Agassiz Rock Formation - Route 1A - Ellsworth, ME - Places of Geologic Significance on Waymarking.com

In Ellsworth, along U.S. Route 1A, is the Agassiz Rock Formation or Outcrop, which has been listed in the National Register of Historic Places.

The ledge is on the south side of the road, south of where Route 1A splits with Maine Route 179. It is on the property that is currently a photography and silk screen operation. The ledge is right next to the road.

The ledge is a highly metamorphosed rock (changed and folded by heat and pressure), named Ellsworth Schist. There are several grooves on the face of the rock and the rock is generally smooth. The grooves are parallel, which indicates scouring by glaciers exerting pressure at the bottom of several thousand feet thick of ice.

Louis Agassiz was a professor at Harvard University, who was also recognized for his work on fish. Later, he turned his interest to glaciers. At the time, much of the features such as wide, eroded valleys and scrapings were attributed to "The Great Deluge" some time in the earth's past. However, as Agassiz traveled through Maine and other places, he pieced together evidence that glaciers, not flooding, alter landscape features. The rocks in this area were referenced in his work.

A presentation on the Maine Geological Survey web site has this quote from Prof. Agassiz about the area:

"Between Bangor and Mount Desert the usual evidence of glaciation is very extensive. I would mention as particularly interesting the hills south of Holden and the hills about Dedham. On the route along Union Bay there are also extensive polished surfaces, especially in the vicinity of Bucksport. Near Ellsworth, they are beautifully preserved, and all the eminences are moutonnees. At Ellsworth Falls, on both sides of the bridge, there are splendid polished surfaces, with scratches and furrows pointing due north. Between Ellsworth and Trenton, and westward of that meridian, in the direction of Bucksport, there are several longitudinal moraines parallel to one another, running from north to south, composed of large, angular boulders, resting upon ground moraines made up of rounded scratched pebbles and sand mixed with clay. Such a superposition is utterly incompatible with currents passing over these tracks. Two miles west of Ellsworth a similar longitudinal moraine runs over the top of the hill, and about one mile farther west there is another, chiefly composed of coarse Dedham granite. The bottom deposit, upon which these moraines rest, consists of fine sand and loam with scratched pebbles. Seven or eight miles west of West Ellsworth the hills, consisting of clay slates on edge, trending from east to west, are abraded, and upon the polished surfaces of their leveled edges rest two other longitudinal moraines, with angular boulders of Dedham granite, running from north to south, and resting upon an extensive ground moraine containing many smaller rounded and striated pebbles. (Agassiz, 1867, p. 285)"

This location was included in the national register in 2003.

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Date Logged Log User Rating   11/27/2016 wildernessmama visited it