Monday, March 11, 2013

Early Harvest

This line of stones was dumped here long ago when pioneers first cleared for farm land.  For the most part, they are irregular, misshapen and twisted making them undesirable for wall building.  Access is easy and some of these stones have parallel planer surfaces.  These workable stones need to be placed in a wall.

The calendar identifies winter as the controlling season. The desire to be outside performing physical work is strong now.  With the ground still frozen, finding a suitable place to work is not easy.  The top layer or two of this stone pile is frost free and the stones can be moved.  Matching the conditions of the day with a task that could be done led me here.

As expected, some of the best wall stones were hidden under brush.  Later in the year green growth will hide these stones from view.  Today when these treasures were in plain sight it required clever thinking to safely remove them.  Brush grabbed my cap several times but no scratches were delivered.

Most of the stones in this wall face were harvested today.  The large red stone with the flat top is a rare find.  Stones like this tend to be round and they rarely split smoothly.  This one came out of the ground neatly trimmed.  Lichen grows on the flat surface so the split happened many years ago.  Usually large stones like this one are placed in the ground in the first course of the wall.  Such placement would partially hide its beauty so a spot at the top of a wall is perhaps a better use of this stone.

This picture may look like a stone wall but it actually shows a temporary stone pile.  Raw material has been gathered in one place so that it can easily be accessed when the next wall is underway.  Many faults are visible in this hastily thrown together pile.  Unsupported stone and large voids are easily seen.  Far to many places for critters to set up housekeeping are provided with this loose pile.

All stones tell the story of their creation but reading it is not easy.  Geology textbooks describe a vast inland sea that once existed here.  Sediments carried into this sea settled out of the water and fell in layers on the sea floor.  Most of the stone here is sedimentary in origin but some are red while most are grey.  How this stone that was once part of the sea floor came to be broken and rounded is a complete mystery.  How could all of that happen without the layers separating?   This stone will be handled with care and securely placed in a wall so that it remains intact.


Anonymous said...

"the ground still frozen, finding a suitable place to work is not easy".

Indeed, having this factor to considered is quite difficult.

Owen said...

Generally, the sedimentary lithification process involves a great deal of pressure. Sediment deposits can be surprisingly deep. The Mississippi River delta is around seven miles deep--the pressure at the bottom is probably incomprehensible to most people, including me. The reason we are able to find so many of these rocks at the surface is because they have been unroofed: the overlying strata have been weathered away and the lithostatic pressure has been reduced greatly. As a result, the rocks begin to expand slightly. Rocks have very low tensile strength, so in order to relieve stress, the rocks begin to separate, preferentially breaking along bedding planes that are weaker due to varying mineral compositions or grain sizes.

Ed said...

Owen, Thank you for your comment. We live very near to a deep narrow gorge that was likely formed by glacial melt water. One of our recent 150 year floods scraped clean red beds that form our bedrock. My red stone and these beds likely share a common origin. The rounded smooth surfaces of my stone were possibly made by water erosion but I cannot understand how the stone was tumbled about without separating along one of the bedding planes. It must be magic.