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Earthquakes and Faults in Connecticut

Name: ___________________________  Period _____

Earthquakes and Faults in Connecticut

On the 16th of May, 1791, in Moodus, Connecticut, the calm of twilight was shattered by a great shaking of the ground. A few years later, a local pastor prepared this description of the events of that night.  

It began at 8 o'clock, P.M. with two very heavy shocks in quick succession. The first was the most powerful; the earth appeared to undergo very violent convulsions. The stone walls were thrown down, chimneys were untopped [the top fell off, of course – Mr. S.], doors which were latched were thrown open, and a fissure [crack] in the ground of several rods [1 rod = 16.5 feet] in extent was afterwards discovered . . . This shock was felt at a great distance. It was so severe at Killingworth (about 20 miles distant), that a Captain Benedict, who was walking the deck of his vessel, then lying in the harbor of that place, observed the fish to leap out of water in every direction as far as his eye could reach.11  [question – why would an earthquake make fish jump???] 

This was the worst of a long history of shakes that have been felt in Moodus over the last four centuries. Usually, these earth tremors have been associated with loud rumbling noises variously described by those who have experienced them as "strange bellowing" (Reverend Jeremiah Hobart, in 1702) and "the noise of a cannon shot, or severe thunder" (Reverend Stephen Hosmer, in 1729).12 John De Forest, a mid-1800s historian, gave the most dramatic description:  

Even of late years, strange noises and rumblings are said to have been heard at times in the bowels of this mountain [Mount Tom, a hill in Moodus], and slight shocks, as of an earthquake, have been felt through the surrounding country . . . The astonished inhabitants have heard terrible roarings in the atmosphere. "  

The whole phenomenon of tremors and noises is often referred to as the "Moodus noises" The name Moodus is said to derive from Machemoodus, a Wangunk Indian name which means "there is a bad noise" or "place of noises."14  

Native Americans reputedly believed that this was the dwelling place of Hobbamock, a powerful spirit angered by the arrival of Europeans to Connecticut. One colonial legend attributed the noises to fights between the black-magic witches of Devil's Hopyard in Haddam and the white-magic witches of Moodus. The fights took place under Mount Tom. Supposedly, the Devil refereed.  

Numerous pseudoscientific [fake] explanations have been put forth, such as this one from 1884:  

    "There is a subterranean [sub = under + terra = Earth] passage leading from a large cave near Mount Tom to the sea, and ... the noises are produced by certain delicate combinations of wind and tide."16  

    Geologists now recognize Moodus as one of the most active earthquake zones in New England. Although people tend to think of New England as rock-steady country, it is actually a region of moderate earthquake activity.  [those old faults from the joining and splitting of Pangaea are still there] 

    The largest earthquake ever to strike the Northeast rocked Quebec in 1663. This quake was a big one even by Californian standards and was felt throughout Connecticut. Fortunately, region had few inhabitants and lies far from New England's cities. But if another quake like the 1663 jolt were to occur, property damage could be considerable throughout New England. Geologists are also concerned about Cape Ann, Massachusetts, which was hit by a big quake in 1755.  Although few earthquakes have occurred there since, this may only mean another big one is building up - instead of releasing pent-up energy with frequent, small shocks, as does the Ossipee, New Hampshire region [remember ��seismic gaps��??]. If a quake like the one of 1755 struck Cape Ann again, the damage could be substantial - especially in downtown Boston. 

    Mount Tom, focus of many of the 
    "Moodus noises" earthquakes, rises 
    above Salmon River Cove on the 
    Connecticut River in this deceptively 
    calm 19th-century scene.

    Although there has been no repeat of the shock of 1791, earthquakes still occur in Moodus. During 1981 and 1982, a swarm of quakes shook the region more than 500 times in the course of several months. Almost all of these tremors were too small to be felt, except by sensitive instruments. The potential remains for another moderate quake, or even a repeat of 1791.  

    There are many more inactive faults than active ones. Connecticut, for example, is cut by hundreds of faults of various sizes, almost all of which are completely inactive. No spot in the state is more than five miles from a fault. They often mark the boundary between two contrasting rock types (terranes!) brought in contact by crustal motions long ago.       

    Remember that Avalonia was a volcanic island arc at a subduction zone! 

    500 million years ago: The oceans begin to close. 

                       250 million years ago: The collision is complete.


    The present: The Atlantic Ocean continues to widen.

    One of the most important faults in Connecticut is the Eastern Border Fault, which is where the central valley tilted.  

    Another is the Cameron's Line Fault which divides the [Proto-North America.] Northwest Highlands from the rest of the Western Uplands [Iapetos Ocean Mud].  

    In eastern Connecticut lies the Lake Chargoggagogg manchauggagogg chaubunagungamaug Fault, named for a lake in Massachusetts (also called Lake Webster) which lies on the fault. The name translates roughly as "You fish on your side, I fish on my side, nobody fish in the middle - no trouble".  

    Connecticut has the oldest record of earthquakes in the United States.  The earliest settlers learned of seismic activity in this area, dating back to 1568 in Moodus, from the native Indians.  Earthquakes measuring more than 4.3 on the Richter scale have shaken our largest cities.    

    Connecticut is considered to be a in a moderate seismic risk zone as defined by the Federal Emergency Management Agency. 

    The hard rock in Connecticut can transmit seismic waves over an area 4 to 40 times more efficiently than the soft rock and sand in California.  People in our region can be at greater risk since many buildings are not built with reinforced materials nor seismically designed.   The chance of a damaging earthquake of magnitude 5.0 or greater is 1 in 20 each year.  The odds of a magnitude 6.0 earthquake in Connecticut are about 1 in 300 annually. 

    Earthquake Magnitude Richter scale

    Magnitude Earthquake Effects Estimated Number 
    Each Year
    2.5 or less Usually not felt, but can be recorded by seismograph. 900,000
    2.5 to 5.4 Often felt, but only causes minor damage. 30,000
    5.5 to 6.0 Slight damage to buildings and other structures. 500
    6.1 to 6.9 May cause a lot of damage in very populated areas. 100
    7.0 to 7.9 Major earthquake. Serious damage. 20
    8.0 or greater Great earthquake. Can totally destroy communities near the epicenter. One every 5 to 10 years

    Adapted from 

     BULLETIN 110



    The Face of Connecticut

    People, Geology, and the Land


    Michael Bell

                                             ISBN 0-942081-01-3 


    Mr. Schwartz Earth Science      Earthquakes in CT 20% Summary                               /16 

    Objective:  Your job is to write a summary of the attached article, 1/5th the length of the original, then respond to the article.   

    Instructions:  Before writing your summary, do the following: 

    • Read the article once through quickly, then take care to re-read the few paragraph and the first sentence of each following paragraph carefully.   
    • Slash! Cross out as much as you can in each paragraph, leaving only the most important parts.  You are successful when there is nothing left to take away. 
    • Write a draft of your summary.  You may want to keep a running word count.  Your goal is approximately 20% of the words (this article contains 1055 words, so you want to write between 180 and 220 words).   
    • After your summary, write another paragraph that extends the information:  what do you want to know next, what do you not understand?  Possible ways to start your response are:  ��This connects to my life����,   ��I wonder���� , ��This is important because����,   ��I don��t understand ___ because����,    ��I want to remember ___ because����,   ��The most important passage is ___ because���� 
    • Either read this out loud to someone else, have them read it to you, or read it out loud to yourself.  Does it make sense?  Does it accurately summarize the original article? Rewrite it with your improvements. 


    1. You must include the following terms in a way that shows you know what they mean.  If you can not tell from the reading, use a dictionary:      tremor   fissure   fault
    1. You must include one short, correctly punctuated quotation (3 to 9 words) in your summary.  Remember that the purpose of a quote is to use someone else��s opinion or words to make your summary more interesting!  This is extra -  NOT just part of the article!  Who said it?? 
    1. No more than 4 words in a row may be taken from the original text (excluding your quote).  More than that is plagiarism and will cost you 16 points. 
    1. You must use correct spelling, complete sentences, correct capitalization and punctuation, and I must be able to read your work  (typed preferred – 12 point double-spaced or blue/black pen.  No pencil or colored pens/markers). 
    Content Knowledge

    5 Points

    All main ideas are included and explained clearly and are correct.  5 points Most main ideas included and explained clearly, or all ideas included, not all are clear and correct.  3.5 Many main ideas included and explained clearly, or most ideas are included but not clear and correct. 2.5 Only a few ideas included and explained clearly, or no ideas clear and correct. 1
    Technical Terminology 1 points All expected technical terms included and used correctly. 1 points 1 term missing or not used correctly.


    2 terms missing or not used correctly.


    3 terms missing or not used correctly.



    1 point

    Quotation provided that adds emphasis or opinion of original source with citation.  1 Quotation provided that adds emphasis or opinion of original source without citation.  0.5   Appropriate quotation not provided.  0
    Grammar and Spelling 1 No misspellings or grammatical errors. 

    1 point

    No more than two misspellings and/or grammatical errors.  .6 Three misspellings and/or grammatical errors. 


    Four or more spelling errors and/or grammatical errors. 


    Correct  Length 1 Summary is 20% of original article length  1     Summary is not close to 10% of original article length 0

    7 points

    Your comments show a good understanding of the events, and evidence of reflection 3 Your comments show a fair understanding of the events, and some evidence of reflection  2 Your comments show some understanding of the events, and a little evidence of reflection  2 Your comments show a lack of  understanding of the events, and no evidence of reflection  0

    Homework - Standard Earthquakes in CT 10 Percent New.doc

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