Erratic

Glaciers have done mighty things. During their existence they scour out areas that become large lakes, transport rocks and boulders, and alter climates. A nice walk along the beach in North East, PA revealed one of those events to me the other day. The indigenous bedrock is nearly all shale in various sizes and mostly gray to dark gray. However, frequently there will be a rock obviously not from the local bedrock area. Notice in the first photo (top) the frequent shale dispersed along the beach; but with a small nonnative rock standing out (white small boulder in lower center).

Flat shale stones

Some glacial deposited rocks show amazing colorful swirls and layers (below three images). Second is closeup showing some red garnets within the bands

The boulder in the photo below is a fine grained granite,which according to the density of granite (168 lbs/ft3) and a rough guestimate of the volume, it likely weighs 10,000 - 15,000 pounds (5-8 tons!). Hard to believe and I am going to go back to confirm my volume estimate. What could have placed this here since this is not a local rock type?

Erratic weighing 10,000 - 15,000 pounds. Fine grained granite only to be transported by a glacier from the Canadian north