RANGELEY – Would you like to find out how volcanic islands, ocean basins, granite magmas, rivers and glaciers shaped the landscape of the Rangeley Lakes region, and why geologists say that Rangeley, like most of Maine, is not part of ancestral North America?

Geologist John Slack will offer a field trip to discuss those ideas at 1 p.m. Tuesday, Aug. 14. The trip, which is free, is part of the Rangeley Public Library’s Literary Gala.

Designed for the public, the field trip will start from the Ecopelagicon Nature Store at 7 Pond St. and will last until approximately 5 p.m.

The trip will begin with the oldest rocks in the region and end with the youngest ones. Slack has planned five stops, time permitting. The first two stops are at roadcuts along Route 16 west of Dodge Pond, followed by a stop in a creek along Route 4 between Madrid and Phillips, then a stop along the Sandy River just north of Phillips (off Route 142), with a return to Rangeley and a last stop along Route 4 west of town.

Because parking is limited at several of the stops, participants will car pool. Also, the number of people will be limited to 16, so call the Ecopelagicon at 864-2771 before 5 p.m. Monday, Aug. 13, to reserve a space.

Everyone should wear sturdy sneakers or hiking boots. Since some of the spots require careful footwork, trip organizers recommend that children who would like to go should be about age 12 or over.

Raised in Gorham, Slack has been a geologist at the United States Geological Survey in Reston, Va., for 30 years. His first geological job, after receiving his BS in geology in 1970, was working in the woods north of Flagstaff Lake, mapping and sampling submarine volcanic rocks that formed about 500 million years ago when the Rangeley region was located in the southern hemisphere.

Slack has done geological work on five continents; his studies in the United States have chiefly been in Maine, Vermont, Virginia, Colorado, Arizona and Alaska. He is working on projects in northern Alaska, northern New Mexico and central Idaho. His research focuses on mineral deposits of copper, lead, zinc, silver and gold, using chemical and isotopic techniques to better understand their origins.

In the summers, Slack lives at his camp in Rangeley Plantation with his wife, Peggy Yocom.