Acadia National Park 

Geologic Resources Inventory Report 

Natural Resource Report NPS/NRPC/GRD/NRR—2010/232 

National Park Service 

U.S. Department of the Interior 

Natural Resource Program Center 
THIS PAGE:

Visitors navigate along the beautiful 

Acadia coast. National Park Service

photograph by Cynthia Ocel. 

ON THE COVER:

Hiking to the tops of summits offers

views of ocean and fall colors. Gorham Mtn Trail. National Park Service 

photograph by Ginny Reams. 
Acadia National Park 

Geologic Resources Inventory Report 

Natural Resource Report NPS/NRPC/GRD/NRR—2010/232 

Geologic Resources Division 

Natural Resource Program Center 

P.O. Box 25287 

Denver, Colorado 80225 

August 2010 

U.S. Department of the Interior 

National Park Service 

Natural Resource Program Center 

Ft. Collins, Colorado
The National Park Service, Natural Resource Program Center publishes a range of reports that 

address natural resource topics of interest and applicability to a broad audience in the National 

Park Service and others in natural resource management, including scientists, conservation and 

environmental constituencies, and the public. 

The Natural Resource Report Series is used to disseminate high-priority, current natural 

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recommendation for use by the U. S. Government. 

Printed copies of this report are produced in a limited quantity and they are only available as 

long as the supply lasts. This report is available from the Geologic Resources Inventory website 

(http://www.nature.nps.gov/geology/inventory/gre_publications.cfm) and the Natural 

Resource Publications Management website (http://www.nature.nps.gov/publications/

NRPM). 

Please cite this publication as: 

Graham, J. 2010. Acadia National Park: geologic resources inventory report. Natural Resource 

Report NPS/NRPC/GRD/NRR—2010/232. National Park Service, Ft. Collins, Colorado. 

NPS 123/105335, August 2010 

ii NPS Geologic Resources Division 
ACAD Geologic Resources Inventory Report iii

Contents

Lists of Figures and Tables ........................................................................................... iv

Executive Summary ....................................................................................................... v

Acknowledgements...................................................................................................... vi

Credits........................................................................................................................................................................ vi

Introduction ................................................................................................................... 1

Purpose of the Geologic Resources Inventory ...............................................................................................................1

Regional Information ...................................................................................................................................................1

Geologic Setting ..........................................................................................................................................................2

Cultural History ............................................................................................................................................................4

Geologic Issues ............................................................................................................ 11

Mass Wasting and Slope Failure .................................................................................................................................11

Coastal Erosion ..........................................................................................................................................................11

Sustainability of Sand Beach.......................................................................................................................................12

Seismic Activity ..........................................................................................................................................................12

Global Climate Change ..............................................................................................................................................13

Visitor Impact to Natural Resources............................................................................................................................14

Other Potential Issues.................................................................................................................................................14

Geologic Features and Processes................................................................................ 23

Bedrock Features .......................................................................................................................................................23

Glacial Features..........................................................................................................................................................27

Coastal Features.........................................................................................................................................................29

Map Unit Properties .................................................................................................... 39

Geologic History .......................................................................................................... 43

Paleozoic Era (542 to 251 million years ago)...............................................................................................................43

Mesozoic Era (251 to 65.5 million years ago)..............................................................................................................44

Cenozoic Era (the past 65.5 million years)...................................................................................................................44

Glossary........................................................................................................................ 52

Literature Cited............................................................................................................ 56

Additional References ................................................................................................. 60

Appendix A: Overview of Digital Geologic Data....................................................... 61

Appendix B: Scoping Session Participants ................................................................. 63

Attachment 1: Geologic Resources Inventory Products CD
iv NPS Geologic Resources Division 

List of Figures

Figure 1. National Park Service location map for Acadia National Park, Maine...................................................................5

Figure 2. Detail maps of Acadia National Park: Mount Desert Island, Isla au Haut, and the Schoodic Peninsula..................6

Figure 3. Legislated Acadia National Park boundaries and conservation easements as of April 2010..................................7

Figure 4. Blocks of granite form the rocky coastline at Bass Harbor Head..........................................................................8

Figure 5. Bedrock and surficial geologic units in Acadia National Park...............................................................................9

Figure 6. Stone bridge along a carriage road, Mount Desert Island .................................................................................10

Figure 7. Slumping above the path to Thunder Hole.......................................................................................................16

Figure 8. Slope failure and slumping along Hunters Brook, Mount Desert Island.............................................................17

Figure 9. Examples of mass wasting on Mount Desert Island caused by the October 2006 earthquake............................18

Figure 10. Waves from Hurricane Bill come ashore at Mount Desert Island, August 23, 2009 .........................................19

Figure 11. Winter seas hammer the coastline of Acadia National Park ............................................................................20

Figure 12. Aerial view of Sand Beach, Mount Desert Island ............................................................................................20

Figure 13. Erosion and deposition of Sand Beach ...........................................................................................................21

Figure 14. Erosion of the dune ridge..............................................................................................................................21

Figure 15. Boulders dislodged by the 2006 earthquake twisted this iron railing ..............................................................22

Figure 16. Flooded shoreline and fire rings Nos. 2, 3, 4 at the Thompson Island picnic area ............................................22

Figure 17. Igneous diabase dikes in Acadia National Park ...............................................................................................30

Figure 18. The shatter zone at Little Hunters Cove, Mount Desert Island.........................................................................31

Figure 19. Schematic cross section through Cadillac Mountain granite illustrating a possible origin for the shatter zone..31

Figure 20. Metamorphic and sedimentary bedrock features in Acadia National Park .......................................................32

Figure 21. Glacial erosional features in Acadia National Park ..........................................................................................33

Figure 22. Glacial depositional features in Acadia National Park......................................................................................34

Figure 23. Emergent coastline features exposed along Cadillac Cliffs on the Gorham Mountain Trail...............................35

Figure 24. Boulder beach and sea stack at Monument Cove, Mount Desert Island ..........................................................36

Figure 25. Thunder Hole slot and sea cave on Mount Desert Island.................................................................................37

Figure 26. Geologic timescale ........................................................................................................................................46

Figure 27. Middle Cambrian paleogeographic map ........................................................................................................47

Figure 28. Schematic illustration of the Taconic Orogeny................................................................................................48

Figure 29. Middle Devonian paleogeographic map.........................................................................................................49

Figure 30. Late Permian paleogeographic map...............................................................................................................50

Figure 31. Quaternary paleogeographic map .................................................................................................................51

List of Tables

Table 1: Cranberry Island series (SDcif, SDcit, and SDcis on the Map Units Property Table) ..............................................24

Table 2: Glacial Features in Acadia National Park............................................................................................................27

Table 3: Summary of Geologic Features and Processes visible within Acadia National Park ..............................................38
ACAD Geologic Resources Inventory Report v

Executive Summary

This report accompanies the digital geologic map data for Acadia National Park in Maine, 

produced by the Geologic Resources Division in collaboration with its partners. It contains 

information relevant to resource management and scientific research. This document 

incorporates preexisting geologic information and does not include new data or additional 

fieldwork.

Arguably one of the most geologically remarkable sites 

along the Atlantic Coast, Acadia National Park 

represents the only National Park along the eastern 

seaboard with a coastline carved by Pleistocene 

continental glaciers. The park’s landscape captures the 

interplay between older episodes of tectonic 

deformation, Pleistocene glaciation, and more recent 

depositional and dynamic erosional processes of the 

ocean. The park’s Mount Desert Island, the largest of 

many islands located along the coast of Maine, contains 

Cadillac Mountain, the highest point on the U.S. Atlantic 

coast.

The official park boundary includes parts of Mount 

Desert Island, Isle au Haut, and the southern tip of the 

Schoodic Peninsula about 8 km (5 mi) east of Mount 

Desert Island. Baker Island, Porcupine Islands, and a 

small parcel on Little Cranberry Island are federally 

administered. Other areas protected by conservation 

easements and managed by the park include all or parts 

of Swans Island, Ironbound Island, Jordan Island, and 

Long Island.

Geologic issues relevant to park management include:

• Mass wasting and slope failure

• Coastal erosion

• Sustainability of Sand Beach

• Seismic activity

• Sea level rise

• Visitor impact to natural resources

Rockfalls and slumping close roads and damage trails 

and campgrounds in Acadia National Park. Precipitation 

falls in each month in the park, and winter and early 

spring ice storms are common. The potential for mass 

wasting and slope failure increases with saturated soils, 

spring thawing, precipitation, and storm waves. 

Storm surge and the relentless pounding of the surf 

erode coastlines and may damage nearby trails and 

infrastructure. When storm surge combines with high 

tides, beach erosion and coastal flooding may damage or 

destroy sea walls, boardwalks, bulkheads, and piers.

Erosion of a Pleistocene delta deposit may change the 

composition of Sand Beach. Sand Beach and a beach on 

Cranberry Island, which is not on park property, are the 

only two beaches north of Cape Hatteras that contain 

both dunes and a beach composed almost entirely of 

calcium carbonate shell fragments. Not only are beaches 

composed of sand-sized particles rare in Acadia National 

Park but also calcium carbonate beaches are rare in cold 

water climates. The delta deposit underlies the Sand 

Beach parking lot, and quartz and feldspar wash onto the 

beach. Because quartz and feldspar are naturally harder 

than calcium carbonate, the quartz and feldspar particles 

abrade and destroy the calcium carbonate fragments. 

The shell fragments that currently dominate the beach 

may diminish over time.

Earthquakes with epicenters close to the park have 

triggered landslides and damaged roads and trails. 

Earthquakes occur at a low but steady rate in Maine and 

generally have magnitudes less than 4.8 on the Richter 

scale. While smaller than west-coast earthquakes, they 

do increase the potential for rockfall and mass wasting. 

Beach erosion will increase with continued sea level rise. 

Rising sea level may flood the picnic area on Thompson 

Island and inundate cobble beaches in the park. If the 

severity of storms increases, the potential for shoreline 

erosion and damage to park infrastructure may also 

increase. Groundwater levels will rise with sea level and 

may cause leach fields to flood and septic systems to fail. 

Rising sea level will also change the salinity in estuaries 

and coastal wetlands.

Acadia National Park is a popular park, and increased 

visitation has taken its toll on some of the park’s natural 

resources. Trails that were once vegetated are now bare. 

Visitors illegally collect cobbles from beaches for 

souvenirs or for landscape decoration. Increased 

visitation may also be one reason for the decline in 

anemones in Anemone Cave.

Other potential geologic issues that may impact the park 

include the rupturing of natural gas pockets in Somes 

Sound and potential flooding if the glacial moraines that 

dam Jordan Pond and Long Pond were to fail. Activities 

external to the park boundaries may also raise 

management issues in the future. Some of these activities 

include aquaculture, offshore sand and gravel mining, 

and alternative ocean energy development.

Bedrock, glaciers, and the sea combined to shape the 

exceptional landscape of Acadia National Park. The 

bedrock includes metamorphic, igneous, and 

sedimentary rocks that record significant tectonic 

deformation, volcanic activity and the resulting 

sedimentary response. Acadia National Park offers an 

excellent outdoor laboratory in which to examine the 
vi NPS Geologic Resources Division 

timing and geologic processes recorded in the bedrock. 

Excellent examples include the emplacement of 

previously molten rocks as part of the Cadillac Mountain 

intrusive complex on Mount Desert Island, the granite 

on the Schoodic Peninsula, and the volcanic episodes 

recorded in the Cranberry Island Series. In addition to 

the pink granite that forms the core of Mount Desert 

Island, other spectacular features include the shatter 

zone that borders the Cadillac Mountain granite, diabase 

dikes that cut the granitic units, and joint sets that 

fractured the bedrock.

Massive continental glaciers that covered the highest 

peaks of Mount Desert Island and flowed into the Gulf 

of Maine created both depositional and erosional 

features of the landscape. Abrasion by debris in the 

glacial ice polished the bedrock and carved striations, 

grooves, and chatter marks in the granite. The grinding 

force of the glaciers sculpted bedrock knobs known as 

roches moutonnées and carved characteristic U-shaped 

valleys that extended to the sea. Meltwater channels 

within the glaciers transported sediment that was 

deposited at the glacial margin in fluvial outwash and 

delta deposits. Debris dumped at the front of melting 

glaciers became thick moraines of glacial till that 

dammed the U-shaped valleys. As the glaciers melted, 

boulders that had been transported far from their place 

of origin, known as glacial erratics, were left stranded on 

mountain sides. 

The complex interaction between glaciation, crustal 

rebound, and fluctuations in sea level resulted in features 

representing both coastal emergence and submergence. 

As glaciers melted at the end of the Pleistocene, sea level 

rose rapidly, inundating valleys with sea level reaching 

approximately 70 m (230 ft) higher than it is today. 

Remnants of this ancient coastline include boulder beach 

deposits, sea caves, undercut cliffs, and wave-cut 

platforms. Exposures of marine clay appear incongruous 

in present-day terrestrial stream beds indicating an 

offshore marine depositional environment for those 

locations. However, sea level did not remain at this 

elevated level. Unburdened by the weight of the 

continental ice sheet, the crust rebounded, causing a 

retreat of sea level to a position approximately 55 m (180 

ft) lower than its current position. 

Today, the Atlantic surf relentlessly batters the Acadian

shoreline. Wave action erodes less resistant rocks, 

forming such popular attractions as Thunder Hole. 

Constant hydraulic action modifies the sea cliffs, sea 

caves, wave-cut platforms, and other coastal features that 

enhance the grandeur of Acadia National Park.

The glossary contains explanations of many technical 

terms used in this report, including the Map Unit 

Properties Table. Figure 26 is a geologic time scale.

Acknowledgements

The Geologic Resources Inventory (GRI) is one of 12 inventories funded by the National 

Park Service Inventory and Monitoring Program. The GRI is administered by the 

Geologic Resources Division of the Natural Resource Program Center.

The Geologic Resources Division relies heavily on 

partnerships with institutions such as the U.S. Geological 

Survey, Colorado State University, state geologic surveys, 

local museums, and universities in developing GRI 

products.

Special thanks to: Joe Kelley (University of Maine), Chris 

Koteas (University of Massachusetts), Bob Marvinney 

(Maine Geological Survey), and Tom Weddle (Maine 

Geological Survey) for their geological expertise. Special 

thanks also to Sonya Berger, Charlie Jacobi, David 

Manski, and Kirk Lurvey of Acadia National Park for 

their insight into the geologic issues important to park 

management and for organizing an exceptional field trip 

on Mount Desert Island. Karen Anderson (Acadia 

National Park) provided the land ownership map for 

Acadia National Park and the surrounding area (fig. 3).

Credits

Author

John Graham (Colorado State University)

Review

Robert Marvinny (Maine Geological Survey)

Tom Weddle (Maine Geological Survey)

David Manski (Acadia National Park)

Rebecca Cole-Will (Acadia National Park)

Sonya Berger (Acadia National Park)

Jason Kenworthy (NPS Geologic Resources Division)

Editing

Jeff Matthews (Write Science Right)

Digital Geologic Data Production

Matt Schaefer (Colorado State University)

Stephanie O’Meara (Colorado State University)

Victor de Wolfe (Colorado State University)

Digital Geologic Data Overview Layout Design

Phil Reiker (NPS Geologic Resources Division)

John Gilbert (Colorado State University)
ACAD Geologic Resources Inventory Report 1

Introduction

The following section briefly describes the National Park Service Geologic Resources 

Inventory and the regional geologic setting of Acadia National Park.

Purpose of the Geologic Resources Inventory 

The Geologic Resources Inventory (GRI) is one of 12 

inventories funded by the National Park Service (NPS) 

Inventory and Monitoring Program. The GRI, 

administered by the Geologic Resources Division of the 

Natural Resource Program Center, is designed to 

provide and enhance baseline information available to 

park managers. The GRI team relies heavily on 

partnerships with institutions such as the U.S. Geological 

Survey, Colorado State University, state geologic surveys, 

local museums, and universities in developing GRI 

products.

The goals of the GRI are to increase understanding of the 

geologic processes at work in parks and to provide sound 

geologic information for use in park decision making. 

Sound park stewardship requires an understanding of 

the natural resources and their role in the ecosystem. 

Park ecosystems are fundamentally shaped by geology. 

The compilation and use of natural resource information 

by park managers is called for in section 204 of the 

National Parks Omnibus Management Act of 1998 and in 

NPS-75, Natural Resources Inventory and Monitoring 

Guideline. 

To realize these goals, the GRI team is systematically 

conducting a scoping meeting for each of the 270 

identified natural area parks and providing a parkspecific digital geologic map and geologic report. These 

products support the stewardship of park resources and 

are designed for nongeoscientists. Scoping meetings 

bring together park staff and geologic experts to review 

available geologic maps and discuss specific geologic 

issues, features, and processes. 

The GRI mapping team converts the geologic maps 

identified for park use at the scoping meeting into digital 

geologic data in accordance with their Geographic 

Information Systems (GIS) Data Model. These digital 

data sets bring an interactive dimension to traditional 

paper maps. The digital data sets provide geologic data 

for use in park GIS and facilitate the incorporation of 

geologic considerations into a wide range of resource 

management applications. The newest maps contain 

interactive help files. This geologic report assists park 

managers in the use of the map and provides an overview 

of park geology and geologic resource management 

issues.

For additional information regarding the content of this 

report and current GRI contact information please refer 

to the Geologic Resources Inventory web site 

(http://www.nature.nps.gov/geology/inventory/).

Regional Information

Unique among all national parks along the Atlantic coast, 

Acadia National Park protects 64 km (40 mi) of rocky 

shoreline and contains 19,323 ha (47,748 ac) of rugged, 

primarily island topography carved and shaped by a 

succession of continental glaciers (figs. 1 and 2). With its 

bare, rounded mountain summits, verdant forests, sea 

cliffs, boulder beaches, deeply indented coastline, 

carriage trails, pristine ponds and lakes, headlands jutting 

into the sea, and remote islands, the park captures the 

extraordinary beauty and charm of the Maine coast. 

The glacially-carved ridges and valleys of Mount Desert 

Island form the core of the park, which lies southeast of 

Bangor, Maine, and is approximately 113 km (70 mi) 

southwest of the U.S.–Canada border. The park also 

includes about half of Isle au Haut, the southern tip of 

the Schoodic Peninsula about 8 km (5 mi) east of Mount 

Desert Island, and Federally-owned (fee-owned) 

properties on nearby islands, including Baker Island, Bar 

and the Porcupine Islands, Western Ear Island, and 

Schoodic Island. Additionally, the park manages 

approximately 207 conservation easements on various 

islands between Penobscot Bay and the 

Washington/Hancock county line (fig. 3). Some of the 

larger islands with conservation easements include 

Ironbound Island and Jordan Island in Frenchman Bay 

and Long Island in Blue Hill Bay. For example, the 

conservation easement on Ironbound Island protects 

high granite cliffs, nesting eagles, and old growth pine.

Over twenty mountains in the park rise directly from the 

sea. At 466 m (1,530 ft), Cadillac Mountain, the 

centerpiece of Mount Desert Island, is the highest point 

along the Atlantic Seaboard from the international 

border with Canada to Rio de Janeiro in Brazil. At certain 

times of the year, sunrise touches the slopes of Cadillac 

Mountain in Acadia National Park before any other 

place in the United States. From the rounded, pink 

granite summit of Cadillac Mountain, a green tapestry of 

pine and spruce trees stretches to a coastline constantly 

battered by icy Atlantic waters.

Acadia’s lakes and ponds add shimmering contrast to the 

park’s forests and rocky landscape. Lakes and ponds 

cover about 1,052 ha (2,600 ac) of the park, or 

approximately 7.4% of its area. Of these, 14 are ‘Great 

Ponds’ (natural bodies of water greater than 4 ha [10 ac]). 

In addition, over 20% of Acadia National Park includes 

wetlands of all types (marine aquatic beds, intertidal 

shellfish flat, salt marshes, freshwater marshes, forested 

wetlands, and peatlands) (National Park Service 2009a).

The rocky shoreline wraps around the irregular border 

of Acadia National Park (figs. 2 and 4). Waves and 

currents continually modify the park’s shoreline. The
2 NPS Geologic Resources Division 

3 to 4 m (10 to 12 ft) tidal range leaves behind tide pools 

inhabited by diverse and abundant sea life. 

The bedrock, past glaciation, and sea combine to give 

Acadia National Park its exceptional character. The 

bedrock provided the foundation upon which the 

glaciers carved the landscape. Each headland, bay, and 

inlet reveals the magnificent interface between land and 

sea that allows Acadia National Park to sparkle like a 

multi-faceted gem.

Geologic Setting

Acadia National Park contains all three basic types of 

rocks: sedimentary, igneous, and metamorphic (fig. 5). 

Sedimentary rocks begin as sediments, like the sand on 

Sand Beach. With burial, sediments compact and squeeze 

together. In the process of lithification, increased 

pressure causes some minerals to dissolve and enrich the 

fluids that occupy spaces between the grains. New 

minerals precipitate out of the fluid and act as glue or 

cement to bind the sediments into sedimentary rock. 

Common cementing materials include quartz, iron 

oxides, carbonate minerals like calcite, and clay minerals.

The magma that solidifies to form igneous rocks may be 

produced in two ways. First, deeply buried rocks and 

sediments associated with ocean plate subduction heat 

up and release water, which rises and lowers the melting 

point of rocks in its path to produce magma. This 

process, for example, is occurring in the subduction zone 

along the western margin of Washington and Oregon 

where the oceanic plate is being subducted beneath the 

North American continent. Mount St. Helens provides 

proof that magma continues to be generated beneath the 

Cascade Mountains.

Secondly, magma may also be produced from hot rocks 

that are under extreme pressure in the mantle. Pressure 

is released at divergent plate boundaries (Mid Atlantic 

Ridge and Iceland) and at hot spots (Hawaiian Islands) in 

the mantle. The rocks melt due to the pressure drop in 

much the same way that liquid water flashes to steam 

when the lid of a pressure cooker is removed. 

Once magma solidifies, the resulting igneous rocks are 

classified based on their mineral composition and 

whether they formed within the earth (intrusive) or 

solidified on the surface (extrusive). Extrusive igneous 

rocks cool very quickly and do not have the opportunity 

to form larger crystals. In general, they have an aphanitic 

texture (crystals too small to see with the unaided eye). 

Intrusive igneous rocks cool slowly into a phaneritic 

texture in which interlocking crystals are clearly visible. 

Magma may begin cooling slowly below the surface, 

allowing some larger crystals to form, and then erupt at 

the surface and cool rapidly, creating a rock with a 

bimodal texture of large crystals (called phenocrysts) 

embedded in a fine-grained groundmass. Such a bimodal 

igneous rock is call porphyritic. Once an igneous rock is 

identified as either extrusive or intrusive, the minerals 

are identified and the classification refined.

Granites, which are on one end of the intrusive igneous 

scale, are silica-rich and contain abundant aluminum, 

sodium, and potassium. Minerals formed from these 

elements tend to convey a pink, cream, or greenish-gray 

color to the granite in Acadia National Park. Granite 

contains the same minerals as its extrusive equivalent, 

rhyolite. On the other end of the scale, gabbros are dark 

colored intrusive igneous rocks with abundant iron, 

magnesium, and calcium and a lack of silica, aluminum, 

sodium, and potassium. Basalt is the extrusive equivalent 

of gabbro.

With increased temperature and pressure, all three types 

of rocks may undergo recrystallization of some or all of 

their minerals and metamorphose, without melting, into 

metamorphic rocks, such as phyllite, schist, and gneiss. 

Regional metamorphism occurs at great depth and over 

large areas where rocks encounter increased temperature 

and pressure. Contact metamorphism occurs near the 

surface when heat from rising magma bakes the adjacent 

bedrock (country rock). Limestone that doesn’t contain 

much silt or clay metamorphoses to marble; relatively 

pure sandstone metamorphoses to quartzite; and 

siltstone and shale metamorphose to a rock called a 

hornfels.

In addition to bedrock, Acadia National Park contains 

glacial deposits and ancient and modern coastal and 

near-shore sediments. Pleistocene glaciers sculpted the 

modern landscape of Acadia National Park and the sea 

continues to modify the present coastline.

Bedrock Units

The 509 million year old Middle Cambrian Ellsworth 

Schist is the oldest rock exposed on Mount Desert Island 

(Gilman and Chapman 1988; Gilman et al. 1988; Schulz 

et al. 2008). The dark- green to gray Ellsworth Schist 

consists of volcanic sediments that were originally 

deposited in an extensional (pulling apart) oceaniccontinental rift setting similar to today’s Gulf of 

California–Salton Trough and Red Sea–Gulf of Aden rift 

systems (Schulz et al. 2003; Schulz et al. 2008). This rift 

setting bordered the coast of a micro-continent called 

Ganderia. At the time, much of the global landmass 

formed a larger paleocontinent known as Gondwana that 

was centered on the South Pole. Ganderia separated 

from Gondwana and was drifting north towards 

Laurentia (proto-North America). 

During the Early Ordovician, a subduction zone 

developed along the Ganderia coast. Compression 

related to subduction coupled with regional 

metamorphism intensely deformed the volcanic 

sediments and transformed them into the chlorite-rich 

Ellsworth Schist (Reusch and Rust 2001; Reusch 2002). 

These schists contain abundant quartz, muscovite, and 

chlorite minerals. 

Elsewhere in Maine, Late Cambrian rocks overlie the 

Ellsworth Schist, but these units are missing in Acadia 

National Park. In the park, the Ellsworth Schist is 

overlain by the Silurian Bar Harbor Formation, the 

second oldest rock in Acadia National Park (Wiebe et al. 
ACAD Geologic Resources Inventory Report 3

1997b). The units are separated by an unconformity that 

represents a gap in time of over 65 million years. 

The Bar Harbor Formation derives its name from the 

excellent exposures of brown to gray siltstones and 

sandstones along the shoreline at Bar Harbor, Maine. 

Because of these exposures, Bar Harbor became the type 

locality for the Bar Harbor Formation. A type locality is 

the geographic location where a geologic unit is formally 

defined and described. 

Volcanic rocks that define the Cranberry Island series 

overlie the Bar Harbor Formation (Gilman et al. 1988). 

Named from exposures on Great Cranberry and Little 

Cranberry Islands, the Cranberry Island series was 

considered Silurian and Devonian until those dates were 

refined by radiometric dates corresponding to the 

Middle Silurian (approximately 424 million years ago). 

Field evidence suggests that their deposition is related to 

the Cadillac Mountain intrusive complex (Seaman et al. 

1995; Seaman et al. 1999). 

Felsic tuffs (formed from eruptions of volcanic ash) and 

felsic lava flows define the approximately 1.8 km (1.1 mi) 

thick lower unit of the Cranberry Island series (Seaman 

et al. 1999; Seaman 2000). Felsic rocks contain abundant 

light-colored minerals such as quartz, feldspar, and 

muscovite. The composition of these Cranberry Island 

felsic rocks is similar to the composition of the 

Southwest Harbor granite (Wiebe et al. 1997a). The 

upper unit, approximately 0.8 km (0.5 mi) thick, consists 

of mafic basaltic tuffs and basaltic lava flows (Seaman et 

al. 1999). The mafic rocks, which form the upper unit, are 

rich in dark-colored minerals containing magnesium and 

iron. 

Since the Cranberry Island series overlies the Bar Harbor 

Formation, the Bar Harbor Formation must have been 

deposited before the Cranberry Island series. Previously 

interpreted to be partly Devonian, the Bar Harbor 

Formation, like the Cranberry Island series, appears to 

be restricted to the Silurian. Contrary to previous 

interpretations (Gilman et al. 1988), Devonian rocks may 

be absent in Acadia National Park (Berry 2007).

Remarkably, the Bar Harbor Formation and Cranberry 

Island series underwent little deformation compared to 

the Ellsworth Schist. Metamorphism resulted in some 

meta-sedimentary and meta-volcanic units, but these 

units were not strongly affected by the intense regional 

metamorphism and compression evident in the folded 

Ellsworth Schist. Geochemical evidence, the bimodal 

character of the volcanic rocks in the Cranberry Island 

series, and the lack of deformation suggest that these 

stratified deposits originated from tectonic extension 

rather than compression (Seaman et al. 1999). 

Intrusive igneous rocks underlie most of the landscape of 

Mount Desert Island, the Schoodic Peninsula, and Isle au 

Haut (Gilman and Chapman 1988; Gilman et al. 1988). 

The intrusive units in Acadia National Park form the 

Cadillac Mountain intrusive complex, which, in turn, is 

part of the Coastal Maine Magmatic Province, a geologic 

province that consists of over 100 mafic and felsic 

plutons emplaced over a time span from the Late Silurian 

to the Mississippian (from approximately 420 million 

years ago to 360 million years ago) (Hogan and Sinha 

1989; Wiebe et al. 1997b). The Cadillac Mountain 

intrusive complex includes three major units: the 

Cadillac Mountain granite, a gabbro-diorite unit, and the 

Somesville granite (Wiebe et al. 1997b). Two minor units 

include the sheet-like Southwest Harbor granite and 

irregular masses and dikes (tabular igneous intrusions 

that cut through older rock) of the Pretty Marsh granite 

that cut the gabbro-diorite unit. 

The Cadillac Mountain intrusive complex was once 

thought to be emplaced during the Devonian, but recent 

radiometric data indicate an older, Silurian age for the 

intrusive complex (Wiebe et al. 1997a, 1997b). The 

gabbro-diorite unit is about 418 million years old, and 

the granites range between 424 and 419 million years old 

(Seaman et al. 1995; Wiebe et al. 1997b). Basaltic magma 

intruded before, during, and after these granites, and the 

gabbro-diorite unit was injected multiple times into the 

Cadillac Mountain magma chamber (Wiebe 1994; Wiebe 

et al. 1997b). The age and composition of the Cadillac 

Mountain intrusive complex suggests that the Cranberry 

Island series may have erupted from these magma bodies 

(Seaman et al. 1999).

Surficial Units

The surficial deposits in Acadia National Park record a 

remarkable interaction of glacial activity and sea level 

fluctuations. Glacial till was deposited directly by glaciers 

and consists of an unsorted collection of clay, silt, sand, 

pebbles, cobbles, and boulders. As the glaciers melted, 

ridges of mixed rock debris (ranging in size from clay to 

boulders) known as glacial moraines were left along the 

glaciers’ margins. Meltwater streams flowing from 

melting glacial ice deposited sand and gravel in outwash 

deposits in front of the glacier or in deltas building along 

the coast (Lowell and Borns 1988). 

About 21,000 years ago, the continental ice sheet reached 

its maximum extent. The ice sheet flowed across the Gulf 

of Maine and extended onto the continental shelf 

approximately 600 km (370 mi) from the present Maine 

coastline. Because so much water was trapped in the 

continental ice sheets, sea level fell about 100 m (330 ft) 

below its current level (Gilman et al. 1988; Kiver and 

Harris 1999). 

In the Acadia region, ice may have been 1.6 km (1 mi) 

thick. Each acre of ice 1.6-km (1-mi) thick weighs 

approximately 7 million tons (Kiver and Harris 1999). 

Continental glaciation displaces the upper mantle so that 

the land surface subsides about 30 m (100 ft) for every

91 m (300 ft) of ice. During the last period of glacial 

activity, known as the Wisconsin glaciation, the mass of 

the ice depressed the coastline (isostatic depression) so 

that areas on Mount Desert Island that are now above 

sea level were submerged. At that time, the shoreline on 

Mount Desert Island lay just south of Jordan Pond, 

which was approximately 70 m (230 ft) higher than it is 

today (Gilman et al. 1988).
4 NPS Geologic Resources Division 

Glacial melting resulted in a complex interplay between 

crustal rebound and sea level change. Unburdened from 

the mass of ice, Maine’s crust began to rise. With crustal 

rebound (isostatic uplift), relative sea level fell. 

Submerged sediments that had been deposited in marine 

environments became exposed on the slopes of Mount 

Desert Island (Lowell and Borns 1988). Sea level lowered 

to approximately 55 m (180 ft) below its present position, 

and streams cut valleys into previously submerged 

coastal areas and continental shelf deposits (Barnhardt et 

al. 1995). 

As crustal rebound slowed, glaciers continued to melt 

and sea level rose to its present position. Rising sea level 

drowned the lower ends of valleys and produced the 

submerged or drowned shoreline typical of New 

England (fig. 2). With rising sea level, peaks have become 

islands, and once rocky ridges have been transformed 

into headlands and peninsulas. The famous offshore 

fishing ground of Georges Banks, exposed as islands 

during the height of glaciation, became submerged 

during this time.

Sea level continues to rise along the Atlantic Coast, and 

the Atlantic surf relentlessly pounds the Acadia 

shoreline. Periodically, waves generated by violent 

nor’easters unleash an enormous amount of energy 

against the parks’ cliffs and headlands. The constant 

hydraulic action creates and modifies the sea cliffs, sea 

caves, wave-cut platforms, and other coastal features that 

enrich the splendor of Acadia National Park.

Cultural History

Native People

For the past 12,000 years, American Indians have 

inhabited the land now known as Maine, and American 

Indian encampments in Acadia National Park date back 

6,000 years (National Park Service 2006a). Today, the 

Maliseet, Micmac, Passamaquoddy, and Penobscot 

(known collectively as the Wabanaki) still consider 

Mount Desert Island and the surrounding Gulf of Maine 

area as the center of their traditional homelands. To 

some of the Wabanaki, Mount Desert Island was known 

as “Pemetic,” meaning “the range of mountains.” 

The Wabanaki Indians traveled in exquisite birch bark 

canoes, a craft that would prove indispensible to the 

French Voyageurs and fur trade in North America. They 

hunted seals, porpoises, deer, moose, beaver, and birds 

and fished for sculpin and flounder. They gathered sea 

urchins, clams, blue mussels and berries and traded with 

other Wabanaki. Using local resources, the Wabanaki 

fashioned harpoons, needles, awls, and fishing hooks 

from animal bone, and chipped arrowheads, knives, 

scrapers, and heavy wood working tools such as chisels 

and gouges from local stone. Clay mixed with crushed 

rock grit or shells was used to make pottery.

In the nineteenth century, Wabanaki people sold 

handmade ash and birch bark baskets to wealthy 

travelers, and in the summer, they performed elaborate 

dances at venues such as Acadia National Park’s Sieur de 

Monts. Wabanaki guides took visitors on canoe trips 

around Frenchman Bay and the Cranberry Islands 

(National Park Service 2006a).

Today, each Wabanaki tribe maintains a reservation and 

has a tribal government headquarters within their 

territories. The Wabanaki continue their unique 

association with Mount Desert Island. The National Park 

Service recognizes the deep history and cultural 

continuity Wabanaki people have with the landscape and 

consult with the Tribal Historical Preservation Officers 

from the Passamquoddy and Penobscot Tribes (Rebecca 

Cole-Will, Cultural Resources Program Manager, Acadia 

National Park, written communication, April 23, 2010). 

The first-ever ethnographic study of the Wabanaki in the 

Mount Desert Island area was commissioned by Acadia 

National Park and completed in 2007. The report is now 

available at the Acadia National Park website (National 

Park Service 2009b).

European Explorations

In 1524, the Italian explorer, Verranzano, visited the 

Delaware, Maryland, and Virginia region and named the 

area “Arcadie” after a pastoral region in ancient Greece. 

As exploration continued to the north, mapmakers soon 

started labeling the Nova Scotia area as “L’Arcadie.” In 

later maps, the “r” was dropped. By the 1700s, settlers in 

eastern Canada were known as Acadians (Hebert 2009).

In 1603, Henry IV, King of France, granted the French 

explorer, Pierre Dugua, Sieur de Monts, exclusive right 

to colonize lands in North America between 40° and 60° 

north latitude. While overseeing the construction of his 

ill-fated settlement on St. Croix Island, Dugua sent his 

navigator and cartographer, Samuel de Champlain, to 

explore the coast further south. Sailing past the bare, 

rocky summits of Mount Desert Island in 1604, 

Champlain named the island Isles des Monts Desert—

“Isle of Bare Mountains.” 

Another French adventurer, Antoine Laumet, landed at 

Mount Desert in 1688. The French government granted 

Laumet, who called himself Sieur de la Mothe Cadillac, 

40,500 ha (100,000 ac) of land along the Maine coast, 

including all of Mount Desert. Lord Cadillac, however, 

grew restless and moved inland to establish a settlement 

that would later be named Detroit. 

Settlers, Early Tourism and the Beginning of the Park

Land speculators became interested in the Maine coast 

after the British defeated the French in 1759. Farming, 

logging, fishing, and shipbuilding industries blossomed. 

Paintings by prominent artists of the day attracted 

visitors to the region, and by 1860, tourism had become 

the major industry of the area.

In the late 1800s and early 1900s, extremely wealthy 

people discovered the region and subsequently 

protected much of the area from logging and unplanned 

development. Large estates served as summer retreats for 

such notable families as the Rockefellers, Morgans, 

Vanderbilts, Carnegies, Fords, Astors, and Kennedys. 
ACAD Geologic Resources Inventory Report 5

Concern about overdevelopment in the Bar Harbor area 

and the invention of the gas-powered portable sawmill 

prompted one wealthy landowner, George B. Dorr, to 

establish a non-profit corporation in 1901 to preserve as 

much of the Mount Desert landscape as possible. For the 

next 43 years, Dorr’s corporation received land 

donations and purchased points of interest such as 

Cadillac Mountain to preserve them for public use. By 

1913, Dorr’s corporation had acquired 2,400 ha (6,000 

ac), and he offered the land to the federal government. In 

1916, President Wilson created the Sieur de Monts 

National Monument.

Dorr continued to acquire property and to push for full 

national park status. John D. Rockefeller, Jr. donated 

over 4,000 ha (10,000 ac) and constructed 92 km (57 mi) 

of narrow carriage roads. Expert stone masons built 17 

stone bridges along the carriage roads (fig. 6). In 1919, 

President Wilson signed the act establishing Lafayette 

National Park, the first national park east of the 

Mississippi, and Dorr, whose efforts have been described 

as “the greatest of one-man shows in the history of land 

conservation” (qtd. in Rothe 1995), became the first park 

superintendent (Kiver and Harris 1999; National Park 

Service 2006a).

In 1929, more area was added to the park and its name 

was changed to Acadia National Park. In 1986, Congress 

established a permanent fee boundary for Acadia 

National Park. At this time, between fee-owned land and 

conservation easements, Acadia National Park protects 

over 19,000 ha (47,000 ac). Additional historical 

information may be found at the Acadia National Park 

website (http://www.nps.gov/acad).

Figure 1. National Park Service location map for Acadia National Park, Maine. Refer to the detail maps of Mount Desert Island, Isle au 

Haut and Schoodic Peninsula for more information (fig. 2). National Park Service graphic.

ACAD Geologic Resources Inventory Report 7

Figure 3. Legislated Acadia National Park boundaries which are known as fee boundaries and conservation easements as of April 2010. 

National Park Service graphic courtesy Karen Anderson (Acadia National Park).
8 NPS Geologic Resources Division 

Figure 4. Blocks of granite form the rocky coastline at Bass Harbor Head on the southwestern side of Mount Desert Island. The coastline 

of Acadia National Park primarily consists of blocks of granite, steep headland cliffs, or boulder/cobble beaches. Note that the rocks 

come in a variety of sizes (i.e., poorly sorted) and that abrasion from waves knocking the rocks against one another has rounded their

edges. Well-rounded boulders (black arrows) mix with angular rock fragments (yellow arrows). The lighthouse was built in 1858 and 

stands 17 m (56 ft) above mean high water. National Park Service photograph by John Chelko, available online: http://www.nps.gov/

acad/photosmultimedia/scenic.htm (accessed January 7, 2010).
ACAD Geologic Resources Inventory Report 9

Era Period* Formation/Unit Description Geological Events CENOZOIC

Quaternary

Holocene 

Epoch

Alluvial and coastal 

sediments; Talus 

(angular rock 

fragments).

Beach, fluvial (river), 

marsh deposits of sand, 

gravel, and organic-rich 

sediments. Talus forms 

at the base of cliffs.

Opening of present-day Atlantic Ocean.

Crustal rebound, 

rising sea level, and 

formation of presentday landscape and 

shoreline.

Pleistocene 

Epoch

Glacial Deposits and 

Emerged Marine 

Deposits.

Glacial till, outwash, 

and delta sediments. 

Marine deposits of clay, 

silt, sand, gravel, 

cobbles, and boulders.

Continental 

glaciation. Glacial 

melting. Fluctuating 

sea level and 

shoreline.

Unconformity

(Represents over 413 million years

of missing time)

Extensive uplift and 

erosion. (Gilman and 

Chapman 1988).

Tertiary Neogene

Paleogene

MESOZOIC

Cretaceous

Jurassic

Triassic

PALEOZOIC

Permian

Pennsylvanian

Mississippian

Devonian Acadian Orogeny: Collision 

of Avalon micro-plate with 

North America. Closing of 

Iapetus Ocean.

Silurian

Cadillac Mountain 

Intrusive Complex 

(CMIC)

Cranberry Island Series

Granite of 

Schoodic Peninsula

CMIC: Pink, greenishgray,light- gray, fine- to 

coarse-grained granite 

and dark-colored 

gabbro and diorite.

Cranberry Island Series

Lower unit: Felsic 

rocks. Upper unit: 

Mafic rocks.

Granite of S.P.: Felsic 

granite; diabase dikes.

Granite and pegmatite 

emplacement. Shattering and 

contact metamorphism. 

Hydrothermal activity. 

Intrusive dikes and sills. 

Recrystallization. Intrusions 

accompanied by volcanic 

activity.

Bar Harbor Formation Siltstones and 

sandstones. Marine sedimentation.

Ordovician Unconformity Folding, metamorphism, 

uplift and erosion of 

Ellsworth Schist.

Cambrian Ellsworth Schist

Dark- green or gray 

schist. Streaked 

appearance

Marine deposition of 

volcanic rocks in a rift 

(extension) setting.

Unconformity

* See the geologic timescale (fig. 26) for absolute age boundaries of geologic eras and periods.

Figure 5. Bedrock and surficial geologic units in Acadia National Park. The Cadillac Mountain intrusive complex (CMIC) has been updated 

from the data used for the GIS map and includes all of the igneous intrusive units of Gilman and Chapman (1988). The columns are not 

to scale with regards to geologic time intervals.
10 NPS Geologic Resources Division 

Figure 6. Stone bridge along a carriage road, Mount Desert Island, Acadia National Park. Constructed in 1920, the bridge is one of 17

stone bridges within the park. Melanie Ransmeier, NPS Air Resources Division, for scale. Photograph by John Graham (Colorado State 

University).
ACAD Geologic Resources Inventory Report 11

Geologic Issues

The Geologic Resources Division held a Geologic Resources Inventory scoping session for

Acadia National Park on June 9–10, 2008, to discuss geologic resources, address the 

status of geologic mapping, and assess resource management issues and needs. This

section synthesizes the scoping results, in particular those issues that may require 

attention from resource managers. Contact the Geologic Resources Division for 

technical assistance.

Participants attending the 2008 scoping workshop 

identified the following geologic issues as relevant to 

park management:

• Mass wasting and slope failure

• Coastal erosion

• Sustainability of Sand Beach

• Seismic activity (earthquakes)

• Sea-level rise

• Visitor impact to natural resources

Mass Wasting and Slope Failure

Rain falls every month in Acadia National Park. Although 

temperatures can fall to below -18° C (0° F), frequent 

thawing periods prevent large, long-term snow 

accumulations. Ice storms are common in winter and 

early spring (National Park Service 2006b). Every spring, 

saturated soils, thawing, precipitation, and storm waves 

lead to rockfalls that impact the Park Loop Road on 

Mount Desert Island and slumping along coastal bluffs. 

Undercutting of the paved surface above the path leading 

to Thunder Hole has caused the slope to fail and 

required the installation of a safety fence (fig. 7). 

Mass wasting of marine clay (deposited at a time when 

sea level was much higher) occurs along Hunters Brook, 

which drains into the cove protected by Hunters Head 

on Mount Desert Island. Slumping of the greenish- gray 

clay has destabilized the stream bank and changed the 

course of the stream (fig. 8). Exposures of eroded and 

gullied slopes, characteristic of this marine clay, may also 

be found on the eastern end of the beach at Otter Cove. 

Potential mass wasting and slope failure may be an issue 

wherever this marine clay is exposed on Mount Desert 

Island (Lowell and Borns 1988).

On the Schoodic Peninsula, slumping occurs along 

Frazer Creek, south of the park entrance, and erosion 

cuts into the picnic area. Monitoring these areas may 

help to predict future mass wasting and erosion. 

Earthquakes also may trigger landslides (see the “Seismic 

Activity” section below for more information on Maine’s 

potential for earthquakes). The park contains over 160 

km (100 mi) of trails, some of which are along steep cliff 

faces. Dislodged, mega-blocks of Cadillac Mountain 

granite and other debris from an October 2006 

earthquake closed the Precipice Trail, East Face Trail on 

Champlain Mountain, and Homans Path on Dorr 

Mountain (fig. 9A). Homans Path and Precipice Trail 

reopened in 2007. Landsliding blocks of granite closed 

the Park Loop Road for one day (fig. 9B).

Several large boulders tumbled off the mountainside, 

crashing through a job site, while crews worked on a 

section of the East Face Trail (renamed the Orange and 

Black Path) in October 2007. Deanna Greco (NPS 

Geologic Resources Division) performed an on-site 

analysis, and found that the 2006 earthquake had opened 

new fractures in the bedrock and destabilized rocks and 

boulders on the slope above the trail. To allow the slopes 

to stabilize, the trail remained closed until October 8, 

2009.

Landslides related to the 2006 earthquake generated 

interest in assessing potential movement along the 

abundant horizontal to gently sloping joint surfaces in 

Acadia National Park (Vollmer 2009). This research may 

prove useful to park management in the future. 

Wieczorek and Snyder (2009) have suggested monitoring 

strategies for slope stability.

Coastal Erosion

Regardless of the season, the North Atlantic surf 

continues its relentless modification of the coastline, 

buffeting headlands and redistributing beach sediment. 

Occasionally, hurricanes pound the coastline. On August 

23, 2009, waves from Hurricane Bill hammered the 

Acadia coastline (fig. 10A). These waves battered the 

rocky headlands and flooded Sand Beach (fig. 10B). 

Swells 4 to 5 m (12 to 15 ft) high combined with high tide 

to produce exceptionally dangerous surf conditions 

requiring the closure of Sand Beach and the Thunder 

Hole viewing platform. An estimated 10,000 people 

converged on the Park Loop Road, trying to get a good 

view of the violent waves, some of which were more than 

5 m (15 ft) high. Ignoring park rangers’ warnings, visitors 

crowded close to the rocky coastline. Suddenly, an 

unusually large wave careened against the cliffs and the 

cavernous inlet of Thunder Hole, washed over a crowd 

of spectators, and swept seven visitors into the ocean. 

Tragically one of the seven was lost to the sea (National 

Park Service 2009c). 

A tremendous amount of beach erosion and coastal 

flooding occurs when storm surges combine with high 

tides. The 1991 Perfect Storm (October 31, 1991) 

generated sustained winds of 49 to 53 knots (91 to 98 
12 NPS Geologic Resources Division 

km/hr; 56 to 61 mph) with gusts up to 65 knots (120 

km/hr; 75 mph) and wave heights of 9 to 12 m (31 to 39 

ft). Sea walls, boardwalks, bulkheads, and piers were 

heavily damaged or destroyed all along the eastern 

seaboard from North Carolina to Nova Scotia. Total 

damage was in the hundreds of millions of dollars 

(National Oceanic and Atmospheric Administration 

2008). 

During the Patriots Day Storm on April 16-17, 2007, tidal 

flooding in Maine was greater than the storm tide of the 

Perfect Storm (National Oceanic and Atmospheric 

Administration 2007). High tide in Portland, Maine, was 

the 7th biggest tide on record at 4.05 m (13.28 ft).Waves

9 m (30 ft) high pounded the coastline and caused 

extensive damage to homes, businesses, coastal roads, 

and beaches. 

Such storm surges may damage trails and infrastructure. 

On Mount Desert Island, major storms have caused 

boulders to wash onto the road at Seawall Beach. If 

shoreline erosion and retreat continue, sections of the 

Park Loop Road may have to be moved (Joseph Kelley,

University of Maine, personal communication, June 10, 

2008). At Thunder Hole, high energy waves erode the 

retaining wall so that the trail and stairs often need repair 

(National Park Service 2008). Storm surges coupled with 

high tide and overall rising sea level present significant 

future potential danger to the park. In general, rising sea 

level is causing the shoreline to migrate inland.

Coastal erosion is a natural process at Acadia National 

Park. The hydraulic energy of the waves at high tide may 

present management issues for the park, but the 

tremendous force of the waves also creates some of the 

remarkable features found along the park’s coastline, 

such as undercut cliffs, sea arches, sea caves, boulder 

beaches, sea stacks, wave-cut platforms, and thunder 

holes (fig. 11).

Bush and Young (2009) have suggested monitoring 

strategies for coastal features and processes.

Sustainability of Sand Beach

Sea level rose following the melting of the Pleistocene 

glaciers so that sand accumulation along the coast of 

Acadia National Park has been minor. Sandy beaches are 

relegated to small pockets in coves and a few sandbars in 

protected areas. Most of the pocket beaches contain 

more cobbles than sand. Sustaining Sand Beach is 

important not only because the beach is one of the few 

sandy beaches on Mount Desert Island but also because 

of the composition of its sand. 

Sand Beach, sheltered between Great Head and Otter 

Cliff, is exceptional because its sand is composed of 

sand-sized shell fragments (calcium carbonate) and not 

quartz. Deposited by waves, these shell fragments are 

thousands of years old. Sand Beach and a beach on 

Cranberry Island (not on park property) hold the 

distinction of being the only beaches along the Atlantic 

coastline north of Cape Hatteras, North Carolina, that 

contain both dunes and beaches composed almost 

entirely of calcium carbonate sand.

Sand Beach also provides an important visitor contact 

area for interpretation. Ranger-led interpretive walks 

begin at Sand Beach, and educational signs are posted in 

the area. 

Recently, the beach has become threatened by sediments 

eroded from a Pleistocene delta deposit that underlies 

the Sand Beach parking lot (fig. 12). Both natural 

processes and human activity have exposed the slope 

leading to the beach. Eroded slope sediments contain 

abundant quartz and potassium feldspar. With constant 

wave action, the harder quartz and feldspar grains abrade 

the softer calcium carbonate fragments breaking them 

down. Over time, the amount of shell fragments that 

currently dominate the beach may diminish. Monitoring 

and mitigating slope erosion in this area may help sustain 

the calcium-carbonate composition of Sand Beach.

Because natural processes are allowed to take place along 

the shoreline at Sand Beach, the beach may appear to be 

deteriorating at an alarming rate during certain storm 

events. Erosion of beach sand during storms in 2007 

exposed a rocky boulder deposit at the base of the steps 

leading to the beach (fig. 13A). Access to the beach 

became a visitor safety issue. However, the sand was 

naturally restored to the beach (thus eliminating the 

safety issue within a few months) (fig. 13B). 

In the past, visitors were allowed to cross the dune area, 

and trampling damaged the dunes and their distinctive 

vegetation. A fence now prevents foot traffic and humaninduced erosion of the dunes (fig. 14). 

At times, sediment chokes the tidal inlet connecting the 

sea to the lagoon behind the dunes, preventing tidal 

flushing of the lagoon (fig. 12). Without tidal flushing, 

bacterial levels in the lagoon can rise to unsafe levels. 

However, the park monitors bacteria levels in the lagoon 

on a weekly basis, and has yet to find levels sufficiently 

high to close the beach.

Seismic Activity

According to the Maine Geological Survey, earthquakes 

occur at a low but steady rate in Maine, which is typical 

of seismic activity in New England (Berry 2006). 

Earthquakes have been reported from all counties in 

Maine although higher activity occurs in the eastern, 

central, and southwestern parts of the State. In 1904, 

chimneys collapsed in Calais and Eastport during the 

largest earthquake recorded in Maine (estimated 

magnitude of 5.1 on the Richter Scale) (U.S. Geological 

Survey 2009). This earthquake was felt over 

approximately 390,000 sq km (150,000 sq mi). Magnitude 

5.0 earthquakes occur in Maine at an estimated average 

of once in 52 years. By comparison, magnitude 6.0 

earthquakes are estimated to occur, on average, once in 

363 years and magnitude 7.0 earthquakes occur once in 

about 2,512 years (Berry 2006). 
ACAD Geologic Resources Inventory Report 13

However, it is important to note that these are not actual 

rates of earthquake occurrence. These numbers 

represent probabilities of occurrence rather than 

predictions of frequency. Because of historical averages, 

the probability that a 7.0 earthquake will happen more 

than once in 2,512 years is low, but that does not mean 

7.0 earthquakes could not occur several times in one 

decade. Likewise, a 5.0 magnitude earthquake may not 

occur for a thousand years, although historical averages 

suggest at least one 5.0 magnitude earthquake will occur 

within 52 years of the previous one.

The largest accurately measured earthquake was a 

magnitude 4.8 recorded on June 15, 1973 on the Quebec 

side of the border across from Oxford County, Maine. 

From April 29, 1997 to February 26, 2007, 49 earthquakes 

occurred in Maine. The epicenters of all but 6 of these 

were located in Maine, and magnitudes ranged from 1.3 

to 4.2. Magnitudes of all but 14 of these earthquakes 

were less than or equal to 3.0. Of 507 earthquakes that 

occurred from 1747 to 1992, only one originated beneath 

Mount Desert Island.

On October 2, 2006, a 3.8 magnitude earthquake 

triggered landslides and rockfalls in Acadia National 

Park and damaged roads and trails (fig. 15). The 

Precipice, Homans, and East Face trails were closed, and 

rocks fell onto the Park Loop Road (fig. 9B). 

The 2006 earthquake also caused the water level in a U.S. 

Geological Survey monitoring well to drop more than 

0.76 m (2.5 ft). Although earthquakes often cause minor 

changes in water levels in wells, a decrease of this 

magnitude was dramatic for Maine (U.S. Geological 

Survey 2006). The well, located in Acadia National Park 

in Bar Harbor, was drilled 30 m (98 ft) into bedrock, and 

on a normal day, water level fluctuates about 8 to 10 cm 

(3 to 4 in).

The epicenter of the 2006 earthquake was in the Atlantic 

Ocean, just off Great Head on the eastern side of Mount 

Desert Island. The earthquake followed several smaller 

aftershocks produced by a magnitude 3.4 earthquake on 

September 22, the epicenter of which was approximately 

located near the Precipice Trail parking area on the Park 

Loop Road. No damage was reported from this 

earthquake.

Maine lies along a passive tectonic margin, and in 

general, passive margins have a low rate of seismic 

activity. The cause of earthquakes in the Northeast 

involves movement along preexisting faults in the ancient 

bedrock. These faults formed millions of years ago when 

the eastern seaboard collided with the ancient 

Gondwana landmass to form the supercontinent known 

as Pangaea. Later, tectonic forces rifted Pangaea causing 

the present-day Atlantic Ocean to open. Precisely 

identifying individual geologic faults and fractures that 

are directly responsible for modern earthquakes has 

proven difficult though investigation continues (Kafka 

2008). Braile (2009) has suggested monitoring strategies 

for seismicity.

Global Climate Change

Sea-level rise and a possible increase in storm intensity 

and frequency due to global warming may increase beach 

erosion, modify the hydrodynamics of tidal flushing in 

the Sand Beach area, and negatively impact many of the 

park’s iconic visitor destinations. Some significant 

cultural resources that are located immediately in the 

coastal zone may also be damaged. According to the 

Intergovernmental Panel on Climate Change, global sea 

level will rise an estimated 0.19 to 0.58 m (7.5 in to 1.9 ft) 

by 2100 (Meehl et al. 2007; Karl et al. 2009). Sea-level is 

expected to rise 36 cm (14 in) by 2100 along the mainland 

coast west of Isle au Haut (New England Climate 

Coalition 2003). 

Most of the Acadia National Park’s coast consists of 

rocky cliffs. In general, Maine’s coast shows a relatively 

low vulnerability to future sea-lever rise due to steep 

coastal slopes, rocky shorelines, and large tidal range 

(Thieler and Hammar-Klose 1999). Most of the park’s 

coastal zone lies at least 3.5 m (11 ft) above mean sea level 

and may be less vulnerable to relative sea level rise than 

the areas on the eastern coast of Mount Desert Island 

that are less than 1.5 m (4.9 ft) above mean sea level 

(Titus and Richman 2001). Low areas that might be 

flooded by rising sea level include Sand Beach, the 

cobble beaches in the park, and the picnic area on 

Thompson Island (fig. 16).

The few coastal marshes and estuaries in Acadia National 

Park will also be impacted by rising sea level. As sea level 

rises, the salinity will change in the salt marsh behind the 

dune ridge at Sand Beach. Salinity may increase in 

Seawall Pond and the freshwater ponds in the Seawall 

area. Outside of the park boundaries on Mount Desert 

Island, salinity changes may occur in the saltwater 

marshes at Seal Cove, Pretty Marsh Harbor, and Fresh 

Meadow.

If storms become more frequent and more intense with 

climate change, coastal zone erosion and damage to park 

infrastructure, visitor sites, and cultural resources may 

also increase. Some areas likely to be negatively impacted 

by rising sea level and storm frequency include Thunder 

Hole, parts of the Park Loop Road, and the Otter Cove 

Causeway and bridge. In addition, many park septic 

systems currently located near the coast or in areas with 

high groundwater will be damaged by rising sea levels. As 

sea level rises, groundwater levels will also rise, causing 

potential flooding of leach fields, subsequent pollution, 

and/or non-functioning restroom facilities (David 

Manski, Chief of Resource Management, Acadia 

National Park, written communication, April 19, 2010).

Refer to the National Park Service Climate Change 

Response Program web site for additional information 

and links: http://www.nature.nps.gov/climatechange/

index.cfm (accessed 5 August 2010).
14 NPS Geologic Resources Division 

Visitor Impact to Natural Resources

Cobble Collecting

Visitors collect cobbles as souvenirs and for landscaping 

purposes. Although signs in the park discourage illegal

cobble collecting, cobble theft continues. Because many 

cobble beaches and access points exist in the park, 

monitoring cobble theft presents a difficult and timeconsuming task. Relatively few citations are issued each 

year for cobble theft.

Anemone Cave

The population of anemones in Anemone Cave has 

declined dramatically since 1999. Anemone Cave, one of 

the few sea caves in Acadia National Park and along the 

Maine coast, contains the most anemones in the park 

and is especially accessible to visitors. Consequently, the 

sea cave has been a popular visitor attraction for years. 

High visitor impact has been proposed as one possible 

reason for the decline in the anemone population in 

Anemone Cave.

In the 1960s to early 1970s, the park removed all 

references to Anemone Cave from maps and the parking 

lot. Visitor developments, such as the handrail, were also 

removed, thereby inhibiting easy access to the cave. 

Unless specifically asked about the Anemone Cave, park 

rangers avoid mentioning the cave to visitors.

Fresh water runoff from the parking lot may be a second 

reason for the decline of anemones. Fresh water influx 

can decrease the salinity of the tide pools, required to 

sustain anemones. Additional data are needed to 

determine if a relationship exists between fresh water 

input and the decline in anemones in Anemone Cave 

(Petraitis et al. 2002).

Overuse

Some of the geologic features, such as Cadillac Mountain 

summit and Bubble Rock, a large and highly visible 

glacial erratic, are quite popular and attract a large 

number of visitors each year. The popularity of these 

sites results in erosion and trampling of the naturally thin 

soils and sensitive sub-alpine vegetation (fig.22B). 

Other Potential Issues

Gas pockets in Somes Sound

Abundant organic matter has generated pockets of 

natural gas in the sediments of Somes Sound. If these 

pockets of gas were disturbed (by earthquakes, for 

example), the resulting pressure release may form craters 

in the marine embayment. Waves generated from these 

releases could have unusual, though brief, erosive 

potential. Existing craters that have been mapped in the 

sound are quite deep, although whether or not these 

craters originated from violent outbursts of natural gas 

remains to be determined (Robert Marvinney, Maine 

State Geologist, written communication, April 16, 2010).

Potential Flooding if Glacial Moraines Erode

Glacial moraines—composed of a thick unit of relatively 

impermeable glacial till—form natural dams at the 

southern ends of both Jordan Pond and Long Pond on 

Mount Desert Island. At the scoping meeting in 2008, 

park participants noted that flooding may negatively 

impact park infrastructure, primarily roads, if the 

moraines ceased to act as dams. However, no evidence 

exists to indicate that erosion is causing these moraines 

to deteriorate or that they may cease to act as dams in the 

near future. Responsibility for maintaining the damming 

effect of the moraines does not lie with Acadia National 

Park, but park management may wish to contact the 

National Park Service Safety Manager regarding 

potential dam failure, response options should a dam 

rupture, and any monitoring data.

Mining

No mines are active in the park, and mining is not a 

major issue of concern for park management. At one 

time, copper was produced from a mine on Beech Hill, 

Mount Desert Island. No tailings are associated with this 

mine. A mine on Stave Island, located off the west coast 

of the Schoodic Peninsula, produced copper and silver, 

but Stave Island is not managed by Acadia National Park. 

The Schoodic Peninsula once contained active gold and 

silver mines, but their locations with regard to Acadia 

National Park’s current boundary are unknown 

(National Park Service 2008). 

In the late 1800s and early 1900s, Somesville granite, 

exposed on the western portion of Mount Desert Island, 

was extensively quarried for building stone (Gilman et al. 

1988). The Hall Quarry on Mount Desert Island supplied 

large quantities of Somesville granite to many major 

cities. Today, historic quarries in the area still provide 

rock that is used to maintain the trails and roads that 

were originally built with local stone. Active boutique 

quarries on the Schoodic Peninsula outside of the park 

still provide sculpture and building stone. 

In 1993, the Geologic Resources Division (GRD) of the 

NPS conducted on-site surveys of granite quarry sites 

within and immediately adjacent to Acadia National 

Park. In order to accelerate long-term recovery, minor 

reclamation was recommended for six of twelve internal 

sites, although total restoration was not recommended 

due to the historic significance of the quarries. At the 

time, the park was encouraged to pursue assistance from 

Bar Harbor’s Planning Director on two external sites that 

were not grandfathered or exempt from the city’s 

cleanup regulations (John Burghardt, NPS Geologic 

Resources Division, written communication, February 8, 

2010).

Also in 1993, the GRD conducted a Level I Hazardous 

Materials Survey of a 1980 Canadian molybdenum 

exploration program that had occurred on Long Island, 

located between the mainland and Mount Desert Island. 

The core-drilling program consisted of 6 drill holes 

totaling 621.2 m (2,038 ft). With the exception of a 

discarded pile of drill steel, the site had been thoroughly 

cleaned (John Burghardt, GRD NPS, written 
ACAD Geologic Resources Inventory Report 15

communication, February 8, 2010). Since 1993, Long 

Island, which is the large island east of Mount Desert 

Island (fig. 3), has been added as a conservation 

easement to the park.

In the future, offshore sand and gravel deposits may 

become potential mining targets. Although they now lie 

in coastal waters, these deposits consist of river and delta 

sediments that are a legacy of the Pleistocene ice age 

when sea level was much lower than today.

Alternative Ocean Energy Development

The Gulf of Maine may prove to be an exceptional 

resource for both wind and tidal energy. Offshore wind 

facilities benefit from greater and more constant wind 

velocities, and if placed far enough from shore, they have 

little or no aesthetic impact on coastal landowners. At 

water depths of 60 to 80 m (197 to 262 ft), optimal wind 

velocities may exceed 9.5 m/s (21 mph). Wind energy 

potential for the Gulf of Maine is estimated to be 

approximately 100 gigawatts, approximately 10% of the 

United States’ energy needs for one year (Waterman 

2008). 

In order to comply with legislation passed by the Maine 

State Legislature in June, 2009, the Maine Department of 

Conservation (MDOC), in consultation with the Maine 

State Planning Office and following a comprehensive 

public outreach effort, designated three locations (Boon 

Island, Damariscove Island, and Monhegan Island) as 

“Ocean Energy Testing Areas” on December 15, 2009 

(Maine Department of Conservation 2005). Monhegan 

Island, which lies approximately 60 km (40 mi) southeast 

of Isle au Haut, was the closest location to Acadia 

National Park. However, the Monhegan Island site was 

subsequently dropped from consideration (David 

Manski, Chief of Resource Management, Acadia 

National Park, written communication, August 10, 2010). 

The sites were chosen because they lie within state 

boundaries, have an average annual wind speed of 27 

km/hr (17 mph), a water depth of 60 m (200 ft) or more, 

and they are free of obstructions. In October 2009, the 

U.S. Department of Energy extended grants to the 

University of Maine for offshore wind energy research. 

The MDOC worked to designate sites that would result 

in minimal disruption and inconvenience to existing 

offshore users, including fishermen, sailors, birds, marine 

life, and others. In 2001, environmental and economic 

concerns blocked a proposed wind farm off the coast of 

Cape Cod (Waterman 2008). 

In 2009, Statoil, a Norwegian oil and energy firm, 

installed the world’s first full-scale floating wind turbine 

about 10 km (6 mi) off the southwest coast of Norway. 

The University of Maine is consulting with Statoil about 

their Gulf of Maine project. To date, no impact on 

Acadia National Park has occurred.

Tidal energy potential lies primarily in the Bay of Fundy, 

an embayment shared by Maine, New Brunswick and 

Nova Scotia. More than 115 billion tons of water each 

day is channeled through the Bay of Fundy. With a tidal 

range that can reach 15.2 m (49.9 ft), the embayment 

holds abundant potential energy (Waterman 2008). 

There is some interest in tidal energy research near the 

park boundary, and a research permit application may be 

filed (David Manski, Chief of Resource Management, 

Acadia National Park, written communication, August 

10, 2010). 

Water Quality and Quantity

Acadia National Park contains near-pristine water 

resources and protects some of the last remaining 

undeveloped portions of New England’s coastal 

mountains, islands, and coastline. The water resources in 

Acadia National Park provide visitors with a variety of 

recreational activities including fishing, canoeing, sailing, 

swimming, and sightseeing. In addition to the 14 Great 

Ponds, Acadia and the surrounding area contain 10 

smaller lakes, more than 24 named streams, and 10 

named wetland areas (National Park Service 2006c). 

Major water quality concerns for park management 

include private water well development, salt water 

intrusion into the groundwater aquifer, and 

contamination of water resources from septic systems. 

Since the early 1980s, park staff have been monitoring 

Acadia’s lakes. Most lakes have excellent water quality. 

Three remote springs in the park (Sieur du Mont Spring, 

Birch Spring, and Maple Spring) reported high metal 

content in some samples, but the high levels may be the 

result of dissolution of bedrock (National Park Service 

2008). Two primary concerns for resource managers 

result from sources beyond the park’s boundaries: 

mercury and acid precipitation.

Industrial emissions from sources far removed from the 

park contribute to mercury levels in Acadia’s surface 

water. Maine’s fish, loons, and eagles contain mercury 

levels that are among the highest in North America 

(Maine Department of Environmental Protection 2005). 

Exhaust from industrial smokestacks and vehicle 

tailpipes contribute to atmospheric sulfur dioxide and 

nitrogen oxides, the primary contributors to acid rain 

(Maine Bureau of Air Quality 2005). Acid precipitation 

from rain, snow, and fog alters lake and stream 

chemistry. Park monitoring indicates that most of the 

surface water in Acadia has near-neutral pH levels 

(National Park Service 1994, 2006c). 

The ponds on Mount Desert Island are bordered by 

Cadillac Mountain granite, and the bedrock on Isle au 

Haut consists of granite, gabbro, and diorite. These 

igneous rocks do not act as buffering agents to acid 

deposition. If acid precipitation increases, the park’s soil 

and bedrock have little buffering capacity.

The NPS Water Resources Division (WRD) addresses 

water quality and quantity issues in the nation’s 

parklands. For baseline surface-water-quality data refer 

to National Park Service (1994). Contact the WRD for 

additional information or technical assistance regarding 

water issues within the park.
16 NPS Geologic Resources Division 

Figure 7. Slumping above the path to Thunder Hole due to undercutting of the pavement and the stone wall. A fence has been installed 

for visitor safety. Bedrock consists of Cadillac Mountain granite. View is from the path to Thunder Hole, June 10, 2008. Photograph by 

John Graham (Colorado State University).
ACAD Geologic Resources Inventory Report 17

Figure 8. Slope failure and slumping along Hunters Brook, Mount Desert Island. Erosion of the greenish- gray marine clay (foreground) 

undercuts the overlying slope, causing slumping and further instability, including collapse of large trees into the stream (June 10, 2008).

Photograph by John Graham (Colorado State University).
18 NPS Geologic Resources Division 

A) Large slab of rock overhangs Homans Path.

B) Park Loop Road debris.

Figure 9. Examples of mass wasting on Mount Desert Island caused by the October 2006 earthquake. A) A great slab of granite, 

dislodged by the earthquake, overhangs Homans Trail. The person (indicated by the white arrow) poking his head through the opening 

is standing on the old trail. B) Blocks of Cadillac Mountain granite close the Park Loop Road. National Park Service photographs, 

available online: http://www.nps.gov/acad/photosmultimedia/earthquakephotos.htm (accessed January 8, 2010).
ACAD Geologic Resources Inventory Report 19

A) Waves from Hurricane Bill at Thunder Hole.

B) Waves from Hurricane Bill at Sand Beach.

Figure 10. Waves from Hurricane Bill come ashore at Mount Desert Island, August 23, 2009. A) Thunder Hole. Spray and splash reached 

in excess of 30 m (100 ft). B) Sand Beach minutes before park rangers cleared the beach of spectators and the sea swept across the 

entire beach. Photographs used with permission from DownEast Maine Online, available online: 

http://www.downeastmaineonline.com/HurricaneBill-Acadia-Natonal-Park.htm (accessed January 8, 2010).
20 NPS Geologic Resources Division 

Figure 11. Winter seas hammer the coastline of Acadia National Park. Storms and high seas continually modify the coastline by eroding 

headlands and transporting and abrading rock material. Waves such as these can easily move the boulders found on the beaches in the 

park. National Park Service photograph by S. West, available at: http://www.nps.gov/acad/photosmultimedia/seasonphotos.htm, 

(accessed January 8, 2010).

Figure 12. Aerial view of Sand Beach, Mount Desert Island, Acadia National Park. Erosion of quartz and potassium feldspar from the 

slope adjacent to the parking lot (left) diminishes the proportion of calcium carbonate sand on the beach. The lagoon (salt marsh) lies 

behind the dune ridge. Periodically, the stream connecting the lagoon to the sea is blocked by sand. Aerial imagery from U.S. Geological 

Survey Seamless Server (http://seamless.usgs.gov).
ACAD Geologic Resources Inventory Report 21

 

A) Erosion of Sand Beach following a 2007 storm. B) Deposition of sand on Sand Beach one month

after the 2007 storm in (A).

Figure 13. Erosion and deposition of Sand Beach. A) A 2007 storm eroded beach sand and exposed boulders at the base of the stairway 

leading to the beach from the parking lot, creating an unsafe condition. B) After only 1 month, sand was beginning to cover the 

boulders. The black arrow points to the same boulder in each photograph. Photographs courtesy of Joseph Kelley (University of Maine). 

A) Dune ridge prior to the dune fence. B) Dune ridge after installation of the dune fence

Figure 14. Erosion of the dune ridge (A) was substantially reduced with the installation of a dune fence (B) at Sand Beach. Photograph

(A) courtesy of Joseph Kelley (University of Maine). Photograph (B) courtesy of the author.
22 NPS Geologic Resources Division 

Figure 15. Boulders dislodged by the 2006 earthquake twisted this iron railing on Precipice Trail and made the footbridge impassable. 

Bedrock consists of Cadillac Mountain granite. The sheer cliff face resulted from glacial plucking along vertical fractures in the rock. 

National Park Service photograph, available at: http://www.nps.gov/acad/photosmultimedia/earthquakephotos.htm (accessed January 

8, 2010). 

Figure 16. Flooded shoreline and fire rings Nos. 2, 3, 4 at the Thompson Island picnic area at high tide during the Patriots Day storm, 

April 17, 2007. Photograph courtesy of Joseph Kelley (University of Maine).
ACAD Geologic Resources Inventory Report 23

Geologic Features and Processes

This section describes the most prominent and distinctive geologic features and processes 

in Acadia National Park.

Tectonic activity, glaciation, and the relentless erosion of 

the sea formed the geologic features in Acadia National 

Park. The bedrock records episodes of marine 

deposition, igneous activity, and intense deformation 

that occurred hundreds of millions of years ago. 

Pleistocene continental ice sheets sculpted the present 

landscape and left both erosional and depositional 

features. The modern sea coast serves as an analogue to 

coastal features found well inland that testify to a time 

when sea level was much higher than it is today. 

Bedrock Features

Bedrock that forms the archipelago and Schoodic 

Peninsula of Acadia National Park includes an 

assortment of igneous, metamorphic, and sedimentary 

rocks. Igneous rocks of the Cadillac Mountain intrusive 

complex and the granite on the Schoodic Peninsula are 

the primary rock types in the park (Appendix A). The 

granitic plutons, dikes, and unique shatter zone on 

Mount Desert Island provide an exceptional glimpse into 

a magma chamber that was once 5 to 7 km (3 to 4 mi) 

beneath the surface (Wiebe et al. 1997b). The igneous 

rocks of the Cranberry Island series are the extrusive 

compliment to the Cadillac Mountain intrusive complex.

Metamorphic rocks, the oldest rocks in the area, border 

the western margin of Mount Desert Island. Sedimentary 

rock units exposed along the northeastern shoreline of 

Mount Desert Island take their name from Bar Harbor, 

Maine. All of these rock units record numerous tectonic 

events that affected eastern North America.

Cadillac Mountain Intrusive Complex

Granitic exposures in Acadia National Park continue to 

provide clues to the coastal evolution of North America’s 

eastern seaboard. Research over the last 20 years 

redefined an age (Silurian) for the Cadillac Mountain 

intrusive complex and defined its components (Wiebe et 

al. 1997a; Wiebe et al. 1997b). Radiometric age dates and 

field evidence established a significant genetic 

relationship among the individual igneous intrusive 

bodies and the extrusive units of the Cranberry Island 

Series (Seaman et al. 1995; Wiebe et al. 1997a; Wiebe et 

al. 1997b; Seaman 2000).

Mount Desert Island offers excellent exposures of the 

three major units (Cadillac Mountain granite, a mixed 

gabbro and diorite unit, and the Somesville granite) and 

the two minor units (Southwest Harbor granite and the 

Pretty Marsh granite) of the Cadillac Mountain intrusive 

complex (Gilman and Chapman 1988; Wiebe et al. 1997a; 

Wiebe et al. 1997b). Analysis of the crystallization 

process indicates that the emplacement of the Cadillac 

Mountain intrusive complex took place at approximately 

5 km (3 mi) below Earth’s surface. This relatively shallow 

emplacement of the intrusive complex appears to have 

been controlled by the unconformity between the 

Ellsworth Schist and the gently dipping Bar Harbor 

Formation (thus making the Ellsworth Schist and Bar 

Harbor Formation older than the units in the Cadillac 

Mountain intrusive complex). 

The older Southwest Harbor granite sharply intrudes the 

Ellsworth Schist and the Bar Harbor Formation. The fine 

grained, light-gray granite forms a sheet-like mass that is 

overlain by a sheet of gabbro. Minor amounts of the 

dark-colored ferromagnesian minerals biotite and 

hornblende speckle the granite of Southwest Harbor, 

whereas the primary accessory mineral in Cadillac 

Mountain granite is hornblende. Isle au Haut contains 

granite similar to Southwest Harbor granite.

Cadillac Mountain granite forms the bedrock of most of 

Mount Desert Island (figs. 9 and 15). In contrast to the 

fine-grained Southwest Harbor granite, the coarsegrained Cadillac Mountain granite contains easily visible 

grains of translucent, gray, glassy-looking quartz and 

pink or gray feldspar. The granite’s color derives from a 

distinctive type of feldspar known as perthite, which is 

pinkish when weathered and greenish on a freshly 

exposed surface (Gilman et al. 1988). 

Exposures of the Cadillac Mountain granite and the 

gabbro-diorite unit on Bartlett Island and near Crystal 

Cove indicate that the 2 to 3 km (1.2 to 1.9 mi) thick 

gabbro-diorite unit overlies a lower unit of Cadillac 

Mountain granite that has an unknown thickness. On the 

western part of Mount Desert Island, an upper unit of 

Cadillac Mountain granite, which is approximately 3 km 

(1.9 mi) thick, overlies the gabbro-diorite unit (Wiebe et 

al. 1997a). South of the Somesville granite, upper Cadillac 

Mountain granite is interlayered with gabbro-diorite. 

Once the granite solidified, hydrothermal solutions 

flowed into fractures and formed the quartz veins that 

are a common feature in the Cadillac Mountain granite 

(Wiebe et al. 1997b). 

Sparsely distributed blobs of mafic rock material 

(enclaves) occur in the Cadillac Mountain granite. These 

enclaves range in size from less than 1 cm (0.4 in) to over 

1 m (3.3 ft) in diameter. The enclaves are strongly 

flattened, suggesting that they conform to the shape of 

the magma chamber floor (Gilman et al. 1988; Wiebe et 

al. 1997b). Research continues into the origin of the 

enclaves, but initial data from Mount Desert Island 

indicates that the enclaves formed at different times 

during the evolution of the granite and that the chemical 

character of the enclave sources also changed with time 

(Wiebe et al. 1997b). 
24 NPS Geologic Resources Division 

The gabbro-diorite unit resulted from multiple injections 

of basaltic magma into the Cadillac Mountain magma 

chamber (Symchych 1994; Wiebe et al. 1997a). The unit 

consists of layers, typically 2 to 50 m (6.6 to 160 ft) thick, 

that grade upward from fine-grained, rapidly-cooled 

gabbro to coarser-grained gabbroic, dioritic, or granitic 

rocks (Wiebe et al. 1997a). Silica-rich pipe-like intrusions 

extend through the lower Cadillac Mountain granite and 

into the gabbro-diorite unit. Orientation of these silicic 

pipes indicate that the gabbro-diorite layers were 

originally deposited close to horizontal and subsequently 

bowed downward as the magma chamber evolved 

(Wiebe et al. 1997a).

Dark gray, coarse-grained gabbro and lighter gray diorite 

outcrop primarily on the northwest side of Mount 

Desert Island and on the east side of Isle au Haut 

(Gilman and Chapman 1988). Good exposures of diorite 

occur along Route 3 west of Salsbury Cove on the north 

side of the island. Exposures of gabbro – diorite may also 

be found in Hulls Cove and on the summit of Great Head 

on the east side of Mount Desert Island. On the 

Porcupine Islands, the gabbro – diorite occurs as thick 

layers that intrude into the Bar Harbor Formation. 

The pink, medium-grained Pretty Marsh granite is 

named for exposures bordering Pretty Marsh Harbor, 

western Mount Desert Island. As with the above igneous 

intrusions, the Pretty Marsh granite displays evidence of 

mechanical mixing with rapidly cooling basaltic magma 

(Wiebe et al. 1997a). 

Somesville granite occurs at the head and to the west of 

Somes Sound. At first glance, the pink and gray 

Somesville granite appears to be similar to the granite of 

Cadillac Mountain. However, the Somesville granite has 

smaller mineral grains, a different type of feldspar, and 

minor amounts of biotite mica rather than hornblende 

(Gilman et al. 1988; Schuh 1994). In addition, the

Somesville granite cuts the upper Cadillac Mountain 

granite along steep contacts that appear to dip about 60° 

to 70° inward towards the center of the Cadillac 

Mountain Intrusive Complex (Wiebe et al. 1997a). 

Extensive quarrying of Somesville granite (from quarries 

that are now in the park) supplied building stones to 

many major cities in the early part of the twentieth 

century.

Acadia National Park offers a unique opportunity to 

study the evolution of shallow plutons over a large, 

relatively undeveloped area. Research on the Cadillac 

Mountain intrusive complex has provided a record of 

the beginning, development, and solidification of a 

shallow-level silica-rich magma chamber that existed in 

an extensional terrane during more or less continuous 

basaltic magmatism (the development and movement of 

magma, and its solidification to igneous rock).

Extrusive Igneous Rocks: Cranberry Island Series

The lower felsic (light-colored; rich in silica) unit and 

upper mafic (dark-colored; low in silica) unit of the 

approximately 2.6-km (1.6-mi) - thick Cranberry Island 

series can be subdivided into eight informal members 

(table 1) (Seaman 2000). Rhyolite dominates the lower 

six members while basalt is the primary volcanic rock in 

the overlying two members. The voluminous amount 

and type of volcanic deposits suggest the evolution of a 

caldera-like eruptive sequence typical of a setting 

involving crustal extension (Seaman 1994; Seaman et al. 

1995; Seaman et al. 1999; Seaman 2000). 

Table 1: Cranberry Island series (SDcif, SDcit, and SDcis on the Map 

Units Property Table)

Felsic (F) and 

Mafic (M) units General Description

M2 Basaltic lava flows with possible 

pillow structures

M1 Basaltic and andesitic ignimbrites 

with some sedimentary layers

F6 Rhyolitic ignimbrite with 

abundant inclusions of basalt

F5 Andesitic ignimbrite with rare 

pods of basaltic inclusions

F4 Rhyolite ignimbrite lava flow

F3 Flow-banded rhyolite lava flow

F2 Rhyolite ignimbrite (pyroclastic 

flow)

F1

Clast-supported lahar (volcanic 

mudflow with rhyolite, siltstone, 

basalt, and granite fragments)

In the table, the sequence from rhyolite (F1 through F4) 

to andesite (F5) to basalt (M1 and M2) represents a 

classification based on composition in which rhyolite 

lacks iron and magnesium-rich minerals, but contains 

abundant quartz and feldspar; basalt is rich in iron and 

magnesium-rich minerals; and andesite is a transition 

between the two end members. Pillow basalts are pod- or 

pillow-shaped and form as basaltic magma rapidly cools 

upon emerging from an underwater fissure. The series 

represents a classic inversion pattern showing the initial 

extrusion of the felsic top of the magma chamber and 

evolving to the extrusion of the more dense, basic lava 

that forms near the base of the magma chamber.

Previous interpretations subdivided the Cranberry Island 

series into the three members that are listed in the Map 

Units Property Table (Gilman et al. 1988). However, the 

unit of felsites and flows (SDcif), which occurs only on 

Mount Desert Island, has been reinterpreted as a shallow 

intrusive unit that may be related more to the Cadillac 

Mountain intrusive complex than to the Cranberry 

Island volcanic sequence (Seaman 2000).

In the park, exposures of the Cranberry Island series 

occur on Isle au Haut and near Seawall campground. The 

most complete section of the Cranberry Island series lies 

outside the park, along the shore of Great Cranberry 

Island (Gilman and Chapman 1988; Seaman 2000). The 
ACAD Geologic Resources Inventory Report 25

north side of Little Cranberry Island also contains 

excellent exposures. 

Granite of the Schoodic Peninsula

Previously considered to be part of the Cadillac 

Mountain intrusive complex, the Late Silurian 

(approximately 419 million years old) granite that forms 

the landscape of the Schoodic Peninsula contains a 

significantly different composition than the Cadillac

Mountain granite and lacks a shatter zone (Chris Koteas, 

University of Massachusetts, personal communication, 

June 9, 2008). The contact between the Schoodic 

Peninsula granite and the Cadillac Mountain intrusive 

complex lies within Frenchman Bay.

The Schoodic Peninsula contains excellent exposures of 

the upper portion of the magma chamber and mafic dike 

swarms that show an intermingling of two hot, plastic 

magma bodies (fig. 17A). Pulsed injections of mafic 

magma into the magma chamber produced zones of 

mingling of intermediate magma with felsic magma. 

These zones point to a long-lived, dynamic episode of 

volcanism. Rounded blocks of greenstone 

(metamorphosed mafic igneous rock) found within the 

diorites of the Schoodic Peninsula and the lack of a 

shatter zone indicate that the Schoodic Peninsula granite 

formed from a different method of intrusion than did the 

Cadillac pluton.

Diabase Dikes

Stripes of fine-grained, black diabase dikes are especially 

noticeable in the light-colored Schoodic Point granite 

(fig. 17A). Chemically similar to gabbro and basalt, 

diabase is a fine-grained intrusive igneous rock that 

forms a transition between deeply-buried gabbros and 

extrusive basalts. The dikes are mostly less than 3 m

(10 ft) wide. However, some exceed 18 m (60 ft) in width 

(Gilman et al. 1988). In all units of the Cadillac Mountain 

intrusive complex, the dikes trend roughly north-tosouth to 340° (Wiebe et al. 1997a). They appear to be 

more abundant in the Cadillac Mountain granite than in 

the younger Somesville and Pretty Marsh granites. 

Schoodic Point and Cadillac Mountain offer excellent 

exposures of diabase dikes (fig. 17B). Two 1.5- to 3-m (5-

to 10-ft)-wide dikes cut through the granite at the hairpin 

turn 2.9 km (1.8 mi) from the entrance gate on Cadillac

Mountain Road (Gilman et al. 1988). The trail on the 

south side of the mountain that leads to Black Woods 

Campground offers excellent exposures of the black 

dikes. The southern end of the Schoodic Peninsula also 

offers exceptional exposures of the dikes as well as their 

cross-cutting relationships.

Other Schoodic Peninsula Dikes

On the Schoodic Peninsula, dikes with three different 

compositions have been identified. These include: 1) 

fine-grained felsic dikes, 2) felsic dikes with plagioclase 

phenocrysts, and 3) banded rhyolite dikes (Chris Koteas, 

University of Massachusetts, personal communication, 

June 9, 2008). Blobs and chunks of granite that only 

partially dissolved appear to ‘float’ within the dikes, and 

some of the granite within the dikes contains the mineral 

hornblende that formed within the granite from the heat 

of the intrusion. Some of the dikes on the Schoodic 

Peninsula appear to have intruded into granite and then 

reversed their flow direction to inject back on 

themselves, indicating a dynamic process of intrusion. 

Shatter Zone (Intrusive Breccia)

One of the most spectacular features on Mount Desert 

Island is the shatter zone that borders the Cadillac 

Mountain granite to the north, east, and south (Gilman 

et al. 1988; Gilman and Chapman 1988). Ranging in 

width from 300 m (1,000 ft) to more than 1.6 km (1 mi), 

the shatter zone consists of severely shattered, angular 

fragments of gabbro-diorite, Ellsworth Schist, volcanic 

and sedimentary rock from the Bar Harbor Formation, 

and other rock rubble from veins and dikes all congealed 

in a matrix of granite (fig. 18). The rock pieces 

surrounded by granite are up to hundreds of meters 

across (Gilman et al. 1988).

Investigation continues into how the shatter zone 

formed. Current data suggests that the shatter zone 

formed suddenly, perhaps associated with an explosive 

eruption triggered by an influx of basaltic magma into 

the Cadillac Mountain granite chamber (Coombs 1994). 

Gilman and others (1988) proposed that roof pendants 

(rocks above the magma chamber) and fractured country 

rock adjacent to the chamber walls became weakened by 

the intrusion and began to sag and sink into the magma. 

The magma then surged upward, filling spaces created by 

the foundering country rock in a process called cauldron 

subsidence. The inclusions of country rock appear to 

have settled to the floor of the magma chamber as the 

magma crystallized, (fig. 19). The shatter zone would 

then represent the outermost edge of a collapsed central 

region and contain brecciated country rock that did not 

completely assimilate into the magma (Gilman et al. 1988; 

Kiver and Harris 1999). 

Excellent exposures of the shatter zone are present at 

Otter Cliffs, Western Point south of Black Woods 

Campground, and in Little Hunters Cove (fig. 18). The 

east end of Sand Beach also offers good exposures as 

does the parking lot for the overlook at Schooner Head.

Regional Metamorphic Rocks: Ellsworth Schist

Schist (from the Greek word meaning “to split”) refers to 

a metamorphic rock that is layered (foliated) and splits 

along this layering. While the Ellsworth Schist may exist

elsewhere in Maine, in Acadia National Park, the 

Ellsworth Schist has undergone a higher degree of 

regional metamorphism to forming a gneiss. The gneiss 

contains complexly-folded bands of light and darkcolored minerals. In the Ellsworth Schist, darker layers 

of the mineral chlorite and lighter layers of quartz and 

feldspar give the rock its distinctive streaked appearance 

(fig. 20A). 

Composed of intensely deformed and metamorphosed 

volcanic rocks, the Ellsworth Schist records two 

significantly different tectonic regimes: 1) an extensional 
26 NPS Geologic Resources Division 

regime in a rift setting, and 2) a compressional regime 

resulting from plate subduction along an active margin 

(Reusch 2002; Schulz et al. 2007; Schulz et al. 2008). The 

Ellsworth Schist consists of basalt and rhyolite, volcanic 

rocks with quite different mineral compositions. 

Ellsworth basalts have compositions similar to midocean-ridge basalts that originate from the 

asthenosphere while the rhyolite tuffs that are 

interlayered with the basalts reflect a shallower source in 

the crust. The compositional similarity of the Ellsworth 

basalt to others found in the present Gulf of California 

suggests that the Ellsworth evolved in a similar 

extensional tectonic regime (see the “Geologic History” 

section). 

Detailed measurements of larger scale asymmetrical 

folding (fig. 20A), analysis of the orientation of small 

scale foliation (called crenulation cleavage), and analysis 

of the metamorphic grade (i.e., low temperature but high 

pressure) suggest that the Ellsworth Schist was intensely 

deformed during regional metamorphism associated 

with a subduction zone that formed along an active plate 

margin (see the “Geologic History” section) (Reusch and 

Rust 2001; Reusch 2002). 

Across the bridge from the mainland to Mount Desert 

Island, the Ellsworth Schist is the first rock exposed 

along the shore. Excellent exposures of the Ellsworth 

Schist may be found at the picnic area opposite the 

Acadia National Park information center on Thompson 

Island, on the northwest side of Mount Desert Island, 

and on the west side of Bartlett Island (Gilman and 

Chapman 1988).

Stratified Sedimentary Rocks: Bar Harbor Formation

The second oldest group of rocks in the park, the 

Silurian Bar Harbor Formation consists of siltstone and 

sandstone beds generally a few centimeters to 1 m (3.3 ft) 

thick. These sedimentary rocks are stratified, forming 

relatively undeformed layers in comparison to the 

Ellsworth Schist (fig. 20B). However, like the Ellsworth 

Schist, Bar Harbor sediments were products of offshore, 

marine deposition. Volcanic material, transported by 

waves and currents in an ancient sea, form thin white 

layers in the formation (Harris et al. 1997). Contact 

metamorphism from the emplacement of the Cadillac 

Mountain intrusive complex fused the grains of the Bar 

Harbor Formation but did not change its mineral 

composition. Because the grains have been welded 

together by contact metamorphism, the unit is referred 

to as a metasedimentary rock.

Coarser-grained beds in the Bar Harbor Formation may 

contain quartz pebbles up to 0.64 cm (0.25 in) in 

diameter. Some individual beds display graded bedding, 

which shows a gradual change from coarse material at 

the bottom of the layer to fine silt at the top. Graded 

bedding results from a sediment gravity flow where 

different-size particles settle through the sediment-water 

mix. In these conditions, the graded beds likely resulted 

from a pulse of sediment. The triggering mechanism for 

the pulse of sediment that produced these normally 

graded beds (coarser at the base and fining upward) may 

have come from a variety of sources including 

earthquakes, volcanic eruptions, channel margin collapse 

from channel undercutting, collapse of oversteepened 

beds, and erosion caused by intense rain storms. 

Graded bedding is extremely useful for telling 

directionality and patterns of sediment transport within a 

basin. Using graded bedding, geologists can also tell if the 

rock layers have been overturned during a deformational 

event. The rock strata at Bar Harbor are right-side-up, 

suggesting they have undergone little deformation since 

they were deposited approximately 420 million years 

ago. Alternatively, the strata may have been tilted during 

one deformational event and returned to a relatively 

original position during a subsequent deformational 

event.

Bar Harbor, Maine, was designated as the type locality 

for the Bar Harbor Formation because of excellent 

exposures along the shoreline. In this area, bedding is 

inclined gently toward the ocean, and the strata lack any 

folding or complex faulting (Gilman et al. 1988). Rocks 

exposed along the shore at The Ovens and on the north 

side of Mount Desert Island in road-cuts along Route 3 

at Ireson Hill also belong to the Bar Harbor Formation. 

However, bedding in these locations is difficult to 

distinguish, and the rock is more flint-like than the strata 

at Bar Harbor. Some of the beds may be accumulations of 

ash that settle out of the atmosphere following a volcanic 

eruption (Gilman et al. 1988).

Joints and Faults

On Cadillac Mountain, prominent vertical joint sets have 

directions of 90° (east-to-west), 40° (northeast-tosouthwest), and 335° (northwest-to-southeast) (Gilman 

et al. 1988). Joints typically form in conjugate joint sets 

where two joints intersect at acute angles of roughly 60° 

and obtuse angles of 120° (fig. 17). Conjugate joint sets 

are compressional features and may resemble a squashed 

“X”. Regional study of conjugate joint sets gives 

tremendous insight to the tectonic regime at the time 

deformation took place.

The broad exposures of smooth, gently sloping rock on 

Cadillac Mountain, Pemetic Mountain, and Dorr 

Mountain originated from horizontal joints during a 

process known as exfoliation. As erosion removed the 

weight of overlying rock, the underlying rock expanded 

and cracked parallel to the surface. Recent field studies 

have shown that the three mountains are part of a single 

exfoliation dome that formed prior to glaciation 

(Vollmer 2009). Glaciers carved the exfoliated sheets of 

rock that had been weakened by vertical and horizontal 

fractures, leaving behind today’s smooth, gently rounded 

topographic domes of Mount Desert Island (Gilman et 

al. 1988). 

Very little movement or displacement took place along 

the joints, but in some situations, forces not only 

fractured the rock, but also displaced it, forming a fault. 

Faults are not as easily found on Mount Desert Island as 

are joints for several reasons. Faults usually contain 

ruptured and broken rock, which weathers easily, so that 
ACAD Geologic Resources Inventory Report 27

many faults now lie in low areas, covered by soil, 

vegetation, or glacial material. The limited amount of 

bedrock exposures also limits the number of faults 

exposed at the surface (Gilman et al. 1988). 

Along the north shore of Mount Desert Island, several 

small, nearly vertical faults interrupt the bedding in the 

Bar Harbor Formation. Vegetation obscures the faults 

farther inland. Inference of a larger fault may be found at 

Salsbury Cove where sheared and broken Ellsworth 

Schist terminates abruptly against the gabbro-diorite. 

The eastern boundary of the Ellsworth Schist south of 

Salsbury Cover may be a continuation of this fault.

Both chemical and physical weathering processes tend to 

enhance the fractured bedrock surfaces. Water 

percolates into the fractures, dissolving some of the 

mineral cements, and then expands upon freezing, 

forcing individual grains apart. When the ice thaws, 

water washes away the loosened pieces of granite from 

the widening fractures. More water is trapped, and the 

cycle repeats. Fractures are also desirable habitats for 

lichen and plants whose roots contribute to the physical 

destruction of bedrock.

Glacial Features

In the Devonian, continental collision resulted in the 

northern Appalachian Mountain Range. In the Triassic, 

the supercontinent, Pangaea, began to rift apart as the 

Atlantic Ocean opened. In the Pleistocene, continental 

glaciers sculpted today’s New England landscape. The 

last glacier to extend into the Gulf of Maine left two 

major types of geologic features, erosional features and 

depositional features summarized in table 2.

Table 2: Glacial features in Acadia National Park.

Erosional Features Depositional Features

Glacial polish, striations, 

grooves and chatter marks 

(abrasion) 

Glacial till

Cliffs (plucking) Moraines

Roches moutonnées Glacial erratics

U-shaped valleys Deltas

Fjard of Somes Sound Outwash deposits

Meltwater channels

Glacial Polish, Striations, Grooves, and Chatter Marks

The major landforms seen today in Acadia National Park 

owe their origin to glacial erosion caused by southflowing ice sheets during the Pleistocene. Rock 

fragments dragged along by the Wisconsinan-aged 

glacier acted like grit on sandpaper to scratch, gouge, 

grind, and polish the underlying bedrock (fig. 21A). 

Abrasion was stronger on the north sides of hills, which 

offered more resistance to the southward-flowing ice. 

Striations (scratch marks), which are oriented parallel to 

ice flow, may be used to plot the direction of glacial 

movement. On Mount Desert Island, glacial grooves and 

striations show a generally north-south orientation 

(Lowell and Borns 1988). Boulders and rocks embedded 

in the ice may bear down against a bedrock surface to 

produce crescent-shaped grooves known as chatter 

marks. Chatter marks document areas where some of the 

greatest pressures were exerted against the bedrock 

(Gilman et al. 1988). 

Glacial-derived Cliffs

Glacial plucking removed large amounts of rock and 

produced many of the spectacular cliffs in Acadia 

National Park (fig. 15). Because the glacier was advancing 

from the north, increased pressure on the north side of 

hills caused ice to melt at the bottom of the glacier. 

Meltwater seeped into fractures and refroze on the 

southern side of hills. Upon freezing, the ice expanded 

and forced the rock apart. Blocks of bedrock pried loose 

in this manner were subsequently frozen into the glacier 

and carried away. The prominent cliffs along the 

Precipice Trail and on the southeast side of The Bubbles 

are examples of cliffs created by glacial plucking (Gilman 

et al. 1988). 

Roches Moutonnées

Glacial abrasion and plucking caused many of the hills in 

Acadia National Park to develop a distinctly asymmetric 

profile. Abrasion smoothed and polished the north sides 

that faced into the ice flow. Glacial plucking generated a 

steep, rugged south side. These glacially sculpted 

bedrock knobs form roches moutonnées, a term coined 

by Horace-Bénédict de Saussure, a French alpine 

explorer in the eighteenth century. De Saussure thought 

the rocks (roche) looked like the fashionable wigs of the 

day that were smoothed with mutton fat (moutonnée) to 

keep the hair in place. 

Because of its shape, a roche moutonnée is also known as 

a whaleback or sheepback. The roches moutonnées on 

Mount Desert Island tend to be elongated and 

streamlined in a north-south direction, relatively parallel 

to the direction of ice movement. Two of the more 

famous roches moutonnées in the park are The Bubbles, 

the two rounded mountains located north of Jordan 

Pond (fig. 21B). Viewed from the side, The Bubbles 

appear asymmetrical, with the steeper side to the south.

U-shaped Valleys

While streams tend to erode an alpine valley into a 

characteristic V-shape, glaciers cut flat-bottomed, steep, 

relatively straight, distinctive U-shaped valleys (fig. 21B). 

Like the striations and roches moutonnées, the U-shaped 

valleys on Mount Desert Island trend north to south 

(Gilman et al. 1988). When the glaciers melted, lakes 

formed in the U-shaped valleys. Sargent Mountain Pond 

became the first post-glacial lake in Maine. Jordan Pond, 

which covers 76 ha (187 ac) and reaches a maximum 

depth of 46 m (150 ft), holds the distinction of being 

Maine’s clearest lake with normal visibility reaching 14 m 

(46 ft) and occasionally up to 18 m (60 ft). Other lakes 

that formed in U-shaped valleys include Seal Cove Pond, 

Long Pond, Echo Lake, and Eagle Lake. 
28 NPS Geologic Resources Division 

Fjard

In the past, Somes Sound, one of the most magnificent 

bays on the Maine coast, has been categorized as a fjord 

(Gilman et al. 1988; Harris et al. 1997). Fjords are long, 

narrow, glacially-eroded arms of the sea, usually 

hundreds of meters deep, with steep rock cliffs and a 

shallow sill at the entrance to the ocean. The great depths 

of fjords inhibit mixing of marine waters so that the 

bottom is anoxic. 

Although glacially derived, Somes Sound lacks features 

required by the strict definition of a fjord. The relief of 

Somes Sound, almost 300 m (980 ft), is relatively small 

compared to the 1,000 m (3,300 ft) relief of fjords found 

in Norway. Somes Sound opens to the sea through The 

Narrows, an entrance sill similar to those found in fjords. 

However, The Narrows is not large enough to alter the 

circulation within the sound, and the bottom of the 

sound remains oxygenated. 

The Scandinavian term, fjard, may be a more accurate 

description of Somes Sound. Smaller, shallower, and 

broader in profile than a fjord, a fjard is simply a glacially 

carved embayment that is drowned by the sea (Maine 

Geological Survey 2005a).

Meltwater Channels

Near the close of the Pleistocene, the climate warmed 

and the glaciers melted, vast amounts of water flowed 

either directly off the glacial surface or found its way to 

the bottom of the ice (Gilman et al. 1988). Strong 

currents and abundant sediment in these internal 

meltwater channels eroded trough-like features into the 

bedrock hills. All the mountains on Mount Desert Island 

contain evidence of meltwater channels. A meltwater 

channel formed the notch between Cadillac Mountain 

and Dorr Mountain and is visible from the Park Loop 

Road where it crosses Otter Cove (Lowell and Borns 

1988).

Glacial Till

Glaciers transport all sizes of debris, from fine dust to 

boulders, and deposit this debris along its sides, on the 

valley floor through which it flows, and at its farthest 

extent. The general term for the poorly sorted mixture of 

fine to coarse rock debris deposited by melting ice is till 

(fig. 22A). On Mount Desert Island, intense grinding and 

crushing pulverized much of the rock debris carried near 

the base of the last glacier, resulting in a basal till of 

compact, fine-grained sediment containing many striated 

stones (Gilman et al. 1988). Glacial till has been mapped 

throughout the northern part of Mount Desert Island, 

and although hidden by vegetation, till may be exposed 

in new construction, fresh road cuts, or along the 

borders of many lakes.

Terminal Moraines

Terminal moraines are landforms that are shaped by 

rock debris that is carried along by the flowing ice, as if 

on a conveyor belt, and dumped at the front edge of the 

ice as glaciers melt. Terminal moraines cap Clark Ridge 

and dam the southern end of Long Pond, Echo Lake, and 

Jordan Pond on Mount Desert Island (Lowell and Borns 

1988). Jordan Pond House was constructed on the crest 

of a terminal moraine. The moraine consists of rock 

debris ranging in size from clay to the boulders strewn 

about the field below the manicured lawn (fig. 21B).

Glacial Erratics

Glacially plucked rocks transported away from their 

point of origin are termed glacial erratics. Flowing ice 

carried boulders of Cadillac Mountain granite to the 

southern part of Mount Desert Island and into the Gulf 

of Maine. In addition, rock fragments from the mainland 

were transported onto Mount Desert Island. Gray 

granite boulders on the top of Cadillac Mountain, for 

example, came from the Lucerne granite, located 31 km 

(19 mi) to the north. One of the most far-traveled erratics 

in Acadia National Park is the famous balanced boulder 

called Bubble Rock perched high on the side of South 

Bubble Mountain (Gilman et al. 1988). Bubble Rock is 

composed of white granite with large feldspar crystals, 

which is clearly different from the pink granite that 

forms the surrounding mountains. Its location provides 

evidence that the glaciers were as thick as the island’s 

present mountain tops (fig. 22B).

Glacial Outwash Deposits and Deltas

During periods of glacial retreat, meltwater streams 

produced outwash deposits from the front of the glacier. 

These consist primarily of mixtures of sand and silt. 

Streams transported silt and clay particles out to sea, but 

larger clasts were left behind as lag deposits. One of the 

better exposures of outwash on Mount Desert Island 

extends from Bubble Pond southward along Hunter 

Brook (Lowell and Borns 1988). Outwash deposits may 

also be found at the north end of Upper Hadlock Pond 

and near the campground southeast of Long Pond.

In three locations on southern Mount Desert Island 

(south of Jordan Pond, south of Jordan Ridge, and south 

of Upper Hadlock Pond), the sand and gravel entered 

the ocean and built up to the water surface, forming flattopped delta deposits (Lowell and Borns 1988). 

Herodotus, the Greek historian, coined the term “delta”

because the mouth of the Nile River formed a feature

shaped like the upper-case Greek letter Delta, Δ. As they 

do today, deltas in the Pleistocene formed at the 

shoreline. Thus, the deltas on Mount Desert Island 

establish the location of at least one shoreline during the 

Wisconsin glacial period.

The delta deposit southeast of Jordan Pond began to 

form when the ice margin stood behind the Jordan Pond 

moraine (Gilman et al. 1988). The flat-topped delta 

documents a time when sea level was approximately

70 m (230 ft) higher than it is today. 
ACAD Geologic Resources Inventory Report 29

Coastal Features

Before the coast of Maine rebounded following 

deglaciation, the sea flooded much of the low-lying 

portion of Mount Desert Island. As a consequence, 

Acadia National Park contains features representing 

both ancient and modern coastlines.

Emergent Shorelines of an Ancient Coast

Acadia National Park preserves significant exposures of 

ancient sea stacks, sea caves, sea cliffs, boulder beaches, 

and thunder holes that record the dynamic interaction 

between post-glacial shorelines and sea level change. The 

pockets of offshore marine clay that once blanketed the 

low areas on Mount Desert Island provide the most 

widespread evidence of a past high-stand (transgression) 

by the sea. Exposures of marine clay occur along Ocean 

Drive, on the east side of Otter Cove where it is crossed 

by Park Loop Road, at the east end of Sand Beach, and 

along Hunters Brook (fig. 8). 

In places, the marine clay contains fossil shells of clams, 

mussels, and other mollusks (Tweet et al. 2010). Some 

species of these invertebrates live today in cold, subarctic 

waters, indicating that the late-glacial marine 

environment of coastal Maine probably resembled that 

of present-day southern Greenland. Carbon-14 

radiometric age analysis from some shells found in a clay 

deposit in Goose Cove establish an approximate age of 

12,250 years old for these deposits (Gilman et al. 1988).

Concentrated deposits of pebbles, cobbles, and boulders 

exposed at higher elevations in the park document 

ancient shorelines. Similar to modern beach deposits, 

well-rounded boulders on the east side of Day Mountain 

have been tossed about and rounded in the former surf 

zone when sea level was approximately 64 m (210 ft) 

higher than its present level (Gilman et al. 1988). A wavecut platform, an undercut notch in a cliff of granite, a sea 

stack (known as Chimney Rock) and a sea cave similar to 

those found along the present coastline of Mount Desert 

Island are exposed on Cadillac Cliffs, along the Gorham 

Mountain Trail above Monument Cove (fig. 23A). The 

entrance to the sea cave cut into the granite sea cliff 

measures approximately 10 m (33 ft) high. Seaward of the 

cliff, rounded boulders are reminiscent of the boulder 

beach at Monument Cove (Maine Geological Survey 

2005b).

Remarkably, a rounded boulder, approximately 1 m

(3.3 ft) in diameter, is lodged securely in the back of the 

ancient sea cave (fig. 23B). This boulder may have been 

hurled into the cave during a storm 13,000 years ago, or it 

may represent a post-glacial tsunami deposit along a 

coastline located much higher than it is today (Joseph

Kelley, personal communication, June 10, 2008). Another 

possibility involves ice rafting. If the boulder was 

embedded in ice and currents or storm waves pushed the 

ice toward the back of the cave, the ice may have melted 

or cracked and dropped the boulder.

Modern Sea Coast

The sea continually modifies the coastal landscape of 

Acadia National Park. The sea erodes the coast in a 

process known as differential erosion, which means that 

areas of weakness erode more quickly than other areas. 

Fractures, joints, and intrusive dikes have made some of 

the igneous rocks in the park less resistant than others 

(fig. 17A). Currents and waves transport eroded rock 

debris away from high-energy zones and deposit the 

material in areas of quiet water. Some of the more 

spectacular features along the park’s coastline include 

the sea cliffs, a variety of beaches, sea caves, sea arches, 

wave-cut platforms, and other features developed along 

the shore from the process of differential erosion.

The dense, granitic bedrock in the park forms the 

characteristic sea cliffs exposed along the park’s

coastline. With glacial melting and sea level rise, 

headlands such as Great Head, Otter Cliff, and Schooner 

Head on Mount Desert Island resisted erosion and now 

extend prominently out to sea. Waves batter the 

headlands and sea cliffs, and their hydraulic action 

dislodges blocks of granite that pulverize and abrade less 

resistant or fractured rock (fig. 4). 

Rounded by constant rolling, the boulder and cobble 

beaches in Acadia National Park pay tribute to the 

incessant pounding by North Atlantic swells. Storm 

waves (fig. 11) tumble boulders into near-spherical 

shapes, such as those on the boulder beach in Monument 

Cove (fig. 24). The classification for a boulder is a rock 

that is greater than 25.6 cm (10 in) in diameter, about the 

size of a volleyball. A cobble measures from 6.4 to 25.6 

cm (2.5 to 10 in) in diameter. In Acadia National Park, 

some of the boulders reach 0.5 to 1 m (1.6 to 3.3 ft) in 

diameter. Typically the beaches grade from boulders 

near the cliff edge to cobbles closer to the surf. 

Sandy shores are rare at Acadia National Park. Even 

more scarce are beaches like Sand Beach that are 

composed of sand-sized particles of calcium carbonate. 

Nestled between the headlands of Great Head and Otter 

Point on eastern Mount Desert Island, the 265-m (870-ft) 

-long Sand Beach presents the longest continuous stretch 

of sandy beach in the park (fig. 12). Calcium carbonate 

forms slowly in cold waters, such as those found in the 

Gulf of Maine so that marine invertebrates encased in 

calcium-carbonate shells are not as common as they 

would be in warm, tropical, shallow marine 

environments. South of Cape Hatteras (North Carolina), 

carbonate beaches are composed of shell fragments from 

recently deceased invertebrates, but at Sand Beach, some 

of the shell fragments are from animals that lived 

thousands of years ago. In addition to the beach, 

geomorphic features at Sand Beach include a dune ridge, 

tidal creek, and lagoon (figs. 12, 13, and 14). 

The sea stack at the eastern end of the boulder beach in 

Monument Cove looks remarkably similar to Chimney 

Rock, which now lies along the Gorham Mountain Trail 

60 m (200 ft) above present sea level (fig. 24). Wave 

erosion focused on vertical fractures in this column of 

granite and eventually separated it from the mainland. 
30 NPS Geologic Resources Division 

The boulder beach also contains a minor exposure of 

hydrothermally altered granite. Flecks of molybdenite 

may be found embedded in some of the granite boulders 

along the beach. In 1980, exploration for molybdenite, an 

alloy in stainless steel, occurred on Long Island, which is 

now a conservation easement in the park and protected 

from mining activities (see “Mining” in the “Geologic 

Issues” section).

Boulders at Seawall Beach in Southwest Harbor may 

wash onto the road when major storms occur. Raised 

ridges of gravel form a natural seawall (Lowell and Borns 

1988). The boulder beach in Little Hunters Cove also 

provides access to excellent exposures of the shatter 

zone.

Sea caves are rare in Acadia National Park. Anemone 

Cave remains a spectacular exception, and sea caves are 

currently forming on the Schoodic Peninsula and above 

the high tide line in Frenchman Bay at Ironbound Island 

due to differential erosion. Ironbound Island is currently 

protected by a conservation easement. 

Thunder Hole, a popular site for visitors, formed from 

waves battering against an intrusive, less resistant diabase 

dike and joints in the adjacent Cadillac Mountain granite 

(fig. 25). The narrow, vertical-walled slot and sea cave 

booms like thunder when an exceptionally large wave 

suddenly compresses the air and displaces it from the 

cave.

Although not on park property, the craggy cavities 

known as The Ovens on the northeastern coast of Mount 

Desert Island have piqued the curiosity of visitors for 

years. Located on the headland between Salsbury Cove 

and Hulls Cove, The Ovens form a series of natural 

arched caves in the Bar Harbor Formation. At The 

Ovens, a massive, more resistant rock layer overlies a 

thinly stratified unit. Long, vertical fractures cut through 

the massive layer and combine with small, inclined faults 

to break apart the thin horizontal layers so they can be 

excavated by the sea. The mechanical breaking and 

erosion by the ocean proves to be an effective agent at 

removing broken material and carving the caves that 

stretch along the base of the cliff.

Where sea caves enlarge sufficiently to penetrate through 

a headland, sea arches form. At Sand Point, northeastern 

Mount Desert Island, erosion along a prominent vertical 

fracture created a high narrow arch (Kiver and Harris 

1999).

The relentless hydraulic action of waves continues to 

undercut sea cliffs and bevel the bedrock into modern 

examples of the emergent wave-cut platform and 

undercut cliff exposed on the Gorham Mountain Trail. 

South of Thunder Hole, Otter Cliffs rise vertically 33 m 

(107 ft) above a smooth, well-developed wave-cut bench 

or platform. At Schoodic Point, waves continue to wash 

over a smooth platform cut into the granite bedrock.

Table 3 summarizes the geologic features visible within 

Acadia National Park.

A) Diabase dike on Schoodic Point. B) Diabase dike intruding Cadillac Mountain granite.

Figure 17. Igneous diabase dikes in Acadia National Park. A) A massive diabase dike intrudes light-colored granite on Schoodic Point, Acadia 

National Park. Note the preferential weathering that has eroded the contact between the dike and granite. Also visible are horizontal joints 

that form “steps” and vertical joint sets that form an “X” pattern in the granite. Photograph by John Graham (Colorado State University). B) 

Diabase dike cutting through (intruding) the Cadillac Mountain granite on Mount Desert Island, Maine. The granite is fractured by intense 

horizontal jointing. Photograph from Gilman and others (1988), available on the Maine Geological Survey website, 

http://www.maine.gov/doc/nrimc/mgs/explore/bedrock/acadia/igneous.htm (accessed February 20, 2010).
ACAD Geologic Resources Inventory Report 31

Figure 18. The shatter zone at Little Hunters Cove, Mount Desert Island. Exotic deformed and angular fragments of rock create a unique rock 

unit associated with the intrusion of the Cadillac Mountain intrusive complex. Mechanical pencil is 14.5 cm (5.7 in), for scale. Photographs 

courtesy of the author.

Figure 19. Schematic cross section through Cadillac Mountain granite illustrating one possible origin for the shatter zone. The granitic 

intrusion fractures the country rock, causing angular pieces of country rock to be surrounded by intruding magma. When the magma 

chamber’s roof collapses, a process called cauldron subsidence, magma fills the spaces. The inclusions of country rock settle to the floor of the 

magma chamber. Support for this idea comes from the orientation of the inclusions, which are essentially horizontal in the interior of the 

granite body, but tilt downward towards the interior on the outside margin of the granitic body. Diagram from Gilman and others (1988), 

available on the Maine Geological Survey website, http://www.maine.gov/doc/nrimc/mgs/explore/bedrock/acadia/igneous.htm (accessed 

July 30, 2010). 
32 NPS Geologic Resources Division 

A) Ellsworth Schist

B) Bar Harbor Formation

Figure 20. Metamorphic and sedimentary bedrock features in Acadia National Park. A) Ellsworth Schist. Deformation during metamorphism 

contorted the thin layers into complex, asymmetric folds with one limb of the fold steeper than the other. Measurement of these folds can 

provide clues as to the direction of compression. Quartz and feldspar compose the light-colored layers; chlorite and other mica minerals form 

the dark bands. Note the penny in the center of the photograph for scale. Photograph from Gilman and others (1988), courtesy of the Maine 

Geological Survey and available online: http://www.maine.gov/doc/nrimc/mgs/explore/bedrock/acadia/strat.htm, (accessed January 8, 2010). 

B) Strata (layers) in the Bar Harbor Formation along the shoreline near Bar Harbor, Maine. The Bar Harbor Formation changes from regular 

thin and medium bedded sedimentary rock, as seen here, to a massively-bedded unit at The Ovens, farther north along the coast. Photograph 

courtesy of the Maine Geological Survey, available online: http://www.maine.gov/doc/nrimc/mgs/explore/bedrock/sites/jul03.htm, (accessed 

January 8, 2010).
ACAD Geologic Resources Inventory Report 33

A) Glacial polish, striations, and chatter marks.

B) The Bubbles.

Figure 21. Glacial erosional features in Acadia National Park. A) Abrasion from rock material carried by the glaciers polished the bedrock and 

left chatter marks (arc-shaped indentations) and striations (lines scratched into the rock surface). Striations are parallel to the pen (for scale) 

and indicate the direction of the flowing ice. Photograph from Gilman and others (1988), courtesy of the Maine Geological Survey and 

available online: http://www.maine.gov/doc/nrimc/mgs/explore/bedrock/acadia/strat.htm, (accessed January 8, 2010). B) View to the north 

across Jordan Pond to The Bubbles (left Bubble summit shrouded in clouds), two roches moutonnées in the park. Glacial plucking shaped the 

steep, southern slopes of The Bubbles, seen in this photograph (black arrows). The vegetated, hummocky terrain in the foreground is the 

glacial moraine that dammed the U-shaped valley to form Jordan Pond. Note the boulders (yellow arrows) strewn randomly upon the typical 

hummocky surface of a moraine. Boulders are common in the poorly sorted glacial till. Photograph by John Graham (Colorado State 

University).

Moraine

U-shape
34 NPS Geologic Resources Division 

A) Glacial Till.

B) Bubble Rock.

Figure 22. Glacial depositional features in Acadia National Park. A) Glacial till exposed during the construction of the Jordan Pond House. Tills 

are poorly sorted, containing a wide range of particle sizes from clay to boulders. Note the rounded edges to some of the boulders, indicating 

abrasion during transportation prior to deposition. Shovel blade is 18 cm (7 in) across. Photograph from Gilman and others (1988), courtesy of 

the Maine Geological Survey and available online: http://www.maine.gov/doc/nrimc/mgs/explore/bedrock/acadia/strat.htm, (accessed 

January 8, 2010). B) Bubble Rock, a glacial erratic over 3 m (10 ft) tall. Composed of white granite with large feldspar crystals, Bubble Rock 

probably came from the Lucerne plutonic complex, approximately 31 km (19 mi) to the north. Bubble Rock is a popular attraction, and 

trampling has destroyed the vegetation that once covered the trail. National Park Service photograph by Charlie Jacobi (Acadia National 

Park).
ACAD Geologic Resources Inventory Report 35

A) Emergent coastline feature; a sea cave on Gorham Mountain Trail.

B) Boulder lodged in emergent sea cave on Gorham Mountain Trail.

Figure 23. Emergent coastline features exposed along Cadillac Cliffs on the Gorham Mountain Trail, Mount Desert Island, Acadia National 

Park. A) Features similar to those found at the present sea coast include the steep sea cliff, previously undercut by the hydraulic action of 

waves, and the smooth wave-cut platform at the base of the cliff. Visitors are standing on an ancient shore and staring at a sea cave that 

formed along the post-glacial coastline. B) In the recesses of the sea cave, a rounded boulder, approximately 1 m (3.3 ft) in diameter, remains 

securely lodged within the horizontally fractured Cadillac Mountain granite. One interpretation suggests that a tsunami transported the 

boulder into the sea cave. Photographs courtesy of the author.

Wave-Cut Platform

Boulder
36 NPS Geologic Resources Division 

Figure 24. Boulder beach and sea stack (indicated by the yellow arrow) at Monument Cove, Mount Desert Island. Note that some of the 

boulders are larger than others and some are more rounded, indicating various abrasion and transportation histories. Wave erosion, focused 

on the vertical fractures in the rocks, has separated the sea stack from the mainland. Photograph by John Graham (Colorado State University).
ACAD Geologic Resources Inventory Report 37

Figure 25. Thunder Hole slot and sea cave on Mount Desert Island, Acadia National Park. The narrow slot formed as waves eroded the contact 

between the dike (containing the viewing platform) and the Cadillac Mountain granite. The yellow lines indicate the planes of two near 

vertical joints that intersect each other at an acute angle of approximately 45 degrees, further reducing rock stability. Paired joint sets such as 

these, which are common on Mount Desert Island, are known as conjugate joint sets. Waves rushing into the cave (below the photographer) 

displace air, which produces a booming, thunderous sound. Photograph by John Graham (Colorado State University).
38 NPS Geologic Resources Division 

Table 3: Summary of geologic features and processes visible within Acadia National Park

Bedrock Features

Cadillac Mountain Intrusive Complex

• Cadillac Mountain Granite

• Gabbro – Diorite Unit

• Somesville Granite

• Southwest Harbor Granite

• Pretty Marsh Granite 

Regional Metamorphic Rocks: Ellsworth Schist 

Stratified Sedimentary Rocks: Bar Harbor Formation 

External Igneous Rocks: Cranberry Island Series

Granite of Schoodic Peninsula

Diabase (and other) Dikes

Shatter Zone

Joints and Faults

Glacial Features

Erosional Features

• Glacial polish, striations, grooves and chatter marks (process of glacial abrasion)

• Cliffs (process of glacial plucking)

• Roches moutonnées

• U-shaped valleys

• Fjard of Somes Sound

• Meltwater stream channels 

Depositional Features

• Glacial till

• Moraines

• Glacial erratic

• Deltas

• Outwash Plains

Coastal Features

Emergent Shorelines: sea cliffs, sea caves, boulder beaches, wave-cut platforms, sea caves, 

marine clay

Modern Coastline: sea cliffs, sea caves (including Thunder Hole and The Ovens), Sand Beach, 

boulder beaches, sea arch, examples of differential erosion
ACAD Geologic Resources Inventory Report 39

Map Unit Properties

This section identifies characteristics of map units that appear on the Geologic Resources 

Inventory digital geologic map of Acadia National Park. The accompanying table is 

highly generalized and for background purposes only. Ground-disturbing activities 

should not be permitted or denied on the basis of information in this table. 

Geologic maps facilitate an understanding of Earth, its 

processes, and the geologic history responsible for its 

formation. Hence, the geologic map for Acadia National 

Park provided information for the Geologic Issues, 

Geologic Features and Processes, and Geologic History

sections of this report. Geologic maps are twodimensional representations of complex threedimensional relationships; their color coding illustrates

the distribution of rocks and unconsolidated deposits. 

Bold lines that cross or separate the color patterns mark 

structures such as faults and folds. Point symbols 

indicate features such as dipping strata, sample localities, 

mines, wells, and cave openings. 

Incorporation of geologic data into a Geographic 

Information System (GIS) increases the usefulness of 

geologic maps by revealing the spatial relationships 

among geologic features, other natural resources, and 

anthropogenic features. Geologic maps are indicators of 

water resources because they show which rock units are 

potential aquifers and are useful for finding seeps and 

springs. Geologic maps are not soil maps, and do not 

show soil types, but they do show parent material—a key 

factor in soil formation. Furthermore, resource managers 

have used geologic maps to make connections between 

geology and biology; for instance, geologic maps have 

served as tools for locating sensitive, threatened, and 

endangered plant species, which may prefer a particular 

rock unit. 

Although geologic maps do not show where earthquakes 

will occur, the presence of a fault indicates past 

movement and possible future seismic activity. Similarly, 

map units show areas that have been susceptible to 

hazards such as landslides, rockfalls, and volcanic 

eruptions. Geologic maps do not show archaeological or 

cultural resources, but past peoples may have inhabited 

or been influenced by depicted geomorphic features. For 

example, alluvial terraces may have been preferred use 

areas and formerly inhabited alcoves may occur at the 

contact between two rock units.

The geologic units listed in the following table 

correspond to the accompanying digital geologic data. 

Map units are listed in the table from youngest to oldest. 

Please refer to the geologic timescale (fig. 26) for the age 

associated with each time period. The table highlights 

characteristics of map units such as: susceptibility to 

erosion and hazards; the occurrence of paleontological 

resources (fossils), cultural resources, mineral resources, 

and caves or karst; and suitability as habitat or for 

recreational use. Some information on the table is

conjectural and meant to serve as suggestions for further 

investigation.

The GRI digital geologic maps reproduce essential 

elements of the source maps including the unit 

descriptions, legend, map notes, graphics, and report. 

The following references are the sources for the GRI 

digital geologic data for Acadia National Park: 

Gilman, R. A. and C. A. Chapman. 1988. Bedrock geology 

of Mount Desert Island. Bulletin 38. Maine Geological 

Survey, Augusta, Maine, USA (scale 1:50,000).

Lowell, T. V. and H. W. Borns, Jr. 1988. Surficial geology 

of Mount Desert Island. Bulletin 38. Maine Geological 

Survey, Augusta, Maine, USA (scale 1:50,000).

The GRI team implements a geology-GIS data model 

that standardizes map deliverables. This data model 

dictates GIS data structure including data layer 

architecture, feature attribution, and data relationships 

within ESRI ArcGIS software, and increases the overall 

utility of the data. GRI digital geologic map products 

include data in ESRI personal geodatabase and shapefile 

GIS formats, layer files with feature symbology, Federal 

Geographic Data Committee (FGDC)-compliant 

metadata, a Windows help file that contains all of the 

ancillary map information and graphics, and an ESRI 

ArcMap map document file that easily displays the map 

and connects the help file directly to the map document.

GRI digital geologic data are included on the attached 

CD and are available through the NPS Data Store

(http://science.nature.nps.gov/nrdata/).

ACAD Geologic Resources Inventory Report 43

Geologic History

This section describes the rocks and unconsolidated deposits that appear on the digital 

geologic map of Acadia National Park, the environment in which those units were 

deposited, and the timing of geologic events that created the present landscape.

In general, the bedrock and surficial deposits of Acadia 

National Park record two major events in the evolution 

of eastern North America: the growth of the Paleozoic 

Appalachian mountain chain and the sculpting of the 

landscape by much younger Pleistocene glaciers (fig. 26). 

The Appalachian chain extends from eastern Canada to 

encompass the Oachitas of west Texas ending in Big 

Bend National Park and evolved as a result of three main 

mountain-building episodes (orogenies): the Taconic 

(Ordovician), Acadian (Silurian and Devonian), and 

Alleghanian (Carboniferous and Permian) orogenies

(fig. 26). Although relegated to specific geologic periods 

for convenience, the three orogenies represent an active 

tectonic margin that existed along the eastern seaboard 

of North America throughout most of the Paleozoic (542 

to 251 million years ago). The Avalonian Orogeny 

occurred far from the proto-North American continent, 

but its history can be found in rocks exposed in 

Newfoundland, eastern New England, and the southern 

Appalachian Piedmont region (Suppe 1985).

Bedrock exposures in Acadia National Park document a 

complex early Paleozoic history involving regional and 

contact metamorphism, igneous intrusions, volcanism, 

and intricate folding from intense deformation. Events 

involving both active tectonic margins and passive 

tectonic margins established the foundation upon which 

the glaciers of the last ice age carved the present 

landscape. 

Geologic events over time have been accurately dated 

using rock geochemistry, paleontological classification of 

organisms from cores, and radiocarbon analyses on 

mollusk shells and on bulk organic material from cores.

Paleozoic Era (542 to 251 million years ago)

The geologic units that compose the bedrock of Acadia 

National Park originated far from the eastern seaboard 

of North America. By the beginning of the Cambrian 

period, most of the global continental landmass clustered 

around the South Pole as part of the supercontinent, 

Gondwana. Exceptions included smaller continents to 

the north, such as Laurentia, which formed the

continental core of North America, and Baltica, the core 

of Western Europe (fig. 27). 

In the Middle Cambrian, approximately 509 million 

years ago, micro-continents began to separate from 

northern Gondwana. Similar to what is currently 

occurring in the Gulf of California, rifting pulled apart 

the crust to create a submarine rift system that allowed 

basaltic magma to erupt through fissures onto the sea 

bed. Between eruptions, felsic deposits of rhyolite tuff 

settled over the basalt (Reusch 2002; Schulz et al. 2007; 

Schulz et al. 2008). These deposits would later be 

metamorphosed into the Ellsworth Schist.

Eventually, the rift widened and Ganderia, along with 

other micro-continents such as Avalonia (which would 

become the coast of Maine) and Meguma (modern-day 

Nova Scotia), split away from northern Gondwana 

(Murphy et al. 2006). Sometime between the Late 

Cambrian and Early Ordovician, the leading edge of 

Ganderia changed from a passive margin to an active 

margin with a subduction zone and a chain of volcanic

islands, called the Penobscot arc, forming above the 

down-going slab of crust. Collision of the Penobscot arc 

with the Ganderia mainland, which lay many kilometers 

east of Laurentia, resulted in regional metamorphism and 

deformation that transformed the interlayered basalt and 

rhyolite into the Ellsworth Schist (Reusch 2002; van Staal 

2007).

Ganderia, Avalonia, Meguma and the other microcontinents formed an island chain bordered by the 

Iapetus Ocean to the north and the Rheic Ocean to the 

south (fig. 27). The ocean names are based upon Greek 

mythology: Iapetus was the father of Atlas, just as the 

Iapetus Ocean was the predecessor of the Atlantic 

Ocean. Rhea was the sister of Iapetus. As Ganderia and 

the other micro-continents drifted away from 

Gondwana, the Iapetus Ocean between Laurentia and 

the micro-continents narrowed (Bradley 1997; Murphy 

et al. 2006). 

During the Late Cambrian to Middle Ordovician, a 

convergent boundary with an east-dipping subduction 

zone developed along the northeastern margin of this 

island chain. Partial melting of the down-going slab of 

crust generated magma, which returned to the surface to 

form a volcanic island arc system between the microcontinents and Laurentia. By the Late Ordovician, 

igneous and sedimentary rocks in the volcanic arc had 

been folded, faulted, metamorphosed and accreted to 

Laurentia as part of the Taconic Orogeny, named for 

exposures in the Taconic Mountains of New York and 

Vermont (fig. 28). Today, these rocks form the fold-andthrust belt of western Vermont, eastern New York, and 

northernmost Maine (Bradley 1997).

As the volcanic arc accreted to the Laurentian mainland, 

Ganderia and the other micro-continents were 

approaching from the east. Sediments eroded from 

Ganderia were deposited offshore and solidified into the 

Silurian Bar Harbor Formation. An unconformity (gap in 

time in the geologic record) separates the Bar Harbor 

Formation from the Ellsworth Schist, signifying a period 

of either nondeposition or uplift followed by erosion. 
44 NPS Geologic Resources Division 

Episodic deformation of the Northern Appalachians 

occurred from the southeast as the Acadian Orogeny 

progressed across Maine and adjacent areas (fig. 29) 

(Bradley et al. 2000). The first micro-continent to collide 

with Laurentia in the developing Acadian Orogeny was 

Ganderia during the Late Silurian (a pre-Acadian phase 

also referred to as the Salinic Orogeny) (van Staal 2007). 

The docking of Avalonia soon followed in the Late 

Silurian or Early Devonian (van Staal et al. 2002). 

Discussion continues regarding whether or not Ganderia 

became part of Avalonia before it became attached to 

Laurentia in the Silurian (van Staal et al. 2002; Murphy et 

al. 2007). In the Late Devonian or Early Mississippian, 

Meguma became part of Laurentia (a phase also known 

as the Neoacadian Orogeny) (van Staal 2007). 

Magmatic and plutonic activity associated with the 

Acadian Orogeny resulted in the emplacement of over 

100 mafic and felsic plutons in the Coastal Maine 

Magmatic Province, which includes the Cadillac 

Mountain intrusive complex (Hogan and Sinha 1989; 

Wiebe et al. 1997). Field evidence and radiometric data 

suggest the following sequence for the emplacement and 

solidification of the granitic units within the Cadillac 

Mountain intrusive complex (Wiebe et al. 1997b):

• Somesville granite (emplaced last)

• Pretty Marsh granite

• Cadillac Mountain granite

• Southwest Harbor granite (emplaced first)

Basaltic magma intruded before, during, and after these 

granites, and the gabbro-diorite unit injected multiple 

times into the Cadillac Mountain magma chamber 

(Wiebe 1994; Wiebe et al. 1997b). Heat from the 

emplacement of the Cadillac Mountain intrusive 

complex hardened the Bar Harbor Formation into metasedimentary rocks. 

The Cranberry Island Series may represent the extrusive 

equivalent of the Cadillac Mountain intrusive complex. 

Debate continues regarding the tectonic setting for the 

Cranberry Island Series, with some geologists proposing 

a compressional origin while others suggesting crustal 

extension. Currently, geochemical and outcrop data 

support an origin involving an extensional tectonic 

setting (Seaman and Wobus 1995; Wiebe et al. 1997; 

Seaman et al. 1999; Seaman 2000). In an active margin 

setting, magmatism associated with extension may occur 

in backarc basins (the region between a volcanic arc and 

the mainland), in association with transcurrent faulting, 

or with rifting of the coastal Maine volcanic belt from 

another continental margin (Hogan and Sinha 1989; 

Seaman et al. 1999; Seaman 2000)

The tectonic welding of Gondwana with Laurentia 

closed the Iapetus Ocean (fig. 29). Similar to the on-going 

collision between India and Asia, this continent-tocontinent collision in the Devonian resulted in an 

impressive Acadian mountain range. The Pennsylvanianto-Permian Alleghanian Orogeny brought closure to the 

Rheic Ocean and established the Southern Appalachian 

and Ouachita mountains. Gondwana finished colliding 

with Laurentia and together, they formed the 

supercontinent, Pangaea (fig. 30).

Mesozoic Era (251 to 65.5 million years ago)

Over 300 million years of erosion following the Devonian 

left little record to decipher prior to the Pleistocene. 

Approximately 200 million years ago, (fig. 26), the 

impinging plates relaxed and Pangaea began to rift apart. 

Plate separation produced Triassic and Jurassic rift 

basins, including one under the Bay of Fundy about 240 

km (150 mi) northeast of Mount Desert Island (Bradley 

1997; Harris et al. 1997; Kiver and Harris 1999). By the 

Jurassic, plates had separated enough to open the North 

Atlantic. The Atlantic Ocean continues to widen at 

approximately 2.5 cm (1 in) per year (Gilman et al. 1988). 

In general, the eastern landmass detached along zones of 

weakness, primarily along old fault planes. Separation 

left behind pieces of the microplates. For example, the 

Meguma terrane (Nova Scotia) was left behind when 

North Africa drifted away from North America (Bradley 

1997). Similarly, rocks once contiguous with Scotland 

remain in Maine and Quebec. 

With the end of the Alleghanian Orogeny, the opening of 

the Atlantic Ocean, and the creation of the mid-Atlantic 

Ridge system, the eastern seaboard of North America 

became a passive tectonic margin on the trailing edge of 

the North American plate. Extensive erosion wore away 

the mountain peaks and eventually exposed the igneous 

intrusions that had originally cooled several kilometers 

below Earth’s surface.

Cenozoic Era (the past 65.5 million years)

Paleogene and Neogene (Tertiary)

Erosion in the Paleogene and Neogene (Tertiary) (fig. 26) 

may have created a landscape where resistant, deepseated rocks such as those in the Mount Desert Range 

stood high above the surrounding landscape. The term 

for such a rock island surrounded by low country is 

monadnock, which is Algonquin for “a mountain that 

stands alone.” Uplift during the Tertiary rejuvenated 

streams, which deepened valleys. Valleys were aligned in 

a north-to-south direction, parallel to the main, vertical 

fractures. 

Approximately 2.6 million years ago, the Mount Desert 

area probably formed an east-to-west trending peninsula 

attached to the mainland (Gilman et al. 1988; Harris et al. 

1997; Kiver and Harris 1999). As erosion removed the 

overlying rock that buried the massive granites, the 

confining pressure decreased, and fractures developed 

that paralleled the rock surface in a process known as 

exfoliation. By the end of the Neogene, the stage was set 

for the continental glaciers that would put the final 

touches on the landscape that forms today’s Acadia 

National Park.
ACAD Geologic Resources Inventory Report 45

Pleistocene Glaciation

Preglacial topography strongly influenced glacial flow. 

Valleys deepened and widened, soil and loose debris was 

relocated, and eventually continental ice overtopped the 

highest mountains in New England. In Acadia National 

Park, the Wisconsin glaciation, the last period of ice 

advance, destroyed most of the evidence of older 

glaciations (fig. 31). During times of maximum glaciation, 

glaciers locked up such vast amounts of water that sea 

level fell by as much as 100 m (330 ft) (Gilman et al. 1988; 

Kiver and Harris 1999). When the ice melted during 

interglacial episodes, outwash and glacial lake sediments 

filled lowlands. Retreating glaciers left behind local 

deposits of glacial till and glacial erratics. 

On Mount Desert Island, an advancing ice lobe scoured a 

particularly deep trough that is now occupied by Somes 

Sound. Other ice lobes carved the U-shaped, elongate 

valleys that are filled today by Jordan Pond, Eagle Lake, 

Echo Lake, Long Pond, and Seal Cove Pond. Ice 

continued to thicken on Mount Desert Island so that by 

21,000 years ago, glaciers covered the entire island, 

including Cadillac Mountain. Glacial plucking removed 

fractured bedrock from the hillsides. Abrasion and 

plucking began to shape the present landscape.

About 18,000 years ago, glaciers began thinning and 

melting to the extent that more ice melted than was being 

replenished. Between 14,000 years and 13,000 years 

before present, the ice-margin retreated approximately 

20 km (12 mi) (Kaplan and Borns 1994). The relatively 

slow, overall rate of approximately 20 to 30 m (66 to 98 

ft) per year was accompanied by minor ice-margin readvances and numerous times when relative sea level did 

not fluctuate greatly. By 13,000 to 14,000 years ago, the 

rocks of Mount Desert Island began to be exposed. 

Sargent Mountain, which lies south of the higher 

Cadillac Mountain, emerged as the first visible landform 

above the massive glacial ice in the Acadia National Park 

region. 

Global sea level rose as water returned to the ocean. 

Eventually, rising sea level caused the seaward edge of 

the ice sheet to float and disintegrate into icebergs. As the 

glaciers melted, meltwater streams emerging from the toe 

of the glaciers deposited extensive outwash material. 

Deltas formed at the edge of the sea. Receding glaciers 

left behind mounds of glacial till. By 12,500 years ago, the 

continental glacier had receded from the area, leaving 

behind a tongue of ice in Jordan Pond valley. The ocean 

flooded the depressed land surface, and marine clay 

settled on the ocean floor. As the continental glaciers 

melted, sea level rose to approximately 60 m (200 ft) 

above its present level. 

Glacial till left behind by the receding ice formed a 

moraine at the southern end of Jordan Pond valley 

(Jordan Pond House is constructed on the Jordan Pond 

moraine). By 11,000 years ago, the ice had disappeared 

from Jordan Pond valley. Jordan Pond formed behind 

the natural dam created by the southern moraine. Sea 

level dropped and the delta that had formed south of 

Jordan Pond began to emerge (Gilman et al. 1988).

Holocene (Post-Glacial) History

Over the past 14,000 years, the coast of Maine and the 

inner continental shelf record two marine transgressions 

(relative sea level rise) separated by a regression (relative 

sea level fall) (Belknap et al. 1987; Barnhardt et al. 1995). 

Initially, the sea transgressed across the depressed crust 

following the retreating ice (Kaplan and Borns 1994). 

Crustal rebound halted this transgression approximately 

13,000 years ago (Barnhardt et al. 1995). Sea level fell 

rapidly, passing the present coast by approximately 

11,500 years ago (Anderson et al. 1990; Barnhardt et al. 

1995). Relative sea-level fluctuations in the Gulf of Maine 

and Atlantic Canada vary widely, but in Maine, the shortlived, relative sea-level lowstand reached 55 m (180 ft)

below the current shoreline at 10,500 to 11,000 years 

before present (Barnhardt et al. 1995). Regression led to 

a reworked littoral zone and deep fluvial valleys cut into 

the inner continental shelf (Belknap and Kelley 1993). 

These valleys often connect to present estuaries and 

embayments, or they lie just offshore of rivers.

Sea level rose rapidly to 20 m (66 ft) below modern sea 

level approximately 9,000 years ago and then rose slowly 

for another 2,000 years. By 6,000 years before present, 

sea level had risen to -15 m (-49 ft) and continues to rise 

slowly in the late Holocene (Belknap and Kelley 1993). 

Modern beach deposits are being created and the 

relentless erosive power of the sea continues to modify 

the shoreline. 

Acadia National Park preserves one of the premier places 

in the world to observe evidence of such dramatic crustal 

rebound and sea level changes. For example, the paleosea stacks, paleo-sea caves, and paleo-thunderholes that 

are exposed along Gorham Mountain Trail provide 

evidence of the post-glacial shoreline. Such features as 

moraines, glacial erratic, whalebacks, U-shaped valleys, 

glacial polish, and striations provide silent reminders of 

the dynamic and formidable effects of past glacial 

activity. 

Today, Acadia National Park is dominantly an erosional 

landscape. Notches in bedrock cliffs and sea caves form 

from wave action along the high tide mark. Differential 

erosion causes less resistant rocks such as diabase and 

schist to erode more easily than granite, forming such 

features as Thunder Hole and Anemone Sea Cave. 

Acadia National Park preserves a magnificent outdoor 

laboratory where geological processes of the past may be 

studied along with similar terrestrial and marine 

processes that are shaping the current landscape.
46 NPS Geologic Resources Division 

Figure 26. Geologic timescale. Included are major life history and tectonic events occurring on the North American continent. Red lines 

indicate major unconformities between eras. Radiometric ages shown are in millions of years (Ma). Compass directions in parentheses 

indicate the regional location of individual geologic events. Adapted from the U.S. Geological Survey, http://pubs.usgs.gov/fs/2007/3015/

with additional information from the International Commission on Stratigraphy. http://www.stratigraphy.org/view.php?id=25.
ACAD Geologic Resources Inventory Report 47

Figure 27. Middle Cambrian paleogeographic map. Approximately 510 million years ago, a volcanic arc (VA) and micro-continents separated 

the Iapetus Ocean and Laurentia from the Rheic Ocean and Gondwana. The black lines represent approximate locations of paleo-subduction 

zones (dashed lines are possible paleo-transform faults). At this time, the Baltic landmass was closing on Laurentia. The yellow star (not to 

scale) marks the approximate location of today’s Acadia National Park. Modified from the Middle Cambrian map of Ron Blakey (Northern 

Arizona University), available online at: http://jan.ucc.nau.edu/rcb7/namC510.jpg, (accessed January 9, 2010).

Iapetus Ocean

Rheic Ocean

Volcanic 

Arc

Gondwana

Baltic

Laurentia

(proto-North America)

510 million years ago
48 NPS Geologic Resources Division 

Figure 28. Schematic illustration of the Taconic Orogeny. The volcanic island chain that lay between the micro-continents and Laurentia 

eventually collided with the eastern seaboard as the Iapetus Ocean closed. Illustration courtesy of the U.S. Geological Survey, available at: 

http://vulcan.wr.usgs.gov/LivingWith/VolcanicPast/Notes/taconic_orogeny.html, (accessed January 9, 2010).
ACAD Geologic Resources Inventory Report 49

Figure 29. Middle Devonian paleogeographic map. Approximately 385 million years ago, during the Acadian Orogeny, Avalonia and other 

micro-plates were accreting to the eastern seaboard of Laurentia. The suture zone of Baltica to Laurentia is marked by a Canadian mountain 

range. The east-to-west closure of Laurentia with Gondwana was closing the Rheic Ocean. The black lines represent approximate locations of 

paleo-subduction zones. By this time, the western margin of Laurentia had also become an active tectonic margin. Note that the global 

landmasses were converging near the equator. The yellow arrows suggest the direction of movement of the lithospheric plates; the white 

arrow indicates the direction of north in the Middle Devonian. The white line is the paleo-Equator. The yellow star (not to scale) marks the 

approximate location of today’s Acadia National Park. Modified from the Middle Devonian map of Ron Blakey (Northern Arizona University), 

available online at: http://jan.ucc.nau.edu/rcb7/namD385.jpg, (accessed January 9, 2010).

Laurentia

(proto-North America)

Gondwana

Rheic 

Ocean

Baltica

385 million years ago
50 NPS Geologic Resources Division 

Figure 30. Late Permian paleogeographic map. Approximately 260 million years ago, Gondwana and Laurentia collided to form the 

supercontinent, Pangaea. Collisions throughout the Paleozoic had created the Appalachian Orogen, which stretched from Canada to west 

Texas. The black lines represent approximate locations of paleo-subduction zones. The yellow star (not to scale) approximates the location of 

today’s Acadia National Park. Modified from the Late Permian map of Ron Blakey (Northern Arizona University), available online at: 

http://jan.ucc.nau.edu/rcb7/namP260.jpg, (accessed January 9, 2010).

PANGAEA

(Laurentia)

(Gondwana)

260 million years ago
ACAD Geologic Resources Inventory Report 51

Figure 31. Quaternary paleogeographic map of North America. Approximately 126,000 years ago, during the Pleistocene ice age, continental 

glaciers flowed southward and covered the upper Midwest and New England. The yellow star is the approximate location of today’s Acadia 

National Park (not to scale). Modified from the Quaternary map of Ron Blakey (Northern Arizona University), available online at: 

http://jan.ucc.nau.edu/rcb7/namQ.jpg, (accessed January 9, 2010).

126,000 years ago
52 NPS Geologic Resources Division 

Glossary

This glossary contains brief definitions of technical geologic terms used in this report. Not all 

geologic terms used are referenced. For more detailed definitions or to find terms not listed

here please visit: http://geomaps.wr.usgs.gov/parks/misc/glossarya.html. Definitions are 

based on those in the American Geological Institute Glossary of Geology (fifth edition; 2005).

absolute age. The geologic age of a fossil, rock, feature, 

or event in years; commonly refers to radiometrically 

determined ages.

active margin. A tectonically active margin where 

lithospheric plates come together (convergent 

boundary), pull apart (divergent boundary) or slide 

past one another (transform boundary). Typically 

associated with earthquakes and, in the case of 

convergent and divergent boundaries, volcanism. 

Compare to “passive margin.”

alluvium. Stream-deposited sediment.

andesite. Fine-grained volcanic rock commonly 

associated with subduction zone volcanoes. Named 

for the subduction zone volcanoes of the Andes 

Mountains.

aquifer. A rock or sedimentary unit that is sufficiently 

porous that it has a capacity to hold water, sufficiently 

permeable to allow water to move through it, and 

currently saturated to some level.

ash (volcanic). Fine material ejected from a volcano (also 

see “tuff”).

asthenosphere. Earth’s relatively weak layer or shell 

below the rigid lithosphere.

basalt. A dark-colored, often low-viscosity, extrusive 

igneous rock.

basin (sedimentary). Any depression, from continental to 

local scales, into which sediments are deposited.

batholith. A massive, discordant pluton, larger than 100 

km2 (40 mi2

), and often formed from multiple 

intrusions of magma.

beach. A gently sloping shoreline covered with sediment, 

commonly formed by the action of waves and tides.

beach face. The section of the beach exposed to direct 

wave and/or tidal action.

bed. The smallest sedimentary strata unit, commonly 

ranging in thickness from one centimeter to a meter or 

two and distinguishable from beds above and below.

bedding. Depositional layering or stratification of 

sediments.

bedrock. A general term for the rock that underlies soil 

or other unconsolidated, surficial material.

biotite. A widely distributed and important rock-forming 

mineral of the mica group. Forms thin, flat sheets.

breccia. A coarse-grained, generally unsorted 

sedimentary rock consisting of cemented angular 

clasts greater than 2 mm (0.08 in).

caldera. A large bowl- or cone-shaped depression at the 

summit of a volcano. Formed by explosion or collapse.

carbonate. A mineral that has CO3

-2 as its essential 

component (e.g., calcite and aragonite).

carbonate rock. A rock consisting chiefly of carbonate 

minerals (e.g., limestone, dolomite, or carbonatite).

cauldron subsidence. The process in which a more or less 

cylindrical block of rock above a magma chamber 

collapses into the space left as the magma moves 

toward the surface.

cementation. Chemical precipitation of material into 

pores between grains that bind the grains into rock.

chemical sediment. A sediment precipitated directly from 

solution (also called nonclastic).

clast. An individual grain or rock fragment in a 

sedimentary rock, produced by the physical 

disintegration of a larger rock mass.

clastic. Describes rock or sediment made of fragments of 

pre-existing rocks (clasts).

coastline. A broad zone of land and water extending 

indefinitely both landward and seaward from a 

shoreline.

concordant. Strata with contacts parallel to the 

orientation of adjacent strata.

conglomerate. A coarse-grained, generally unsorted, 

sedimentary rock consisting of cemented, rounded 

clasts larger than 2 mm (0.08 in).

continental crust. Crustal rocks rich in silica and alumina 

that underlie the continents; ranging in thickness from 

35 km (22 mi) to 60 km (37 mi) under mountain ranges.

continental rise. Gently sloping region from the foot of 

the continental slope to the deep ocean abyssal plain; it 

generally has smooth topography but may have 

submarine canyons.

continental shelf. The shallowly submerged part of a 

continental margin extending from the shoreline to the 

continental slope with water depths less than 200 m 

(660 ft).

continental shield. A continental block of Earth’s crust 

that has remained relatively stable over a long period 

of time and has undergone minor warping compared 

to the intense deformation of bordering crust.

continental slope. The relatively steep slope from the 

outer edge of the continental shelf down to the more 

gently sloping ocean depths of the continental rise or 

abyssal plain.

convergent boundary. A plate boundary where two 

tectonic plates are colliding.

country rock. The rock surrounding an igneous intrusion 

or pluton. Also, the rock enclosing or traversed by a 

mineral deposit.

craton. The relatively old and geologically stable interior 

of a continent (also see “continental shield”).

cross section. A graphical interpretation of geology, 

structure, and/or stratigraphy in the third (vertical) 

dimension based on mapped and measured geological 

extents and attitudes depicted in a vertically oriented 

plane.
ACAD Geologic Resources Inventory Report 53

crust. Earth’s outermost compositional shell, 10 to 40 km 

(6 to 25 mi) thick, consisting predominantly of 

relatively low-density silicate minerals (also see 

“oceanic crust” and “continental crust”).

crystalline. Describes a regular, orderly, repeating 

geometric structural arrangement of atoms.

crystal structure. The orderly and repeated arrangement 

of atoms in a crystal.

crystal tuff. A tuff that consists chiefly of crystals and 

fragments of crystals.

dacite. A fine-grained extrusive igneous rock similar to 

andesite but with less calcium-plagioclase minerals and 

more quartz.

deformation. A general term for the processes of faulting, 

folding, and shearing of rocks as a result of various 

Earth forces such as compression (pushing together) 

and extension (pulling apart).

delta. A sediment wedge deposited where a stream flows 

into a lake or sea.

dike. A narrow igneous intrusion that cuts across 

bedding planes or other geologic structures.

diorite. A type of plutonic igneous rock. It is the 

approximate intrusive equivalent of andesite.

dip. The angle between a bed or other geologic surface 

and horizontal.

dip-slip fault. A fault with measurable offset where the 

relative movement is parallel to the dip of the fault.

discordant. Describes contacts between strata that cut 

across or are set at an angle to the orientation of 

adjacent rocks.

divergent boundary. An active boundary where tectonic 

plates are moving apart (e.g., a spreading ridge or 

continental rift zone).

dune. A low mound or ridge of sediment, usually sand, 

deposited by wind. 

estuary. The seaward end or tidal mouth of a river where 

freshwater and seawater mix; many estuaries are 

drowned river valleys caused by sea-level rise 

(transgression) or coastal subsidence.

exfoliation. The breakup, spalling, peeling, or flaking of 

layers or concentric sheets from an exposed rock mass 

caused by differential stresses due to thermal changes 

or a reduction in pressure when overlying rocks erode 

away.

extrusive. Describes molten (igneous) material that has 

erupted onto Earth’s surface.

fault. A break in rock along which relative movement has 

occurred between the two sides.

feldspar. A group of abundant (more than 60% of Earth’s 

crust), light-colored to translucent silicate minerals 

found in all types of rocks. Usually white and gray to 

pink. May contain potassium, sodium, calcium, 

barium, rubidium, and strontium along with 

aluminum, silica, and oxygen.

felsic. Describes an igneous rock having abundant lightcolored minerals such as quartz, feldspars, or 

muscovite. Compare to “mafic.”

felsite. A general term for any light-colored, fine-grained 

extrusive rock composed chiefly of quartz and 

feldspar.

fjard. A small, narrow, irregular inlet or bay, typically 

formed by submergence of a glacial valley excavated in 

a lowland along the margin of a flat rocky coast. A fjard 

is shorter, shallower, and broader in profile than a 

fjord.

footwall. The mass of rock beneath a fault surface (also 

see “hanging wall”).

formation. Fundamental rock-stratigraphic unit that is 

mappable, lithologically distinct from adjoining strata, 

and has definable upper and lower contacts.

fracture. Irregular breakage of a mineral; also any break 

in a rock (e.g., crack, joint, or fault).

gabbro. A group of dark-colored, intrusive igneous 

rocks. The intrusive equivalent of basalt. 

groundmass. The material between the large crystals in a 

porphyritic igneous rock. Can also refer to the matrix 

of a sedimentary rock.

hanging wall. The mass of rock above a fault surface 

(also see “footwall”).

hornblende. The most common mineral of the 

amphibole group. Hornblende is commonly black and 

occurs in distinct crystals or in columnar, fibrous, or 

granular forms.

hornfels. A fine-grained rock composed of a mosaic of 

grains that are the same size in each dimension without 

preferred orientation. Typically formed by contact 

metamorphism, which occurs near the contact with an 

intrusion of molten material.

igneous. Refers to a rock or mineral that originated from 

molten material; one of the three main classes of 

rocks—igneous, metamorphic, and sedimentary.

intrusion. A body of igneous rock that invades (pushes 

into) older rock. The invading rock may be a plastic 

solid or magma.

island arc. A line or arc of volcanic islands formed over 

and parallel to a subduction zone.

isostacy. The condition of equilibrium, comparable to 

floating, of the units of the lithosphere above the 

asthenosphere. Crustal loading (commonly by large ice 

sheets) leads to isostatic depression or downwarping; 

removal of the load leads to isostatic uplift or 

upwarping.

joint. A break in rock without relative movement of 

rocks on either side of the fracture surface.

keratophyres. A term applied to salic (silicon or 

aluminum-rich minerals) or hypabyssal rocks.

lacustrine. Pertaining to, produced by, or inhabiting a 

lake or lakes.

lamination. Very thin, parallel layers.

landslide. Any process or landform resulting from rapid, 

gravity-driven mass movement.

lava. Still-molten or solidified magma that has been 

extruded onto Earth’s surface though a volcano or 

fissure.

lithic tuff. A dense deposit of volcanic ash in which the 

fragments are composed of previously formed rocks 

that first solidify in the vent and are then blown out.

lithification. The conversion of sediment into solid rock.

lithosphere. The relatively rigid outmost shell of Earth’s 

structure, 50 to 100 km (31 to 62 miles) thick, that 

encompasses the crust and uppermost mantle.

littoral zone. The benthic ocean environment or depth 

zone between high water and low water.

mafic. Describes dark-colored rock, magma, or minerals 

rich in magnesium and iron. Compare to “felsic.”
54 NPS Geologic Resources Division 

magma. Molten rock beneath Earth’s surface capable of 

intrusion and extrusion. 

mantle. The zone of Earth’s interior between the crust 

and core.

mass wasting. A general term for the downslope 

movement of soil and rock material under the direct 

influence of gravity.

matrix. The fine grained material between coarse (larger) 

grains in igneous rocks or poorly sorted clastic 

sediments or rocks. Also refers to rock or sediment in 

which a fossil is embedded.

mechanical weathering. The physical breakup of rocks 

without change in composition. Synonymous with 

“physical weathering.”

member. A lithostratigraphic unit with definable 

contacts; a member subdivides a formation.

meta–. A prefix used with the name of a sedimentary or 

igneous rock, indicating that the rock has been 

metamorphosed.

metamorphic. Describes the process of metamorphism 

or its results. One of the three main classes of rocks—

igneous, metamorphic, and sedimentary.

metamorphism. Literally, a change in form. 

Metamorphism occurs in rocks through mineral 

alteration, formation, and/or recrystallization from 

increased heat and/or pressure.

mid-ocean ridge. The continuous, generally submarine 

and volcanically active mountain range that marks the 

divergent tectonic margin(s) in Earth’s oceans.

mineral. A naturally occurring, inorganic crystalline solid 

with a definite chemical composition or compositional 

range.

normal fault. A dip-slip fault in which the hanging wall 

moves down relative to the footwall.

obduction. The process by which the crust is thickened 

by thrust faulting at a convergent margin.

oceanic crust. Earth’s crust formed at spreading ridges 

that underlies the ocean basins. Oceanic crust is 6 to 7 

km (3 to 4 miles) thick and generally of basaltic 

composition.

orogeny. A mountain-building event.

outcrop. Any part of a rock mass or formation that is 

exposed or “crops out” at Earth’s surface.

outwash. Glacial sediment transported and deposited by 

meltwater streams.

paleogeography. The study, description, and 

reconstruction of the physical landscape from past 

geologic periods.

Pangaea. A theoretical, single supercontinent that 

existed during the Permian and Triassic periods.

parent material. Geologic material from which soils 

form.

passive margin. A margin where no plate-scale tectonism 

is taking place; plates are not converging, diverging, or 

sliding past one another. An example is the east coast 

of North America (compare to “active margin”).

perthite. A variety of feldspar consisting of parallel or 

subparallel intergrowths in which the potassium-rich 

phase (usually microcline) appears to be the host from 

which the sodium-rich phase (usually albite) separated 

at a critical temperature.

plastic. Capable of being deformed permanently without 

rupture.

plate tectonics. The concept that the lithosphere is 

broken up into a series of rigid plates that move over 

Earth’s surface above a more fluid asthenosphere.

pluton (plutonic). A body of intrusive igneous rock that 

crystallized at some depth beneath Earth’s surface.

porphyry. An igneous rock consisting of abundant coarse 

crystals in a fine-grained matrix.

potassium feldspar. A feldspar mineral rich in potassium 

(e.g., orthoclase, microcline, sanidine, adularia).

pyroclastic. Describes clastic rock material formed by 

volcanic explosion or aerial expulsion from a volcanic 

vent; also pertaining to rock texture of explosive 

origin. In the plural, the term is used as a noun.

radioactivity. The spontaneous decay or breakdown of 

unstable atomic nuclei.

radiometric age. An age expressed in years and 

calculated from the quantitative determination of 

radioactive elements and their decay products. 

regression. A long-term seaward retreat of the shoreline 

or relative fall of sea level.

relative dating. Determining the chronological 

placement of rocks, events, or fossils with respect to 

the geologic time scale and without reference to their

numerical age.

reverse fault. A contractional high-angle (greater than 

45°) dip-slip fault in which the hanging wall moves up 

relative to the footwall (also see “thrust fault”).

rhyolite. A group of extrusive volcanic rocks, typically 

porphyritic and commonly exhibiting flow texture, 

with phenocrysts of quartz and alkali feldspar in a 

glassy to cryptocrystalline groundmass. The finegrained extrusive equivalent of granite.

roche moutonnée. An elongate, eroded ridge or knob of 

bedrock carved by a glacier parallel to the direction of 

motion with gentle upstream and steep downstream 

surfaces.

rock. A solid, cohesive aggregate of one or more minerals.

sand. A clastic particle smaller than a granule and larger 

than a silt grain, having a diameter in the range of 1/16 

mm (0.0025 in) to 2 mm (0.08 in).

sandstone. Clastic sedimentary rock of predominantly 

sand-sized grains.

seafloor spreading. The process by which tectonic plates 

pull apart and new lithosphere is created at oceanic 

ridges.

sediment. An eroded and deposited, unconsolidated 

accumulation of rock and mineral fragments.

sedimentary rock. A consolidated and lithified rock 

consisting of clastic and/or chemical sediment(s). One 

of the three main classes of rocks—igneous, 

metamorphic, and sedimentary.

shale. A clastic sedimentary rock made of clay-sized 

particles that exhibit parallel splitting properties.

silicate. A compound whose crystal structure contains 

the SiO4 tetrahedra.

sill. An igneous intrusion that is of the same orientation 

as the surrounding rock.

silt. Clastic sedimentary material intermediate in size 

between fine-grained sand and coarse clay (1/256 to 

1/16 mm [0.00015 to 0.002 in]).

siltstone. A variably lithified sedimentary rock composed 

of silt-sized grains.
ACAD Geologic Resources Inventory Report 55

slump. A generally large, coherent mass movement with a 

concave-up failure surface and subsequent backward 

rotation relative to the slope.

stock. An igneous intrusion exposed at the surface; less 

than 100 km2 (40 mi2) in size. Compare to “pluton.”

strata. Tabular or sheet-like masses or distinct layers of 

rock.

stratigraphy. The geologic study of the origin, 

occurrence, distribution, classification, correlation, 

and age of rock layers, especially sedimentary rocks.

stream. Any body of water moving under gravity flow in 

a clearly confined channel.

strike. The compass direction of the line of intersection 

of an inclined surface with a horizontal plane.

strike-slip fault. A fault with measurable offset where the 

relative movement is parallel to the strike of the fault. 

Said to be “sinistral” (left-lateral) if relative motion of 

the block opposite the observer appears to be to the 

left. “Dextral” (right-lateral) describes relative motion 

to the right.

structure. The attitude and relative positions of the rock 

masses of an area resulting from such processes as 

faulting, folding, and igneous intrusions.

subduction zone. A convergent plate boundary where 

oceanic lithosphere descends beneath a continental or 

oceanic plate and is carried down into the mantle.

subsidence. The gradual sinking or depression of part of 

Earth’s surface.

suture. The linear zone where two continental 

landmasses become joined via obduction.

tectonic. Relating to large-scale movement and 

deformation of Earth’s crust.

terrane. A large region or group of rocks with similar 

geology, age, or structural style.

terrestrial. Relating to land, Earth, or its inhabitants.

theory. A hypothesis that has been rigorously tested 

against further observations or experiments to become 

a generally accepted tenet of science.

thrust fault. A contractional dip-slip fault with a 

shallowly dipping fault surface (less than 45°

) where 

the hanging wall moves up and over relative to the 

footwall.

topography. The general morphology of Earth’s surface, 

including relief and locations of natural and 

anthropogenic features.

transgression. Landward migration of the sea as a result 

of a relative rise in sea level.

trend. The direction or azimuth of elongation of a linear 

geologic feature.

tuff. Generally fine-grained, igneous rock formed of 

consolidated volcanic ash.

type locality. The geographic location where a 

stratigraphic unit (or fossil) is well displayed, formally 

defined, and derives its name. The place of original 

description.

unconformity. An erosional or non-depositional surface 

bounded on one or both sides by sedimentary strata.

An unconformity marks a period of missing time.

uplift. A structurally high area in the crust, produced by 

movement that raises the rocks.

volcanic. Describes anything related to volcanoes. Can 

refer to igneous rock crystallized at or near Earth’s 

surface (e.g., lava).

volcanic arc. A commonly curved, linear, zone of 

volcanoes above a subduction zone. 

weathering. The physical, chemical, and biological 

processes by which rock is broken down.
56 NPS Geologic Resources Division 

Literature Cited

This section lists references cited in this report. A more complete geologic bibliography is 

available from the National Park Service Geologic Resources Division.

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2010.

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2010.

National Park Service. 2009c. Park news: High surf 

washes visitor into ocean at Acadia National Park. 

Acadia National Park website, Bar Harbor, Maine, 

USA. (http://www.nps.gov/acad/parknews/high-surfwashes-visitor-into-ocean.htm). Accessed 28 July 

2010.

National Oceanic and Atmospheric Administration. 

2007. The Patriot’s Day Storm of 2007. National 

Weather Service Forecast Office, Gray, Maine, USA. 

(http://www.erh.noaa.gov/gyx/patriots_day_storm_20

07.htm). Accessed 28 July 2010.

National Oceanic and Admospheric Administration 

Satellite and Information Service. 2008. The perfect 

storm: October 1991. National Climatic Data Center, 

Washington, D.C. (http://www.ncdc.noaa.gov/oa/

satellite/satelliteseye/cyclones/pfctstorm91/pfctstorm.

html). Accessed 28 July 2010.
58 NPS Geologic Resources Division 

New England Climate Coalition. 2003. Global warming 

in New England states. 

(http://www.newenglandclimate.org/

effectsbystate.htm). Accessed 28 July 2010.

Petraitis, P. S., S. R. Fegley, and B. F. Beal. 2002. 

Ecological assessment of the Anemone Cave in Acadia 

National Park. Acadia National Park files.

Reusch, D. N. 2002. The Ellsworth Schist, Maine: 

Acadian-telescoped rift sequence or Penobscottian 

accretionary complex? Geological Society of America, 

Northeastern Section, Abstracts with Programs 34 (1): 

76.

Reusch, D. N. and K. L. Rust. 2001. Post-rifting fate of 

the peri-Gondwanan Ellsworth Schist, Newbury Neck, 

Maine. Geological Society of America, Northeastern 

Section, Abstracts with Programs 33 (1): 79.

Rothe, R. 1995. Acadia: The story behind the scenery. KC 

Publications, Las Vegas, Nevada, USA.

Seaman, S. J. 2000. Physical volcanology and 

petrogenesis of the Late Silurian Cranberry Island 

series, coastal Maine. Pages 23-37 in M. G. Yates, R. R. 

Lux, and J. T. Kelley, editors. Guidebook for field trips 

in coastal and east-central Maine. University of Maine, 

Orono, Maine, USA.

Seaman, S. J. and R. A. Wobus. 1995. The Cranberry 

Island Series of coastal Maine: Bimodal volcanism on 

pre-Acadian Avalon. International Union of Geodesy 

and Geophysics Abstracts 21: 439.

Seaman, S. J., R. A. Wobus, R. W. Wiebe, N. Lubick, and 

S. A. Bowring. 1995. Volcanic expression of bimodal 

magmatism: The Cranberry Island – Cadillac 

Mountain Complex, coastal Maine. Journal of 

Geology 103 (3): 301-311.

Seaman, S. J., E. E. Scherer, R. A. Wobus, J. H. Zimmer, 

and J. G. Sales. 1999. Late Silurian volcanism in coastal 

Maine: The Cranberry Island series. Geological 

Society of America Bulletin 111 (5): 686-708.

Schuh, K. J. 1994. Petrology of the Somesville granite, 

Mount Desert Island, Maine. Geological Society of 

America, Northeastern Section, Abstracts with 

Programs 26 (3): 71.

Schulz, K. J., D. B. Stewart, and R. D. Tucker. 2003. 

Geochemistry of the Cambrian Ellsworth Schist and 

Castine Volcanics, Penobscot Bay area, Maine: 

Implications for paleotectonic setting. Geological 

Society of America, Northeastern Section, Abstracts 

with Programs 35 (3): 78.

Schulz, K. J., D. B. Stewart, R. D. Tucker, J. C. Pollock, 

and R. Ayuso. 2008. The Ellsworth Terrane, coastal 

Maine; geochronology, geochemistry, and Nd-Pb 

isotopic composition: Implications for the rifting of 

Ganderia. Geological Society of America Bulletin 120: 

1134-1158.

Suppe, J. 1985. Principles of Structural Geology. 

Prentice-Hall, Inc., Englewood Cliffs, New Jersey, 

USA.

Symchych, E. M. 1994. Evidence of periodic basaltic 

injections into the crystalline mush of the Cadillac 

Mountain granite magma chamber, Mount Desert 

Island, Maine. Geological Society of America, 

Northeastern Section, Abstracts with Programs 26 (3): 

75.

Thieler, E. R. and E. S. Hammar-Klose. 1999. National 

assessment of coastal vulnerability to sea-level rise: 

Preliminary results for the U.S. Atlantic coast. OpenFile Report 99-593. U.S. Geological Survey, Reston, 

Virginia, USA. (http://pubs.usgs.gov/of/1999/of99-

593/index.html). Accessessed February 19, 2010.

Titus, J. G. and C. Richman. 2001. Maps of lands 

vulnerable to sea level rise: Modeled elevations along 

the U.S. Atlantic and Gulf coasts. Climate Research 18 

(3): 205-228. (http://www.int-res.com/articles/

cr/18/c018p205.pdf). Accessed 29 July 2010.

Tweet, J. S., V. L. Santucci, and J. P. Kenworthy. 2010. 

Paleontological resource inventory and monitoring: 

Northeast Temperate Network. Natural Resource 

Technical Report NPS/NRPC/NRTR—2010/326. 

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U.S. Geological Survey. 2006. Maine earthquake lowers 

ground water. U.S. Geological Survey Newsroom, 

Reston, Virginia, USA. (http://www.usgs.gov/

newsroom/article.asp?ID=1562). Accessed 28 July 

2010.

U.S. Geological Survey. 2009. Maine: Earthquake history. 

U.S. Geological Survey, Earthquake Hazards Program, 

Reston, Virginia, USA. (http://earthquakes.usgs.gov/

earthquakes/states/maine/history.php). Accessed 28 

July 2010.

Van Staal, C. R. 2007. Pre-Carboniferous tectonic 

evolution and metallogeny of the Canadian 

Appalachians. Pages 793-818 in W. D. Goodfellow, 

editor. Mineral deposits of Canada: A synthesis of 

major deposit-types, district metallogeny, the 

evolution of geological provinces, and exploration 

methods. Geological Association of Canada, Special 

Publication 5, St. John’s, Newfoundland, Canada.
ACAD Geologic Resources Inventory Report 59

Van Staal, C. R., S. M. Barr, L. R. Fyffe, V. McNicoll, J. C. 

Pollock, D. N. Reusch, M. Thomas, P. ValverdeVacquero, and J. Whalen. 2002. Ganderia – an 

important peri-Gondwanan terrane in the northern 

Appalachians. Geological Society of America, 

Northeastern Section, Abstracts with Programs 34 (1): 

28.

Vollmer, F. W. 2009. Relationship between exfoliation 

dome geometry and topography on Cadillac 

Mountain, Mount Desert Island, Maine. Geological 

Society of America, Northeastern Section, Abstracts 

with Programs 41 (3): 14.

Waterman, M. 2008. Harnessing the Gulf’s winds, tides 

for reliable energy independence. Gulf of Maine Times

12 (3). (http://www.gulfofmaine.org/times/

fallwinter2008/energy.php). Accessed 28 July 2010).

Wiebe, R. A. 1994. Silicic magma chambers as traps for 

basaltic magmas: The Cadillac Mountain intrusive 

complex, Mount Desert Island, Maine. Journal of 

Geology 102: 423-437.

Wiebe, R. A., J. B. Holden, M. L. Coombs, R. A. Wobus, 

K. J. Schuh, and B. P. Plummer. 1997a. The Cadillac 

Mountain intrusive complex, Maine: The role of 

shallow-level magma chamber processes in the 

generation of A-type granites. Pages 397-418 in A. K. 

Sinha, J. B. Whalen, and J. P. Hogan, editors, The 

nature of magmatism in the Appalachian Orogen. 

Geological Society of America Memoir 191, Boulder, 

Colorado, USA.

Wiebe, R. A., D. Smith, M. Sturm, E. M. King, and M. S. 

Seckler. 1997b. Enclaves in the Cadillac Mountain 

Granite (coastal Maine): Samples of hybrid magma

from the base of the chamber. Journal of Petrology 38 

(3): 393-423.

Wieczorek, G. F. and J. B. Snyder. 2009. Monitoring 

slope movements. Pages 245-271 in Geological 

Monitoring. Geological Society of America, Boulder, 

Colorado, USA.
60 NPS Geologic Resources Division 

Additional References

This section lists additional references, resources, and web sites that may be of use to 

resource managers. Web addresses are current as of August 2010.

Geology of National Park Service Areas

National Park Service Geologic Resources Division 

(Lakewood, Colorado). http://nature.nps.gov/geology/

NPS Geologic Resources Inventory. 

http://www.nature.nps.gov/geology/inventory/gre_pu

blications.cfm

U.S. Geological Survey Geology of National Parks 

(includes 3D photographs). 

http://3dparks.wr.usgs.gov/

Harris, A. G., E. Tuttle, and S. D. Tuttle. 2003. Geology of 

National Parks. Sixth Edition. Kendall/Hunt 

Publishing Co., Dubuque, Iowa, USA.

Kiver, E. P. and D. V. Harris. 1999. Geology of U.S. 

parklands. John Wiley and Sons, Inc., New York, New 

York, USA.

Lillie, R. J. 2005. Parks and Plates: The geology of our 

national parks, monuments, and seashores. W.W. 

Norton and Co., New York, New York, USA.

[Geared for interpreters].

NPS Geoscientist-in-the-parks (GIP) internship and 

guest scientist program. 

http://www.nature.nps.gov/geology/gip/index.cfm

Resource Management/Legislation Documents

NPS 2006 Management Policies (Chapter 4; Natural 

Resource Management): 

http://www.nps.gov/policy/mp/policies.html#_Toc157

232681

NPS-75: Natural Resource Inventory and Monitoring 

Guideline: 

http://www.nature.nps.gov/nps75/nps75.pdf.

NPS Natural Resource Management Reference Manual 

#77: http://www.nature.nps.gov/Rm77/

Geologic Monitoring Manual

R. Young and L. Norby, editors. Geological 

Monitoring. Geological Society of America, Boulder, 

Colorado.

[Website under development]. Contact the Geologic 

Resources Division to obtain a copy.

NPS Technical Information Center (Denver, repository 

for technical (TIC) documents): http://etic.nps.gov/

State Geological Survey Websites

Maine Geological Survey: 

http://www.maine.gov/doc/nrimc/mgs/mgs.htm

Association of American State Geologists: 

http://www.stategeologists.org/

Geological Societies

Geological Society of America: 

http://www.geosociety.org/

American Geological Institute: http://www.agiweb.org/

Bates, R. L. and J. A. Jackson, editors. American 

Geological Institute dictionary of geological terms (3rd 

Edition). Bantam Doubleday Dell Publishing Group, 

New York.

Unites States Geological Survey (USGS):

U.S. Geological Survey: http://www.usgs.gov/

U.S. Geological Survey National Geologic Map Database 

(NGMDB): http://ngmdb.usgs.gov/

U.S. Geological Survey Geologic Names Lexicon 

(GEOLEX; geologic unit nomenclature and summary): 

http://ngmdb.usgs.gov/Geolex/geolex_home.html

U.S. Geological Survey Geographic Names Information 

System (GNIS; search for place names and geographic 

features, and plot them on topographic maps or aerial 

photos): http://gnis.usgs.gov/

U.S. Geological Survey Seamless Server (download 

digital data, including imagery, elevation, boundaries): 

http://seamless.usgs.gov

U.S. Geological Survey Publications Warehouse (many 

USGS publications are available online): 

http://pubs.usgs.gov

U.S. Geological Survey, description of physiographic 

provinces: http://tapestry.usgs.gov/Default.html
ACAD Geologic Resources Inventory Report 61

Appendix A: Overview of Digital Geologic Data

The following page is an overview of the digital geologic data for Acadia National Park.

For a poster-size PDF of this overview and complete digital data, please see the included 

CD or visit the Geologic Resources Inventory publications web site: 

http://www.nature.nps.gov/geology/inventory/gre_publications.cfm.

ACAD Geologic Resources Inventory Report 63

Appendix B: Scoping Session Participants

The following is a list of participants from the GRI scoping session for Acadia National 

Park, held on June 9–10, 2008. The contact information and email addresses in this 

appendix may be outdated; please contact the Geologic Resources Division for current 

information. The scoping meeting summary was used as the foundation for this GRI 

report. The original scoping summary document is available on the GRI publications 

web site: http://www.nature.nps.gov/geology/inventory/gre_publications.cfm.

Name Affiliation Position Phone E-Mail

Anderson, Karen NPS-Acadia National 

Park GIS Specialist 207-288-8724 karen_b_anderson@nps.gov

Borrelli, Mark Texas A&M University GRD Coastal Geologist 303-969-2171 mark_borreli@partner.nps.gov

Berger, Sonya NPS – Acadia 

National Park Gorham District Interpreter 207-288-8803 sonya_berger@nps.gov

Graham, John Colorado State 

University Geologist, GRE Report Writer 970-225-6333 rockdoc250@comcast.net

Greco, Deanna NPS – Geologic 

Resources Division Reclamation Specialist 303-969-2351 deanna_greco@nps.gov

Heise, Bruce NPS – Geologic 

Resources Division Program Lead 303-969-2017 bruce_heise@nps.gov

Hybels, Georgia NPS – Geologic 

Resources Division GRE GIS Specialist 303-969-2173 georgia_hybels@nps.gov

Jacobi, Charlie NPS- Acadia National 

Park Recreation Specialist 207-288-8727 charlie_jacobie@nps.gov

Johnson, Beth NPS – Northeast 

Region Office I&M Regional Coordinator 401-874-7060 beth_johnson@nps.gov

Kelley, Joe University of Maine Chair, Department of Earth 

Science 207-581-2162 JTKelley@maine.edu

Koteas, Chris University of 

Massachusetts Grad Student –UMass 413-658-8187 ckoteas@geo.umass.edu

Manski, David NPS – Acadia 

National Park Chief, Resource Management 207-288-8720 david_manski@nps.gov

Marvinney, Bob Maine Geologic 

Survey State Geologist 207-287-2804 robert.g.marvinney@maine.gov

Ransmeier, Melanie NPS – Geologic 

Resources Division

GRE GIS Specialist/Report 

Coordinator 303-969-2315 melanie_ransmeier@nps.gov

Weddle, Tom Maine Geologic 

Survey Geologist 207-287-2801 thomas.k.weddle@maine.gov

Kirk Lurvey

NPS-Acadia National 

Park; Mount Desert 

Island High School

Interpreter and Science teacher 

at MDI High School klurvey@u98.k12.me.us 

The Department of the Interior protects and manages the nation’s natural resources and cultural heritage; provides scientific and other 

information about those resources; and honors its special responsibilities to American Indians, Alaska Natives, and affiliated Island 

Communities. 

NPS 123/105335, August 2010 
National Park Service 

U.S. Department of the Interior 

Natural Resource Program Center 

1201 Oakridge Drive, Suite 150 

Fort Collins, CO 80525 

www.nature.nps.gov 

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