Trails explore Voyageur NP’s geology

Ancient rocks and Lake Kabetogama behind the Ash River Visitor Center
at Voyageurs National Park.

Eons ago, the area that now makes up Voyageurs National Park sat near the southern edge of Canadian Shield – a gigantic dome of volcanic bedrock that birthed North America. In fact, the park is one of the few places where you can see and touch rocks older than 2.8 billion years, more than half of the planet’s age.

This early rock appears in multiple places. The bedrock on the shore of Sand Point Lake’s Brown Bay is about 2.7 billion years old. Other outcroppings of the ancient stone can be seen elsewhere throughout the park, including the Echo Bay Trail.

During the Archean, mountains were building in what is now the park as another tectonic plate slid under the Canadian Shield. It was similar to the Pacific plate sliding against the North American plate in modern day California, leading to the rising of the Coast Ranges there. The result at Voyageurs was the creation of the bedrock that makes up the current state south to the Minnesota River Valley.

This same process caused volcanic islands to form offshore. The lava basins along the ancient fault lines eventually became greenstone belts that held a variety of metals and minerals, such as gold, silver and copper. An attempt was made to mine gold from this belt during the 1890s; the abandoned mine can be hiked on the Little American Island Trail.

Eventually, erosion wore down the volcanic mountain ranges. What happened afterward until about 190,000 years ago is a mystery, though.

That’s because repeated periods of glaciation during the intervening years scraped off the topsoil and rock layers, exposing the Canadian Shield and ancient mountain building that left behind granite, biotite, schist, migmatite and greenstone. The last ice age about 11,000 years ago also finished gouging out several depressions; as retreating glaciers melted, the water settled in those massive troughs, creating the park's major lakes. Park visitors can walk across some of this rock next to those ice age lakes behind the Ash River Visitor Center.

Learn more about the park's day hiking trails in my Best Sights to See at Voyageurs National Park guidebook.