YELLOWSTONE, Wyo. — With the North Entrance to Yellowstone National Park (YNP) open year round and other entrances opening soon for the season, spring can be a good time to visit the park’s sites.
According to the National Park Service (NPS), the Sheepeater Cliff geological site provides a unique setting for fishing, hiking and enjoying a picnic. The formation can be found off a small side road on the highway between Mammoth Hot Springs and Norris Junction. The parking lot provides easy access to fishing the upper section of Gardner River and the trailhead of Sheepeater Creek Trail.
Sheepeater Cliff was named by Yellowstone Superintendent Philetus Norris in 1879. The site was named after the band of Eastern Shoshone Native Americans who frequented the Yellowstone area and were known as the Tukudeka, or “Sheepeaters,” because of the bighorn sheep they hunted.
In a past edition of Caldera Chronicles by the Yellowstone Volcano Observatory (YVO), U.S. Geological Survey (USGS) Geophysicist Michael Poland highlighted the unique structural formation of Sheepeater Cliff. Poland wrote that the formation of adjoining vertical columns was the direct result of the slow cooling of a basaltic lava flow that erupted outside of Yellowstone Caldera about 500,000 years ago. According to the USGS, if cooling happens quickly, rock can break in random patterns. But, when the cooling happens over a long period of time, the fracturing is not random and creates the formation of hexagonal columns.
“These sorts of lava flows, which are similar to those erupted in Hawaii, 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,” Poland wrote.
Poland described the hexagonal shape of the cliff as “peculiar” with each column when viewed from the top almost looking artificial.
“Columnar jointing forms upon slow cooling of a volcanic or shallow intrusive deposit,” Poland wrote. “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 Gardner River, which flows through the valley, exposes the flow and formation of Sheepeater Cliff.
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