The 1,000-Mile Great Lakes Adventures

Friday, July 16, 2010

Torch Lake & Lake Michigan

I just returned home from a few days up north on the shores of Torch Lake. My friend Ann (relaxing in photo above with her dog, Rocky) graciously shared her special spot on the lake.

Torch Lake is the second largest inland lake (Houghton Lake is the largest) in Michigan. Torch is actually deeper at over 300 feet deep. At the northern end of Torch, it almost touches Lake Michigan, and was surely once connected to the Great Lake like many other 'orphan' inland lakes.

This little getaway allowed me the opportunity to revisit some of the most unusual geology I saw while on my Lake Trek, where the Antrim Shale deposit is exposed on the shoreline of Lake Michigan. In the photo below, I am kneeling near and touching a concretion, a geode that formed within the shale. These formations pop out of the shale as it flakes off over multiple freeze/thaw cycles.

In my hand is a collection of the shale fragments. The Antrim Shale is dark grey or black. The Ellsworth Shale found just south of here is a greenish grey (I'll show photos of that deposit in another post).

To the right, Ann sits on a concretion most recently liberated from within the shale wall.

The photo below shows the shoreline dotted with these concretions (please don't disturb or damage these formations if you do visit them).

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