Man and the Glacial PeriodWright, G. Frederick (George Frederick)
History
Man and the Glacial Period
Wright, G. Frederick (George Frederick)
Glacial epoch; Prehistoric peoples
In addition to these two lines of evidence of glacial action in New
England, we should mention also the innumerable glacial grooves and
scratches upon the rocks which can be found on almost any freshly
uncovered surface. In New England the direction of these grooves is
ordinarily a little east of south. Upon the east coast of Massachusetts
and New Hampshire the scratches trend much more to the east than they
do over most of the interior. This is as it should be on the glacial
theory, since the ice would naturally move outwards in the line of least
resistance, which would, of course, be towards the open sea wherever
that is near. In the interior of New England the scratches upon the
rocks indicate a more southerly movement in the Connecticut Valley than
upon the mountains in the western part of Massachusetts. This also is as
it should be upon the glacial theory. The scratches upon the mountains
were made when the ice was at its greatest depth and when it moved
over the country in comparative disregard of minor irregularities of
surface, while in the valleys, at least in the later portion of the Ice
age, the movement would be obstructed except in one direction. In the
interpretation of the glacial grooves and scratches it should be borne in
mind that they often represent the work done during the closing stages
of the period. Just as the last shove of the carpenter's plane removes
the marks of the previous work, so the last rasping of a glacial movement
wears away the surfaces which have been previously polished and striated.
In various places of New England it is interesting as well as instructive
to trace the direction of the ice-movement by the distribution of
boulders. My own attention was early attracted to numerous fragments
of gneiss in eastern Massachusetts containing beautiful crystals
of feldspar, which proved to be peculiar to the region of Lake
Winnepesaukee, a hundred miles to the north, and to a narrow belt
stretching thence to the southwestward. In ascending almost any of the
lower summits of the White Mountains one's attention can scarcely
fail of being directed to the difference between the material of which
the mountains are composed and that of the numerous boulders which lie
scattered over the surface. The local geologist readily recognises these
boulders as pilgrims that have wandered far from their homes to the
northward.
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