First geological cross sections and schematic plan of the Kaalijärv crateriform structure, published by Wangenheim von Qualen (1849, pl. 5 in the Moscow edition; A) and Eichwald (1854, p. 8; B1), as a visualization of two opposing endogenic models, maar-type volcanic and sinkhole, respectively (compare with later graphical elucidation of the crater as the meteorite impact site – Figs. 2B and 5C, D). In the hypothesized ground collapse, “A” means a funnel-like depression, “+” – the layers of limestone at the lake are subsided, they are strongly bent and broken and they show the layers at the wall “a” from it downfallen position, almost as at “b” where “+” means that there has been similar downwashing of clay layers between the limestone layers. It shows directly that there is a subterranean connection between the lake and the spring at Salla.