Friday, July 26, 2013

New England's 50 Finest

Maine's 21 Finest.  Mountains with the tallest stature
independent of taller mountains
Recently a fellow blogger posted a list of New England's 50 Finest Peaks, or peaks with the tallest stature independent of another peak in the New England region. Maine is host to 21 of these. The map got me thinking. The peaks follow mostly straight line parallel to the slant of many of Maine's rock formations - the primordial continent that makes up the Chain of Lake region, the host of (once) tropical islands that collided 450 million years ago and the Japan-sized micro-continent that asserted itself onto the continent (and later split up) 350 million years ago.  So what is the source of our 21 finest?  The answer seemed to be none of the above.

The Grenville province makes an appearance in Maine
though not sufficient to host our tallest mountains.
The Blue Ridge Mountains in the southern United States and the Adirondacks in New York are formed from the remains of the Grenville mountain building event that plastered the Chain of Lakes onto North America around a billion years ago.  These monumental ranges may add credence to the idea that this billion year old collision led to our region's greatest mountains, but the evidence falls short.  First, although a few of the high peaks (Caribou, Kibby and Snow) reside in the area, the Grenville Province makes only a brief appearance in the left most corner of Maine.  The gneisses here, though mountainworthy, cannot claim the majority of the 21.
A fleet of ancient islands remain hidden in northern
Maine.  The 50 finest do not grace their shores.
Mount Greylock in Massachusetts, one of the 50 Finest, is a hunk of ocean bottom that got shoved up over the early North American continent in an event called the Taconic mountain building.  During this event an arc of small islands rode the tectonic plates onto the coast of pre-America.  Looking at a geological map of Maine reveals a clear series of these islands across northern Maine, not far from our largest mountains.  But none of these peaks grace the shores of these former islands - the heights are highest in the spaces in between.  So, the question remains, where did we get our giants?
A smaller continent, called Avalonia collided with
a proto-North America 350 million years ago, but could the
collision create a chain of islands 50 miles inland?
The Camden Hills are part of Avalonia, a microcontinent that slid into position on the coast of Maine 350 million years ago.  The ruffled sediments of this invading island continent make up Mount Megunitcook, Mount Battie and the rest. Could this collision also have created Maine's greatest peaks? The answer, finally, is yes and no.  The colliding of continents is no small thing, no matter how micro they may be.  The smashing was enough to give rise to the coastal mountains, but not sufficient to create the peaks almost 50 miles from the point of impact, so what was?

Almost all of Maine's largest mountains are underlain by
igneous rocks that welled up to the surface when Avalonia
collided with Maine.  A similar series of rocks got shoved
under Avalonia earlier in time creating smaller giants,
like Cadillac Mountain in Acadia.
The slab of Avalonia that got shoved underneath Maine traveled the 50 mile distance as it melted with depth.  Without crumpling, some of this molten rock floated up to Earth's surface forming volcanoes and much of the rest remained as underground stores of magma that cooled in place.  During its formation, this mountain range wouldn't have looked too different from the modern Andes, but 350 million years takes its toll.  Much of the volcanic rock has been eroded away (though some remains, notably as the Travelers in Baxter), so what has persisted is the roots of those mountains, particularly granite.

"Blue Ridge Province." The Geology of Virginia. William and Mary Department of Geology. Web. 26 July 2013 <>. Website

"Camden Hills State Park." Camden Maine Sightseeing Attractions. Take Me 2 Camden Maine. Web. 26 July 2013. <>.

"Maine Geologic Map Data." Maine Geologic Map Data. 05 Apr. 2013. Web. 03 July 2013.

"Taconic and Acadian Orogenies." Jamestown, Rhode Island. Web. 26 July 2013. <>.

1 comment: