Geology Guide to Mt. Cardigan


If you’ve ever hiked up Mount Cardigan, stayed at AMC’s Cardigan Lodge, or simply driven by the rounded granite summit topped by a fire tower, you may be interested in a new website that explains the geology of the peak.

Dartmouth College earth sciences professor Brian Dade teamed up with retired doctor and hiker Howie Frankel to create a guide to the geological makeup of five popular hikes in the Upper Connecticut River Valley. The online guide includes Mount Cardigan and a 2-mile section of the Appalachian Trail known locally as the Velvet Rocks Trail. Mount Cardigan is one of what Dade calls a “string of pearls” — granite-based mountains formed during an intense period of volcanic activity 500 million years ago along the coastline of what would become the Atlantic Ocean. These mountains, now many miles inland, are thought to be “ancient magma chambers from a chain of volcanic islands,” Dade says.

Glaciers planed smooth the north side of Cardigan during the Ice Age. But each time a glacier crested the peak, it plucked and pulled rocks off the southern face, creating a more broken topography. Dade says, “Carpenters, think of trying to plane across the grain” at the end of a two by four: “All you get is cracks, chips, and splinters.” It’s an image I’ll keep in mind the next time we picnic in the lee of a big boulder.

Geologists learn to take the long view of history. In an overview of the area’s geology, Dade and Frankel describe a history of upheaval and change. The region’s abundance of slate, granite, marble, and gneiss — all metamorphic rocks that have been altered by heat, pressure, and folding — have been used as building materials around the world, and have created many a fine stone wall at home. The Appalachians were once like the Himalayas, the authors remind us, and the Himalayas will someday be like the Appalachians are now. Now that’s a long view.

The short guide, illustrated by gorgeous photos, is like hiking with a geologist. Take a look at it before your next hike up this popular small mountain.

Learn more
- Geology Guide to the Upper Connecticut Valley

Photo showing glacial "plucking" on the south side of Mt. Cardigan courtesy of the geology guide's authors.

Great Kids, Great Outdoors” is an AMC Outdoors blog, written by Kristen Laine.

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