Geology

The area's geology provides prominent evidence of large and powerful earth-changing events that have shaped the landscape as we know it today.

Photo Credit: NPS

The geology within the monument showcases the large and powerful events that helped shape the landscape including the rise of the Appalachian Mountain range and nearby Katahdin. The thirty miles of the International Appalachian Trail (IAT) that pass through the monument connects elements of the unique geology. Some of the highlights include:

• Erratics (large boulders that seem out of place) and eskers (rocky ridges) left from the glaciers that covered the area until about 15,000 years ago. Erratics record the story of a glacier's travels. To learn more about glaciers, glacier features, and glacial landforms, see the Glaciers & Glacial Landforms Page.
• Katahdin granite -Traveler Rhyolite rocks are the remains of a supervolcano that erupted in the area approximately 407 milliion years ago.
• Grand Pitch is a set of rapids that flow over rocks that are more than 500 million years old.
• The Owen Brook limestone and the fossils within it provides evidence that parts of the monument were once a coral reef.