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The Bar Harbor Shore Path

The Shore Path is a lovely trail which starts at the pier and runs along the coast in the town of Bar Harbor.  From the path you can see some of the Porcupine Islands, Egg Rock Light, and Schoodlic Peninsula, all on Frenchmen Bay.  While it is a beautiful place to take a stroll and sight-see it also holds many fascinating geological features. 

Eastern View of the Bar Harbor Shore Path and Frenchmen Bay. This is a half mile walk that takes the hiker past some amazing geologic history stored in the rocks. It's also common to spot impressive sea birds like Eider Ducks and Double Crested Cormorants.
Make sure to take care while beach combing and climbing on the rocks as they can be slippery.

Geologic Features of the Bar Harbor Shore Path

If you're starting from the northern end of the shore path, the first thing you may notice are large red blocks of rock 'balanced' on skinnier columns of the same rock. These are the Bar Harbor sea stacks. The lower portions of the structures have been carved away by the ocean waves which become particularly rough in the winter.

The second feature you may notice is a giant white boulder that looks out of place. It's actually a piece of Lucerne granite that was carried many miles across Maine by glaciers more than 10,000 years ago. Large boulders that have been lifted and transported to other places by glaciers are called glacial erratics. This one has been nicknamed the "Balance Rock" by Bar Harbor residents. It's common to see residents and tourists alike trying to tip the Balance Rock off its perch.

The third feature on the map doesn't stick out like the sea stacks or Balance Rock. It's a series of basalt dikes that run through the surrounding meta-sedimentary rock The Bar Harbor Formation. These dikes were formed when lava made its way to the surface of the earth through surrounding fractures and then cooled into basalt.

Sea Stacks

Glacial Erratic (nicknamed the Balance Rock)

Basalt Dikes

Geologic History

We can see evidence of many geological events at the Shore Path.  From deposition (Bar Harbor Formation), weathering and erosion (Sea Stacks), volcanism (set of dikes), and glaciation (Balance Rock).  We can also see evidence of tectonic activity.  There is a structure known as an anticline present at the Shore Path.  An anticline is a fold in the rock formation where two bedding planes are dipping away from each other.  This is caused by plate tectonics.  270 million years ago the landmass of MDI was compressed between North America, Africa, and other micro-continents, which caused mountains to form (Braun, Ruth and Duane, 2012).  We can see evidence of this in the anticline structure and also in fractures in the rock that we see all over the Shore Path,  These fractures were caused by the rock experiencing stress from compression. (Marshak, 2010).

Bar Harbor Formation

The Shore Path mainly consists of a meta-siltstone known as the Bar Harbor Formation. This rock is 465 million years old (Braun, Duane and Ruth, 2012). It formed from the accumulation of sediments in a deep sea environment.  Over time these sediments were buried and lithified and then exposed, forming the rock that we see today.  You may also notice small, white veins running through the formation.  These are quartz veins. 

Here we see meta-siltstone, properly named the Bar Harbor Formation.  Notice how layered the rock is!

There are many quartz veins running through the Bar Harbor Formation.

Sea Stacks

You may also notice hour-glass shaped rock formations while visiting the Shore Path.  These outcrops are shaped this way because of weathering and erosion.  These outcrops are smaller on the bottom and wider on top because the motion of the waves is constantly making contact with the bottom portion.  Eventually, the bottom half will become so eroded that it will weather away completely.  (Marshak, 2010).

Sea Stacks are present at the Shore Path and are caused by erosion.

Dikes

There are multiple igneous dikes at the Shore Path.  These dikes consist of Basalt and Diorite. Basalt is extrusive meaning that it cooled on the surface of the earth.  The Basalt has very small grains because it cooled quickly. Diorite is intrusive meaning it cooled within the earth. If you visit the Shore Path you will notice that the Diorite has larger grains than the Basalt because it cooled more slowly. These dikes are around 420 million years old (Braun, Duane and Ruth, 2012).  

Here we see a closeup view of the intrusive basalt. Notice the gray color and tiny grains which are characteristic of extrusive igneous rock.  

Balance Rock

A much visited feature on the Shore Path is the Balance Rock,  The Balance Rock is made of Lucerne Granite which is not native to MDI but came from Lucerne, Maine, 45 miles west of the island.  Through the movement of glacial ice the boulder was picked up and carried to where we see it today.  The exact location of the Balance Rock can also be attributed to wave energy which has helped to push it into its current placement.

The Balance Rock was brought to MDI from Lucerne, ME, by glacial activity.

Watch this video to learn more!

Video by Nora Hyman
References

Marshak, Stephen.  Portait of a Planet.  New York: Norton, 2012.  Print.

Braun, Ruth, and Duane Braun.  "2012 Revised Mount Desert Island Bedrock Map Explaniation." N.p., n.d. Web. 9 Nov. 2015. 

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