A mountain is land that rises above the surrounding plain. But it is not simply higher than a hill; the very word mountain also implies a brand of majesty. On a mountain, normal processes are magnified—their steep slopes, for instance, mean streams flow faster and carry more rock of larger size, accelerating erosion. Mountains can create their own weather, as clouds dump their cargo on the windward side. And they carry their own heightened psychological charge as well: Thoreau, in a spiritual fright as he bushwhacked up Maine’s Katahdin, imagined that “some part of the beholder, even some vital part, seems to escape through the loose grating of his ribs as he ascends.” Though by conventional measurement the planet’s tallest mountains are all in Asia, Hawai‘i can claim its most massive: by the reckoning of one geologist, measuring from the seafloor, the Mauna Loa volcano is the “largest projected landmass between Mars and the Sun.”

Bill McKibben