Odds and Ends
14 10, 5:29am
Sorry, I was replying blind, without actually looking up what the discussion was about.
The finnic epic stories and folklore include creation myths how land arises from the ice lake (Väinamaine, the birds and eggs and such). There has been only two regions that has seen land rise in the last 15 000 years: Baltoscandia and Canada. Everywhere else coastal areas were sunk by the rising sea levels due to glacial melt. And the southern coasts of the Baltic Sea (Poland, Prussia, Denmark, Lithuania, Latvia) stopped rising early on. The birds do colonise new islets and holms first and lay eggs and shit. That shit is the manure for a more flourishing future. The two highest hills of the two highest Estonian uplands are named Egghills. The peak of the third highest upland is Ebavere, which got its name from the Kaali meteorite impact event - the Viru witch bragged that she brought the Sun down to Saaremaa, while in reality the meteorite descended from that direction (from Karelia to Saaremaa, over Ebavere mountain). The Tsõõrikmäe meteorite crater is about 9500 years old and the Paganamaa near the border of Latvia is a subglacial meltwater runoff valley, which makes it at least 14500 years old.
The Kalevipoeg stories about hellgates are about: meteorite craters, karst caves and glacial moulin sinkholes. At the later stages of the ice age, there were a lot of moulins which drain the meltwater lakes on the glacier and after that those moulin holes are empty and theoretically traversable, if one uses ropes and stone nails. The glacial rim is not very thick and one (a team of many) could have descended the moulin to the bottom and under the glacier and discover those large runoff caves and valleys with lakes. A whole cave system hundreds of kilometers long with subglacial rivers running at the bottom of the subglacial valleys ('ürgorg', subglasiaalinen uoma). At least two such subglacial valleys in Finland also carry the name of Pagan. The etymology of those names goes back to the subglacial times.
Edit. And that is likely the source for the myths of the river Tuonela.
"At times living people visited Tuonela to gather information and spells. The trip there required weeks of trekking in a desert, and finally the crossing of the river with the help of a ferryman (similar to Charon in Greek mythology)."
That desert was the tundra landscape and as to the river, there was a river sinkhole (moulin), the river itself was subglacial.