Slow cooling of a basaltic lava flow that was erupted about 500,000 years ago resulted in the formation of hexagonal columns at Sheepeater Cliff, in Yellowstone National Park. Photo: Michael Poland, U.S. Geological Survey.

YELLOWSTONE, Wyo. — Today, The United States Geological Survey (USGS) released an article detailing the history behind the jointing of lava flow seen on Sheepeater Cliff in Yellowstone. The formation can be found off a small side road on the highway between Mammoth Hot Springs and Norris Junction.

In the article, USGS discusses how the formation of hexagonal columns at Sheepeater Cliff is the direct result of the slow cooling of a basaltic lava flow that erupted about 500,000 years ago.

“Sheepeater Cliff is part of a basaltic lava flow that erupted north and outside of Yellowstone Caldera about 500,000 years ago. These sorts of lava flows, which are similar to those erupted in Hawai?i, are common around the edge of the caldera, but they can’t erupt in the caldera because the denser lavas from the basaltic magma chamber are blocked from rising to the surface by the overlying chamber of viscous rhyolite magma,” the article said.

Additionally, Sheepeater Cliff is named after the band of Shoshone Native Americans who frequented the Yellowstone area and were known as the Tukudeka, or “Sheepeaters,” because of the bighorn sheep they hunted.

The cliff is made up of a series of adjoining vertical columns. The hexagonal shape of the cliff is so peculiar that each column when viewed from the top almost looks artificial.

“Columnar jointing forms upon slow cooling of a volcanic or shallow intrusive deposit. As the lava or ash cools, it shrinks, like most materials (except water, which expands when it freezes!). In the vertical dimension, adjusting to this shrinking is easy—the lava or ash flow simply subsides, or sinks. But in a horizontal direction, the contraction is much harder to accommodate, and so the rock fractures,” the article said.

“If the cooling happens quickly, the rock breaks in random patterns. When the cooling happens over a long period of time, however, the fracturing is not random, but rather results in the formation of generally hexagonal columns.”

Sheepeater Cliff is one of the many spectacular treasures of Yellowstone. To read more about its formation click here. 

Buckrail @ Caroline

Caroline Chapman is a Community News Reporter. She enjoys reading non-fiction, skiing, hiking, and playing piano in her downtime. Her favorite aspect about living in Jackson is the genuine admiration that Wyomingites share for the land and the life that it sustains.