Tuesday, February 23, 2016

Trails explore Chippewa Valley’s geology

Waterfall at Devils Punch Bowl near Red Cedar River. These rocks were
formed from sediment at the bottom of a sea some 500 million years ago.
The geology of Wisconsin’s Chippewa Valley – defined loosely as Eau Claire, Chippewa, Dunn and Pepin counties – shows two major periods very distant in time. A number of hiking trails offers access to the geological sights.

While rock can be found in Wisconsin’s Chippewa Valley that dates to at least 1.85 billion years, most of the area’s bedrock was formed much later. Prior to 545 million years ago, the four counties making up what is now the river valley sat off the edge of the North American continent near the equator.

Over the next 50 million years, the bedrock for most of Eau Claire and Chippewa counties formed in the Cambrian period and then in the 50 million years following during the Ordovician, the bedrock for Dunn and Pepin counties developed. Most of the sandstone above this bedrock is visible in road cuts and where the Chippewa and Eau Claire rivers have carved through it.

Much of the geological record between 443 million and 1.8 million years ago has disappeared from the Chippewa Valley. During that time, the area probably lay under a sea for several million years with the rest lost to erosion, both from everyday causes such as rain and wind and from the glaciers that swept through the area.

Much of the landscape today in the Chippewa Valley is shaped by the glaciers of the past ice age, which ended about 10,000 years ago. As the glaciers’ advance stopped in northern Chippewa County, sediment brought from those melting ice sheets formed a thin layer over much of the area’s existing bedrock. How the melting ice shaped the Chippewa Valley – the Chippewa River itself was a major channel for the meltwater flowing into the Mississippi River – is a complex story that varies across the region.

Great hiking trails for discovering the Chippewa Valley’s geology include:
Big Falls Trail (1.85 billion year old rock)
Irvine Park Loop (rock from Cambrian period)
Devils Punch Bowl Trail (rock for Cambrian-Ordovician periods)
Circle Trail (Ice Age moraines)

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