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Barnstable Bay Rises 29 Feet
The sea level in Barnstable Bay during the past five thousand years has experienced a 29-foot rise. The record is written plainly for the eyes of scientists who delve into such subjects.
Such as Patrick Butler of Harvard University, a summer visitor at Woods Hole Oceanographic institution. Mr. Butler investigated the Great Marshes of Barnstable to find changes in sea level and climate that have occurred in southeastern New England during what geologists term “recent time.”
Since the end of the last ice age, about five thousand years ago, the Barnstable marshes have been slowly building themselves upward, the growth consisting of layers of peat. We know that marsh grass grows only in the area between low tide level and high tide level. Therefore, whenever the sea level rises, the grass there grows a little farther up on the land, and the grass at the lower level’s edge is submerged, gathers sediment, and becomes an addition to the layers of peat below.
Under the deepest layer of peat — 29 feet — there is clay. Mingled in the peat is pollen from trees and shrubs, carried to the marshes by the winds, and a study of the pollen shows that the marsh began to form at the end of moist, warm period following the last ice age. Next them was a warm, dry age, indicated by an increase of oak, hickory, and beech pollen. Another change, when the marsh peat level was about 19 feet below the surface, shows that pine and hemlock were the principal pollens, showing that cooler, moister conditions have lasted to about the present time.
The rise in sea level gives little cause for any of us to feel concerned about it. The average rise was but six to seven inches “in a full century”. Such a rise is not unusual.
The U. S. Coast and Geodetic Survey records of tides shows that the sea level at Boston, about forty miles northward of Barnstable, has risen by four inches during the last quarter of a century. This rate, if it held through 29 years, would give Boston harbor a sea level that has risen 66 feet in five thousand years compared with the 29-foot rise at Barnstable.
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Categories: History, Nature
Keywords: geology, history, nature
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