Hiking through geologic time

Folded granite like this rock ledge on Pemetic Mountain in Acadia National Park is evidence that the granite was once molten hundreds of millions of years ago.
Brad Viles | BDN
Folded granite like this rock ledge on Pemetic Mountain in Acadia National Park is evidence that the granite was once molten hundreds of millions of years ago.
By Brad Viles, Special to the News
Posted May 27, 2011, at 5:38 p.m.

Most Maine hikers probably don’t think much about the ground beneath their feet. I know I never gave it much thought until I picked up a geology book on my thru-hike in 1994. I bought the book “Underfoot: A Geologic Guide to the Appalachian Trail” by V. Collins Chew in Harper’s Ferry, W.Va., and carried it all the way to Maine.

The book was easy to understand, with maps that clearly portrayed how the mountains were built, combined with descriptions of the different stages of geologic time. As soon as I got home I bought more books on geology, but with the focus on Maine.

Hiking across our landscape provides a fascinating look at how time spanning hundreds of millions of years shaped this ground under our boots. The evidence lies in the rocky outcrops and soil. Once you start looking and become familiar with a few commonly used geological terms, you can identify the history of how these mountains were created.

That’s where having a geology guide helps. Most have a glossary and break down the sometimes-difficult-to-understand concepts into language that even a nongeologist like me can understand. Here are three of the most comprehensive geologic guides to Maine’s landscape. They are all available locally or online.

“Roadside Geology of Maine,” by D. W. Caldwell, Mountain Press, $18.00.

Despite this book’s title, there are some trail descriptions, particularly in Baxter State Park. The book also describes in detail the forces that shaped Maine, and how most of them can be seen along the main roads that are cut through bedrock.

Most of the rock outcrops along the major highways and secondary roads in the state are described. Illustrations and maps of each of the important major mountain building events are included in the book. The cataclysmic periods of time that created the landscape are portrayed in easily understandable language. Throughout the book are several photos showing examples of the rock types you’ll find along the roads leading to trailheads. The book has great diagrams and cross sections of the landscape. There is a glossary of terms that makes it easier to understand the more difficult concepts and theories.

If you buy only one book on the geology of Maine, make sure it’s this one.

“Glaciers and Granite,” by David L. Kendall, North Country Press, $19.95.

This book is known for the easy-to-understand writing in explaining the effects of glaciers on the mountains of Maine. But it’s not just limited to glaciers. The ages of mountain building that occurred hundreds of millions of years before the glaciers arrived are also clearly diagrammed and depicted.

There are clear maps of the types of rock and soil that cover Maine. There are color plates in the middle of the book that depict the varied landscapes of Maine from Popham Beach to Katahdin. Of the three books, this one’s the most user friendly. The explanations are written using examples that make understanding plate tectonics, fault lines and visual clues less difficult than the other books.

This book also contains descriptions of road cuts along many of the major highways and secondary roads throughout Maine.

“Underfoot: A Geologic Guide to the Appalachian Trail,” by V. Collins Chew, published by the Appalachian Trail Conservancy, $12.95.

Underfoot describes all the rock forms under the entire length of the Appalachian Trail as it winds from Georgia to Maine. The diagrams are clearly drawn and depict each era of geologic time. There is a complete glossary. The best part of this book is that it’s the only one that looks at the geology of Maine from the trail outward.

Even though there’s only a small part of this book describing Maine, it is one of the most comprehensive. Different rock types are clearly mapped and the descriptions are written in a way that’s easily understood.

After reading through any one of these guides, you’ll never look at the rocks under your feet the same way. Bring one of these guides with you on your next hike and you’ll understand why there is so much bare ledge in Acadia. You’ll know why there’s so much slate on the Appalachian Trail north of Monson. And why the rocks look like they were melted, then solidified, on Bigelow.

The evidence of continental drift, earthquake fault lines and ancient volcanic activity is everywhere you look, once you know what to look for. All you need is a geology guide to understand the concepts. Then, get out and hike, look at the ledge under your feet and discover for yourself. And unlike trying to watch moving wildlife, rocks are stationary and they’re everywhere. Pick a trail and head out. There’s an ancient story in the rock and soil just underneath your boots.

http://bangordailynews.com/2011/05/27/outdoors/hiking-through-geologic-time/ printed on July 22, 2014