The Absaroka Range
Near Cody, Wyoming
The dark, rugged mountains rising to the west and south of Cody are the Absaroka Range, and they are the wall that separates the Bighorn Basin from Yellowstone. The name comes from the Hidatsa word for the Crow people, and it means children of the large beaked bird. The Crow people's own name for these peaks translates as pointed mountains, like sand castles, which is a fair description of their crumbling, spired look.
That look comes from how they were born. The Absarokas are volcanic. During the Eocene epoch, roughly fifty three to forty four million years ago, a chain of large stratovolcanoes erupted here, burying the region in ash and rubble that hardened into a rock called volcanic breccia.
The eruptions were enormous. The volcanic field they built covers roughly eight thousand nine hundred square miles, and includes about a third of Yellowstone National Park. Over the ages, wind and water have carved that volcanic pile into the jagged pinnacles you see today.
The highest summit, Francs Peak, rises above thirteen thousand feet. When you drive toward Yellowstone, you are threading a canyon straight through the eroded heart of an ancient volcanic field.
