During the last period of glaciation Michigan was covered with ice up to two
miles thick. There is a diagonal hinge line that runs from some where around
Alpena on the upper NE side of the lower peninsula to Muskegon give or take
a tad. The glaciers were so heavy they pressed the land down considerably.
North of that hinge line the land is still rising. The changes in the
shorelines of Lake Michigan and Lake Huron just a ways south of the big
bridge show this quite plainly.
The glaciers did a good job of flattening the land around here. Unlike the
hills sourrounding the finger lakes in New york the land sourrounding most
of the Great Lakes is quite flat. That is flat to the point of making most
of the great plains look mountainous. Most of the hills are nothing more
than glacerial morains consisting of a sand gravel mix which may be layered.
When we lived to the west of Farwell MI our home was about 300 to 400 yards
past Michigan's "continental divide". Water on our side of the hill drained
into Lake Michigan and water on the other side of the hill drained into Lake
Huron through the Saginaw Valley.
My 50 foot tower was on a secondary ridge slightly lower than the highest,
but at 50 feet all the antennas had a clear shot over the other hill a
couple hundred yards distant. The interesting thing was the composition of
the soil in the hole for the tower base. It was as if some one had drawn a
vertical line down through the hole. The material on the west was almost
pure sand. That on the East was a sand, gravel mix with lots of fossiles and
soft ball sized rocks. It was a real bear to dig through.
When you get down into the center of the state which is "flat" in the
extreme the soil is sand/lome, or clay lome. It's a nice uniform soil, BUT
you will notice that most of the farms have a rock pile. I'm talking rocks
from soft ball size to larger than cars. There is no consistency to the
rocks. They may be Lime, Granite, composit, marble (of different colors), or
what ever. If you can think of it the stuff is probably there.
You may plow the same field to the same depth for 20 years or even more with
out a hitch. Then one day as you are headed across the field the plow
catches on something that stops everything right now. The driver usually
ends up bent over the steeing wheel with the wind knocked out of him. Start
digging and what do you find? A big rock! To stop a big tractor like that
takes a bit rock. It may be from a few feet across to the size of a buss.
We have these rocks courtesy of the glaciers and many of which are from
hundreds of miles up into Canada. Their proper name is "erratics"
Shortly after moving here we had to have the well point pulled and replaced.
No big deal, but a few years later we ended up drilling a new well within 50
feet of the old one. Instead of hitting water at 50 feet it was 150 feet.
They pumped out about 3 truckloads of iron oxide loaded sand to finish, but
the surprise came during drilling. They were using a rotary rig which
around here usually makes fast work of things. They hit so many rocks they
busted the drilling rig three times before they finished. Instead of a day
it took a week to drill that well. Two years later they put in city water
out here.
So you never know for sure what you are going to find when you start driving
ground rods unless you live on a sand hill and then there is no gurantee.
Of course if you live on top of a rock outcroping the odds are pretty good
you know what you'll find.<:-))
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