The Boston Harbor Islands National Recreation Area, authorized in 1996, comprises 34 islands and peninsulas and is managed by various federal, state, municipal, and non-profit agencies. The area is situated within the ancient Boston Basin, shaped by tectonic forces over 252 million years ago and modified by glacial activity during the Pleistocene Epoch. This eroded landscape is notable for its drumlins, which are unique coastal glacial landforms in the U.S.
Key geological features include glacial deposits like till, moraines, and erratics, alongside various coastal formations such as sand beaches and salt marshes. The drumlins have experienced “bluff retreat” due to erosion and rising sea levels, changing their landscape significantly over time. Human activities, including quarrying and military usage, have resulted in abandoned mineral lands, which pose ecological risks. The park’s geology reflects the broader New England Physiographic Province, sharing significant geological characteristics beyond its boundaries.
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