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

Southern Savonia South Savo (or Southern Savonia; fi, Etelä-Savo; sv, Södra Savolax) is a 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 ...

Finland Finland ( fi, Suomi ; sv, Finland ), officially the Republic of Finland (; ), is a Nordic country in Northern Europe. It shares land borders with Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of B ...

. The lake, which is a part of Orivesi, 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 (; grc, σταθερός, statherós, 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 ar ...

period of the Paleoproterozoic) and affected Paleoproterozoic 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, representing a large part of Fennoscandia, northwestern Russia and the northern Baltic Sea. It is composed mostly of Archean and ...

. Because of the unusual shape and associated

magnetic Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particle ...

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 in solid materials. The drill bit is usually a rotary cutting tool, often multi-point. The bit is pressed against the work-piece and rotated at ra ...

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 naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...

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 ''ignis fatuus'' (, plural ''ignes fatui''), is an atmospheric ghost light seen by travellers at night, especially over bogs, swamps or marshes. The phenomenon is known in English folk belief, ...

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

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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