Ear Mountain, Montana

February 20, 2017

SamBeebeEcotrust (2)

February 2017 Viewer's Choice

Photographer: Sam Beebe; Rod Benson
Summary Author: Rod Benson

Ear Mountain stands along the boundary between the mountains and the prairie 70 mi (113 km) northwest of Great Falls, Montana; an area Montanans refer to as The Front. The name probably originates from the view enjoyed by pioneers approaching from the east -- that of a long wall marking the abrupt end of the Great Plains and the beginning of (the front of) the Rocky Mountains. This area, extending northward to Glacier National Park and beyond, is known for its scenic beauty, grizzly bears, Chinook winds, and fascinating geology.

Ear Mountain along with many of its neighboring ridges, peaks, and cliffs consist of the Madison formation; layers of limestone and other carbonates, ranging from  900-1700 ft (275-518 m) thick, and made of sediment laid down 330-340 million years ago when much of what is now the western U.S. was the floor of a shallow, tropical ocean. In places, the Madison is especially fossiliferous. Those adventurous enough to climb Ear Mountain will be treated to an abundance of horn coral as they walk the perimeter of the plateau.

Perhaps the most fascinating aspect the Ear Mountain and the surrounding region is the way the Madison formation and other layers were deformed as these mountains were built. It involved a process called overthrust faulting. In response to the collision of the Pacific Plate and the North American Plate, some 115-50 million years ago, immense slabs of rock broke and then slid up and over younger layers to their west. This process resulted in some of the most scenic mountains in Montana. The orientation of the slabs in the 60 mi (96 km) stretch around Ear Mountain is especially unique. In this area thinner slabs of rock slid eastward over younger rock layers, like shingles on a roof, to form distinct high ridges and deep valleys that run parallel to each other.