Tuesday, November 24, 2015

Discover North Shore geology on park trails

The Gooseberry River tumbles over 1.1- billion-year-old basalt.
Among the best ways to learn about the geology of Minnesota’s popular North Shore are day hiking trails at Gooseberry Falls State Park.

The park provides opportunities to explore the effects of billion-year-old lava flows and the more recent ice age of only 10,000 years ago.

With more than 630,000 annual visitors, Gooseberry Falls is Minnesota’ second most visited state park. More people visit Gooseberry Falls than half of all national parks. To reach the park, from Two Harbors, Minn., drive north about 13 miles on Minn. Hwy. 61.

Billion-year-old lava flows
Gooseberry Falls’ major sites wouldn’t exist but for 1.1 billion-year-old lava flows that formed when North America began to separate into two, forming what today is called the Mid-Continent Rift. The rift extends all across the Great Lakes to as far south as Kansas. In Minnesota, those volcanic flows along Lake Superior are known as the North Shore Volcanic Group. With lava flows occurring over millions of years, they can run up to 30,000 feet in the region. Locally, the basalt rocks that create the park’s waterfalls are referred to as the Gooseberry Lavas. Great trails to see those lava flows include:
River View Trail
Picnic Flow Trail

Ice age
Fast forward to 10,000 A.D. After eons of being buried by sediment, the great glaciers of the last ice age had scraped off most of the terrain, leaving only the basalt and a thin layer of till over them. Cold Lake Superior is merely what remains of a melted glacier in a low spot of the Precambrian rift, and the rivers along the North Shore are carving through the remaining till and sediment often reaching the underlying basalt. A good trail to see the effects of the last ice age is:
Nelsens Creek Trail (clay of Glacial Lake Duluth)

Learn about more day hiking trails at and near Gooseberry Falls State Park in my Day Hiking Trails of Gooseberry Falls State Park guidebook.