We met Luc and his wife on the Ferry back to the mainland - they too had recently become new residents. They described, with a smile, a geologist friend who had spent his entire time on the island "trembling with excitement". And really, the more you know about Grand Manan's geology, the more the reaction seems entirely apt.
What is now Grand Manan has been at the center of a monumental movement of the earth. Over the eons, it has been squeezed, torn apart, layered with lava, raised up, tilted, weighed down, bounced back, and then isolated by water. Now it is being re-shaped by one of the largest tidal flows on earth.
Squeezed: Between 600 and 350 million years ago, the continental masses of North and South America, Europe and Africa drifted together, squeezing out the original Atlantic Ocean, to form the super continent of Pangaea. The Appalachians formed at this time. Some of the volcanic activity that we can currently see in the region also occurred during this period when the Bay of Fundy area, originally closer to the equator, ended up roughly in the middle of the super continent.
After coming together, a vast, shallow inland sea formed on Pangaea, creating sedimentary layers which, after later metamorphosis and upheaval, eventually formed part of Grand Manan's eastern third.
Torn apart: 190 million years ago the drift reversed and the Atlantic Ocean reappeared. As the continents separated, rift valleys formed, extending from Nova Scotia to South Carolina. While most of these quickly filled with the sediments eroding from the continents, the Bay of Fundy is a water-filled remnant of one of these ancient rifts. During this period, most of the volcanic activity directly affecting Grand Manan occurred, creating the three major volcanic members of the island.
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Fifteen to twenty million years ago, the Gulf of Maine was a shallow, submerged gradual seaward slope. This flat coastal sea floor slowly emerged as dry land. However, great rivers, draining the nearby highlands, soon eroded this newly exposed coastal plain, carving out the sediments and softer rocks to form deep valleys and steep-sided gullies.
Weighed down: Over the past 2 million years, a number of ice ages occurred, covering the area with thousand metre thick glaciers. Grinding over the region, they carved out even more of the softer rocks and sediments to form the deep inner Basins of the Gulf.
Bounced back: Thirteen thousand years ago, the last of the glaciers receded and seawater flooded in. With the heavy ice burden removed, the land rose and the sea fell 60 metres below its present level on the shore. The sheltered body of water which developed (known as the DeGeer Sea) was a very different Bay of Fundy than the current one; no massive tides, no tidal bores, no surging currents. It was then that the mammoths and caribou grazed upon Georges Bank.
Isolated: Steadily rising sea levels sank the Georges and Browns banks under 60 metres of seawater, opened the Gulf of Maine to the full influence of the Atlantic Ocean and created the "island" of Grand Manan. The sea level is still rising today.
The Fundy Tides: With the influx of the Atlantic, and in combination with the effect created by the deep, carved valley underlying the Bay of Fundy, the world famous Fundy Tides were born.
In geological terms, the changes the tidal flow is making to Grand Manan's coastline are subtle. However, the sounds of Grand Manan's beaches indicate they are more dramatic than most maritime areas. You not only hear waves crashing, but the sounds of small rocks on larger, large rocks on even larger ones, boulders on boulders. |
A geological journey: From west to east, Grand Manan is a geological journey through time. A thin strip (at sea level) is part of the large, deep swath of sandy red soil which also runs through southern New Brunswick and Prince Edward Island. Anne of Green Gables has a tiny toe-hold on Grand Manan too! Dramatic volcanic basalt columns form the 100 metre high cliffs along Grand Manan's western shore - and in combination with two other major volcanic members, form two thirds of what is now the island.
However, running south, roughly from Whale Cove to Red Point, a third of the island is the remnants, often fully or partially metamorphosed, of the series of sedimentary layers laid down in the past - from the formation of Pangaea's inland lake to the wearing down of the Appalachians and other nearby land formations, to the glacial deposits. These are not simple layers and formations, but often dramatically altered by the various geological upheavals which have affected the region.
Grand Manan is a tiny island, barely 137 km² in size, but features a wide array of geological features, including some of the oldest exposed rocks which form the earth - it is like visiting a living museum. Each beach has collected bits of the past, exposes others - most are quite different from each other. We can recommend the McHone publications below - they can help those even with a casual interest in geology turn a quiet walk on one of Grand Manan's beaches into an adventure.
| We must thank all the sources below, and especially FreshAirAdventure, and J.A. Percy (one of their sources) for the concise overview which also helped to make more sense to the complexity we were seeing. We would also like to thank Greg McHone for providing his online articles below. |
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