Tuesday, June 15, 2010

Rock Pile damage

We have been looking at damaged rock piles (see here) and the question came up about whether the damage is from a blown down tree or from an act of vandalism (or is there another possibility?). Norman Muller sends the following pictures with comments:

Ted’s most recent posting about similar damage to oval stone piles, reminded me of a large platform cairn in Brooklyn, CT, that I saw a number of years ago. It is one of the largest platform cairns I’ve ever encountered. Only one end is well preserved,the other sides are notI don’t think that blowdowns can account for the damage, since the pile is so huge (about 45’ long and 7’ high) and well constructed, at least on the preserved end. Nor does vandalism seem a good explanation. I could be that stones from the pile were used to construct walls and foundations – certainly a logical source. [I would call that "vandalism" - PWAX] And once stones began to be removed, the structural integrity of the mound was compromised and it began to collapse of its own accord.

Norman continues in another email:

There is a long stone mound in Rochester, VT, with a Manitou or standing stone in front Recently a large tree fell on one end of the mound, toppling the standing stone

This stone mound was in a dilapidated condition before the tree fell on it, and because it is stone’s throw from some old colonial foundations, I concluded that the farmers took stones from the mound to build foundations for a barn and house. To see what little effect a large tree will have on a well built stone mound, here is an example from S. Newfane, VT

The next picture shows the mound without the tree: no damage done!

I would add this example: the large platform at Miller's Hill in Holliston, MA (see here):
I felt, when looking at it, that rocks must have been pulled from the bottom of the retaining wall and, as Norman said, the pile would collapse sooner or later after that.

Another small example here.


JimP said...

Well, that tree didn't exactly fall hard. It was pushed over and tore up earth. It's root system acted as a counter-weight, so it went over gently and not fully. I have to wonder what that rock pile would look like if instead it was hit by a 125-year-old oak tree that was split in two by the weight of ice and snow.

Depending on the age of these piles, there could've been a chance to get hit by a falling tree every 125-150 years or so. Divide by the number of trees that could potentially fall on the pile and it seems to me that many of them should show evidence of such damage.

JimP said...

You know, I just keep remembering the loud cracks and the booming thuds to the earth that the oak trees around my house made during various ice storms and blizzards in my lifetime in Rhode Island. If any of those hit any of the beautiful rock piles that I've seen in the area, it's going to damage it no matter how well the pile is made.