Monday, February 15, 2016

Hike heads over ancient rock at waterfalls

Big Falls. Photo courtesy Town of Seymour
Topo map of Big Falls in Eau Claire County, Wis.
Day hikers can amble over the sands of a 550-million-year-old ocean and rock that is at least 1.85 billion years old at Big Falls County Park in western Wisconsin.

Though there’s no designated trail, hikers easily can walk a half-mile along the river, over the sandbars and across the rock. The falls area is great spot for wading in the river, sunbathing on sand, and picnicking upon the exposed rocks.

To reach the park, from Eau Claire, take U.S. Hwy. 12 east. Turn left/north on N. Elco Road. At County Road SS (aka 9 Mile Creek Road), go right/east. This road runs out at County Road K (aka N. 130th Avenue); head left/north onto County K. Just before crossing the Eau Claire River, turn left/west onto Big Falls Forest Road. The sandy road heads straight to a parking lot.

From the lot, walk west toward the river. You’ll hear the rush of water over the falls pointing the way.

The Eau Claire River turns sharply at this spot, spilling in two falls over outcroppings of gneiss. A 25-foot drop, millions of gallons per hour head over the polished gneiss and boulders, forming a deep pool below the falls.

The sandrock on the river’s shoreline belongs to the Mt. Simon formation. It formed about 550 million years ago when sediment settled at the bottom of a shallow ocean covering this part of the world.

The exposed base of the sandstone sits atop even older gneiss that formed many miles beneath the surface of the earth some 1.85 to 1.9 billion years ago. This rock at one time belonged to the Marshfield continent that existed in the Archean era. At that time, the area south of what is now the Wisconsin Northwoods marked the edge of the North American proto-continent with a great sea beyond. A chain of islands known as the Marshfield continent gradually collided with the North American proto-continent, expanding the land area of what is now Wisconsin.

Over time, the Eau Claire River has cut through all of the Mt. Simon sandstone here and is now rushing over and exposing even more of the erosion-resistant gneiss.

The 135-acre county park straddles both sides of the Eau Claire River, and there is a northern entrance on the opposite shoreline. When planning a trip here, be careful to not confuse it with Big Falls County Park near Kennan in Wisconsin’s Price County, which is a couple of hours drive away.

Learn more about nearby day hiking trails in my Day Hiking Trails of the Chippewa Valley guidebook.