Some of it is the visual impact: the scale of the cliffs, the drama of the waterfalls, the strange beauty of the summit landscape.

Some of it is the cognitive impact of the age: two billion years is a number that forces a recalibration of what “old” means and where the human moment fits in the story of the planet.

Some of it is the biological impact: the knowledge that the specific organisms on the summit are found nowhere else on Earth, that they are the products of evolutionary processes operating in this specific place over geological time.

And some of it is less tractable — the quality of feeling that certain landscapes generate, a sense of being in the presence of something that operates at scales and according to principles that human beings are built to sense but not quite to grasp.