Lake Lappajärvi
Lappajärvi is a lake in Finland, in the municipalities of Lappajärvi, Alajärvi and Vimpeli. It is formed in a wide, partly eroded meteorite impact crater. The lake is part of Ähtävänjoki () basin together with Lake Evijärvi that is located downstream (north) of it. The Lappajärvi impact structure is estimated to be 77.85 ± 0.78 million years old (Campanian age of the Late Cretaceous time period). Experts working on Finland's Olkiluoto nuclear waste repository project have studied Lake Lappajärvi to help them project how Finnish landscapes might look one million years in the future and beyond. An island  in the middle of the lake, Kärnänsaari (Kärnä Island), gives the name to the black impact melt rock (impactite) found there, locally called kärnäite. The towns on the shore are Lappajärvi and Vimpeli. Although not very near any, the nearest major city is Seinäjoki. Earlier the lake was thought to have been an ancient volcano crater. In 1967, Swedish geologist Nils Bertil-Svensson examines kärnäite samples, and his article that Lappajärvi is a possible impact crater was published in Nature journal in February 1968.