In September 1604, the French explorer Samuel de Champlain was sailing along the northeast coast of North America–mapping the borders of New France–when his ship crashed into a shoal. While the craft was under repair, Champlain investigated his surroundings, a mountainous island near what is now Maine. Up and down the shore, zigzagged with rocky coves and inlets, huge boulders rose from the sea, their stony faces pummeled by the rhythmic pounding of the Atlantic's foaming, frothy waves. Dense forests paraded down to the shore. Toward the interior of the island, broad, sloping mountains loomed, including one that clearly towered over the others.

On shore, Champlain encountered the Abnaki Indians, who occupied the island for most of the year and called it Pemetic, meaning "the sloping land." Champlain renamed it L'Isle des Monts Deserts, "The Isle of Bare Mountains," but only the pink-and-gray granite summits were barren. The rest of the island supported forests of evergreens and broad-leaved trees, flowering meadows, salt- and freshwater marshes, quiet lakes, rushing streams–and all with an abundance of life. Beavers, in particular, interested Champlain, for their pelts were highly valued in Europe.

Nine years after Champlain's stranding, the English attacked a French mission on the island, starting a series of wars between the two nations that lasted for just about 150 years. England finally triumphed in 1759, and this part of New France was renamed New England; Champlain's island became Mount Desert Island. Today much of this island, together with several smaller islands and part of the Schoodic Peninsula jutting out from the mainland, makes up Acadia National Park.

Islands they are today, but millions of years ago they were part of the mainland. Then the Ice Age began, and a series of glaciers crept southward, slowly covering most of the continent with a frozen white blanket. Before they retreated, the glaciers would alter the landscape forever. The formidable Mount Desert ridge, and unbroken east-west granite barrier, was sliced by the force of the moving ice into 17 individual mountains, their peaks whittled down to rounded domes. Valleys in between were broadened. Lake basins were gouged in high mountain passes and rockbound gorges. South-facing slopes became steeper and were marked with jagged cliffs as downhill glaciers haphazardly plucked away chunks or rock. Boulders were carried across the land; some were left precariously perched on mountain ledges like oversized free-form sculptures displayed on too-small pedestals.

Even more dramatic was the effect of glacial melt water: as it flowed into the ocean, the water level rose, flooding the land. Mountains became islands scattered in the water like so many gemstones; high ridges became peninsulas and rocky headlands jutting into the sea. Mount Desert Island was cut off from the mainland, but only be a narrow waterway, and the island was almost cut in half by a now-flooded valley–Somes Sound, the only fjord in the lower 48 states. (Fjords, which most people generally associate with Norway, are inlets of the sea bordered by steep slopes.) The ocean, a reservoir for melt water from polar ice caps, continues to rise about two inches a century. Over time, more and more of Acadia's coast will be lost to the sea.

The ocean is a tireless sculptor, forever remodeling the shore, and through its designs are temporary, they are spectacular nonetheless. Thunder Hole, a narrow granite chasm on the southeast shore of Mount Desert Island, is a quiet place most of the time. But when just the right conditions of sea, wind, and tide occur, waves hurtle into the rocky gorge, compressing the air toward the back. For a moment, the water and air seem trapped. Then the air rises, escaping with the spray and foam, and expands with thunderous booms that can be heard miles away: the ocean's tremendous power has been transformed into sound.

Water quietly lapping onto the sand creates its own designs. Ceaselessly nibbling at the shore, waves dislodge rocks and pebbles and pile them up at a shallow place until a cobblestoned bar, or neck, is built like a bridge between two islands. (The town of Bar Harbor takes its name from a sandbar connecting Mount Desert and Bar islands.) Eventually, the ocean will dismantle the sandbar, but meanwhile herring gulls and other birds poke in the rocky rubble for clams, crabs, mussels, and fish. Over time, the ocean also builds sandy beaches, depositing finely ground grains of pulverized rock and seashells in protected coves. At Newport Cove, where Sand Beach stretches like a pale, narrow ribbon, the ocean washes away part of the beach each winter. Gentler currents rebuild it in summer, as is nature's way.