Terra Vista (Estabrook Park Falls) EarthCache

An exposed layer of dolomite and shale in Estabrook Park is part of a sedimentary rock formation that creates a low waterfall along the Milwaukee River.

This outcropping dates from the late Devonian Period in earth history, 417-354 million years ago. It differs from the more common Silurian reef deposits found regionally in that just enough shale is associated with the limestone to make high quality water resistant cement. The Milwaukee Cement Company quarried this site for over thirty years in the late 1800's, until a flood redirected the Milwaukee River and operations had to be shut down.

Stratified rock of this type is part of the Michigan Basin, and is believed to be the youngest bedrock found in Wisconsin to contain fish and plant fossils. This layer and its relation to periods in geological history can be seen at the Milwaukee Public Museum's Kids Geology Lab, which exhibits core samples taken from Milwaukee's Deep Tunnel Project.

What geological forces do you think helped contribute to the bluffs around you? Please email me your answer when logging the cache.

Resources:

• Dott, Jr., R. H., & Attig, J. W. Roadside Geology of Wisconsin. Missoula, Montana: Mountain Press Publishing, 2004.
• Dept. of Geology. Geology Section. Milwaukee Public Museum, 2004.
• Schaetzl, Randall J. Geography of Michigan and the Great Lakes Region: Physical Geography. Michigan State University, 2002.