Agassiz Rock

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An 1870s stereoview depicting Little Agassiz Rock
Big Agassiz Rock in 2013

Agassiz Rock is a park in Manchester-by-the-Sea, Massachusetts, that is owned and maintained by The Trustees of Reservations. The park's name is from two dramatic examples of large boulders plucked from bedrock and carried by the glaciers.

As the glaciers scoured this landscape, the mass of bedrock forming the hill proved more resistant than the surrounding soil, forcing the bottom of the glacier up and over the hill. The north side was smoothed and the south side left steep and rugged as the glacier broke off chunks of rock as it passed.

A short loop trail leads up Beaverdam Hill where Little Agassiz Rock appears as a giant granite monolith silhouetted against the sky. It rests precariously on a small jagged stone, leaving an opening below.

A short distance away, other boulders lie perched on the edge of this glaciated upland. Below, in a small shrub swamp, rests thirty-foot-tall Big Agassiz Rock. How far it extends underground is unknown.

The trail to the site is a one-mile, moderate difficulty loop trail that passes both Big and Little Agassiz Rocks. Following long periods of rain the immediate area surrounding Big Agassiz Rock often floods.


In 1874, a group of students named this site to honor Louis Agassiz, the Harvard University professor who first theorized that the rocks that dot New England's landscape were shaped and deposited by glaciers.

Agassiz visited the site and found the erratic physical features fit his theory. Prior to Agassiz's theory, people widely believed that the scattering of rocks throughout New England were the result of Noah's flood. The rock is often used as a type example of a glacial erratic.


Coordinates: 42°35′46.81″N 70°46′2.75″W / 42.5963361°N 70.7674306°W / 42.5963361; -70.7674306