Impact Structures of the World

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Name	LAPPAJÄRVI
Status	Confirmed
Country	Finland
Coordinates	Lat. N 63°09' Long.E 23°42'
Diameter km	17.0
Age Ma or date	76.2 ±0.29
Synonyms	Lake Lappajärvi
Remarks	Largest impact structure in Finland. Impactor most probably H chondrite. Melt rocks contain average of 0.34 wt% material from impactor. ⁴⁰Ar/³⁹Ar age is from Schmieder 2013 and it is the most reliable age for the Lappajärvi impact. That same study suggest that hydrothermal activity due to hot impact melt lasted 0.6-1.6 Ma after the impact. Earlier age for Lappajärvi was from U/Pb dating and it gave age of 73.3 ±5.3 Ma (Mänttäri 2001).
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References
	CoM 1985	Graham, Bevan and Hutchison, ''Catalogue of Meteorites'', 4th Edition, (1985).
	Fregerslev 1976	Fregerslev S. and Carstens H., Contr. Min. Petr., vol.55, p.255 (1976)
	Grieve 1988	Grieve R.A.F. et al, "Astronaut's Guide to Terrestrial Impact Craters", NASA Space Shuttle Earth Observation Project, LPI Technical Report Number 88-03, Lunar and Planetary Institute (March 1988)
	Hodge 1994	Hodge, Paul W., ''Meteorite craters and impact structures of the Earth'', book, 122 pp, Cambridge University Press (1994)
	Lehtinen 1976	Lehtinen M., ''Lake Lappajärvi, a meteorite impact site in Western Finland'', GSF Publication 282, (1976)
	Lehtinen 1998	Lehtinen M., "Meteoriittitörmäyskraatterit - maan ja taivaan kohtauspaikat", (in Finnish) in Lehtinen M., Nurmi P., ja Rämö T. (edit.), "3000 vuosimiljoona - Suomen kallioperä" , Suomen geologinen seura (1998)
	Mänttäri 2001	Mänttäri I. and Koivisto M, ''Ion microprobe uranium-lead dating of zircons from the Lappajärvi impact crater, western Finland'', MAPS, vol. 36, no. 8, pp. 1087-1095 (2001)
	Oja 1978	Oja H., "Tulipalloja taivaalla" (in Finnish), a book published by Ursa Astronomical Association, Helsinki (1978)
	Schmieder 2013	Schmieder M., and Jourdan F., The Lappajärvi impact structure (Finland): Age, duration of crater cooling, and implications for early life, Geochimica et Cosmochimica Acta 112, 321-339 (2013)
	Simonds 1977	Simonds C.H., Phinney W.C. and Warner J.L., "Effect of Water on Cratering: A Review of Craters and Impactities on the Earth, Moon and Mars", LSC VIII abstracts p.874-876 (1977)
	Svensson 1968	Svensson N.B., Nature, vol.217, p.438 (1968)
	Tagle 2007	Tagle T., Öhman T., Schmitt R. T., Erzinger J., and Claeys Ph., ''Traces of an H chondrite in the impact-melt rocks from the Lappajärvi impact structure, Finland'', MAPS 42, Nr 10 (2007)
	Tietohippu 1998b	"Lappajärven meteoriittikraatterista löytyi törmäystimantteja" (in Finnish), an article (no named author) in Tietohippu-magazine of Geological survey of Finland, nro 1-2 (1998)

LAPPAJÄRVI