For the rest of my life, there are two smells that will always initiate memories of this summer’s wilderness journey. The first is the smell of sulfur, or more specifically – hydrogen sulfide. Yellowstone sits atop a supervolcano, a natural source of hydrogen sulfide vapor. Traveling across the volcanic caldera, which covers over 1,200 square-miles, the putrid smell of rotting egg lingers in the air, ever present, if even just barely perceptible.

Sulfur is normally associated with powerful destructive forces. In addition to its association with volcanoes, sulfur is a key ingredient in gunpowder and explosives. The hydrogen sulfide and its smell can come from death when plant and animal materials decompose. It’s what gives swamps and bogs their foul smell. Sulfur is the chemical that produces acid mine seepage and left unchecked can kill every living organism in a river. Sulfur has power. But sulfur is not evil or malicious. It just exists. It is part of the balance and ordered chaos of the natural world.

On the Yellowstone Caldera, that sulfur smell is a reminder of the awesome energy stored just below the Earth’s crust and the destructive ability that comes with it. When the time is right, the supervolcano will erupt again, and all within the caldera, and for thousands of miles beyond, will be consumed or destroyed. There is nothing that man can do to stop it. We have no dominion over this force. It’s a reminder of our human frailty. The smell of sulfur keeps me in my place and humbles me.