File:The geological history of the Connecticut Valley of Massachusetts - a popular account of its rocks and origin (1921) (14580695058).jpg

Identifier: geologicalhistor00mill (find matches)
Title: The geological history of the Connecticut Valley of Massachusetts : a popular account of its rocks and origin
Year: 1921 (1920s)
Authors: Miller, William J. (William John), 1880-1965
Subjects: Geology Geology
Publisher: (Northampton, Mass. : The Hampshire Bookshop)
Contributing Library: Wellesley College Library
Digitizing Sponsor: Boston Library Consortium Member Libraries

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the proofs for the former presence of the great icesheet are the following: (i) polished and scratched rock surfacesat all altitudes which are precisely like those produced by existingglaciers, and which could not possibly have resulted from any otheragency; (2) glacial boulders, called erratics, which are generallymore or less rounded or facetted and often scratched, and which haveoften been transported many miles from their parent ledges andscattered over all parts of the country, high and low; and (3)deposits, including true moraines (see below) and the very widespread 6o The Geological History of the mantle of heterogeneous glacial debris, which are clearly ice tran-sported materials usually resting by sharp contact on the bed rock. Depth and Direction of Movement of the Ice. It was the vastglacier whose center of accumulation was in Labrador which spreadacross New England completely burying the highest summits. Overcentral western Massachusetts the general movement of the ice was
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FIG. 22. A SMOOTHED AND SCRATCHED LEDGE OK LAVA—A RECORD LEFT BY THE VAST GLACIER OF THE ICE AGE AT THE BASE OF THE MOUNT TOM CABLE RAILWAY. PHOTOGRAPHED BY THE AtTTHOR. Connecticut Valley of Massachusetts 6i southeastward with a strong tendency for the current to be deflectedmore directly southward through the Connecticut Valley proper.How are such facts known? The evidence from the distribution ofglacial deposits (including boulders) and the glacial scratches isclear and conclusive. Such phenomena may be observed even onmany of the highest points. For example, on top of Mount Tomthere are not only many glacial pebbles and small boulders of variousrock types entirely different from the rock of the mountain and carriedfrom ledges miles to the north, but also wonderfully well preservedice scratches and smoothed and even grooved rock ledges. Thesescratches and grooves point southward. Many of the exposures oflava from the base to the summit of Mount Tom along the cablerailway are beau

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