Bubble Rock was deposited at the edge of a ledge on the mountain known as South Bubble by the glacier that sculpted Acadia during the last ice age. PHOTO BY DICK BROOM

Historical landscape shaped by mountain of ice



With tall mountains surrounded by the ocean, Mount Desert Island would have been pretty spectacular even if the last ice age had never occurred. But that was the clincher.

Starting roughly 30,000 years ago, a glacier up to half a mile thick began creeping from north to south across the island. As it moved, it scoured the mountains of soil and vegetation, leaving only the granite bedrock.

That is what French explorer Samuel de Champlain saw when he first sailed near the island in 1604. He wrote in his journal that the summit of most of the mountains were “destitute of trees, as there are only rocks on them.”

He named the island “Isle des Monts Déserts,” which translates to “Island of Bare Mountains.”

As the glacier moved over the island, it carved deep gorges where shallow valleys had been, and it created long, narrow basins that became lakes once the ice melted. That explains why the island’s major bodies of fresh water – Eagle Lake, Jordan Pond, Long Pond, Echo Lake and Seal Cove Pond – are all laid out north to south.

So is Somes Sound, which separates the two lobes of the island. It, too, would have become a lake, but the glacier cut an opening through the land at the southern end and allowed the ocean in.

Somes Sound is similar to a fjord – a long, narrow ocean inlet between high cliffs – but geologists have decided that it doesn’t have all the necessary characteristics. Instead, they describe it as a fjard, which is shorter, wider and not as deep as a true fjord.

Some of the rocks that are strewn over and around the mountains are more evidence of the incredible power of the glacier that shaped Mount Desert Island. As it moved south at, well, a glacial pace, it picked up rocks – some as big as minivans – from one place and dropped them in another.

Sometimes it transported rocks hundreds of miles before depositing them here, which explains why sometimes these rocks – called “glacial erratics” –look so different from all the other rocks around them. Well-known ones include Bubble Rock and Balance Rock on the Bar Harbor Shorepath.

They look out of place because, given their origin, they are.

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