SOUTHWEST HARBOR — Geologists Duane and Ruth Braun will talk about the geological makeup of Mount Desert Island Tuesday June 18, at 5:30 p.m at the Southwest Harbor Library.
They will also sign copies of their book, “Guidebook to the Geology of Mount Desert Island and Acadia National Park.” Proceeds will benefit the library and the Maine Granite Industry Museum in Somesville.
Seating for the talk is limited; pre-registration is required.
“The Brauns will take the audience on a geologic history tour,” organizers said. “Their talk will begin around a billion years ago when MDI was attached to the super continent Gondwana and eventually attached itself to North America.
“MDI itself experienced three major geologic events which resulted in the formation of 10 different rock units that now make up the island. The oldest of these formations is the crenulated Ellsworth schist.”
Most of the rock on MDI formed around 420 million years ago as alternating intrusions of pink granite and gray gabbro magma fed a huge volcanic caldera the size of MDI. Two miles of rock have been eroded since then to form the present landscape.
Over the last 2.5 million years glaciers have repeatedly covered the island with up to 5,000 feet of ice. When the glaciers retreated they left behind a number of different deposits and landforms, helping to create a beautiful and striking landscape.
Ruth Braun earned a Master of Science from Johns Hopkins University. Over the years she has taught science, math, and geology courses in a variety of high schools and universities.
Duane Braun earned his doctorate from Johns Hopkins University and before he retired he was the Geosciences Professor at Bloomsburg University. He also mapped the glacial deposits of a 9,000-square-mile area of northeastern Pennsylvania for the Pennsylvania Geology Survey.
Both speakers have been instructors for Acadia Senior College and have written a guidebook to the geology of MDI. Duane Braun has revised the geologic maps of MDI for the Maine Geologic Survey.