Elevated marine shore lines offer means of studying the late-glacial crustal movements and changes of sea level. The east coast of Massachusetts offers excellent material for such a study, for here occur the southernmost exposed shores of the late-glacial ocean, the glacial shores farther south having been submerged. The glacial shores of Massachusetts have interested geologists for many years, but although the altitude of the late-glacial marine limit has been fairly well settled, other problems, such as the differentiation of the marginal shore line from the marine limit, have heretofore received little consideration. The highest level reached by the sea at the close of the Pleistocene is known as the marine limit, whereas by the term, marginal shore, is meant the level of the sea at the ice front at any particular time as it retreated northward along the coast.
Changes of level of land and sea are complex . . .