Skip Maine state header navigation
Skip All Navigation
|Home | Contact Us | Publications|
Sea-Level Change on Mt. Desert Island
The motto of geology is "The present is the key to the past." Before delving into ancient sea level locations, it is worth noting some coastal features which characterize the contemporary shoreline. At Monument Cove, directly below the Park Loop Road from the Gorham Mountain parking lot, there is a magnificent boulder beach (Figure 2). The boulders are worked out of the cliffs by waves and tumbled into near-spherical shapes during storms (Figure 3). At the distant (eastern) end of the cove a sea stack exists (Figure 3). This column of granite was formerly attached to the mainland, but wave erosion, by focusing on the vertical fractures in the rocks, has separated it (Figure 4). At the back of the cove stands a vertical sea cliff that has retreated landward as blocks of granite were quarried away by waves (Figure 2). Another erosional feature, not seen in Monument Cove, but common in Acadia National Park, is a sea cave (Figure 1, Figure 5). Sea caves, like sea stacks, form where fractures are eroded by waves near the high-tide line (Figure 4). The shape of the fractures and their spacing determines whether sea caves, sea arches, or sea stacks will form. None of these features are long-lived, and the waves that create them soon lead to their destruction. Most of the rocks on the Maine coast have too many fractures to allow these features to form or exist for very long, but the granite of Mt. Desert Island appears ideal for their formation.
All of this was known to late 19th-early 20th century geologists, and "Chimney Rock" was recognized as solid evidence for a higher-than-present sea-level position in the late 19th century (Shaler, 1889) (Figure 6). The raised sea stack is about 60 m above present sea level and remarkably similar in appearance to the Monument Cove sea stack (Figure 3). Chimney Rock is such striking testimony to a raised sea level that wealthy Mt. Desert Island summer resident, John Rockefeller, was interested in it, and Chimney Rock was described in local newspapers. Most impressive was the uppermost stone, which must have been last turned by a great storm perhaps 13,000 years ago. Unfortunately vandals read of Chimney Rock and managed to topple the uppermost stone. As testimony to his fondness for science, Mr. Rockefeller had a crane brought up the nearby Carriage Path and replaced the fallen stone.
Behind Chimney Rock and stretching for more than a kilometer is a pronounced sea cliff upon which the Carriage Path is built. Below Chimney Rock, the uneven ground is composed of innumerable rounded granite cobbles (Figure 7). These are strikingly reminiscent of the boulder beach at Monument Cove.
Originally published on the web as the March 2002 Site of the Month.
Last updated on October 6, 2005
|Copyright © 2005 All rights reserved.|