Integrative Natural History of Amnicon Falls State Park, Part 18: Every Time I Was There, Anyway | Wisconsin, USA
(Updated April 16, 2025)
Just a few yd / m to the southeast of the parking lot adjacent to Horton Covered Bridge. And facing southeastward, toward a cascade in the eastern fork of the Amnicon River, which starts above the Upper Falls and rejoins the main stream below the Lower Falls.
This is Now and Then Falls. Its name notwithstanding, it has been flowing every time I've visited the park.
We can treat this photo just as another pretty waterfall picture, or we can do that and learn something from it, too.
What the heck. Let's learn something.
A little examination discloses that while most of the falling water has been aerated white by the turbulent flow, there is a little bit of disconcertingly tan-hued water showing, too. That discoloration is evident in the main stream course as well.
Many North Woods creeks and rivers have this or a considerably darker brown tint. While it often triggers the concern of outlander tourists, it's completely natural and does not signal the presence of pollution or toxic chemicals.
In fact, the staining agents are tannic-acid compounds, originally sequestered in the foliage of coniferous trees. When the leaves fall to the ground to form the surficial O Horizon layer known as duff, rain and meltwater leach out this dark substance and eventually it and the water find their way into nearby streams.
The bedrock that provides such a nice platform for the falls is worthy of some scrutiny as well. Its weathered-light-brown to wetted-black coloration, coupled with its massive, nonstratified aspect tell us that we're back in the zone of the basalt of the Chengwatana Volcanic Group. The slightly younger and distinctly stratified Orienta Sandstone is nearby, but this isn't it.
The Chengwatana basalt began as one of the very-late-Mesoproterozoic mafic lavas that were extruded into the Midcontinent Rift about 1.1 Ga ago. For more on the rift itself, and on the park's Douglas Fault exposure, see Part 2 and the posts that follow it in this series.
You'll find the other photos and descriptions of this series in my Integrative Natural History of Amnicon Falls State Park album.
Integrative Natural History of Amnicon Falls State Park, Part 18: Every Time I Was There, Anyway | Wisconsin, USA
(Updated April 16, 2025)
Just a few yd / m to the southeast of the parking lot adjacent to Horton Covered Bridge. And facing southeastward, toward a cascade in the eastern fork of the Amnicon River, which starts above the Upper Falls and rejoins the main stream below the Lower Falls.
This is Now and Then Falls. Its name notwithstanding, it has been flowing every time I've visited the park.
We can treat this photo just as another pretty waterfall picture, or we can do that and learn something from it, too.
What the heck. Let's learn something.
A little examination discloses that while most of the falling water has been aerated white by the turbulent flow, there is a little bit of disconcertingly tan-hued water showing, too. That discoloration is evident in the main stream course as well.
Many North Woods creeks and rivers have this or a considerably darker brown tint. While it often triggers the concern of outlander tourists, it's completely natural and does not signal the presence of pollution or toxic chemicals.
In fact, the staining agents are tannic-acid compounds, originally sequestered in the foliage of coniferous trees. When the leaves fall to the ground to form the surficial O Horizon layer known as duff, rain and meltwater leach out this dark substance and eventually it and the water find their way into nearby streams.
The bedrock that provides such a nice platform for the falls is worthy of some scrutiny as well. Its weathered-light-brown to wetted-black coloration, coupled with its massive, nonstratified aspect tell us that we're back in the zone of the basalt of the Chengwatana Volcanic Group. The slightly younger and distinctly stratified Orienta Sandstone is nearby, but this isn't it.
The Chengwatana basalt began as one of the very-late-Mesoproterozoic mafic lavas that were extruded into the Midcontinent Rift about 1.1 Ga ago. For more on the rift itself, and on the park's Douglas Fault exposure, see Part 2 and the posts that follow it in this series.
You'll find the other photos and descriptions of this series in my Integrative Natural History of Amnicon Falls State Park album.