Geologists Duane and Ruth Braun will speak at the Southwest Harbor Public Library on Oct. 25. PHOTO COURTESY OF DUANE BRAUN

Brauns assemble geological puzzle

SOUTHWEST HARBOR — Geologists Duane and Ruth Braun will talk about the geological makeup of Mount Desert Island at the Southwest Harbor Public Library on Tuesday, Oct. 25, at 5:30 p.m.

At the end of the talk, there will be a book signing for their book “Guidebook to the Geology of Mount Desert Island and Acadia National Park.” Proceeds will benefit the library.

The Brauns will take the audience on a geologic history tour. Their talk will begin around a billion years ago when MDI was attached to the southern continent, Gondwana. It split from Gondwana and eventually attached itself to North America.

Mount Desert Island itself experienced three major geologic events, which resulted in the formation of 10 different rock units that now make up the landmass. The oldest of these formations is the beautifully crenulated Ellsworth schist.

Most of the rock on MDI formed around 420 million years ago. Two miles of rock have been eroded since then to form the present landscape. Over the last 2.5 million years, glaciers repeatedly have 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 the present beautiful and striking landscape.

Ruth Braun earned her master’s degree 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. He was the geosciences professor at Bloomsbury University. He also mapped the glacial deposits of a 9,000-square-mile area of northeastern Pennsylvania for the Pennsylvania Geology Survey.

The Brauns have been instructors for Acadia Senior College, teaching about the geology of MDI. Duane Braun has revised the geologic maps of MDI for the Maine Geologic Survey. The “Surficial Geology” (glacial deposit) map of MDI is presently available as a free PDF download and the “Bedrock Geology” map should be available later in the year.

Seating is limited. Reservations are required. Call the library at 244-7065.

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