Impact Crater Lakes of the European Part of Russia

The origin of a number of impact formations (astroblemes), including lake depressions in the European part of Russia, is unknown. Many of them are very ancient, having arisen many millions of years ago. They are hidden under the sequences of rocks accumulated after the lake formation and are not visible on the surface of the Earth. The crater lakes are only “hypothesized” on satellite images or in the pattern of a river network. Among these are Kaluga, Karla, Kursk, Gagarin (Gzhatsk), and one of the largest meteorite craters on our planet, Puchezh-Katunki, with a diameter of almost 80 km. These lakes, and even the largest ones, can only be detected by geological methods, and they cannot always be unambiguously attributed to astroblemes. The only ancient crater found in the European part of Russia that is not hidden under the thickness of rocks is located in Karelia. It is occupied by Janisjärvi Lake. To date, there is evidence that the depressions of Smerdyachye, Svetloyar, and Rabiga Kul lakes are “young” (formed in the Holocene) meteorite craters. Morphological signs of the meteorite origin for such lakes are supported by the presence of an asymmetrical uplifted rim surrounding them with steep inner slopes facing the depression and gentle outer slopes. In the structure of the uplifted rim, there are fragments of rocks that have been ejected from the depression during the impact of a meteorite as well as impactites—fragments of rocks cemented by a glassy mass, with melted grains of quartz, feldspar, and zircon. The underlying sediments of the uplifted rims are deformed as a result of their squeezing from the center of the crater by the blast wave and crushing. The depth of such lakes is abnormally deep compared to neighboring lakes. The most studied lake of this type is Smerdyachye Lake located 140 km southeast of Moscow. The meteorite fell not earlier than not earlier than 9–10 ka BP. The appearance and structure of the lake depression combine the features of a meteorite crater and a karst depression. When the meteorite collided with the Earth’s surface, the crater was formed and deep-lying soluble carbonate rocks were opened. The lake that arose in the crater began to develop as a karst lake. Svetloyar Lake (Nizhny Novgorod oblast) is widely known thanks to the legend of the “invisible city of Kitezh,” which once sank to the bottom of the lake. The hills bordering the lake on the south side are composed of deformed Triassic clayey sediments. On the slopes of the hills, there are fragments of the Permian rocks 3–3.2 ka BP, ejected from a depth of at least 70 m during the impact of a meteorite on the Earth. Rabiga Kul Lake is located at the confluence of the Volga and Kama. The depth of the depression from the crest of uplifted rims to its bottom is up to 37 m. The age of the meteorite fall does not exceed 15 ka.