WHAT IS THE OLDEST MOUNTAIN RANGE?
Mountains, in some form, have existed since the Earth began to form 4.51 billion years ago. Impacts produce mountains. So will rising plumes. But mountains, as we know them today, are linked to plate tectonics. And plate tectonics has been the dynamic state of the Earth for only the last 2.5 billion years or so.
In North America, the oldest known mountain-building event is the Algoman Orogeny. It occurred 2.5 billion years ago when two ancient pieces of continental crust—the Superior Province and the Minnesota River Valley Terrane—collided. Evidence of this collision stretches of 750 miles (1200 kilometers) from the middle of South Dakota, east through the Upper Peninsula of Michigan, across the Sudbury region of Ontario to the northern edge of Lake Huron. These early mountains have been eroded away, only the roots are still evidence has highly folded and metamorphosed rock. One of the spectacular places to see such rocks is at Voyageurs National Park in northern Minnesota.
If one wants to stand on a remnant of an ancient mountain range, one of the best choices is the Penokee Range that runs Wisconsin and northern Michigan. This mountain-building event occurred about 1.8 billion years ago and produced mountains that extended for more than a thousand miles. The remnants of these mountains exist today as two ridges, no more than a few hundred feet high.
Debris eroded from the Penokee Range is now exposed in rocks from Arizona to Wisconsin. Known as the Sioux Quartzite, this is the pink hard rock responsible for the cascading water known as Sioux Falls in Iowa.