Maine
Seen in a satellite image, Mount Desert Island is a prime example of Maine’s convoluted coastal geography.
Quick! Which state has a longer coastline: California or Maine? If you measure just oceanfront and exclude tidal inlets, the answer is California, with 840 miles to Maine’s 228. But if you include inlets, Maine rockets to the lead with 3478 miles of coast. That’s a lot of inlets.
Aerial photographs of Maine show how convoluted the coast really is. The mainland swoops in and out of deeply carved tidal waterways, separated by high, rocky bluffs, with a bevy of offshore islands sprinkled along the North Atlantic Ocean. This complicated seascape required billions of years of erosion to shape the coastline into the jagged puzzle of peninsulas and islands we see today.
A scenic and spectacular part of Maine’s coast is Acadia National Park, the state’s only national park, on Mount Desert Island, a rocky bulge of land divided into two lobes by a deep fjord-like inlet called Somes Sound. With its tall granite cliffs, thriving tide pools, and still-wild landscapes, Acadia was a prime choice to become the first national park east of the Mississippi, in 1919. The park covers about half of Mount Desert Island.
The rock underlying Mount Desert Island dates back 550 million years, when mud and volcanic layers accumulated on an ancient seafloor around the time the first complex life was evolving on Earth. Soon afterward, during the Silurian Period, the Acadian orogeny uplifted these sediments and metamorphosed them into schist. During the Devonian Period, around 400 million years ago, mountain-building activity gave rise to three types of granite on Mount Desert Island: Cadillac Mountain granite, fine-grained Somesville granite, and medium-grained Somesville granite, which have long been quarried throughout the region.
More than fifty lighthouses cover rugged coastal Maine, including this one at Pemaquid Point, where swirls of ancient metamorphic rocks and granite dikes have been sculpted and polished by wave action.
The city of Camden, Maine, is built around one of many safe harbors created by the serpentine Maine shoreline.
A vertical dike of 200-million-year-old black basalt intrudes between jagged blocks of 500-million-year-old metamorphic rocks at the Giant’s Stairway, near Harpswell, Maine.
Then, during the last ice age, the Laurentide Ice Sheet buried the coast of Maine under many feet of ice. The weight of all that ice scraped and gouged the coast into myriad inlets and islands. Evidence of the area’s glacial past can be seen most dramatically at Bubble Rock, a giant boulder carried by a glacier and deposited precariously on the side of South Bubble Mountain on Mount Desert Island.
After the ice melted, the weight of all that ice lifting off the land led to significant post-glacial rebound, or rising, of the North American continent, including the coast of Maine. At times in the past, the rate of land rebound was faster than the rate of sea level rise, effectively mitigating the effects of rising sea levels that changed coastlines all over the world after the last ice age. This isostatic rebound is ongoing, uplifting the sea cliffs, headwalls, peninsulas, and islands, though the rate today is minuscule compared to the rate of sea level rise.
You could fly over the coast of Maine en route to Portland, Maine, or Saint John, New Brunswick. Look for a complicated coastline of inlets, peninsulas, and islands stretching from Casco Bay near Portland, Maine, north into Canada.
