of Orivesi is approximately , while the Tampere metropolitan area, metropolitan area has a population of ...

, which is in turn part of the Greater Saimaa, is devoid of islands which makes it different from other lakes in the region. Paasselkä is also unusually deep, 75 m at the deepest point. The Paasselkä impact occurred roughly <1800 million years ago (

Statherian The Statherian Period (; , meaning "stable, firm") is the final geologic period in the Paleoproterozoic Era and lasted from Mya to Mya (million years ago). Instead of being based on stratigraphy, these dates are defined chronometrically. Th ...

period of the

Paleoproterozoic The Paleoproterozoic Era (also spelled Palaeoproterozoic) is the first of the three sub-divisions ( eras) of the Proterozoic eon, and also the longest era of the Earth's geological history, spanning from (2.5–1.6 Ga). It is further sub ...

) and affected

crystalline rocks and some overlying sandstones of the

Baltic Shield The Baltic Shield (or Fennoscandian Shield) is a segment of the Earth's crust belonging to the East European craton, East European Craton, representing a large part of Fennoscandia, northwestern Russia and the northern Baltic Sea. It is composed ...

. Because of the unusual shape and associated

magnetic Magnetism is the class of physical attributes that occur through a magnetic field, which allows objects to attract or repel each other. Because both electric currents and magnetic moments of elementary particles give rise to a magnetic field, m ...

anomalies, Paasselkä was suspected to have an impact origin long until it was confirmed after a deep

drilling Drilling is a cutting process where a drill bit is spun to cut a hole of circular cross section (geometry), cross-section in solid materials. The drill bit is usually a rotary Cutting tool (machining), cutting tool, often multi-point. The bit i ...

in 1999 making it the ninth known impact crater in Finland. Unlike many Finnish craters, it does not seem to have been buried under layers of

sediment Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...

Light phenomenon

Paasselän pirut, or Paasselkä devils, is a claimed

will-o'-the-wisp In folklore, a will-o'-the-wisp, will-o'-wisp, or ; ), is an atmospheric ghost light seen by travellers at night, especially over bogs, swamps or marshes. The phenomenon is known in the United Kingdom by a variety of names, including jack-o'- ...

phenomenon which sometimes occurs at the lake and the marsh and forest area in the immediate vicinity. One has described the light as a ball that moves at different speeds, or are completely at rest, and sometimes there are several spheres. The phenomenon has been known for a long time, written down from the 18th century, and is part of the local folk tales, which have given the name "devils". The locals thought the shining spheres were created by evil beings. The magnetic anomalies in connection with the impact crater might be related to the phenomenon.

References

* *

External links

Paasselkä impact structure
Impact craters of Finland Triassic impact craters Saimaa Lakes of Kitee Nature of Savonlinna Impact crater lakes {{EasternFinland-geo-stub

Light phenomenon

See also

References

External links