Ancient Ripples

Photographed August 3, 2014
Rib Mountain State Park
Wausau, Marathon County, Wisconsin
44.920268,-89.693027 (parking lot to access marker)
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Ancient Ripples
Imagine this area over two billion years ago, covered by the waters of an ancient Precambrian sea. This ocean deposited sand on the sea floor, and these ripple marks on the rocks in front of you formed by wave action in the sand.

Over time, the sand grains cemented and transformed into sandstone, and eventually, with more heat and pressure, into quartzite, a very hard rock. This process preserved these ripple marks.

For the next several hundred years, extensive weathering and erosion reduced the surrounding region to a flat "peneplain." However, Rib Mountain, with its hard, resistant quartzite, projected high above this surface.

Then, about 600 million years ago, expanding oceans covered Wisconsin, depositing thousands of feet of sediment. Slowly, these layers of sediment wore away, once again revealing Rib Mountain and its ancient ripple marks. 
The marker is located at Rib Mountain State Park, 4200 Park Road, Wausau, Wisconsin 54401.

NOTE: There are several interpretative signs at Rib Mountain State Park; some are tricky to locate. Detailed directions on how to locate this marker do not appear on this post. Click here for a Rib Mountain State Park Signs & Sites Tour, with detailed directions and GPS coordinates for all markers at Rib Mountain State Park.

NOTE: Rib Mountain State Park requires an annual pass or daily use fee to enter.






The marker is along the footpath that leads to the observation tower
(see photos below).

Pictured above are algal stromatolites composed of blue-green algae, bacteria, and silt on the bottom of the Pre-Cambrian Sea. They are believed to be the first life-forms to colonize the earth.

Follow this footpath to the marker.


The maker is located at Rib Mountain State Park.

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