Bloody Bluff Fault


I originally wanted to write about fault lines in general, because there are actually a lot of fault lines here. However, it turns out to be too broad a topic, so I decided to settle on just one fault line, a major one running through New England, the Bloody Bluff Fault. Yeah, the Bloody Bluff! How did it get that name? A powerful earthquake demolishing homes and killing people and spilling their blood everywhere. Nope. Not even close. Turns out the fault runs through a large swath of Massachusetts and Connecticut, including the town of Lexington, and there just so happened to be a battle there in 1775, in which a bunch of British soldiers had their collective asses whooped and sacrificed themselves for FREEDOM! or treason, depends on which side of the pond you are on. Perspective is everything.

Anyway, back to the fault line…

The Bloody Bluff fault was formed about 360 million years ago[i] when an island arc called The Avalon Terrane collided with the proto-North American and Eurasian plates before the formation of Pangaea.[ii] The rocks that made up the Avalon Terrane are now found in parts of Britain, Belgium, the Canadian Maritimes, southeastern New England, coastal Maine, and parts of Long Island as well as some of the nearby continental shelf.[iii] The Avalon Terrane was actually just one of three island arcs to collide into the proto-North American continent, the other two being the Nashoba and Merrimack Terranes which collided earlier.[iv] There is also a fourth terrane, the Megume Terrane, with is right on the elbow of Cape Cod, and is a piece of Gondwana – a supercontinent consisting of all continents besides what would become most of North America and Eurasia, and this particular portion would have been next to North Africa.[v]

The collision of the Avalon Terrane created a huge mountain range which would eventually be a part of the modern Appalachian Range in eastern North America.[vi] It also created a created a large strike- slip fault that separated the Avalonian Rocks from the proto-North American rocks.[vii] The fault is visible in Lexington, Massachusetts, and you can see where two rocks meet. And at this particular point along the fault line, the rocks to the west of the fault are granite[viii] while to the east the rock is mostly basalt.[ix] As a strike-slip fault, it would have behaved in a similar fashion to the modern day San Andreas Fault in California.

The Bloody Bluff Fault is still capable of earthquakes, though they are quite uncommon these days, it has unleashed earthquakes off the coast of Cape Ann in 1744 and 1755.[x] These quakes did a lot of property damage and the 1755 one even spawned a tsunami.[xi]

And 20 years later, the fault line would earn its name as Colonial militiamen faced off with British Regulars in the towns of Arlington, Concord and Lexington.[xii] After defeating British troops in Concord, the militiamen would chase the Regulars down what would be known as Battle Road, with other colonials ambushing them along the way, one of the major ambushes was at the Bloody Bluff where the British attempted to rally but then forced to retreat.[xiii] And this battle, which led to the American Revolutionary War, could have been avoided if the British Parliament simply didn’t pass the Intolerable Acts, (which I won’t get into here) pretty much punishing the entire populace of the Boston area instead of dealing with the grievances brought on by the colonists, or just simply going after the people responsible for the Boston Tea Party.[xiv] Stupid. And at the Bloody Bluff, there is a small monument to the effects of Parliament’s stupidity in which anyone can visit. The battle would eventually lead to the war which would create the United States, and would also give the Bloody Bluff Fault its name. Imagine how different things would be if Parliament had simply been smart.



[i] Skehan, James “Roadside Geology of Massachusetts” Pg. 45. Mountain Press, 2001. Missoula, Montana.

[ii] Skehan, James “Roadside Geology of Massachusetts” Pg. 43. Mountain Press, 2001. Missoula, Montana.

[iii] Skehan, James “Roadside Geology of Massachusetts” Pg. 45. Mountain Press, 2001. Missoula, Montana.

[iv] Skehan, James “Roadside Geology of Massachusetts” Pg. 35-42. Mountain Press, 2001. Missoula, Montana.

[v] Skehan, James “Roadside Geology of Massachusetts” Pg. 14. Mountain Press, 2001. Missoula, Montana.

[vi] Author Unknown “Acadian Orogeny” Wikipedia 23JUL2016

[vii] Author Unknown “Acadian Orogeny” Wikipedia 23JUL2016

[viii] Author Unknown “Bloody Bluff Fault Zone” Geologic Resources 23 JUL2016

[ix] Author Unknown “Bloody Bluff Fault Zone” 23JUL2016

[x] Aguirre, Edwin L. “Monster Earthquakes: Are we at Risk?” UMass Lowell 18MAR20111

[xi] Author Unknown “1755 Cape Ann Earthquake” Wikipedia 26JUL2016

[xii] Author Unknown “Battles of Concord and Lexington” Wikipedia 26JUL2016

[xiii] Author Unknown “Areas AF & AQ – Minute Man National Historic Park” Lexington Comprehensive Cultural Resources Survey” 2010 viewed 26JUL2016

[xiv] Author Unknown “The Intolerable Acts” Wikipedia 26JUL2016


Photo Credit: Me


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