Montana Governor and First Lady's Math and Science Initiative
An Island on the Plains - The Bears Paw Mountains
Mile Post 79 on US Highway 87, near Big Sandy
Fifty-five to thirty-four million years ago, volcanoes
erupted in several areas of central Montana. The
upwelling of magma which fed these volcanoes was
largely responsible for the Bears Paw Uplift and for several other
isolated mountain ranges in central Montana. In some places,
as the molten rock pushed its way upward toward the surface,
it up-arched the layered rocks above it to form a magma dome
called a laccolith. In other places, the magma rose vertically to
form dikes. The dikes now look like old fallen-down stone walls
protruding up through the grass of the ranchlands. Some of
the magma crystallized into shonkinite, a rare rock, named for
exposures near the town of Shonkin, Montana. Some of the
laccoliths eroded to form large buttes, the most prominent are
Square Butte northeast of Box Elder and Centennial Mountain
northeast of Big Sandy. While the mountains were rising, an
east-west rift developed near the crest, and rocks slid both to
the north and south on Cretaceous marine shales. The sliding
produced many faults in the adjacent Great Plains. The faults
south of the mountains are especially prominent; while most of
those to the north are covered by glacial deposits.
An Island on the Plains - The Bears Paw Mountains
A Brief History
It is not known how the mountain range got its name. According to one legend, many generations ago, an Indian man killed a deer while hunting in the mountains. Before he could return to his camp, he encountered a bear, which knocked him down and pinned him to the ground. The hunter appealed to the Great Spirit for help, who answered by filling the heavens with lightning and thunder, which killed the bear and severed its paw, releasing the hunter. Or perhaps one of the range’s mountains resembles a bear’s paw and gave the mountain range its name. Another tale states that to Indians looking down from the summit of one of the peaks, the ridges spread out below them resembled a bear’s paw.
