The song lines literally are a record of what has happened to the land over these periods of times - supported by the geology itself.

The formation of islands, the kinds of animals that used to be found there, the movement of lakes, the lowering and raising of the oceans - these are all confirmed, recorded events.

That's the beauty of the claim - it doesn't need to be confirmed!

It isn't confirmed but their stories do match some geological and enviromental events going back that far.