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. <>.

Sunday, July 21, 2013

Tuesday, July 16, 2013

A Trip to Baxter Four Hundred Million Years Ago

To visit Baxter State Park during Devonian time would have been quite an experience.  Devonian time extends from 419 million years ago, when fish were just starting to widen their grip as rulers of the ocean, to 359 million years ago, when amphibians were testing their new toes on continental soil.  It is during this period of prehistory when almost the entirety of Baxter's bedrock was lain down.

419 million years ago, to travel the path that one takes to the north entrance of the park from Patten would require a boat.  Paddling north on the route that 159 takes, you'd hit land not far south of Shin Pond and a long portage would take you over the island arc and continue you on your way.  The island extends into the realm of the park only in so much as the rains tearing apart the island, at a snails pace, were delivering the islands sedimentary fragments into the surrounding ocean.  The heavier sand dropped first in a wide delta, while the smaller silt and clay drifted farther into the ocean, only to be dropped when the stream's energy had been almost fully spent.  The sandstone that was once the delta can be found along the eastern edge of the park, while the old ocean bottom wraps the northern and western sides.

The trip up Katahdin would have, in fact, been a descent.  While the portage island was being torn apart, southern Maine was plunging beneath northern. As the ocean bottom sank, it melted.  As it melted it rose, creating an upside down tear drop of magma not far from the surface, but still a ways down from Baxter Peak's current stature.  As the magma cooled, minerals formed creating the small, but visible crystals of the Katahdin granite.  The magmatic elements paired off, leaving behind the ingredients of water vapor.  The bubbling gas rose to the top of the magma chamber.  As the magma hardened around the bubbles it left cavities in which different minerals could form.  The change from the liquid magma chamber which formed the base of Katahdin to the frothy top, which formed the peaks is visible today as the white, even grained granite evolves into reddish, multi-textured granite.

While the Travelers are smaller in stature now, they literally rose out of Katahdin during the Devonian.  The Traveler Rhyolite was the volcano to Katahdin's magma chamber.  A trip there means braving molten lava, but also burning ash.  A hellish expedition to be sure, but at least there wouldn't be any black flies.  The drifting ash interbedded with the lava and then flowed down slope.  In modern times the flow is visible because the gray ash is flattened amidst the white rhyolite.

Later in the Devonian, a trip down the South Branch Pond Brook, geologically, wouldn't have been too much different than it is now.  The towering volcanoes, like the mountains that now stand, would have provided a prime environment for raging rivers powerful enough to break apart and then round the edges of chunks of rhyolite.  Smaller particles would be taken farther off to sea.   This order is preserved in the sequence of rocks below the falls - rhyolite, conglomerate, finer-grained sedimentary rock.

With current technology as a limit, an adventure in Devonian Baxter State Park is of course an impossibility.  The current landscape becomes our only time machine through which to view this exciting period in Maine's history.

Osberg, Philip H., Hussey, Arthur M., II, and Boone, Gary M. (editors), 1985, Bedrock geologic map of Maine; Maine Geological Survey (Department of Conservation), scale 1:500,000

Rankin, Douglas W., and Dabney W. Caldwell. A Guide to the Geology of Baxter State Park and Katahdin. Augusta, Me.: Maine Geological Survey, Dept. of Conservation, 2010. Print.

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

Wednesday, July 3, 2013

A Tale of Two Conglomerates: Chapter 3

This is Chapter 3 of a 3 part blog post.  Click here to read part 1 or here to read part 2.

Chapter 3: Metamorphism
When we last left our conglomerate heroes Mount Battie was hanging out around the South Pole, and Mars Hill near the equator.  As you can probably guess they didn't stay put.  Mars Hill and what is called the Laurentian Continent sped north, but Mount Battie and the Avalonian microcontinent sped faster.  The result: a Mack truck v. Geo Metro collision of geologic proportions (in other words, incredibly powerful, and extremely slow).  This last segment of the post is the claims adjuster's report, with metamorphism in the rocks marking the damage.

Metamorphism is a process in which rocks are changed by heat and pressure, and the Midcoast certainly endured both during the collision.  Before the collision, the sandstone that made up both the clasts, and the matrix, would have been indiscernible from sand except for the fact that the sand was cemented together into a rock.  After the collision geologists find a set of minerals called amphibolite.  Unable to form under different conditions, amphibolite tells our adjuster that the collision caused a pressure equivalent of between one and six of those Mack trucks resting on every inch of rock, while the temperature rose to around 1000 degrees fahrenheit.  Under these conditions a literal Geo Metro would be obliterated.  Our figurative car is merely transformed.  The heat and pressure of the continents colliding is enough to recrystallize the sand - converting them from discernible grains into an interlocking mass, which is called quartzite.

This is not to say that the Laurentian truck did not take damage.  Androscoggin County endured an equivalent amount of metamorphism.  But if the Midcoast and Androscoggin County were the respective front bumpers of our Metro and our Mack Truck then Mars Hill is the back end of the truck, experiencing little damage.  The clay particles in the shale clasts, under similar conditions to Mount Battie, would have recrystallized.  This would have made the pebbles look like miniature disco balls, called schist, within their matrix.  Limestone can endure a lot of heat. The limestone matrix may have remained limestone, however, it is also possible that other materials like quartz may have been injected through the rock.  In this scenario quartz, or silica, replace some of the elements in a calcium carbonate limestone creating what is called a calc-silicate rock. Instead, what we are left with looks like what we started with a mixture of limestone mud and pieces of rock all piled together heated scarcely above the temperature necessary to turn the amalgamation into stone.

Bartok, Peter. "Geology of Ireland and the United Kingdom." Ireland and United Kingdom. Tarryton, NY: Marshall Cavendish, 2010. 15-16.

Mottana, Annibale, Rodolfo Crespi, and Giuseppe Liborio. Simon and Schuster's Guide to Rocks and Minerals. Ed. Martin Prinz, George E. Harlow, and Joseph Peters. New York: Simon and Schuster, 1978. Print.

"How Much Does a Mack Truck Weigh?" Web. 03 July 2013.

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

Monday, July 1, 2013

A Tale of Two Conglomerates: Chapter 2

This is Chapter 2 of a 3 part blog post.  Click here to read part 1.

Chapter 2: The Matrix
Conglomerates share there stories in several ways.  The pebbles that fall together to make the rock tell a story of what came before.  The stuff that holds the rock together - the matrix - speaks about what was happening when the rock came together.

Four hundred and fifty million years ago, Mars Hill would have been pretty close to the Equator.  This time period also happened to be when coral were distributed widely around the world.  These facts were unknown to me at the time I first visited Mars Hill.  What I did know, however, was that Mars Hill was not far from a town called Limestone.  I looked at those clasts, and I looked at the stuff that held them together (called the matrix in the geology world), and I wondered.  I have since broken my piece of conglomerate and, logically, dropped it in vinegar.  The neat thing about limestone is that you don't have to wonder for long.  Dropping limestone in vinegar causes a reaction between the acetic acid of vinegar and the limestone base, causing carbon dioxide to fizz off.  Soon after the rock hit the bottom of the mug, bubbles started rising to the surface of the vinegar.  Four hundred and fifty million years ago, about the same time that ocean bottom rock was being torn apart, a coral reef, not far from Mars Hill was breaking down as well.  While the majority of this calcium carbonate piled up on flat ocean bottom, creating the substrate for Aroostook County's potatoes, some followed the flow of water over some sort of cliff into some kind of deep water canyon allowing shale pebbles and limestone mud to mix together.

The pebbles that make up the Mount Battie conglomerate are held together by something else.  500 million years ago, Mount Battie was in a part of the world not very likely to host coral.  The Avalonian microcontinent, perhaps similar in form to today's Japan, was on the bottom part of the world, below the 60th parallel.  The matrix here, insoluble in acid, is quartzite, indicating a sandy environment.  Layering at the site indicates the sand gathered in an ocean basin, where wave action swept away most of the smaller sediments, leaving behind sandstone pebbles in a matrix of sand.  This shore line would have been a bit cold for developing coral reefs, excluding the development of limestone in the area.  This gravelly beach the stage for our future coastal mountain.      
Modern World Coral Reef Locations - Credit: NASA

Berry, Henry N., IV. "The Bedrock Geology of Mount Battie, Camden." Maine Geological Survey: , Maine. Maine Geological Survey, 19 Apr. 2012. Web. 01 July 2013. <>.

Scotese, C. R. "Earth History." Plate Tectonic Maps and Continental Drift Animations. PALEOMAP Project. Web. 01 July 2013. <>.

Wang, Chunzeng, Gary Boone, and Bill Forbes. "Geology of Mars Hill Mountain and Vicinity." Http:// Web. 1 July 2013. <>.