Obsidian Cliff

Obsidian Cliff is a dark, glassy rock face on the Grand Loop Road between Mammoth and Norris. The visitor stop is the nearby roadside kiosk, not a walk up to the cliff. If you’re already driving this stretch and like Yellowstone’s human history, give it a few minutes; the payoff is the story, more than a long walk or a sweeping overlook. From the road, the black glass can be easy to miss against the darker rock. For photos, keep the view wide enough to show the creek and meadow in front of the cliff; that context helps the dark face read as a landscape, not just a patch of rock.

Obsidian forms when silica-rich lava cools before crystals can grow. It breaks into sharp, curved flakes that people could shape into tools. The cliff exposes about 98 feet of obsidian, an unusually large face compared with the small pieces scattered through most volcanic rock.

People quarried obsidian here for tools more than 11,000 years ago. Archaeologists have documented 59 quarry and workshop locations on the plateau, along with thousands of flakes and tools. Stone from this source traveled far: it appears in sites from western Canada to the Great Lakes and Ohio. NPS research attributes about 90% of the obsidian found at Hopewell mortuary sites in Ohio’s river valley to this source.

Obsidian Cliff is more than an archaeological site. Tribes with ancestral ties to Yellowstone describe it as spiritually significant, and oral histories recount collecting obsidian here. Its sharp edges made useful tools, but its importance to people also reached beyond the practical.

The roadside kiosk was built in 1931 as the first wayside exhibit in a U.S. national park. It was added to the National Register of Historic Places in 1982, and Obsidian Cliff became a National Historic Landmark in 1996. After the 1988 fires burned much of the plateau forest, surveys of the newly cleared ground helped researchers document how people quarried the bedrock and collected obsidian cobbles from glacial deposits.