A walker heads up a mountain in late autumn and, as the poem goes, the landscape keeps opening onto much older ones. At first the details are small and immediate: deer clashing antlers, gnats dancing as if summer had come back, a mist the speaker admits might be "in my head." The speaker paces out the mountain with their body, and the birches, like "blank pages," suggest a mind ready to be written on.
Then the poem shifts. An old coal railroad bed and a wrecked car below lead the speaker to think about geology: seas, mud, mass extinction, the age of amphibians and giant dragonflies. Climbing becomes a kind of time travel, and the speaker grows "younger" as they rise through the layers.
The mood is quiet, curious, and humbled, but not gloomy. Loss and abandonment are there, yet the ending lifts. The horizon opens "like a rose" onto "ever more mountains," a sense of wonder at how much time the land holds.