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An Acadia Timeline: Geologic History

13.8 Billion Years Ago

The universe forms. 


12 Billion Years Ago

The Milky Way Forms. Billions of stars configure as one of billions of galaxies—the one that will eventually become our home and the grand vista in the night sky above Acadia National Park.


4.6 Billion Years Ago

Our Solar System and Earth Form. A great supernova explosion within the Milky Way Galaxy begins the formation of our home solar system and Earth. Earth forms from belts of particles circling the young sun. These particles contain (approximately) all of the actual atoms that will one day make up the physical manifestation of Acadia National Park—rocks, water, air, flora, fauna, iron trail rungs, stone bridges, popovers, and all.


More than 4.0 Billion Years Ago

Earth Becomes a Well-Watered Planet. Forces acting from within our planet and crashing in from space generate the great water masses on the Earth’s surface that will become oceans rolling relentlessly to the shores of Acadia.


At Least 4.0 Billion Years Ago

Plate Tectonics Begin. As Earth cools and forms a crust and mantle, great convection currents rise from Earth’s molten core to crack apart and move Earth’s crust in the protean plate tectonics that will shape deep geologic history and eventually create the symphony of rocks conserved as Acadia.


From 4.4 to 3.7 Billion Years Ago

Life Begins. At a past time not yet determined, through processes that inspire continuing scientific inquiry, elemental forms of life capable of reproducing are generated from complex matter. All subsequent life on Earth descends from these initial miraculous forms—including all the flora and fauna that today inhabit the lands and the waters of Acadia.


From 542 to 485 Million Years Ago

Cambrian Explosion. Life on Earth, still mostly in the seas, becomes much more complex. Many more multi-cellular, larger, and more diverse life forms compete for survival in the evolving environment.


More Than 500 Million Years Ago

Gondwana Riffs Ganderia. The supercontinent Gondwana, formed from the continental plates now in the southern hemisphere, sheds Ganderia, a smaller sub-continental plate that drifts across an ancient sea to fuse with Laurentia, ancient North America. This passage forms the two oldest bedrocks of Acadia: Ellsworth Schist and the Bar Harbor Formation.


423 to 418 Million Years Ago

The Acadian Caldera. The arrival and accretion of tectonic domains moving from Gondwana to Laurentia – especially Ganderia and Avalonia – generate volcanic arcs that form much of what we now call Mount Desert Island, the Cranberry Islands, Isle au Haut, and, later, the Schoodic Peninsula. In the most dramatic event in this passage, mighty magma intrusions from below blow the top off this then-dynamic region in a caldera collapse more than twice the size of the one that created Crater Lake in Oregon. The remains of this major passage, uplifted and eroded for more than 400 million years, will become the iconic Acadia landscape conserved today.


From 250 Million Years Ago

Atlantic Ocean Opens. Changes in the upwelling mantle convection currents begin to break apart the supercontinent Pangaea, opening a riff that widens to become the new Atlantic Ocean. The proto-coastal history of Acadia begins.


85,000 to 16,000 Years Ago

Wisconsin Glaciation. The most recent of several continental glaciers forms over much of northeastern North America, extending a sheet of ice up to two miles thick to the terminal moraines we call Long Island, Martha’s Vineyard, Nantucket, Cape Cod, and the Banks of the Gulf of Maine. As this mighty force flows over this region, it scrapes perhaps six feet off the top of our granite mountains, smoothing their northern slopes, plucking their southern faces, and deepening the valleys between them to define the lakes and ponds of Mount Desert Island. As the great glacier retreats north across Mount Desert Island between 17,000 and 16,000 years ago, it sloughs and scatters a lithic load that will form much of the surface geology of Acadia National Park and the surrounding communities.


15,000 Years Ago

High Stand. The prolonged great weight of the Wisconsin Glacier has depressed the plastic asthenosphere, lowering the height of the land in relation to the sea—which at the same time has been rising worldwide as melting glaciers in high latitudes north and south return water to the oceans. At this time Mount Desert Island is an archipelago of more than twenty islands. The peak we call Cadillac is 230 feet closer to the sea than it is today. Sea waves make cobble beaches that today sit high on the flanks of Gorham and Day mountains. The high ocean floods the Penobscot River Valley all the way to the forks at Medway.


12,000 Years Ago

Low Stand. When the compressed asthenosphere does rebound, the land quickly rises in relation to the sea so that by 12,000 years ago Mount Desert and all its surrounding islands are part of the mainland. The coast at this Low Stand is more than six miles south of Great Duck Island. After this, the sea rises quickly at first, then more gradually. Eventually Mount Desert becomes an island again.


For the Past 16,000 Years

Life Returns to the Mount Desert Island Archipelago.The land released by the retreating glacier is, at first, scoured and barren rock. But in subsequent millennia, various and abundant life forms return to compete for existence, leading to the robust endowment of flora and fauna in Acadia National Park—and the challenge to conserve this rich heritage in the dynamic environment of the Anthropocene. Since well before its creation as a park, the lands of Acadia have been situated at the boundary of the Boreal and Temperate Deciduous biomes. But climate change may move that boundary north, inevitably changing the flora and fauna that can exist within the park.


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