Finland A geophysical anomaly was noted in early 2000's. Followed detailed geophysical mapping showed clear round but shallow anomal in bottom of the lake about 2,6 km wide. In 2017 first shatter cones were found and later planar deformation features was found in those shatter cone samples. Summanen was 12th confirmed impact structure found from Finland. Age is not know, but it is less than 1880 Ma.