Then it was tundra, then birch forest, then pine forest, then alder, linden, elm and ash, then most recently oak, but beech was coming.

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The episode is known as the Younger Dryas, because in Scandinavia abundant pollen from a tundra flower called the mountain avens, Dryas octopetala, reappears in soil from this date, indicating that the forest had once more given way to tundra.

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And then move up into Ponderosa pines, then in upper elevations spruce and fir forest, and then finally to some sort of alpine tundra up at the top.

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