Monday, January 01, 2018

Bullion Butte, ND

Southwestern Billings County, ND. Photo 6/3/03; Penstemon albidus in the foreground

There be better buttes but this be a butte.

This is a 3350-foot tall butte, rising about 1000 feet above the Little Missouri River which is 1.5 miles to the northeast. The cliffs along the rim of the butte are about 120 feet high. Prairie Falcons nest in the rocky rim and the overhangs and caves have sheltered mountain lions. The winds get strong up high on the prairie, nothing holds them back.

This butte is one of several dozen prominent buttes in the western Dakotas (Thunder, Sentinel, Square, Round Top, Haystack, Castle Rock...). They are the product of differential erosion, where erosion occurs at differing rates in a unit of land due to varying hardnesses of the surface material. The harder material that remains while the rest of the softer surface material erodes away is called a caprock. The landform that is created by the caprock is called a butte, a reminder of the elevated plateau that once was.

Climbing to the summit of Bullion Butte in low hanging clouds and a cold mist, one might expect to discover a lost world of Titanotheres, Oreodonts, and Entelodonts peacefully grazing on the short grasses as a giant meteorite streaks overhead towards Chesapeake Bay. No, not today. But, these summits have some unique plant species generally not found on the surrounding plains that may be relicts of the pre-Pleistocene Ice Age landscape, the elevated plateau. One species is Phlox alyssifolia. The sideslopes, scree, and talus surrounding the butte have thousands of specimens. But it is not found on the surrounding plains. It is thought that the species had a wider distribution on the elevated landscape that was eroded away. These remaining populations are relict populations, like the buttes, reminders of what once was.

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