An Overview of The Three Sisters

An Overview of The Three Sisters

Example Formal Discussion Question:
After reviewing your textbook and website information about volcanoes, choose one specific volcano in the modern Cascade Range.  Discuss the volcanic and geologic

history of your chosen volcano.  Appropriate topics include: How long has it been active?  What type of activity has it exhibited in the past?  What is the probability

of future activity?  What are the geologic hazards likely associated with future eruptions?

Example Student Post:

Subject: An Overview of The Three Sisters      Reply Modify Set Flag Remove

In the Central Cascade Range in Central Oregon, sit Oregon’s tallest trio of sisters. Each sister stand over ten thousand feet tall and none of the sisters have

erupted for nearly two thousand years. Appropriately named, The Three Sisters, it is speculated that the name was created by church members of an early Methodist

church in the mid 1800’s. The Church members gave name to the three peaks, calling them Mount Faith (The Northernmost point), Mount Hope (The middle), and Mount

Charity (The southernmost) (1). The sisters consist of three volcanoes, two of which are still active. The northern most volcano, a shield volcano, is the oldest of

the three, dating at about .3 million years old (2). According to geologists, it last erupted in the late Pleistocene, nearly 100,000 years ago (2).  The Middle

sister, a stratovolcano, is also middle in age (its age is still unknown) between the sisters. It is one of the two active volcanoes. The middle sister was last active

in late Pleistocene age and last erupted 50,000 years ago. The youngest sister, the southernmost peak of the trio stands as the tallest of the three, at 10,300 plus

feet tall. (3) It is considered the most active of the three and last erupted about 2,000 years ago. (3)  The eruption was described as, “explosive eruptions produced

small pyroclastic flows and tephra fallout from several aligned vents low on the south flank.” (3). The South sister also holds the highest lake in Oregon, Tearpool

drop. (3) Although it is commonly thought of that the sisters do not pose a threat to any of the nearby cities and resorts by eruption, in 2004 a series of small

earthquakes occurred near the epicenter of the South Sister, however, no activity has been recorded since that event.  Of course, since the Juan de Fuca plate is still

subducting, there is still a source of magma and these volcanoes could become active again at any time.  They are currently being monitored by the Cascade Volcano

Observatory. (2)

References

1.    U.S. Forest Service Website, Deschutes National Forest, 2002. http://www.usgs.gov/

2.     Scott and Gardner, 1990, Field trip guide to the central Oregon High Cascades, Part 1: Mount Bachelor-South Sister area: Oregon Geology, September 1990, v.42,

n.5. http://www.usgs.gov/

3.     Scott, et.al., 2001, Volcano Hazards in the Three Sisters Region, Oregon: USGS Open-File Report 99-437.  http://www.usgs.gov/

4.     Three Sisters. 08/13/08, Lyn Topinka http://vulcan.wr.usgs.gov/Volcanoes/Sisters/description_three_sisters.html

Example of Peer Evaluation:

Subject: Evaluation      Reply Modify Set Flag Remove       ‹ Previous Post
Show Parent Post
1. Positive feedback:
•    Criteria 1: Your word count is 336.  Good job with this.
•    Criteria 2: You picked an appropriate volcano to cover and discussed the volcanic history.  You used several facts, figures and statistics to support your

post.
•    Criteria 4: Your source material (the USGS) is of good quality and you had 4 sources.  (Although there were some issues, please see below)  All these sources

were original and you did not use sources that other student’s used.

2. Suggestions for improvement:
•    Criteria 2: There was a sentence that included information that was extraneous to the post: ‘Appropriately named, The Three Sisters, it is speculated that the

name was created by church members of an early Methodist church in the mid 1800’s.’  While that sentence is interesting, it is not related to the discussion question

or to the geologic history of the volcano.
•    Criteria 3: You missed several citations that were necessary within the text of the post.  The following sentences needed citations:
“Each sister stand over ten thousand feet tall and none of the sisters have erupted for nearly two thousand years.” needs a citation because you provide a statistic,

two thousand years, and you need to provide the source for that statistic.
“Appropriately named, The Three Sisters, it is speculated that the name was created by church members of an early Methodist church in the mid 1800’s.”  needs a

citation because you need to specify what your source for this ‘speculation’ is.
“The middle sister was last active in late Pleistocene age and last erupted 50,000 years ago.” Needs a citation because you provide a fact about the volcano being last

active and a date.
“Although it is commonly thought of that the sisters do not pose a threat to any of the nearby cities and resorts by eruption, in 2004 a series of small earthquakes

occurred near the epicenter of the South Sister, however, no activity has been recorded since that event.” Needs a citation because you provide a date and a fact about

the series of small earthquakes.
•    Criteria 4: You did not provide the correct web addresses for sources 1, 2 and 3.  The web address you provided is for the general usgs.gov website, which does

not contain the information that you cite in your post.  You needed to provide the specific web address for the page that you got the information from.   For example,

I found the information you cited for your source 1 at http://vulcan.wr.usgs.gov/LivingWith/Historical/volcano_names.html.  It was not available from the web address

you provided.  I could not find a web address for your second source, it looks like you copied the citation from another webpage that included a quote from that

source.  Your third source web address should be: http://geopubs.wr.usgs.gov/open-file/of99-437/ not www.usgs.gov.

Your post was interesting to read and I enjoyed it.

I have decided to post about the recent earthquake near Puerto Madero, Mexico.  This earthquake did not cause many deaths, but did do a lot of damage over a wide area

and caused several secondary hazards.  I think that earthquakes should not be considered only as isolated incidents.  They can be triggers for other incidents that are

sometimes more destructive than the earthquake itself.
On July 7th, 2014 at 06:23 am local time, a magnitude 6.9 earthquake struck two kilometers north east of Puerto Madero in the state of Chiapas in southern Mexico.  The

epicenter was estimated to be at 14.742 degrees north by 92.409 degrees west at a depth of 37.3 miles.  It has been determined that this was a thrust type earthquake

along the boarder of the North American and Cocos tectonic plates.  In this location the Cocos plate is sub-ducting under the North American plate at a velocity of 79

millimeters per year (M6.9-2km).
A thrust type earthquake is caused by a reverse fault with a slope of less than 45 degrees.  This type of fault creates vertical movement of the ground during an

earthquake.  The action of sub-duction (where one tectonic plate is forced to dive below and under another tectonic plate) creates localized reverse faults (Earthquake

Glossary).
This particular earthquake was sited by Guatemalan President Otto Perez Molina as causing the death of one newborn who was hit by falling debris, and 33 injuries.  He

also sited widespread damage to homes and businesses, power outages, school closures, and numerous landslides as being caused by the earthquake.  One of the landslides

reportedly buried a highway outside of Quetzaltenango.  In the Mexican state of Chiapas there were two reported deaths and 36 injuries as well as damage to buildings

and power outages (LA Times).
The National Weather Service did not issue any tsunami warnings or watches as a result of this earthquake (NOAA).  Even though it happened along the Pacific Rim, it

happened on land.  Thrust type earthquakes usually only make tsunamis if the epicenter is located near or under water.  The last earthquake along this fault rated

above magnitude 6.0 happened on October 21st, 1995.  It was measured at magnitude 7.1 at a depth of 159 kilometers (NEIC).
Los Angeles Times. Reported by Tracy Wilkinson.  “6.9 Earthquake Hits Mexico and Central America”.  7/7/2014 2:44 pm.  www.latimes.com/world/mexico-americas/la-fg-

strong-quake-hits-mexico-guatemala-2-dead-20140707-story.html.  Web. 7/8/2014.
National Oceanic and Atmospheric Administration (NOAA). National Weather Service (NWS). Pacific Tsunami Warning Center.  “Bulletin Number 001, 11:27z 07 July, 2014″.

www.tsunami.gov. Web. 7/8/2014.
United States Geological Survey.”Earthquake Glossary”.N.p.  N.d.  earthquake.usgs.gov/learn/glossary.  Web. 7/9/2014.
United States Geological Survey.  “M6.9-2km NNE of Puerto Madero, Mexico”.  N.p.  7/7/2014 11:28 am.  earthquake.usgs.gov/earthquakes/eventpage/usc000rrba#summary.

Web. 7/8/2014.
United States Geological Survey.  National Earthquake Information Center (NEIC).  “Earthquake Archive Search & URL Builder”.  N.p. N.d.

earthquake.usgs.gov/earthquakes/search.  Web. 7/9/2014.

The earthquake I chose for this discussion was the 2004 Sumatra-Andaman earthquake that occurred in the Indian Ocean. The “9.1 magnitude earthquake occurred on Sunday

December 26th, 2004 off the coast of northern Sumatra” (USGS). The main reason I picked this earthquake was the sheer devastation it brought upon Sumatra.The Sumatra

earthquake did not affect me at first, but after watching the horrific coverage of the earthquakes aftermath, it made me feel very pained for those people. The

earthquake did not really impact the city because the epicenter was roughly a hundred miles from the coast. The 9.1 magnitude earthquake has the longest duration of

faulting ever recorded and it brought one of the deadliest tsunamis to date. “The death toll was nearly 150,000 lives because of the 10 meter high walls of water”

(Cluff). When I saw the coverage of the tsunami I was stunned because I could not believe the destruction it brought; the 2004 Sumatra-Andaman earthquake was a 9.1

magnitude earthquake, third most powerful earthquake ever recorded, and the point where the fault split was roughly ten kilometers deep. The earthquake caused a

“tectonic subsidence resulting in 20 to 100 centimeters of down-warping of the earth’s crust beneath the Aceh region” (Cluff). The fault had then ruptured the ocean

floor and the two tectonic plates; the Indian plate subducted beneath the Burma plate. As for the history of earthquakes in that area there have not been any major

earthquakes that have occurred. People will definitely remember this earthquake for a long time, the 2004 Sumatra-Andaman; one of the most powerful earthquakes to date

and the destruction of the coastal towns due to the 10 meter high tsunami was just devastating. This earthquake was intriguing to research and I learned a lot of

interesting information about, earthquakes, faults, and there affects.
USCG. “Magnitude 9.1 – OFF THE WEST COAST OF NORTHERN SUMATRA.” Earthquake Hazards Program. U.S Geological Survey, 26 Dec. 2004. Web. 20 Jan. 2014.

<http://earthquake.usgs.gov/earthquakes/eqinthenews/2004/us2004slav/>.
Cluff, Lloyd. “Engineering for the Threat of Natural Disasters.” News Rss. National Academy of Engineering, 23 Apr. 2007. Web. 21 Jan. 2014.

<http://www.nae.edu/Publications/Bridge/EngineeringfortheThreatofNaturalDisasters/Effectsofthe2004Sumatra-AndamanEarthquakeandIndianOceanTsunamiinAcehProvince.aspx>.

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