Volcanoes in Massachusetts?
Whoever heard of a red-hot volcano in Massachusetts? You would have hard work to find one; in fact, you could not find one today. Yet, we are told by geologists that once upon a time active volcanoes poured out black and red felsites, (which were dense, igneous fire-made rocks consisting of feldspar and quartz) under the sea in Nantasket, Hingham, and Mattapan, Boston.
That was when the famous granites of Quincy and other places on the South Shore welled up from below, and through the interstices or spaces between these came the molten traprock, which was fine-grained, colored, igneous rock in somewhat columnar shape. You can see some of this traprock in the greenish ledges of Cohasset today.
There were so many of these volcanic eruptions, as well as violent earthquakes, that the disgorged materials covered the bottom of Boston’s water basin with varied patterns of deposits. Eventually, as we realize, the submarine disturbances quieted down and ceased.
At that time also, the edge of the entire continent along our shoreline was lifted up higher than it is now. You would therefore have had to walk some distance to reach the ocean shore, for it was farther east than at present. All the gravel-formed hills of today were missing, and the ponds and small lakes that we now find everywhere here, simply did not exist.
Blue Hill, just southwest of Quincy, would be perhaps the only place which we of today would recognize if we were whisked by magic back into that distant era. The ancient river, which in those days had for its mouth the area which we call Massachusetts Bay, emptied into the sea somewhere beyond Provincetown. There, deep in the ocean bottom, six hundred or more feet down, still lie the grooves or canyons through which this vast river for ages cut its way oceanward. By then, even the fiery volcanoes which had spewed their molten contents into the Bay, were quenched and dead.
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