Wikipedia says they date back 480 million years, during the Ordovician period. I think the atmosphere would have been pretty breathable, but plants wouldn't conquer the land in a serious way for at least another 60 million years or so, with bugs following them. Nothing saw those mountains. If you time-traveled to the Pangean mountains, you would be the only being to ever observe them in their formative years. Eons would pass before the first plant set root at their feet. The sterile and desolate emptiness would be beyond human experience.

Sharks are older than the North Star. Not as in Polaris wasn't pointing north yet when the sharks evolved, but as in it hadn't formed yet.

Older than trees.

Older than bones.

Drones from land masses that don’t exist anymore.

There is rock in the Appalachian mountains without coal seams, because many formed in places before the land biomass that made coal and oil existed.

They contain layers of fossils from ancient whales back to small crustaceans.

480 million years ago trilobites were being heft out of the sea by the Appalachians.

The Appalachians existed for 20 million years before bearing witness to a million year long meteor shower from the L-chondrite debris that gave the earth temporary rings.