Monday, February 13, 2012

Twice Pressed

That the area where we live was once covered by one mile thick ice is now accepted scientific conjecture.  Our surface soil is not from around here.  Glaciers brought it here from perhaps as much as 200 miles north northeast of here.  Pieces of the Adirondack Mountains may litter the surface of our soil.  Exactly how our land was formed has always puzzled me.  This one rock sent me looking for answers. Amy found a geologic history of New York State but it was written in 1914.  Glacial theory was only 75 years old when that book was written.  A more recent book has yet  to be found.  Still there is this rock that was found lying on the surface at the margin of our gravel bank.  Its rich moss coating speaks to the abundant recent rainfall.

We frequently find rock similar to this one.  They are extremely heavy for their size and usually do not split cleanly.  Their core is sometimes more dense, darker in color and loaded with shell fossils.  The differences between the inner and outer layers are many.  The interior is light gray, dense and hard while the brown exterior is porous, damp and soft.  Most of the rock found here is sedimentary in origin but this one seems to have been buried and pressed twice.

Frequent freeze thaw cycles and generous rainfall have already begun to separate the two layers of this freshly split stone.  When found, the outer layer was continuous and unbroken.  Hammer and chisel easily separated the rock into several slices.  Now the weather is stripping away the soft crumbly outer layer.  The heavy gray interior slice will wait on the ground until it can be placed as a capstone on the next built stone wall.  The broken soft exterior fragments will be left to weather to dust ready for their return trip to the ocean where they will help form a new layer of sediment.

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