Wednesday, December 4, 2013


We believe that our gravel bank was first opened about one half  century ago to bury the remains of the barn that burned following a lightening strike.  More recently, town road crews had removed gravel to repair roads.  In the two decades that we have owned this land, gravel has been taken only by me using hand tools.  A four tined stone fork is used to pull the material down hill separating out some of the larger stones.  Various sized screens are then used to sift according to the demands of the job.  A level pile is kept between me and the undercut bank.  So far any slide that has happened while I was working has been stopped by the level ground.  This small car sized slide happened while no one was working the bank face.  Much material slid closer to the spot where I sift and I was not trapped in it.  Luck continues to be with me.

We understand that the most recent glacier created this feature.  The hill is cone shaped in sharp contrast to the surrounding landscape.  Surface material is unsorted stone, gravel and mud.  Beneath this top layer are bands of water sorted deposits.  Wide brown bands of fine sand are overlain with a thin layer of clean black sand with larger grains.  These sorted layers are not level but occur on a slope.  How these slanted layers happened has puzzled me.

Many of the gravel mines in the area feature deposits that were dropped in standing water.  Sediments fall out of the stream in a some what orderly fashion if the stream empties into a lake.  Recently I read a description of streams pouring over the edge of the ice face.  Sediment laden water falling some distance into a pool of water would pile material in a cone shape.  Since all of the sediment load was dropped in a heap, no sorting by size occurred.  During periods of low water volume only fine material could be carried by the stream.  This change in the force of the stream flow would explain the sorted sloped deposits.

I stand in wonder when I work this material that has been buried for thousands of years.  When new gravel is exposed I am looking at stones that are just as the glacier melt water left them.  The occasional fossil bearing rock is seen for the first time by me.  Then I destroy all traces of historical record by sifting the gravel and adding it to my driveway.

No comments: