I used to think that Whitefield
was a good place to find erratics because of the dense bedrock, common in our Sheepscot River Valley
that helped guide the glaciers into a narrow relative deep channel -
all the while widening and deepening the "Sheepscot valley".
BUT, when I checked with
Robert G. Marvinney, our State
Geologist, he said "
Actually, the continental glacier overtopped the
entire state and was at least a mile thick, maybe two, in the
Whitefield area. All the ice flow indicators that we have found in
the region show transport from the northwest to the southeast, not
parallel to the bedrock (northeast-southwest) nor the river.
However, the hard rock, with many fractures, allowed large blocks to
be plucked by the glacier and deposited somewhere “down glacier”
when the glacier melted."
He replied " Eskers form by flowing melt water in tunnels beneath the glacial ice, not by “plowing” of sedimentary materials by the prow of the glacier. Ridges formed by plowing or deposition of material at the leading edge of a melting glacier are called moraines. They are made of till – a mixture of every size material from clay to boulders – which is quite different from the sorted sand and gravel (little silt or clay) common in eskers"
We are so fortunate to have these experts at our beck and call... !