Underwater tree-ring science
Finland is a county of numerous small lakes. Some of the lakes are sourced by
cold spring water. If the bottom is also covered by a thick mud layer, the conditions are excellent
for preserving sunken pine logs in mud.
The oldest Scots pine remains, or so called megafossils, have remained completely undecayed more than 7600 years. The logs, however, do not resist very well physical movement of water and ice. That is why they get worn. See a collection of worn samples.
It is quite hard to core samples in muddy water (almost zero seeing). If lucky in getting a core out in one piece, moving it to a plastic container is qúite a challenge. Jouko Laitinen, the president of the Finnish Scuba Diver Association, demonstrates storing in a mud "storm". Using a frame saw and cutting a cross-section is a better idea. But one might use the whole bottle of air in that kind of work! That is why we prefer winching the logs into shoreline and using a chain saw.
Kari Mielikäinen, Marjukka Laine, Timo Pennanen and a Finnish tv-company (MTV3) interviewing Jouko Laitinen in Pieni Hossalaislampi. Year 1995, Hossa (close to Kuusamo in Eastern Lapland).