Barton Hill looms above Route 146 as it descends to the village of Gallupville and extends north as a series of impressive limestone cliffs along Route 443 to its intersection with Route 30.

Sand Beach, Maine, geology

— Photo by Mike Nardacci

Sand Beach, Acadia National Park's most popular attraction, is a "pocket beach" sheltered by a rocky shoal and by the rocky peninsula known as "Great Head," featuring popular hiking trails.

My first experience with Acadia National Park on Mount Desert Island in Maine was in the summer of 1987 when I went as a graduate student to the College of the Atlantic in Bar Harbor for a course in the island’s geologic foundations.  I was assigned a dorm room in a refitted mansion from Bar Harbor’s Victorian heydays, one of several on the college’s campus.

With the enigmatic name of “Seafox,” the building sat on a low cliff right above Frenchman Bay and had a view out over the cluster of fir-tree crowned, rocky islands known as the Porcupines to the far shore of the Schoodic Peninsula and the Gulf of Maine beyond it.

It is a stunning view, and it evoked in me a line from John Denver’s ballad “Rocky Mountain High”:  “…Comin’ home to a place he’d never been before.”

Mount Desert Island — the locals insist on pronouncing the middle word “dessert,” as in baked Alaska — is roughly 12 by 17 miles and shaped like a huge lobster claw.  Its interior is rugged:  30 or so named peaks with steep slopes and barren, wind-blasted summits that belie their fairly low elevations, making them seem far higher than they really are and posing a challenge to even experienced climbers.

The glacially-sculpted valleys between them are thick with deciduous trees — oaks, maples, and birches — as well as balsams, spruces, and other conifers.  One mountain-bordered valley called Somes Sound is a deep, briny body of water with an uncanny resemblance to Lake George; it is Maine’s only fiord, a U-shaped glacially-cut valley filled with sea water.

The ocean water surrounding Mount Desert Island — MDI for short — is achingly cold, and even at the climax of a hot summer it is unusual for it to get above 55 degrees; tourists visiting an MDI beach for anything more than a very brief, bracingly cold dip are usually well-advised to head inland to one of the island’s numerous ponds and lakes which commonly reach 70 degrees by August.

Waves meet bedrock

But most visitors to the island’s ocean beaches are not there for swimming: They are there to take in the stunning scenery that results when the powerful waves come in off the Gulf of Maine and crash into the hard bedrock of the island.  It is mostly granite, but in a few places it is made up of hard sedimentary rock and a metamorphic rock called schist.

All of these rock types are very ancient, the youngest being from the Devonian period — roughly 400 million years old, while the oldest — the schist — dates from the Cambrian and Ordovician times, roughly 550 million years in age.  When the powerful Atlantic waves meet the bedrock of Mount Desert Island, the results are what the tourist brochures call “eye-popping.”

And fortunately, some of the most spectacular are easily viewed from Acadia’s Park Loop Road, which skirts a long section of the coast before heading into the fragrant forest of interior Mount Desert Island.

Every high school student is familiar with the diagram in the Earth Science Reference Tables showing the relationship between the velocity of water and its consequent ability to move rock particles.  To describe it simply, the higher the yearly average velocity of a stream or a wave, the larger the particles it can move.

Very slow-moving water — a meter (roughly one yard) per second or less — can transport tiny particles such as silt, clay, and sand, and some diminutive pebbles; but as the water’s average velocity increases to 4 or 5 meters per second or higher, it develops the ability to transport increasingly huge boulders, and sometimes to hammer away at bedrock, leaving nothing but sheer cliffs rising from the sea.

“Sand Beach”

Given the island’s location off the coast of Maine, exposing much of it to the full power of the ocean, it is not surprising that sandy beaches are uncommon on MDI.  In fact, there are just two, and one is artificial, with truckloads of sand required every few years to keep up with the ocean’s erosive power to take it away.  But the other is natural, and it affords one of the most breathtaking views on the island.

Named perhaps a bit too literally “Sand Beach,” it sits on the side of the island that faces directly east making it a tempting target for the huge waves that roll in off the Atlantic all the year around.  But Sand Beach is what geographers call a “pocket beach.”

It sits tucked back into a broad, shallow valley, protected partially on its east side by the craggy peninsula called “Great Head” and to its south by a large rocky shoal known as “Old Soaker.” Against both of these features, powerful waves break and lose much of their power.

Thus they are unable to blast away completely the sand that ends up on the beach, either washed down from higher areas on the island or transported along the coast by off-shore currents.  Probably the singular most popular visitor draw on the island, it offers in summer a gorgeous place to sunbathe, picnic, and perhaps to test one’s ability to withstand the numbing but bracing waters without fear of the ocean’s ability to create crushing waves and rip currents.

Safe haven

The picturesque village of Bar Harbor is located on the edge of Frenchman’s Bay, named for the explorer Samuel De Champlain.  The bay has been known since the days of sailing ships as a safe haven from the wild Atlantic waves.

 
Several small beaches at Bar Harbor village face open water, and wave action washes away small sediments, leaving them covered in pebbles.

 

Still, not far off the coast the surrounding waters are very deep, and in spite of the existence of a scattering of islands and an artificial breakwater, relatively strong waves frequently break against Bar Harbor’s shores, washing away small sediments such as silt and sand but leaving larger ones such as pebbles in place.

The village sits on the sedimentary sandstone and siltstone bedrock known as the “Bar Harbor formation.”  When the rock is eroded by waves, it tends to break down in layers, which in turn weather into small, flat fragments, resulting in what is known as a “shingle beach.”

During times of accelerated wave velocity, such as in a storm, the fragments clatter against each other, becoming smooth from the grinding and producing a haunting sound.  Those who remember Matthew Arnold’s beautiful poem “Dover Beach” from their school days may recall that it was just such sounds on an English beach that inspired his philosophical musings.

Given the fact that vast stretches of Mount Desert Island have harder bedrock than underlies Bar Harbor and are exposed to waves more powerful than those at the village, it follows that many of the island’s beaches are scenically rugged, especially along the east coast of MDI, both north and south of Sand Beach.   In these locations, waves are on average powerful enough the year around to wash away all but the largest sediments.

Little Hunter’s Beach

A number of cobble beaches have formed, with some of the sediments produced directly from their underlying bedrock, and vast quantities were transported there by the great glaciers that covered the island 20,000 years ago.  A particularly photogenic example is Little Hunter’s Beach, named for a stream that spills down and into the ocean from the high forest looming above the beach.

The rounded cobbles that bury the bedrock several meters deep here come from numerous  points to the beach’s north, many from inland Maine.  They are of many kinds and brilliant colors:  granite, basalt, schist, and other rock types, rounded and polished by centuries of wave erosion.

 

Little Hunter's Beach is an example of a "pocket beach," tucked back into the coastline but in this case facing unobstructed wave action.

 

There is a direct relationship between the force of the waves and the steepness of a beach surface, so traversing Little Hunter’s is a challenge, akin to walking on an enormous, slanted pile of billiard balls. Like Sand Beach, Little’s Hunter’s is also a pocket beach, tucked back a couple of hundred feet into the landscape — but Little Hunter’s faces open ocean, and only the distant Cranberry Islands somewhat lessen the waves’ power to remove sediments.

Hence the beach is made largely of cobbles, with smaller pebbles visible only at the waterline at low tide, when wave energy is often much lower. The beach is bordered by woods filled with balsam firs, spruces, and bayberry, and the cold breeze that blows over it carries their fragrance for great distances.

Powerful waves

A few miles north of Little Hunter’s is a section of coast open to the full fury of the Atlantic and here are found what geologists call “high energy” beaches. In these areas, the waves have sufficient energy to leave behind nothing but boulders or have blasted away all sediments and left massive cliffs rising starkly from the raging ocean waters.

A boulder-strewn beach that is easily visible from the Park Loop Road is called “Monument Cove,” a recess cut back a couple of hundred feet into the bedrock, which consists of the beautiful deep-pink Cadillac Mountain Granite, forming 60-foot cliffs that tower above a jumble of boulders, some a meter or more in diameter.

 
Monument Cove with its sheer cliffs and massive boulders is easily accessible from Acadia's Park Loop Road.

 

It can take waves moving 1,000 centimeters per second — over 30 feet — to move rocks of that size; but the rounded and smoothed appearance of the rocks testifies to waterflow of that power, providing a spectacle of furious waves and foam and the roar of the sea during the occasional off-shore hurricane or one of the many winter storms that pound the Maine coast.

And yet — areas of Maine’s coast can be subjected to even greater wave velocities, and the stretch near Anemone Sea Cave is a sobering example. Anemone Cave harbors a population of sea anemones, in addition to sea stars, sponges, and other delicate life, and to protect it the National Park Service has long stopped publicizing its location.

However, that location makes it hazardous to humans as well.  The water immediately off the shore here plunges to great depths, permitting enormous waves to blast away at the coast with very little frictional drag from the bottom.  The result is that, in this stretch of Mount Desert Island, there is no beach in the conventionally understood sense of the word at all.

Instead, there are high cliffs rising directly out of the sea, featuring precipitous drops, and a combination of the relentless forces of frost action in winter and the rhythmic, endless surges of giant waves have blasted out a sea cave.  Such caves are relatively rare on the east coast of the United States, but common farther north and on the west coasts of both the United States and Canada where waters tend to be deeper and waves more powerful the year around.

Great diversity

Mount Desert Island has long been known to naturalists and oceanographers as a tremendous outdoor laboratory where creatures ranging in size from tiny ones such as plankton to far larger ones such as whales and a spectacular variety of plants may be studied; to geologists, it offers beautiful examples of all of the major rock types and the forces that from ancient times have created and weathered and eroded them.

But the island has also for many centuries drawn a great diversity of visitors as well:  Native American Indians fishing the rich waters, sailing ships seeking a safe harbor during storms, and city-dwellers looking to escape summer heat. But it has also drawn lovers of the island’s natural beauty and artists seeking to capture the astounding landscapes created when the angry ocean meets rock.

Location:

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