File:The geological history of the Connecticut Valley of Massachusetts - a popular account of its rocks and origin (1921) (14580627640).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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24). By way of illustration of someof the geological history which these boulders represent, a group ofthree within a rod of each other at Mountain Park will be brieflydescribed. They are shown in figure 25. The one in the middle isa very hard altered sandstone (or quartzite) from an early Paleozoicformation deposited under the sea at least 25 million years ago. Itwas torn from a ledge in southwestern Vermont and carried to itspresent position by the ice ot the great Ice Age. On the left is a 66 The Geological History of the boulder of granite representing once molten material which was forcedinto the earths crust in late Paleozoic time at least 12 million yearsago. It was carried by the ice from a ledge north or west of North-ampton. The boulder on the left represents lava which flowed inmolten condition upon the earths surface in late Triassic time atleast S million years ago. It was carried not more than a few milesby the ice. Veritably, these three erratics form a strange company.
Text Appearing After Image:
FIG. 25. A STRANGE COMP.\XY OF THREE GLACIAL BOULDERS NEAR MOUNTAIN PARK. THE MID-DLE ONE WAS CARRIED BY THE GREAT GLACIER OF THE ICE AGE FROM SOUTHWESTERN VERMONT; THEONE ON THE LEFT FROM THE VICINITY OF NORTH.\MPTON; AND THE ONE ON THE RIGHT FROM THEMOUNT TOM RANGE. PHOTOGRAPHED BY THE AUTHOR. Of special interest are the boulders commonly called hard-heads which are widely scattered over the region. They are likethe first one of the group of three described just above. They aregenerally well rounded, exceedingly hard, and of a light gray to lightbrownish-yellow color. These very ancient (early Paleozoic) rockswere transported across northwestern Massachusetts from south-western Vermont. Boulders of the late Paleozoic igneous rocks(mainly granite) are also very common and widespread not onlybecause th^ ice plucked off many masses of these widely exposedrocks, but also because of their great hardness which prevented themfrom being ground to pieces by the action of the ice. Connecticut

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