Maine's ~600 Million Years of Heritage

PLATE TECTONICS

The geologic history of Maine involves the formation of mountain ranges (“orogeny”) and ocean basins (“rifting”) through plate tectonic collisions and separations. The Appalachian Mountains of eastern North America formed during ~600-200Ma of plate collisions and are still present in the modern landscape although greatly denuded after millions of years of erosion. The Atlantic Ocean, an iconic feature of coastal Maine, began opening about 200Ma with the breakup of Pangea, and is still widening today along the Mid-Atlantic Ridge.

Ancient Volcanoes

A chain of super volcanoes formed along the eastern margin of the continent from subducting plate tectonics forming large plutons of intrusions granite rock. Mount Desert Island was once one of those volcanoes.

GLACIATION

Over the last million years, the coast of Maine has been shaped by a series of continental glaciers that have carved valleys, deposited sediment, and changed sea levels.

HUMANS

After Maine was ice-free around 12,000 years ago, people started to settle in the region. Since then we have modified the landscape in many ways.

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1. Damariscotta River Shell Midden

Oyster shell midden which is a vulnerable and important cultural geoheritage site, protected as a Maine State Historic Site.

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4. Marshall Point

Quartzite, mica schist, basalt dikes, granite and a lighthouse that is culturally significant. 

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2. La VernaPreserve

Impressive folded metamorphic rocks along the shoreline with igneous intrusions, along with slightly metamorphic igneous rocks

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5. Rockland Limestone Quarry

Several old limestone quarries that have been economically important for the area.

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3. Pemaquid Point

Folded metamorphic rocks along the shore with more resistant igneous rocks in larger block formations; culturally important lighthouse.

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6. Vinalhaven

Vinalhaven rhyolite and volcanic breccia that make up the bedrock. The island is an important cultural and archaeological heritage site that was first discovered by the Red Paint people around 5000 years ago due to its abundance of shell and fin fish.

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7. Mt Battie

Battie quartzite – a metamorphic rock that is more resistant compared to the surrounding rocks in the region. The distinct "whaleback" shape was an important landmark for Native Americans. The site is part of the Camden State Park.

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8. Gridle Point (Isleboro)

Islesboro Formation: bedrock is dominated by sandstone, slate, and limestone cut by many small faults. There are also outcrops of metamorphic rocks with outstanding examples of folding. The Gindle Point lighthouse is an important cultural heritage site.

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9. The Passagassawakeag Rail Trail

The trail follows a historic railway path, with exposed Bucksport Formation and Appleton Ridge outcrops along the path. Also, just beyond the site in the Belfast bay there are pockmarks (round depressions on the sea floor) seen from bathymetric surveys.

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10. Sear Island

The entire island is made from the Penobscot Formation with outstanding examples of folding. The island is an important cultural heritage location with vulnerable and important archaeological sites.

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11. Mt. Waldo

Mt Waldo granite that was an important type of granite for the granite industry and shipped across eastern North America.

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12. Penobscot Narrows

Outstanding views of surrounding landscape and river from the Penobscot Narrows Observatory.

Blue Hill Peninsula
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13. Blue Hill Mountain

Lucerne granite and outstanding views of the coastal islands from the summit.

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14. Caterpillar Hill

Important blueberry barren protected by a land trust. Also great views of the Penobscot Bay and the Deer Isles.

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15. Pine Hill

Serpentinized peridotite that hosts some of the world’s rarest ferns, plans, and lichen.

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16. Settlement Quarry

Historic and culturally important quarry. Deer Isle granite features a rare formation called rapakivi.

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17. Isle au Huat

Impressive granite formation with gabbro intrusions, and outcrops of volcanic ash and tuff. The island is an important cultural and archaeological location, with many preserved features protected by Acadia National Park.

MDI/ Schoodic 
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18. Agassiz Outcrop

Important site for the development of the study of geology due to the presence of glacial striations that Louis Agassiz, Swiss biologists and glaciologist, discovered on a trip to Maine.

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20. Bubble Rock

Famous glacial erratic perched on the side of a glacially carved mountain made from Cadillac granite.

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19. MacQuinns Quarry

Impressive esker

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20. Bubble Rock

Famous glacial erratic perched on the side of a glacially carved mountain made from Cadillac granite.

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20. Bubble Rock

Famous glacial erratic perched on the side of a glacially carved mountain made from Cadillac granite.

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20. Bubble Rock

Famous glacial erratic perched on the side of a glacially carved mountain made from Cadillac granite.