Home > Lectures > Geology and history of Mt. Desert Island

Geology and history of Mt. Desert Island

I. Geology of Mount Desert Island

A. Formation of the coast of Maine - occurred between 600 to 250 million years ago.

1. Devonian period - 400 - 360 MYA, as East Coast of US collided with Europe, the Acadian mountains were pushed up. At this same time, the Alleghany Mountains were formed due to the collision of N. America with Africa.

2. This is the collision which formed Pangea (not the first super continent - that was the Grenville continent) and this occurred during the Permian period, about 260 MYA.

3. Opening of the Atlantic Ocean - Late Triassic, about 200 MYA, shortly after the appearance of dinosaurs. This event placed the Acadian mountains on the coastline of a new ocean. No sedimentary rock was laid down during the period from 200 MYA to current times, this was primarily a period of weathering (hence the low, rounded nature of the east coast mountains.

B. Glacial weathering - last 2 million years, only evidence of the last ice age can be seen in Maine (it swept away traces of the previous ones) 40, 000 - 12, 000 years ago.

1. Mount desert range was perpendicular to the direction of the ice flow - Ice built up behind the range, then spilled over between the peaks and down the V-shaped valleys carved by streams.

2. The ice carved deep, parallel U-shaped valleys between the peaks.

3. The ice later reached such depths (2+ miles) that it covered the entire range, scouring the tops of the hills as well as the valleys (hence the rounded shape of the MDI hills).

4. Ice retreated, sea level rose, as the melt water returned to the sea.

5. Lakes, ponds, & Somes Sound. Valleys filled up: With fresh water, if glacial debris blocked the ends of the valley. i.e. Jordan Pond, Eagle Lake, Bubble Pond, etc. Or by the rising sea, forming the only fjord on the east coast of the US, Somes Sound.

6. Deposits of fine clay, sand and gravel left by the glaciers can be found all over the island, but infrequently larger boulders, called erratics, were also left behind (Balance Rock on the South Bubble).

7. Abrasion & plucking - sandpaper action on smooth, gradual, north-facing slopes, and formation of jagged, steep south-facing slopes are due to the movement of the ice and the gravel it carried with it. Think about the gradual limb up N Cadillac and the jagged cliffs on S coast, or the two sides of the S Bubble.

C. Rock formations

1. Igneous rock - forms from rock heated by earth's core
   a. Volcanic - lava & ash from volcanic activity
   b. Plutonic - forma from magma that was never spewed from a volcano - solidified while still beneath the surface. - the bulk of MDI rock is plutonic

2. Cadillac granite - plutonic, makes up the bulk of the island
   a. pink color due to orthoclase feldspar, also contains grains of quartz & black hornblende
   b. joints/fractures, those parallel to surface are due to erosion.

3. Bar Harbor formation - sandstone and siltstone - can be seen east of the town dock in BH, laid down by turbidity currents
   "The Porcupine Islands are part of a sill (or ridge) of diorite formed during the Devonian age (400-360 million years ago) that intruded into the Bar Harbor series of volcanic sediments. The sill, which dips gently towards the north (reason for the lower islands to the north of the chain?), Fractured into columns. Look for them (the columns) on the steep south of each island, where they make cliffs . . . " Parenthetic comments are mine, the quote comes from Roadside Geology of Maine, D.W. Caldwell, Mountain Press Publishing Co., Missoula, Montana, 1998, pp 83-8

4. Shatter zone - breccia (mixture of rock types) or Bar Harbor sandstone, Ellsworth schist, and Cranberry Island rhyolite embedded in Cadillac granite.
   a. can be seen at cliff near sand beach
   b. formed when hot granite magma rapidly intruded these rocks and shattered them, then cooled around the pieces rapidly (preventing metamorphosis)

D. Sand beach - 70% of the sand grains are CaCO3, the remainder are quartz and feltzbar.

1. Most temperate or cold water beaches are made of quartz because CaCO3 goes into solution easily at low temps.

2. Georgia is the next beach with as much CaCO3.

3. Extreme productivity of Maine waters responsible for this concentration of CaCO3 (comes from the shells of living organisms)
   - how to read a contour map

II. History of Mt. Desert Island

A. Discovery, naming & ownership

1. Samuel De Champlain - French captain, saw and named the island in 1604. Called it L'Isle des Monte Déserts - island of the deserted or barren mountains
   Désert = deserted, barren, not after dinner sweets, Desert = arid place did not become a word until American entered the arid west of the US.

2. King Louis XIV gave the island to Sieur de La Mothe Cadillac in 1688
   a. Hence the name of Cadillac mountain
   b. Cadillac went on to found Detroit

3. French forced to give Maine to the English in 1713 - it became part of Mass. became popular as a vacation site for rich New Yorkers and Bostonians in the 1870 and 1880s

B. The first national park east of the Mississippi

1. Sieur de Monts National Monument - 1916
   Charles Eliot (Pres of Harvard Univ), George B. Dorr (wealthy Bostonian) and John D. Rockefeller (wealthy New Yorker) were important in donating land and pushing the park effort forward.

2. Lafayette National Park - 1919

3. Acadia National Park - name changed in 1929
   a. 75% of Mount Desert Island, approx. 35,000 acres.
   b. Smallest and second most visited National Park

4. The year MDI and the Park burned - 1947
   read from article

5. Endangered peregrine falcons breeding in the Park
   read from article

C. The trail system

1. Carriage trails
   45 miles within the park
   16 ft wide crushed rock roads with stone copings & retaining walls
   donated and built by John D. Rockefeller between 1913 and 1940 (a skilled horseman, he wanted motor-free routes into the heart of the park).

2. Hiking trails - over 120 miles of trails in the park
   a. Some trail pre-date Western colonization of the continent.
   b. Creation and upkeep of trails began in earnest in the 1880s, when the Bar Harbor Village Improvement Association was formed.
   c. Waldron Bates & George B. Dorr had a huge impact on the creation of trials in the park.
   d. CCC, a New Deal program started during the Depression, was involved in trial building and maintenance during the 1930s.
   e. The trails are currently maintained by the 4 man Acadia National Park Trail crew.

3. Trail characteristics
   a. Many trails consist of individually places stone steps and copings, to reduce erosion due to foot traffic.
   b. Single or double board plank-ways reduce erosion & foot traffic damage in some boggy trail areas.
   c. Simple foot bridges span small streams and ravines
   d. Some trails climb natural talus fields - a rock slide pattern of angular boulder fragments
   e. Iron rungs and ladders have been place on particularly steep sections
   f. Trials are marked with splotches of blue paint and cairns
   

D. Mount Desert Island Biological Laboratory

1. Founded as the Harpswell lab in 1898
   a. By John Sterling Kingsley of Tufts University
   b. The site was approximately an hour from Portsmouth and only a few miles from Bowdoin College

2. Moved to Salsbury Cove and renamed Mount Desert Island Biological Laboratory in 1921
   a. Lab supplies were moved by boat.

3. Has always been a center for summer research, both basic and biomedical, and for short summer courses.

4. The lab is a non-profit organization, and is not directly affiliated with any colleges or universities.

5. The spiny dogfish (Squalis acanthias) is the symbol of the lab because of the large number of studies carried out on this animal at the lab.
   many studies in the lab have focused on renal function

Back to top

Course Basics | Lectures | Photo Galleries | Student Reports
Interesting Science | Contact Information | Site Map