[NASA] Why Maine’s Sandy Shorelines Turn Jagged

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3. Why Maine’s Sandy Shorelines…

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The stark contrast between the curved, sandy beaches south of Portland and the indented, rocky coastline to the northeast is clear in this image captured by the

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(Operational Land Imager) on

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on August 31, 2025.

NASA Earth Observatory/Michala Garrison

The

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have a deep well of creation myths explaining the rocky coastlines of the

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,

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, and

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. Many involve

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—a magical figure said to have floated down the Bay of Fundy in a

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, sculpting coastal features by scraping the vessel across the landscape and scattering enormous boulders during battles with primordial beavers, frogs, moose, whales, and other gigantic animals.

Fewer Indigenous creation myths survive to explain the origins of the sandy and marshy shorelines of southern Maine and the rocky, indented coasts of the state’s

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. But the sharp contrast between the sandy shoals and beaches south of Portland and the rocky shoreline of promontories,

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, and narrow peninsulas to the east—visible in the

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image above—has long drawn the attention of coastal geologists, whose scientific explanations on its origins abound.

The coastal transition reflects both differences in the

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and the distribution of

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left behind by the

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, coastal geologists say. Southern Maine has broad deposits of sand, much of it sourced from rivers. The sandy beaches of Saco Bay, for instance, home to Maine’s

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and the state’s

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, received sediment from the

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and breakdown of the

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, with material transported to the coast largely by the Saco River, explained Peter Slovinsky, a geologist with the Maine Geological Survey. Waves and tides reworked these soft sediments over time, sculpting them into the arch-shaped

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and sprawling salt marshes found around Saco Bay and the broader region.

While erosion-resistant granite juts from the sandy shorelines in southern Maine to form rocky headlands,

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bedrock becomes the dominant surface feature east of Portland. There, whole ridges and valleys made of rock layers transformed by exposure to high pressures and temperatures define the landscape. During the last ice age, glaciers scoured and widened many of these coastal valleys, which later flooded as the

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melted and sea levels rose.

Around

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, these ridge-and-valley systems, combined with the

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of the shoreline, produce the jagged, highly indented shoreline and many long, narrow islands seen today. “The tortured folds of these old landscapes also set up a sharp directional preference for erosion to exploit,” said Nicholas Whiteman, also a geologist with the Maine Geological Survey. “This led to the eye-catching difference in the orientation of the islands and necks that dominate Casco Bay compared with those to the northeast.”

The various forms that coastlines take fascinate geologists, but they also carry everyday implications for the economies of Maine’s coastal communities. While tourists flock to the sandy beaches of communities like Saco and Kennebunkport, the state’s

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are concentrated in Midcoast Maine. The crustaceans thrive in the cold waters of the region’s many rocky, protected inlets, turning communities such as

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into leaders in lobster landings.  

The state’s oyster farms are also concentrated in this region. Casco Bay and the Damariscotta Estuary, sheltered from winds and waves, offer waters that farmers can easily access without large boats. These waters provide a range of temperatures, salinities, and other characteristics that create numerous

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where oysters can grow quickly and take on a variety of tastes, known as

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, explained Tom Kiffney, a researcher at the University of Maine. Kiffney is part of a team of researchers using Landsat and other satellite observations to

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and help identify the most

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for new oyster farms in Maine based on water temperatures and quality.

NASA Earth Observatory image by Michala Garrison, using Landsat data from the 

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. Story by Adam Voiland.

Downloads

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August 31, 2025

JPEG (12.20 MB)

References & Resources

• Kelley, J. (1987)
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  . Glaciated Coasts, 151-176.
• Kiffney, T., et al. (2026)
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  . Aquaculture, 612(1), 743133.
• Leland, C. (1884)
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  . Accessed July 17, 2026.
• Maine.gov (2026)
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  . Accessed July 17, 2026.
• Maine Geological Survey (2002)
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  . Accessed July 17, 2026.
• Maine Geological Survey (1999)
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  . Accessed July 17, 2026.
• Merroir (2026)
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  ? Accessed July 17, 2026.
• NASA (2026, January 15)
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  . Accessed July 17, 2026.
• NASA Earth Observatory (2017)
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  . Accessed July 17, 2026.
• Snyder, J., et al. (2017)
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  . Frontiers in Marine Science, 4(190).
• World History Encyclopedia (2025, February 6)
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  . Accessed July 17, 2026.

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