Contents

• Introduction
• Bedrock
• Glacial geology
• Recent processes
• Conclusion
• Additional_reading
• Glossary
• Geologic maps

The Geology of Mount Desert Island A Visitor's Guide to the Geology of Acadia National Park by Richard A. Gilman Department of Geosciences State University of New York, College at Fredonia Carleton A. Chapman Department of Geology, Emeritus University of Illinois Thomas V. Lowell Department of Geology University of Cincinnati Harold W. Borns, Jr. Department of Geological Sciences University of Maine at Orono Maine Geological Survey Department of Conservation Augusta, Maine 04333 Originally published in 1988 as Bulletin 38

This bulletin is a companion to Bedrock Geology of Mount Desert Island (2.5 Mb PDF file) and Surficial Geology of Mount Desert Island (2.5 Mb PDF file) Bulletin 38 is also available in print: Price: $8.00 plus 40¢ sales tax

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Preface

Maine has long been famous for the beauty of its coast. Mount Desert Island in particular has attracted numerous tourists and summer residents for well over a century. Visitors and residents alike enjoy the scenic vistas at Bar Harbor, Cadillac Mountain, Jordan Pond, Sand Beach, Thunder Hole, and many other places within Acadia National Park and elsewhere on the island. The purpose of this visitor's guide is simple: we hope that an understanding of the geologic processes which formed the island's spectacular scenery will leave the reader with a greater appreciation for both Mount Desert Island and the national park.

Location Map

Mount Desert Island is the largest of the many islands located along the coast of Maine (see Location Map). Measuring almost 108 square miles in area, the island is located 150 miles northeast of the Maine-New Hampshire border and 70 miles southwest of the U.S.-Canadian boundary. Access to the island is via Maine Route 3 south from Ellsworth.

Named in 1604 by the French explorer Samuel de Champlain, the island and much of the adjacent coastal area were the site of continual skirmishing between the British and French during the French and Indian Wars. English colonists settled the island after the British victory over the French and the signing of the Treaty of 1763. Farming, lumbering, shipbuilding, and fishing were major industries for the new settlers, and fishing remains important today.

Although one of the nation's smallest national parks, Acadia is one of the most scenic and most visited. Much can be viewed from the state routes and park roads that wind around the island, or from the various hiking and carriage trails within the park. Unlike most other national parks, Acadia was not purchased with public funds or set aside from public lands. During the middle and late 1800's, the island became a summer colony for wealthy patrons from southern New England, Philadelphia, and New York. Concerned about the dangers of overdevelopment of the island, a number of prominent citizens, among them George B. Dorr, Charles W. Eliot (a former president of Harvard University), and John D. Rockefeller, Jr., together with many other Maine residents and summer visitors, worked to preserve the island's beauty. Out of their efforts came the donations of land that formed the nucleus of Acadia National Park. Legislation enacted by Congress in 1986 established permanent park boundaries, addressing concerns of adjacent towns that continued expansion of the park would hurt their economic growth.

This website summarizes the geologic history of Mount Desert Island and serves as a guide to geologic features located within and adjacent to the park. This history begins more than 500 million years ago with the formation of the oldest rocks on the island and continues today with the geologic processes that are presently shaping the face of the landscape. The accompanying bedrock (pdf format) and surficial (pdf format) geologic maps, used in conjunction with the text, allow readers to identify various geologic features on Mount Desert Island and understand how they came into being.

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Table of Contents

Introduction

Bedrock Geology of Mount Desert Island

• The Rocks of Mount Desert Island
  • Stratified Rocks
    • Ellsworth Schist
    • Bar Harbor Formation
    • Cranberry Island Series
  • Intrusive Igneous Rocks
    • Gabbro-Diorite
    • Granite of Southwest Harbor
    • Granite of Cadillac Mountain
    • Granite of Somesville
    • Other Granites
    • Diabase Dike
  • Joints and Faults
• Schoodic Peninsula
• Isle au Haut
• Summary of the Bedrock Geologic History of Mount Desert Island

Glacial Geology of Mount Desert Island

• Introduction to Glacial Geology
• Shaping of the Landscape by Glacial Erosion
• Glacial Transportation and Deposition of Rock Debris
• Disappearance of the Glacier
  • Glacial Downdraw into the Sea
  • Melting of Glacial Ice on Land
  • Rebound
• Summary of Glacial History

Recent Geologic Processes on Mount Desert Island

Conclusion

Supplementary Reading

Glossary of Geologic Terms

Geologic maps

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Acknowledgments

Writing an interesting, understandable, yet scientifically accurate geologic summary for the non-geologist is a monumental task, much more difficult in many respects than writing a technical paper. We are grateful for the many helpful comments and suggestions and careful editing by Carolyn Lepage, Marc Loiselle, Sheila MacDonald, Bill Metzger, Ernest Muller, Woody Thompson, and Bob Tucker. Cathy Stultz's assistance with manuscript preparation is also appreciated, as are the illustrations drawn by John Poisson, and the photographs taken by John Poisson, Woody Thompson, and Joe Kelley.

The writers are also indebted to the staff of Acadia National Park for their assistance, especially Lois Winter, Park Naturalist, who read early drafts of the manuscript and offered many suggestions for making it more readable for park visitors.

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Last updated on January 11, 2008

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