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 1

A name should tell you something.  When it comes to rocks this is generally the case.  In sedimentary rocks, the name tends to give away the energy of the sedimentary environment.  Sandstone forms wherever sand might gather - like a beach with strong waves or a fast moving stream.  Shale evolves where clay might gather, say the bottom of the ocean.  Conglomerate, along similar lines, is birthed where gravel collects - perhaps a raging river or a bar in a particularly active part of the ocean.  The name conglomerate tells you that there was enough energy to carry rocks there, but the rock tells you a lot more.

Last summer I visited two conglomerate outcrops; one was Mount Battie in Camden, the other Mars Hill Mountain in Mars Hill.  These two rocks couldn't be any different while sharing the same name.  Each rock tells this history of its own place in three distinct chapters.

Chapter 1: Clasts

Mount Battie Conglomerate - Round Quartzite Clasts Circled

One neat thing about conglomerates is there are two sets of rocks with stories to tell: the conglomerate itself, and the rocks parts that are cemented together within it.  The rock parts (or in geology speak, clasts) at the two sites are surely at odds.  The Mount Battie conglomerate is made up of rounded, light colored clasts about the size and appearance of a pale gray gumdrop.  The gumdrops are quartzite.  If we could turn back the clock we would see that these chunks (like all quartzite) were once sandstone.  Imagine a wave rocked ocean off the coast of some forgotten continent.  Sand piles up (pure sand; we know this because the quartzite is so light in color) and eventually, chemical intrusion turns it from packed sand to sandstone.  Once loose sand, now solid rock, as they say, even this shall pass.  Perhaps the land gets raised and rivers cut through.  The slab of rock, once a beach, is broken by time and water into smaller pieces.  As the water courses the rocks get rounder and rounder.

Mars Hill Conglomerate - Flat Black Clasts Squared, Jagged
Edge Visible on Top Piece

Mars Hill has a different story.  The rocks that comprise this conglomerate are flat and black.  The flatness (and perhaps the darkness) suggests that this rock may be a shale formed in a  low energy environment.  This rock probably sat at the bottom of some ocean.  Layer upon layer of fine-grained sediment coasted to the seafloor at a ridiculously slow pace, with added phytoplankton and low oxygen levels coloring the sediment black.  Here too the land becomes elevated.  Streams shatter the shale and push it downstream.  The current softens the edges a bit before the slivers of rock reach an endpoint.

The endpoint, however is just an endpoint, not the end.  The beach, the ocean bottom, they are just the first step in the stories told by these rocks.  Check back soon for chapter 2 and 3.

Dietrich, Richard Vincent, and Brian J. Skinner. Rocks and Rock Minerals. New York: Wiley, 1979. Print.

Way, Bryan. "Black Shales." 1 Dec. 2006. Web. 28 June 2013. <http://faculty.umf.maine.edu/eastler/public.www/Black%20Shales.pdf>.

Maine's Earthquakes

Today there was a small earthquake about 7 miles from Augusta Maine.  The quake was a 2.6 on the Richter Scale.  Because the Richter scale is logarithmic, each point it rises means the quake is 10 times stronger.  By extension, this quake was about 100 times gentler than the 4.5 that many of us in southern Maine felt last October 16th.

We're used to hearing about big earthquakes: The 2010 Haiti earthquake (7.0), the 2011 Japan earthquake (9.5, 10,000,000 times as powerful as the one felt today) or the ones that occur along the San Andreas in California.  All of these occur on active plate boundaries where one plate is shoving under or, in the case of California, past another, but what's happening in Maine?  There haven't been any active plate boundaries in Maine for more than 200 million years.

If you could look at Maine's Carfax report it would not look good.  Maine is the victim, nay product, of several collisions with other landmasses.  Each one left Maine with several small faults, where the old continents docked.  Then there was the stretching.  When Pangaea split the continent spread to fill up the old space.  Some parts of once solid rock sank down, while others remained aloft.  The result: despite it's beautiful exterior, our state has some pretty severe internal damage.

There are faults on the surface within 15 miles of today's earthquake, but the earthquake occurred 3.1 miles underground.  It's difficult to assign blame for the earth shift that occurred, but we can be assured that it is a result of Maine's storied tectonic history.

"Central Maine Feels 2.6 Magnitude Earthquake." Bangor Daily News. 21 June 2013. Web. 21 June 2013. <http://bangordailynews.com/2013/06/21/news/state/central-maine-feels-2-6-magnitude-earthquake-sidney/>.

"M2.6 - 2km W of Sidney, Maine." Earthquake Hazards Program. United States Geological Survey, 21 June 2013. Web. 21 June 2013. <http://earthquake.usgs.gov/earthquakes/eventpage/usc000hx15#summary>.

"Maine Earthquakes 1997 to Present." Maine Geological Survey. State of Maine. Web. 21 June 2013. <http://www.maine.gov/doc/nrimc/mgs/explore/hazards/quake/quake-recent.htm>.

The Long View: Watching the Earth Move

It surprised me when I read that you could see Mount Washington from a hilltop in Falmouth, so when I climbed Stone Ridge, I was impressed with the amazing view.  My first visit on a clear day in April gave me a Kodachrome view of the mountain and the broad landscape between here and there.  It wasn't until much later that I realized that this might just be the perfect perch from which to watch the earth move.

Of course the White Mountains were just the starting point (well, really Mount Royal in Montreal, Canada, but you can't see that far).  One hundred eighty million years ago there was a hot spot under what would one day become eastern New Hampshire.  In geology, a hot spot is a thin stream of Earth's heated innards bubbling up towards the surface over a long period of time.  When the hot spot underlies a continent the result is violent, explosive eruptions at the surface.  These eruptions and the super-heated magma below the surface built the White Mountains over twelve million years.

The hot spot never moved, and it never stopped bubbling.  The good news for the residents of North Conway, is that New Hampshire did.  When Pangaea split apart, opening the Atlantic Ocean, North America pushed westward, and Africa pushed (relatively) eastward.  By one hundred twelve million years the continent had moved to the point that the hot spot underlay Denmark, Maine, building Pleasant Mountain.  By one hundred eight million the Earth was bubbling in Brownfield, forming Burnt Meadow Mountain.  

The View from Stone Ridge in Falmouth.  Burnt Meadow Mountain is in the center, the White Mountains on the right, and Pleasant Mountain in between.  All are highlighted in red. (a lot of time on Google Earth may not have made up for poor spatial ability; leave comments if you think I've misidentified the mountains).

Soon after the North American continent escaped the fiery clutches of the hot spot, but the hot spot didn't quit.  Between 100 and 75 million years ago it left a trail of underwater mountains (called seamounts) stretching from the continental shelf to the mid-ocean ridge.  At that point, the seamounts seem to sputter out, that is until they emerged on the opposite side of the ridge, where as recently as 10 million years ago they appeared to be approaching Africa and the Canary Islands (or really Africa was approaching the hot spot).

Of course we can't see all of that from Falmouth, but we can see a few million years of continental progress, before the horizon shades our view.  On a clear day, the White Mountains are visible and Pleasant and Burnt Meadow Mountain can be seen as well.  The picture provides not just beautiful scenery, but a window into the tectonic motion that occurs over millions of years.

"Science Reference: Hotspot (geology)." ScienceDaily. ScienceDaily. Web. 19 June 2013. <http://www.sciencedaily.com/articles/h/hotspot_(geology).htm>.

Girty, G. H. "Chapter 2: Volcanoes." Perilous Earth: Understanding Processes Behind Natural Disasters. Department of Geological Sciences, San Diego State University, June 2009. Web. 1 June 2013.<http://www.geology.sdsu.edu/visualgeology/naturaldisasters/Chapters/Chapter2Volcanoes.pdf>.

Watling, Les. "Geological Origin of the New England Seamount Chain." NOAA Ocean Explorer Podcast RSS. Web. 19 June 2013 <http://oceanexplorer.noaa.gov/explorations/03mountains/background/geology/geology.html>.

Zartman, R. E. "Geochronology of Some Alkalic Rock Provinces in Eastern and Central United States." Annual Review of Earth and Planetary Sciences 5.1 (1977): 257-86.