The Ocean Bottom on the Mountain

Ernest Hemingway is rumored to have won a bet by telling the world's shortest story: "For Sale: Baby shoes, never worn."  As I sat on the side of Dorr Mountain, waxing geologically to my brother-in-law, he pointed out to me that the story I was telling was really much shorter than the words I was using.  Perhaps a shorter telling would have gone something like this: "Ocean bottom found on a mountaintop."

Hemingway's story was all about what it implied.  So what is implied by a four-foot boulder of ocean bottom rock?  Time.  Ignoring that this rock was part of a much larger formation, we can conclude that these four feet must have piled up over time.  One resource suggests that clay, likely once a major component of this chunk of sea floor, gathers at 10mm every thousand years.  This isn't a rock; this is a time lapse of 1.2 million years of arduously slow settling of clay.

So what about the mountain itself? The depths at which granite is formed are measured in miles (kilometers really, but this is America, right?).  That means that the bulb of granite that makes up most of Mount Desert Island once rested deep under the Earth's surface; now Dorr Mountain stands nearly a quarter mile above sea level.  Over the hundreds of millions of years since that deep magma cooled, wind, water and ice have excavated the remains of an ancient collision between North America and the ancient land mass on which MDI rests.

A look at the sea bottom rock implies something more. Several flat faces, on many planes, give evidence of glaciers. The glacier that plucked that rock from its original bed dragged the behemoth across the Earth's surface like cheese across a grater. The chaotic innards of the glacier occasionally flipped the mighty stone, smoothing yet another face.  The glacier, perhaps a mile tall, would have both ripped at Dorr, and been slowed by it. As the ice layed the mountain low, it may have slowed sufficiently to drop some of its load - seafloor included.

Hundreds of thousands of years of piling clay, miles of erosion, and an ice sheet a mile thick, all whispered in the language of rocks.  Scenes like this, like the glacier that came before them, cover Maine. Millions of shorts stories, implying so much more.

Ansley, J. E. 2000. The Teacher-Friendly Guide to the Geology of the Northeastern U.S. Paleontological Research Institution, Ithaca, NY.  

Hardcastle, Tim . "Pelagic clay ." Historical Geology- Wikibooks. Wikibooks, n.d. Web. 1 Sept. 2013. <http://en.wikibooks.org/wiki/Historical_Geology/

Miller, Robert B. , Scott R. Paterson, and Jennifer P. Matzel. "Plutonism at different crustal levels: Insights from the ~5–40 km (paleodepth) North Cascades crustal section, Washington." The Geological Society of America Special Paper 456 (2009)

Petford, N. , A. R. Cruden, K. J. W. McCaffrey, and J.-L. Vigneresse. "Granite magma formation, transport and emplacement in the Earth's crust." Nature408 (2000): 669-673. Print.

"Dorr Mountain : Climbing, Hiking & Mountaineering : SummitPost." Climbing, Hiking, Mountaineering : SummitPost. N.p., n.d. Web. 1 Sept. 2013. <http://www.summitpost.org/dorr-mountain/416282>.

A Piece of Ira: Unwrapping Turbidites

The first mistake many potential geology nerds make is to assume that any given rock doesn't have an interesting story.  If they didn't make that mistake I would be sitting here reading their blogs rather than writing my own.  What makes this error so common is that many of these stories are hidden, or written in languages that we can't read.  My friend Jenn brought me a wonderful story from Ira Mountain in a flat sparkly package.

Aww...Schist.  The sparkly covering on this rock is
ancient ocean bottom heated in a continent colliding oven.

Nothing wraps a rock in sparkles cheaper than mica.  Gold and Silver requires hot magma to transport heavy metals from deep within the Earth, where denser metals tend to reside.  Mica is a working man's sparkle.  It's the mud under your fingernails, or more likely the mud at the bottom of the ocean.  Fine-grained particles, like crushed up mica, drift through water under the power of the slightest current. They settle only when wave power is nearly nil.  In other words the deep dark ocean.  This mud is composed of a few things, but mica contributes heavily to the mix.  Of course, you'd never know it because the particles are so small.  Finishing the shiny package means burying the rock and crushing it between a continent, say North America, and a microcontinent, perhaps a prehistoric piece of land that now makes up shoreline on Maine, Greenland, the United Kingdom and Scandinavia called Avalonia. The heat and pressure caused small particles to migrate toward one another creating the large sparkles we now see.

Quartzite Revealed.  Notice the blockier texture on the
bottom half of the rock.  There is a thin layer of schist
below the quartzite,

Of course, you can't just wrap wrapping paper.  A glance between the layers of gray-green mica reveals a reddish blocky layer with a sugary appearance that has been compared to the texture of a gumdrop. This is where the surprise and the story lie.  Quartzite, unironically, is made out of quartz. Because quartz won't break down into to tiny pieces the way mica does, its grain size tends to bottom out at a 0.0025 inch.  The mass provided by this bulk causes even fast moving water like that on a wavy coastline to drop sand grains like they were hot, much to the enjoyment of southern Maine's beach-goers.  Crush that sand in the vise of continents and you get quartzite.

So what brings the unmoving abyss of the ocean bottom next to the active coast.  One possibility is time.  Sea level has fluctuated throughout geologic time.  To whit, the Hannaford in West Falmouth was built on ocean bottom from the ice age, and taking I-95 north of Gray reveals sandy roadsides that may be beaches of the same time period.  This sort of shift in water level is certainly capable of creating a rock that transitions from mudstone to sandstone and back again, or post crushing, a quartzite sandwich, with schist bread.

But there is another possibility.  The Carrabassett Formation, out of which the north half of Ira Mountain has been cut, is known for its turbidites.  Imagine an underwater ridge.  The top of the ridge, exposed to the movement of waves and the final surges of upland streams, plays host to hefty sediments like the aforementioned sand.  The bottom of the ridge, protected from the rigamarole, cradles the tiny clays. Then something happens.  A stream changes course.  A rogue wave mixes things up.  The ridgetop sediments, perhaps already precariously perched, fall down.  The movement stirs up everything, creating a stew of water, sand and clay.  As time passes the turbid water clears again, first dropping the heavy sand, then setting down the lighter clay.  This process would repeat again and again over the life of the ocean and the ridge until these layered sediments became stone.

Which of these possible histories is true is unclear.  Maybe this detail of the story is unwritten, or maybe I just haven't learned how to read this piece of the language.  It is the hope that we might know more, that there is some unwrapped gift, that keeps me looking and keeps me learning.

Adams, Dennis. "About Beach Sand."Beaufort County Library. Beaufort County Library, Web. 14 Aug. 2013. <http://www.beaufortcountylibrary.org/htdocs-sirsi/beachsan.htm>.

Dorais, Michael J., Robert P. Wintsch, Wendy R. Nelson, and Michael Tubrett. "Insights Into The Acadian Orogeny, New England Appalachians: A Provenance Study Of The Carrabassett And Kittery Formations, Maine." Atlantic Geology 45 (2009): 50-71.

Hanson, Lindley . "The many expressions of a New England formation." Vignettes: Key Concepts in Geomorphology. SERC, Web. 15 Aug. 2013. <http://serc.carleton.edu/vignettes/collection/25133.html>.

Schieber, Jürgen . "Sedimentary Structures." Indiana University. Indiana University, n.d. Web. 15 Aug. 2013. <http://www.indiana.edu/~geol105/images/gaia_chapter_5/sedimentary_structures.htm>.

Weller, Roger . "Schist Photos." Virtual Geology Museum. Cochise College , 24 May 2013. Web. 15 Aug. 2013. <http://skywalker.cochise.edu/wellerr/roc

The Long View: The Bones of Casco Bay

In his book, Roadside Geology of Maine, D.W Caldwell compares the islands of Casco Bay to the bones of a hand.  The view from the dock on Mackworth Island provides a view of these bones.  Like paleontologists we can use these bones to tell the stories of the past.

The view from Mackworth Island pier.  The rock that comprises farther islands
formed further in the past, because the land bows upwards.  The space between
islands tells us there was weaker rock there that has since eroded.

The bones were not always the long linear ridges you see before you.  In fact 470 million years ago you would have been looking at a flat landscape lain down by volcanos and the deposition of sediment.  A collision 400 million years ago changed all of that.  If you stood on the coast in Falmouth Foreside you'd be standing on the crest of a wave created by the collision.  The rocks between this apex and the outward islands were folded into a sine curve (a syncline to a geologist) as the microcontinent Avalonia tried to cuddle up closer to prehistoric North America.  The view from the pier provides a look over the trough of this wave and up to the next crest.

A representation of a syncline.  As you look across the bay imagine
standing on the flat edge of the gray near the anticline.  You
look forward past younger rock (brown) toward older (light tan)

While the wave still persists, it is not all it once was.  400 million years of water, ice and wind have shaved off a few pounds.  As you might expect the crests have lost the most weight.  This means the younger rocks on the peaks have been removed, allowing us a look at the older rocks below.  For this reason the farthest islands are the oldest rocks.  Effectively, as you look across Casco Bay, you look back in time.  So, what do you see?

It might be helpful to think of there being two rows of islands - The Great Diamond row and the Peaks Island row.  The back end of each of these islands is made of volcanic rock.  Volcanos form from melted rock and nature makes that happen by plunging older rock beneath Earth's surface.  This tends to happen when a continent (Avalonia) pushes its way across the Earth, submerging ocean bottom as it goes.  The two Atlanticward sides of these islands represent periods of time when Avalonia was encroaching on North America, but one didn't follow the other immediately.

These time periods when Avalonia was hauling across the world were punctuated by peaceful times of rest and erosion.  The front half of the Peaks Island Row, which includes Long Island is made up of the sediments that formed as the first film of volcanic rock broke down.  These sediments would have continued to pile up until volcanos started pumping out lava again.  When Avalonia resumed its movement, the volcanoes recommenced spewing, and the back half of Great Diamond and all of Little Diamond came into being.  When the conveyor belt stopped again, erosion and deposition started anew.  Some layers were tougher, some were weaker.  The strongest became Cow and Chebeauge
Islands and the front half of Great Diamond.  The weakest were torn apart by glaciers or washed away by streams.  Portland Harbor, which divides Portland and South Portland formed as the Fore River provided just this sort of differential erosion clearing schist and limestone from between banks of harder volcanic rock.

The bones of Casco Bay are what's left after 400 million years of erosion have cleaned off the flesh of weaker rock.  These remains tell the story of Avalonia's delivery to the shore of North America, and it can all be seen from Mackworth Island.

Caldwell, Dabney W. Roadside Geology of Maine. Missoula, MT: Mountain Pub., 1998. Print.

Hussey, Arthur M., and Henry N. Berry, IV. "Bedrock Geology of the Bath 1:100,000 Map Sheet, Coastal Maine." Maine Geological Survey: Bedrock Geology Bath 100K Report. Maine Geological Survey, 1 Feb. 2008. Web. 03 Aug. 2013. <http://www.maine.gov/doc/nrimc/mgs/explore/bedrock/b42/casco.htm>.

Marvinney, Robert G. "Simplified Bedrock Geologic Map of Maine." Map. Augusta, ME: Maine Geological Survey, 2002.

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

"Maine Geologic Map Data." Maine Geologic Map Data. 05 Apr. 2013. Web. 03 August 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 <http://web.wm.edu/geology/virginia/provinces/Blueridge/blue_ridge.html>. Website

"Camden Hills State Park." Camden Maine Sightseeing Attractions. Take Me 2 Camden Maine. Web. 26 July 2013. <http://www.camdenmainevacation.com/camden-hills-state-park.php>.
Website

"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. <http://www.jamestown-ri.info/acadian.htm>.

The Iron-y of the Situation

My friend came into town, we climbed a mountain, and we found a puddle.

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.

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.

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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.

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