The Escanaba Cleavage

The dog starts, gives a woof and a faint tremor is felt though the house.

At first blush you might think - earthquake?

Nope.

Actually this happens pretty regularly.

It is blasting from the mining operation up the road a piece.

If any of you have ever traveled the length and breadth of the Door Peninsula you've probably taken notice of the rock.

There is rock everywhere.

The spectacular cliffs. The promontories. The bluffs.

And the views from Cave Point County Park on the Lake Michigan shore.

If you ride your bicycle around the peninsula like I do you will also notice the thin topsoil.

Within the boundaries of the peninsula there are more than 94,000 acres of landmass with an average soil depth of eight inches.

There is bedrock everywhere.

The consequence of which is that if you wish to build a road, bury a utility cable, drill a well or install a sewer you might find yourself having to tunnel, trench or blast your way through dolostone.

You can even see the joints in the bedrock through the thin soil cover because moisture and better rooting conditions support slightly better plant growth.

This would be the Niagara Escarpment.
A very tenacious formation of dolomite limestone that extends all the way from Buffalo, New York through the Fox Valley.

Multiple glaciations were unsuccessful in wearing it down.

About 10,000 years ago when the last ice age visited Wisconsin my part of the world was buried beneath an ice sheet more than a mile thick.

The earth's crust is still rebounding from the weight of all of that ice.

Looking at that map you can see how the escarpment transects the peninsula. Visualize the lake Michigan lobe of the glacier extending south just to the right of the line and the Green Bay lobe of the glacier extending south immediately to the left of the line.

Geologic time is slow but relentless.

And that ice sheet melted and receded.

If you are observant of the coastlines of the peninsula you can actually locate where the ancestral high water mark and beaches are located - including the inland lakes that had previously been part of a much larger Lake Michigan and Green Bay.

I sometimes wonder about what man-made influence conspired to melt an ice sheet a mile thick only a mere 10,000 years ago.

A blink in geologic time.

Paleolithic campfires maybe?

I digress.

Anyway, about a mile or so from the farm is the demarcation line identifying the point where the two lobes of the glacier split and went their separate ways. There is a rocky outcrop of tough-old dolomite limestone that even all that ice could not carve down.

Here it is-

Now it is being mined by modern means.

Into gravel. Hence the blasting.

What nature could not finish - man will complete.

And fast - geologically-speaking.

Turning it into road-base and the raw materials for concrete.

We're pretty lucky having built upon what the Government Land Office Surveyors originally described as a swamp.

Oh sure, we have a seasonally high water table but we also have almost eighteen feet of soil.

To be fair - that would be where the well was drilled. About two hundred feet away is a rock shelf where a rock saw had to be used to cut a passage for the electric utility lines.

See what I mean about that funky average depth of eight inches?

It is complicated for sure.

So, Swamp, you are being long-winded again. What's your point? When are you going to get to the juicy part about the cleavage?

Many years ago I was fishing with my a couple of my deer hunting compadres - the Wench and the Dutchman - the original deer camp.

After a long day on the water - whilst I regaled these two gents of my new-found knowledge of geology and the natural world - we eventually sought landfall and the comfort of Joe and Nancy's Bar in Rosiere.

Joe and Nancy have long-since retired and the establishment is now Why-Lee's.

(Incidentally - I recommend that you go there for the blue gill sandwich on Fridays. Tell Lee that Swamp sent you.)

Somewhere along the line, and after more than a couple of beers, Joe might have asked how the fishing was.

Instead of simply answering the question with a direct answer the Wench went off on a tangent and launched into his own reiteration of what he had learned in his abbreviated geology lesson on the boat that day.

Considering the circumstances he got most of it correct.

Joe was thunderstruck. He was probably thinking - These guys aren't fishermen. Fisherman are liars. These guys sound like scientists.

The Wench was actually doing pretty good with his bar stool geology dissertation.

Everyone else at the bar was now paying attention.

When he got to the part about the formidable rock formation which marked the split between the Green Bay and Lake Michigan lobes of the last glaciation he reached deeply into his arsenal of knowledge.

He employed props.

Grabbing a napkin holder he placed it on the bar to illustrate the Escarpment.

Salt and pepper shakers followed to identify the location of the glacial lobes.

Tap beer glasses we used to show the movement of the glaciers.

Pausing to take a long pull from the western-most lobe of the glacier, he gathered his wits, summoned the reserves of his short-term reservoir of knowledge, slammed the beer glass upon the bar top, thrust his finger in the direction of the napkin holder and bursting forth with enthusiasm for his new-found scientific knowledge, exclaimed...

That is the Escanaba Cleavage!