the earth scientist

Read it online at www.nestanet.org

Volume XXII, Issue 2 Spring 2006

THE EARTH SCIENTIST

Total solar eclipse showing the Sun's corona. Copyright 1995 by Fred Espenak.

INSIDE THIS ISSUE... From the President

2

Revisiting the BOSS Model: Building Resonance

12

From the Executive Advisor

3

Joining NESTA

16

Sharathons at NSTA Anaheim

4

Rock Music in the Geoscience Classroom

17

A Total Eclipse of the Sun

5

Statistical Analysis of Foci Data

23

Earth Science Week 2006

10

Investigating Lava Flows

26

USGS Earthquake Science

11

TES Article Submission Guidelines

31

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FROM THE PRESIDENT From Your (Retiring) President I first joined the NESTA after I went on an NESTA Caving Field Trip, headed by Dr. Harold B. Stonehouse at the NSTA Convention in St. Louis in 1988. A couple of years later, I served two terms as the President of the Iowa Earth Science Teachers. Then in late 1991, I put my hat into the ring and was elected to serve NESTA as the Central Region Director, which I did from 1992 through 1996. In 1996, I was appointed by NESTA to serve two years as the NESTA Liaison on the American Geophysical Union’s Committee on Education and Human Relations. In 1998, I was appointed by the AGU to serve two more years on that same committee, this time as a full member. In 1998, I again put my hat into the ring and became the President Elect of NESTA. I served as President from 2000 through 2002. In Atlanta, in 2004, because of a resignation, instead of going off the board at the end of my term as Past President, I volunteered to step into a vacancy that had occurred in the incoming President’s slot, and serve a second term as NESTA President. At the end of that 2 year commitment, in Anaheim, and I am looking forward to serving NESTA as your Past President.

NESTA Contacts President Parker Pennington IV [email protected] President Elect Michael Passow [email protected] Executive Advisor Roberta Johnson [email protected] Secretary Missy Holzer [email protected] Treasurer Bruce Hall [email protected] Retiring President Tom Ervin [email protected]

In 2008, when I am retired as your Past President, I will have completed 20 years as a member of NESTA, much of that time in a position of service. It is at this point, that two things occur to me: 1.) In the Winter 2006 issue of The Earth Scientist, Volume XXII, Issue I, page 2, I listed the current status of things in the NESTA organization. You can find this TES issue, on-line, at http://www.nestanet.org The upshot of that list is that in a relatively short period of time, NESTA, as an organization, has made many, rather significant, positive strides toward the future. 2.) This is where you come in. We need you! We need you to look at the potential that NESTA has to offer educators who, like you, have an interest in the teaching of earth science primarily at the K–12 level, and then look at yourself as a professional, and decide if you are at a point in your career where you are able to step forward, and place your own name in nomination for one of the various NESTA leadership positions which are annually available. You can serve NESTA, be it as officer, one of the Regional Directorships, or as the volunteer from your state to serve as the NESTA State Contact Person. NESTA is poised on the edge of tremendous growth and excitement. You only need to share with us, your willingness to serve, and you can be a part of the future of Earth Science Education. If you have any questions, please contact me at [email protected] or by phone at 563-289-3139.

Editor & Designer Michael J. Smith Michaeljsmith99@ comcast.net

Tom Ervin NESTA President 2002-2004 & 2004-2006

Volume XXII, Issue 2

FROM THE EXECUTIVE ADVISOR Colleagues, After 15 years (going on 16), this will be my last correspondence to you as the NESTA Executive Advisor. It has been a rewarding journey, full of all kinds of experiences. What has been accomplished by NESTA over these last 15 years has been through the support of the membership. To try and mention all of the wonderful help from volunteers who have put on NESTA events at NSTA regional and national meetings would take up far more space than allotted me here. My thank you goes out collectively and individually to each and every one of you who participated in making NESTA what it is today. This brings me a key theme that has flowed through my EA letters—the importance of you—the member—and your support of NESTA. NESTA works because of volunteerism. Step up to the plate and put your name on the list. There is a place for everyone at this big table. Presenters and helpers are needed for NESTA Share-a-thons, rock raffles, and other sessions at NSTA meetings. Consider putting on one of these events at the next meeting of your state science teachers association. These events are great recruiting tools. As I prepare for the NSTA national conference this week and my last board meeting I would like to say a few words about the state of the Association. In addition to Roberta Johnson taking over my duties there will be a new slate of officers in the Executive positions and on the Board. Go to the NESTA website and find out how to contact these officers and how you can help NESTA. State contacts are needed for several states. These people serve as NESTA representative in their state and relay information about national activities to members in their state and their state activities to the NESTA. One of the highlights over the past year has been seeing our publication, The Earth Scientist, move up several notches in quality. Much of the credit for this goes to Editor Mike Smith who has put together a fine design and to our supporters who have been sponsoring theme issues. We look forward to more theme issues in the future. The Share-a-thons and rock raffles continue to be some of the most popular sessions at NSTA meetings as does the Earth and Space Science Resource day. My thanks go out to those who support these activities, our sponsors, and to the individuals who donate time and materials. As a mark of how NESTA is perceived in the Earth science education community, I have been approached by several organizations who are putting forth proposals to Geo-teach, an NSF-funded initiative. These organizations are seeking NESTA cooperation and involvement in the development of their proposals as they recognize NESTA’s role in the professional development through our sessions at NSTA and recognize that NESTA membership represents the leading edge in classroom instruction. When funded, these organizations will be looking for input from you—the classroom teacher. Farewell and, once again it has been a wonderful ride. Thanks for the memories. M. Frank Ireton, Ph.D. NESTA Executive Advisor 1990-2006

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SHARE-A-THONS AT NSTA ANAHEIM The Earth Science Share-a-thons were very successful at the NSTA National Conference this year in Anaheim. Over 330 participants attended the three share-a-thons. We did not have as many participants as in the past but on the positive side it allowed for more time with them as the circulated around the room. One officer heard the comment from one person leaving one of the sessions that it was the best they had ever attended. On Saturday the share-a-thon was at the same time as Bill Nye’s session which surely impacted our attendance. We had more presenters for the sessions than we have had in several years. Of course NESTA could not do these sessions without these volunteers. A very big THANK YOU to the following people who took the time to prepare and share ideas with others. This is a major way to help promote Earth Science education. Presenters for Earth Science Share-a-thon I were: Debbie Bereki, Karen Blount, Susan Bronz, Jennifer Day, Edna Devore, Nicole DiLuglio, , Marlo Diosomito, Jay Duncan, Jayson Duncan, Toni Enloe, Mary Kay Hemenway, Ryan Hutchings, Roberta Johnson, Carl Katsu, Linda Knight, Marina LaGrave, John Leck, Heather Marshall, Joe Monaco, Susan Moore, Alvin Moses, Michele Olivar, Mike Passow, Carole Reesink, Mike Shaw, Laura Sharp, Susan Sharp, Mark Turski, and Marc Wetzel. Presentes for Earth Science Share-a-thon II were: Debbie Bereki, Cindy Brown, Erin Butkovic, Galen Carlson, Matthew d’Alessio, Jay Duncan, Jayson Duncan, Rosemay Dummond, Tom Ervin, Peter Falcon, Marina LaGrave, Heather Marshall, Cindy Martinez, Chris McLelland, Carolyn Ng, Mike Passow, Randy Russell, Corene Selman, Len Sharp, Amy Spaziani, Sharon Stroud, Michele Svoboda, Elizabeth Trevino, Diann Valentine, Sue Vogel. Presenters for the NESTA/NAGT Share-a-thon were: Lisa Alter, Jeff Callister, Matthew d’Alessio, Howard Dimmick, Jo Dodds, Anne Douglas, Tom Ervin, Mark Francek, Lisa Gardiner, Jodie Harden, Missy Holzer, Rhonda Honore, Iris Hubenthal, Carl Katsu., John Lech, Loresa Loftin, Kristy Love, Heather Ann Marshall, Cindy Martinez, Dave Mastie, Nicole Mitchell, Sharon Porter, Lynda Sanders Linda Selvig, Kristi Shanks, Amy Spaziani, Karen Stocco, Sharon Stroud, Claudia Toback, Marc Wetzel, Pamela Whiffen, Jan Woener Packets of activities are given to the presenters. This involves volunteers to collect materials and compile them. The people that helped with all three share-a-thons included Harold Stonehouse (one of the founders of NESTA), Wilene Rigsby, Kelly Rigsby, and Richard Goode. Also assisting was Lisa Alter, Missy Holzer, Jo Dodds, and Tom Ervin. If we missed naming others who helped, we apologize for not listing their name. A big THANK YOU to these people who worked behind the scenes! Next school year NESTA will hold share-a-thons at each of the area conferences this Fall and three at the national conference. The area conferences are Omaha- Oct 1921, 2006; Baltimore- Nov. 2-4, 2006; and Salt Lake – Dec. 7-9, 2006. The national will be in St. Louis, Missouri- March 29-April 1, 2007. If your are interested in presenting at any of these share-a-thons, please contact Sharon Stroud at [email protected]. While Sharon is not in charge of the area conference share-athons, she will forward your names to those that will be in charge.

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A TOTAL ECLIPSE OF THE SUN Lou Mayo NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, [email protected]

The world as we know it is forever present. It always has been and always will be. The stars will always shine and the sun will always rise. Generations will be born and will die and still the world will endure. It is this sense of certainty that we wake up to each day. We may not always be aware of it but just imagine if there was no world to wake up to, a universe without an Earth, without humanity. Pretty unsettling huh? But these are the thoughts that occupied the minds of whole civilizations for thousands and thousands of years during a solar eclipse. Actually, most changes in the heavens, the realm of gods who determined individual and societal destinies, were met with fear. Meteor showers, lunar eclipses, comets were all viewed as bad omens at best and the end of all things or Armageddon at worst. All of these events rocked our collective sense of security and certainty about the world around us and were very scary. The earliest writings we have showing that people paid attention to eclipses in any official way are around 4,000 years old. Ancient Chinese records (the Shu Ching) of the solar eclipse that occurred (most likely) on October 22, 2134 B.C. translates to: "the Sun and Moon did not meet harmoniously." Sadly, the two royal, court astronomers, Hsi and Ho were reportedly beheaded for failing to predict the event. Apparently, the Emperor found out when he heard much noise in the streets as his subjects tried to drive away the dragon that was eating the sun. Thankfully, they succeeded. The Greek poet, Archilochus spoke of the total solar eclipse of 6 April 648 BC: “Nothing there is beyond hope, nothing that can be sworn impossible, nothing wonderful, since Zeus, father of the Olympians, made night from mid-day, hiding the light of the shining Sun, and sore fear came upon men.” (www.earthview.com/ages/history.htm) Archilochus There are numerous writings about eclipses through the ages. The British poet, John Milton, writes in Paradise Lost As when the Sun, new risen, Looks through the horizontal misty air, Shorn of his beams, or from behind the Moon, In dim eclipse, disastrous twilight sheds On half the nations and with fear of change Perplexes monarchs Solar eclipses were by all accounts events of wondrous and magical proportions. Today, of course, we understand eclipses very well. We know how and why they happen and when they happen. We have seen eclipses from other worlds. We have used eclipses to probe the laws of physics and to discover new worlds outside our own solar system. Still, they hold their ancient magic and are fascinating to watch. Such was the case for the most recent solar eclipse visible on our planet. The eclipse of March 29, 2006 was visible in its partial phases over a large part of Africa, Europe, the Middle East, and Asia (see Figures 1 & 2). The path of totality, the small swath of real estate within which the eclipse is total actually begins on the east coast of Brazil at 08:34 UT where convergence of two large tropical air masses keeps most days fairly cloudy. It precedes form there across the Atlantic Ocean encountering land again near Sekondi, Ghana, West Africa. From there it will cross Ghana, Togo, Benin, Nigeria, the Ivory Coast (slightly). The path then

Figure 1. Path of totality for March 29th 2006 Eclipse

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Figure 2 Path of totality for March 29th 2006 Eclipse

moves through Nigeria, Niger, Chad, Libya and the North West tip of Egypt. Then onto Turkey, Georgia, Russia, and parts of Asia where totality ends at 11:48 UT (Figure 2). The entire eclipse including partial phase begins in South America at 8:34 UT and ends in Asia at 11:48 UT. The maximum duration of totality for this eclipse occurred on the border of Libya and was 4minutes and 6 seconds in duration, which is about average for a solar eclipse. In theory, totality can last as long as just over seven and a half minutes though totality lasting for more than 7 minutes is very rare. The eclipse was not visible in the US but was broadcast on the web through the Exploratorium web site at www.exploratorium.edu/eclipse/.

Experiencing an Eclipse Figure 3. Solar eclipse geometry showing umbral and penumbral shadows

Total solar eclipses are amazing sights which is why people from all over the world travel long distances to remote places to view them. It is said that the difference between viewing a partial eclipse and a total eclipse is the difference between night and day (most literally!). During a total solar eclipse, the sky grows dark very rapidly as totality begins. Stars and planets come out, animals display their nocturnal behaviors: crickets may stop chirping, birds may stop singing, confused

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animals assuming night has fallen often go to their dens or nests for sleep. There is an eerie sense of calm as the mid day sun that we are so used to (the photosphere) all but vanishes. In its place is a black disk about ½ degree in size and the beautiful solar corona that can only be seen on such occasions. There is usually great excitement as eclipse watchers announce the beginning of totality standing firmly in the moon’s shadow, with whoops and hollers. All eyes are on the sun. Camera shutters click randomly as astronomy enthusiasts hurry to capture the event on film and CCD. Then, too soon, the sun peaks out again from behind the moon and totality is over until the next total solar eclipse (which will be August 1, 2008).

Eclipse Geometry OK, we know that solar eclipses happen when the moon moves in front of the sun and so these eclipses happen only at new moon when the sun, moon, and Earth are aligned. From the preceding text, it is clear that at least the Chinese and most probably other cultures knew that sun-moon conjunctions caused eclipses over 4,000 years ago and that they could predict the occurrences of these events with some accuracy. It turns out that only for our Earth is the moon almost precisely the angular size of the sun (about 30’ or ½ degree). This is because though the sun is about 400 times larger in diameter than the moon, it is also 400 times further away. No other planet in our solar system experiences this same geometry because no other planet has a moon similar in angular diameter to the sun. This alignment producing a total solar eclipse would happen every synodic month (one synodic month = 29.5 days which is the time it takes from new moon to the next new moon) if it weren’t for the fact that the orbit of the moon is tilted with respect to the Earth’s orbit around the sun (the ecliptic) by around five degrees. This is not much but it is enough to make the moon’s shadow miss too high or too low most of the time. It is interesting to note that only the Earth’s moon orbits near the ecliptic (most planetary moons orbit in the plane of the planet’s equator). There are two places in its orbit where the moon’s shadow doesn’t miss the Earth and can cause a solar eclipse to occur. These places are cryptically called the ascending and descending nodes. They are the points along the intersection of the Earth and moon’s orbital planes where the orbits intersect (recall from your High School geometry class that two planes intersect in a line and that two points define a line segment). The line defined by these two points is called the line of nodes (Figure 3). Eclipses occur when the moon passes anywhere within +/- 18.5 degrees of a node. This angle of opportunity is called an eclipse zone and the sun, traveling along the ecliptic at close to 1 degree a day, takes 37 days (18.5 degrees X 2) to cross through an eclipse zone. Since the moon’s synodic orbital period is just 29.5 days, at least one solar eclipse must occur during each of the Sun's node crossings. So, there will be at least two solar eclipses every year, though not necessarily total. The period of time when the sun is near a node is called an eclipse season and so as you might imagine, there are two eclipse seasons each year as the sun passes through the ascending and descending nodes. You can simulate this geometry very nicely with two hoola hoops placed one inside another and a bit tilted from one another. Had enough? No? Great! Let’s talk about Saros Cycles!! As you can see, in order for an eclipse to occur, the sun, moon, and Earth must be in just the right positions at just the right times. It turns out that you can characterize eclipses based on exactly where in its orbit the moon is. There are three lunar cycles that, when taken all into account define the path of totality on the Earth. These cycles, the Synodic, Draconic, and Anomalistic months are defined in the table below and conspire to define every solar eclipse.

Figure 4. Total solar eclipse showing sun's corona. Copyright 1995 by Fred Espenak

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Type of Month Synodic Month Draconic Month Anomalistic Month

Definition new moon to new moon node to node perigee to perigee

Length 29d 12h 44m 27d 05h 06m 27d 13h 19m

The harmony or resonance between these periods defines the eclipse geometry such as the path of totality and duration of the eclipse. Taking these cycles into account, eclipses separated by 223 lunar or synodic months = 6,585.321 days (18 years, 11.321 days) or one Saros Cycle (first termed by Edmund Haley) have similar geometries. Notice that a Saros is not an integer number of days. The roughly 1/3 day (.321) extra day means that two eclipses separated by one Saros cycle will indeed have the same geometries but will occur roughly 1/3 of the Earth’s circumference apart or about 120 degrees west, because the Earth will have rotated for an additional 8 hours before the eclipse occurs.

Eclipse Science Today, eclipses are of interest mostly to amateur astronomers and anyone who wonders about the sky. Not much in the way of scientific research is performed any longer. But there have been important research endeavors centering on eclipses in the not to distant past. On May 29, 1919, British astronomer, Sir Arthur Eddington headed two British Expeditions to Sobral, Brazil and Principe, West Africa, to confirm Einstein's predictions from his general theory of relativity that the path of a light ray would be bent in the presence of a strong gravitational field. The goal was to measure the positions of stars just off the limb of the sun (impossible to do under normal sunny day conditions) and to see if their apparent positions would indeed be altered by the sun’s enormous gravitational field. Five stars were selected and photographed. Their positions were compared with pictures taken of the same star field before the eclipse. The results agreed with Einstein’s predictions both qualitatively (yes, the stars’ positions did change) and quantitatively (they changed by the predicted amount). Of his findings, Eddington wrote: Oh leave the Wise our measures to collate One thing at least is certain, LIGHT has WEIGHT One thing is certain, and the rest debate -Light-rays, when near the Sun, DO NOT GO STRAIGHT. During the total solar eclipse of 1868, French astronomer Pierre-Jules-Cesar Janssen discovered a new yellow spectral line (587.49 nm) in the solar chromosphere very close to the yellow sodium Dline. This line was also independently observed by Sir Norman Lockyer who realized it was not attributable to any known Earthly substance. Lockyer and his colleague Edward Frankland proposed the name helium for the new element (from the Greek, “Helios” or Sun).

Eclipse Flavors Figure 5. Annular. Solar eclipse. Copyright 1995 by Fred Espenak

There were always three basic kinds ice cream when I was growing up, vanilla, chocolate and strawberry and obviously for this reason, there are three basic kinds of eclipses, total, partial, and annular. Total eclipses require the moon to be completely in front of the sun, blocking out all light from the solar disk or photosphere. Sometimes, the moon can be directly in front of the sun but because the moon’s orbit is elliptical, the moon is at times closer to (perigee) and further from (apogee) the Earth making it appear smaller or larger. If an eclipse occurs near the moon’s orbital apogee, it will be too small to cover the entire disk of the sun and a ring of light will be seen around the moon’s disk. This is called an annular eclipse (Figure 5). Wherever the moon is in its orbit when it crosses a node, it may not move directly in front of the sun. In this case, you have a partial eclipse and you can see a “bite” being taken out of the sun .

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Figure 6. Total solar eclipse paths for the period 2001 to 2025.

Viewing an Eclipse Eclipses can be safely viewed using a variety of techniques not the least of which is viewing them over the internet or TV. Since most total eclipses occur where you are not, you could decide to rely on others in the path of totality to send pictures of the eclipse to the web or another broadcast medium. The NASA Sun Earth Connection Education Forum is one group that did just this, sending a team of people to Turkey to view and broadcast the March eclipse. For more information on the eclipse and the webcast , go to sunearthday.nasa.gov/2006/index.php or the Exploratorium home page (above). There are many other people and groups that viewed the eclipse and posting their observations to the web. A quick Google search should show most of them. If you would like to view a total or partial phase yourself, there are a number of excellent websites you can go to for safe viewing techniques. Basically, these fall into two categories: direct and indirect viewing. Direct viewing implies you are looking directly at the sun through some sort of filter. The filter can simply be put over your eyes or it can be put at the front end of a telescope for a magnified view. Indirect viewing methods usually involve looking at a projection of the image of the sun using various methods such as a pin hole camera, projection screen attached to a telescope, or perhaps a Sunspotter. Indirect or projection methods are generally recognized as the safest. The NASA Solar Eclipse Page (sunearth.gsfc.nasa.gov/eclipse/solar.html ), authored by Dr. Fred Espenak (Mr. Eclipse) should be very helpful in gathering more information on eclipses and how to safely observe them.

Acknowledgements Maps and Diagrams courtesy of Fred Espenak, NASA's Goddard Space Flight Center.

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EARTH SCIENCE WEEK 2006!

Volume XXII, Issue 2

EARTHQUAKE SCIENCE FROM THE USGS

Earthquake Science Explained—A Series of Ten Short Articles for Students, Teachers, and Families U.S. Geological Survey General Information Product 21 Compiled by Matthew A. d’Alessio 2005

Recent images of massive earthquakeinduced waves washing away entire towns or buildings reduced to rubble by the violent shaking of Earth’s crustal plates have underlined, all too painfully, the importance of understanding our dynamic and everchanging Earth. These natural earthquake hazards will always be with us, but the consequences are not inevitable—if we prepare for them. An essential part of that preparation is education. Education is the key to ensuring that people take appropriate actions when living in earthquakeprone areas and for supporting policies and decisions that will save lives and property. Earthquake Science Explained is a series of short articles for students, teachers, and parents originally published as weekly features in The San Francisco Chronicle. This U.S. Geological Survey General Information Product presents some of the new understanding gained and scientific advances made in the century since the Great 1906 San Francisco Earthquake. Concepts introduced in each feature are designed to address State and national science-education standards. Written by our scientists, the articles go beyond traditional textbook information to discuss state-of-the-art thinking and technology that we use today. We encourage you to explore this informative publication as well as the U.S. Geological Survey’s science education Web site at http://education.usgs.gov/, and we further invite you to become our long-term partners exploring the full range of our science for a changing world. Source: http://pubs.usgs.gov/gip/2006/21/

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REVISITING THE BOSS MODEL TO EXPLORE BUILDING RESONANCE PHENOMENA WITH STUDENTS Michael Hubenthal Education Specialist , IRIS Consortium , Washington, DC 20005, [email protected]

While the Federal Emergency Management Agency’s publication Seismic Sleuths: Earthquakes: A Teacher's Package on Earthquakes for Grades 7-12 (1995), is currently out of print, many of the activities contained within it are well worth revisiting for both interest in use and the opportunity to enhance established curricula. This is especially the case since the entire document is now freely available online as pdf files (www.fema.gov/hazards/earthquakes/nehrp/fema253.shtm). One activity from the curriculum, the Building Oscillation Seismic Simulation (BOSS) model, provides an opportunity to engage students through the use of discrepant event demonstrations, and allows them to experience the process of science as they explore the interaction between buildings and shaking of the ground as a result of an earthquake. The construction of the original BOSS model was achievable by most classroom teachers, however it did require the purchase of some specialize materials; threaded rods, t-nuts, machine bolts, wood, and the use of a saw, drill, hacksaw, and hammer. With a bit of improvisation an equally effective model can almost entirely be constructed with materials found in your desk! The modified design of the BOSS model (Fig. 1) combined with both the detailed description of the pedagogical content knowledge for introducing your students to the model as a discrepant event and the discussion of the science behind the model found in this article can greatly reduce the barriers to implementing this lab with your students. Figure. 1. The simplified BOSS Model is constructed almost entirely from materials found in your desk! Photo Credit: David Tuttle.

Constructing the simplified BOSS model Materials 1 – Heavy manila file folder 5 – Small binder clips 2 – Blocks of wood .5in wide x .5in high x 10in long 1 – Roll of Duct tape or 3 strong rubber bands Tools: Ruler, scissors, pencil Assembly A. Create “buildings” from the manila file folder. Measure and cut the following lengths of 1in wide strips (2) 4 inches long (2) 5 inches long (2) 6 inches long

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(2) 7 inches long (2) 8 inches long B. Place the two equal length strips together and clip at one end with the binder clips. C. Label each building A thru E as shown D. Place all five “buildings” equally spaced, between the two wood blocks. E. Use the Duct Tape to tightly bind the two blocks together; securing the “buildings” in a stable vertical position.

Investigating the discrepant event sequence in-depth When building a house of cards, one quickly realizes that only one or two floors creates a relatively sturdy structure. However, if the building reaches three, four or more floors, the slightest bump of the table easily sends a tall house of cards tumbling down. The lesson many people learn from this experience is that this sturdiness of a house of cards quickly decays as the number of floors in the card house increases. Many people extrapolate the lesson they learned from simplistic building experiences and attempt to apply these to reality. This often results in a naïve mental conception that taller buildings are “less safe” or “more likely to collapse” during shaking resulting from an earthquake. Realizing the role that simple experiences like these play in the development of our understanding of the world is crucial to providing effective science instruction. In the late 1800’s Johann Herbart laid the groundwork for this concept; recognizing that previously existing knowledge served as the starting point for the development of new concepts (DeBoer, 1991). My personal experience teaching this subject matter and using this model with many classes of students and many workshops of in-service educators has provided me with significant anecdotal evidence to support the presence of the naïve misconception described above. Unfortunately due to the relatively thin research base exploring learner conceptions of geophysics content, this claim cannot be further substantiated. Building on the role of pre-existing knowledge; discrepant event demonstrations, such as the BOSS activity, seek to challenge existing knowledge and motivate students to seek and formulate new explanations for the observed phenomenon (Chiappetta & Koballa, 2002). In the BOSS demonstration the instructor presents five cardboard “buildings,” of varying heights to the students. Since middle and high school aged students often think of physical models as copies of reality rather than representations the instructor should lead an explicit discussion of how the model is both like and unlike reality (Grosslight et al., 1991). In this case the cardboard strips represent the elastic nature of buildings; when a great enough force is applied to the buildings, they deform and return to their original position. The binder clips represent features of real buildings like air handling systems or pools that can add large amounts of weight to the top of a building. The model is unlike reality in that it is an extreme over simplification of the system we are modeling. In this case, the cardboard buildings are 2-dimensional and not scaled, they are more elastic than actual buildings, and the binder clips add proportionally too much weight to the top when compared to reality. Even though not exactly like reality, it is important to note to students that models are useful for exploring this phenomenon in real structures that would otherwise be prohibited due to costs and hazards. Once the students and instructor have positioned the model in reality, the instructor asks the students to choose the building they would prefer to be in during an earthquake. Using a Think-WritePair-Share strategy students develop both a building choice and simultaneously develop a reason for their choice. As a result of student’s naïve preconception discussed above, most students will select the shortest building to be safest. Following the student sharing of predictions and associated reasoning, begin to create an “earthquake” by oscillating the base of the model at a low frequency, or back and forth at about once per second. At low frequencies the tallest building will respond with an amplified displacement of the top of the building. Now alter your “earthquake” by oscillating* the base of the building through a range of frequencies from low to high. As you do, the tall building no longer responds. Instead progressively smaller and smaller buildings do! With a bit of practice, you can develop enough “touch” to allow you to shake each building individually and “walk” the shaking up and down the various height buildings in the model. *NOTE: It is important that the amplitude of the oscillations be as consistent as possible for all frequencies. If you do not, students will attribute the discrepant behavior of the buildings to the distance

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you displace the buildings’ bases rather than the rate at which they were displaced. Engaged through the discrepancy between their own personal experience and the behavior of the model, students are primed for learning to occur as they search for a plausible explanation (Piaget, 1971). Exploring the demonstration with students should emphasize the importance of careful observations in science; what did you observed during the demo? Unless your students are already practiced at making careful observations, creating a list of evidence/observations can be more challenging exercises than you might. In fact, you should repeat the demonstration at least once, but are likely to have to repeat it a third or fourth time, while teasing out details with questions like: what was the cause of the shaking of the buildings, was the cause constant, how did it change? Armed with a list of careful and detailed observations, the class is now prepared to develop a logical argument that accommodates the discrepant behavior of the model. Research on the effective use of discrepant events suggests that teacher should neither confirm nor deny students’ tentative explanation of the event, but instead should provide guidance and cues so they can make explanations on their own (Cawelti, 1999). Sequences of questioning can help students develop their own reasoning; how did the actual demonstration compare to your prediction, what appeared to be the variable controlling which building shook, and ultimately… based on our observations can anyone propose a relationship between frequency or rate of shaking and building height? Once students have reached this point and have formulated a stated relationship between the frequency of shaking and building height, questioning should be pushed to the synthesis level; devise a simple experiment that would test such a statement. Given the relatively simple nature of the problem and model the entire sequence described above can be completed in about 10 minutes. Thus, it is worth spending the next 5 minutes encouraging students to write out the steps, in sufficient detail, to “test” the statement of relationship of the model. If you do not plan to use the full lab contained within Seismic Sleuths (Ireton et al, 1995) follow a student’s design and test the relationship they developed as a demonstration. Not only will this provide an opportunity to explore the phenomena, but it also accommodates a class discussion regarding the level of detail and process required for experimental design. If you do plan to use the Seismic Sleuths, allow enough time for students to follow the steps they have developed to test the conclusion and reflect on the process in the journals. Either way, a homework assignment that asks students to explain their results from the experimentation should be given. Thus, through either a 15 - 20 minute discrepant event demo or a the demo connected to a lab, students have been cognitively engaged in the lesson and have participated in the process of science. That is, they have had the opportunity to collect empirical data through observation, develop a logical argument as a class through the linking of observations to reach a stated relationship and finally to undergo skeptical review as they detail their “findings” in their homework assignments.

Why does this Discrepant Behavior Occur? All buildings have a natural resonance, or motion at which the addition or superposition of energy at the same frequency amplifies that motion. For example, when a child is being pushed on a swing, if pushing is applied at random times, the likely result is that swing will slow and stop. However, if the push to the swing is applied at the “right time” or the peak of swing (at the correct frequency) during each swing, the swinging will increase dramatically. Therefore, if seismic waves accelerate the base of a building at a frequency close to the resonance frequency of the building, the resulting amplification of energy can result in an increased and eventually unsafe displacement of the top of the building. While specific building geometries and materials control the resonance of a building, resonance frequency is largely a factor of building height. A buildings resonance frequency can be roughly estimated by using a simple formula; 10Hz divided by the number of floors ~ Natural Resonance (Pratt). Thus, tall buildings have a low natural resonance, and respond to low frequencies; a 30-floor building would have an estimated resonance period of 3.33 seconds and would be most effected by ground shaking at a frequency of 0.3Hz. In contrast, short buildings have high natural resonance and respond to higher frequencies; a five-story building would be most affected by ground shaking at a frequency of 2Hz (Pratt). While building height is a major factor controlling the natural resonance of the building, the distance the building is from the hypocenter influences the frequency of the seismic waves that reach it. When an earthquake occurs, seismic waves with a fairly broad range of frequencies are released.

Volume XXII, Issue 2

As these seismic waves propagate away from the earthquake source, their amplitude becomes smaller and their frequency tends to decrease with distance. Earth materials, while elastic enough to deform and store the potential energy that is released as an earthquake are also anelastic, or deviate from elastic response. This means that as seismic waves travel through the Earth, kinetic energy is converted to heat as the material is permanently deformed, which in turn reduces the frequency of seismic waves. Researchers Stein and Wysession (2004) note in their global seismology textbook, that without anelasticity… “seismic waves from every earthquake that ever occurred would still be reverberating until the accumulated reverberations shattered the earth.” As the waves travel out from the source, geometric spreading decreases the amount of energy per unit area of the expanding wave. This is analogous to a pebble tossed into the pond. Since the pebble released a limited amount of energy and the resulting wave spreads out from the source, the conservation of energy requires that the amount of energy per unit area must also decrease. The wave becomes smaller with increasing distance from the source. In a simplistic summary, taller, more flexible, buildings are susceptible to the smaller, low frequency oscillations of distant earthquakes, while shorter and stiffer buildings are more susceptible to the larger, high frequency shaking of nearby earthquakes.

Real-world Applications to Reinforce the cCncepts Selective building response to shaking such as demonstrated by shaking only one or two buildings of the BOSS model has direct applications in real life. A classic example of this can been seen in the damage resulting from the September 19th, 1985 Mexico City earthquake. While the majority of damage resulting of the quake can be attributed to construction techniques that lacked appropriate earthquake reinforcements not all buildings of similar construction were equally damage. The USGS reports that broad survey of damaged buildings across the city revealed that a disproportionate number of intermediate height buildings, 8-18 stories were damaged, when compared to shorter buildings and skyscrapers. This effect was most pronounced in the area of the city that was situated on an ancient lakebed. Why did this selective damage occur? Think back to our model and the description of the phenomenon above. Intermediate story buildings were at greater risk due to geologic setting of Mexico City. The soft clay sediments deposited by the ancient lake preferentially amplified the seismic waves, resulting in surface waves with approximately a 2 second period, or 0.5Hz. Using our rule of thumb estimation for building response described above, structures of intermediate height, with an estimated resonance frequency of 1.25Hz to 0.55Hz, were most susceptible to these damaging waves. Studying this event with your students can further reinforce students’ new, more complex cognitive framework regarding earthquake effects on buildings of various heights. Below are several resources that can help your explore the Mexico City event with your students: Mexico City Event (USGS) http://neic.usgs.gov/neis/eq_depot/world/1985_09_19.html A 2001 newspaper report revisiting the event http://www.chron.com/disp/story.mpl/first100/1068709.html

References/Acknowledgements * Many thanks to Larry Braile (Purdue University) who originated the modified design of the BOSS Model Barker, Jeff, Building Resonance. Accessed online 4/1/05 at http://www.geol.binghamton.edu/faculty/barker/demos/demo8.txt Bolt, Bruce, Earthquakes, (5th Edition), W.H. Freeman and Company, New York, 378pp., 2004. Cawelti, Gordon, (Ed.) Improving Student Achievement in Science. Educational Research Service, Arlington, VA, 1999. Chiappetta, E.L, and Koballa, T.R., Science Instruction in the Middle and Secondary Schools, (5th Edition), Merrill Prentice Hall, Columbus, Ohio, 2002. DeBoer, G., A History of Ideas in Science Education, Teachers College Press, New York,

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269pp., 1991 Ireton, F., Liepold, M., & Spaulding, K. (Eds.) Seismic Sleuths: Earthquakes: A Teacher's Package on Earthquakes for Grades 7-12 (2nd Edition). 1995 Piaget, J., Biology and knowledge. University of Chicago Press, Chicago, 1971 Pratt, Thomas, Frequencies, periods, and resonance. Accessed online 4/1/05 at http://faculty.washington.edu/tpratt/frequencies.htm Stein, S. and Wysession, M. An Introduction to Seismology, Earthquakes and Earth Structure, Blackwell Publishing, Malden, MA, 498pp., 2004.

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Volume XXII, Issue 2

ROCK MUSIC IN THE GEOSCIENCE CLASSROOM Beth A. Johnson 1 & Kathy Kitts 2 Department of Geology and Environmental Geosciences, Northern Illinois University, Davis Hall 312, Normal Rd., DeKalb, IL 60115-2854 1

[email protected]

2

[email protected]

Introduction Students learn in a variety of different ways and a good teacher will find different methods to present the material at hand. This is not only to help address those differences in learning, but also to spark student interest in the topic. The trick for the instructor is to find ways to encourage interest in those who were less than willing volunteers! Time-honored methods of enhancing geoscience classes include field trips, chemical experiments, and class activities. These methods are interesting and enjoyable for both the students as well as the instructors and help to provide a new way of looking at the world. However, another way that instructors can promote understanding of potentially difficult science concepts is through a common trait that most students already share: an interest in music. With a little thought and interpretation, popular music that students have heard on the radio can be used to teach the same topics that would be addressed in any science lecture, geoscience or otherwise, and can be adapted for nearly any grade level from middle school through undergraduate college settings. Even in settings where students get to choose the courses they take, such as high school or college, few of the students who sign up for science courses will go on to major in those fields. For example, most students who sign up for introductory geology courses at the college level only do so to fulfill general education requirements at that institution. In the 2005-2006 school year at Northern Illinois University, there were seventy-two declared undergraduate majors in the Department of Geology and Environmental Geosciences while an average of approximately 2,300 students a year complete at least one of the introductory courses the department offers. In other words, only about three percent of students who take a course in geology will eventually enter a geoscience-based profession. The remaining ninety-seven percent of students are not always intrinsically motivated to study the science and will benefit a great deal from engaging activities. In recent years, there have been many studies supporting a link between music education and enhanced reading (Nierman, 1995, 1996), writing (Tracy, 2000), mathematic (MENC, 1999), spatial (Rauscher et al., 1994, Waleson, 1995), and science abilities (Rauscher et al., 1997). According to Hanshumaker (1980), the study of music can: 1) enhance creativity, promote selfesteem, positive attitudes and social development, 2) facilitate development in reading, language acquisition, and general intellect, and 3) can even help to lower truancy rates in middle and high school settings. (For further articles linking reading and literacy to music, please visit: www.menc.org/networks/genmus/litarticles.html .) Plummer (1988) investigated the idea of connecting music and the lecture topic at hand. In his experiment, he used primarily classical music, which he played in the ten-minute interval between classes. The link to the geological topic was in the title itself, such as using Orpheus in the Underworld by Offenbach for igneous plutons and intrusive rocks or Hall of the Mountain King from Grieg’s Peer Gynt Suite for the interior of the earth. Based on remarks on class evaluations, he concluded that student reaction to this activity was generally favorable.

Listening Comprehension Exercise An example of a science topic that can be combined easily with music is that of volcanoes and volcanic hazards. Whether it is in a science program on TV or featured in the latest disaster movie, volcanoes are an area of science that is common in today’s pop culture. As a result, there are many songs that feature volcanoes prominently in their lyrics. The example that is demon-

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strated here features the song “Volcano” written by Jimmy Buffett, Keith Sykes, and Harry Dailey and performed by Jimmy Buffett on his album of the same title, but the basic method can be adapted to fit other selections. In any typical textbook such as Modern Earth Science and Holt Science and Technology: Earth Science from Holt, Rinehart and Winston or Prentice Hall’s Earth Science, a chapter about volcanoes will mention several hazards that result from volcanic activity. Hazards that are used for this exercise include: Lava Flows, Earthquakes, Ash Falls, Pyroclastic Flows, Lahars, Volcanic Landslides, and Volcanic Gases. (The list is compiled from Physical Geology, 11th Edition by Plummer, Carlson, and McGeary (2006) as well as Volcanoes: Crucibles of Change by Fisher, Keiken, and Hulen (1997).) Each hazard is defined in class and discussed using specific examples and instances of how they have affected people or the environment. Next, students are assigned an in-class project to test their comprehension of each hazard. Each student is given the lyrics of Jimmy Buffett’s “Volcano.” While the music is playing, they are asked to listen to and/or read the lyrics and identify at least five places in the song where Buffett sings about a volcanic hazard. Some places are fairly obvious (“Lava come down soft and hot”), but others require a bit of thought and interpretation (“Pretty soon we learn to fly”), forcing students to think about how each of the volcanic hazards works in order to find where they can fit in the song. Once the student has found one of these lyrics, it should be marked with the appropriate hazard. In the case of “Volcano,” there are at least nine places in the lyrics where this can be done depending on the students’ interpretations. For example, the lyric “Ground, she’s movin’ under me” can be interpreted to refer to an earthquake that is shaking the ground or the ground physically relocating, such as in a lahar or a volcanic landslide. This activity works well as both an in-class project and as a short quiz. A teachers guide with answers and a student handout of the lyrics are at the end of this article. In order to assess the level of student comprehension of the topic, whether or not music is playing, another series of volcanic texts can be used: the Letters of Pliny the Younger. Pliny the Younger (Gaius Plinius Caecilius Secundus) was an eighteen year-old Roman youth who witnessed the eruption of Mt. Vesuvius in 79 A.D. that buried the cities of Pompeii and Herculaneum near present-day Naples, Italy (DeBoer and Sanders, 2002). His observations of the eruption were recorded in two letters to the Roman historian Cornelius Tacitus and provide volcanologists with valuable information of the events of the eruption (Pellegrino, 2004). Using a similar process that applied with “Volcano,” students are asked to read the texts and interpret the volcanic hazard Pliny described. A. “The sea continued to roll back upon itself, and to be driven from its banks by the convulsive motion of the earth; it is certain at least the shore was considerably enlarged, and several sea animals were left upon it.” (Pliny’s Second Letter to Tacitus, Letter LXVI.) Hazard = Volcanic Tsunami B. “…then again we were immersed in thick darkness, and a heavy shower of ashes rained down upon us, which we were obliged every now and then to stand up and shake off, otherwise we should have been crushed and buried in the heap.” (Pliny’s Second Letter to Tacitus, Letter LXVI.) Hazard = Ash Fall C. “On the other side, a black and dreadful cloud, broken with rapid, zigzag flashes, revealed behind it variously shaped masses of flame…Soon afterwards, the cloud began to descend and cover the sea. It had already surrounded and concealed the island of Capreae and the promontory of Misenum.” (Pliny’s Second Letter to Tacitus, Letter LXVI.) Hazard = Pyroclastic Flow Further assessment can be conducted using Bloom’s Taxonomy to create questions to test student comprehension of volcanic hazards. Examples of assessment that test students’ higher cognitive abilities include composing lyrics for a volcano song (testing synthesis) or examining a series of lyrics and deciding which lyric does not belong with the others and why

Volume XXII, Issue 2

(testing evaluation). Nierman (1995, 1996) has shown that the development of synthetic and evaluative skills increase students’ reading and language abilities across the curriculum.

Other Useful Songs Who knew songwriters were so geologically inclined? Depending on the criteria the instructor uses to select “rock” music, there is a wealth of material to choose from! Johnny Cash, They Might Be Giants, Led Zeppelin, and many others have written songs that many students will be familiar with, but have probably never thought about in a geological context. As Robin Williams said in the film Dead Poets Society, “Just when you think you know something, you have to look at it in another way.” With careful selection, the lyrics of many of the songs listed in Table 1 can be used in a similar manner as the previous example with “Volcano” and still meet educational standards. The standards used in Table 1 are Illinois State Learning Standards, which are aligned with standards from the National Science Teachers Association. Title

Artist

Area of Interest

Standards

“Volcano”

Jimmy Buffett

Volcanology

12.E: 3a, 3b, 4a, & 5

“Volcano”

Volcanology

12.E: 3a, 3b, 4a, & 5

“Galaxy Song”

The Presidents of the United States of America Monty Python

Astronomy

12.F:3a, 3b, & 5b

“Why Does the Sun Shine” “Drops of Jupiter”

They Might Be Giants Train

Astronomy Astronomy

12.C.5a 12.F: 3b, 3c, & 5a 12.F.3b

“We Work the Black Seam “Sixteen Tons”

Sting

Environmental Geology

Merle Travis/ Johnny Cash

Environmental Geology

“Pollution”

Tom Lehrer

Environmental Geology

“Paradise”

John Prine

Environmental Geology

“When the Levee Breaks”

Led Zeppelin

Environmental Geology

“The Elements”

Tom Lehrer

12.C.3b

“California Earthquake” “Naked and Famous”

The Mamas and The Papas The Presidents of the United States of America

Chemistry/ Geochemistry Seismology Geology

12.E.3a

12.E.3c, 4b, & 5 13.B.3a, 3d, & 4d 12.E.3c 13.B.3a 13.B.3d 13.B.4d 12.E.3c 13.B.3f 12.E.3c 13.B.3a 13.B.3d 13.B.4d 12.E.5

12.E.5

Table 1: Song titles and suggested uses. Standards are Illinois State Learning Standards, which are aligned with those of the National Science Teachers Association. While the examples that have been listed in this article so far have mainly been for the geoscience instructor, this method of linking science to music can be used in any science class at any educational level. For example, Pye (2004) discusses a method used in General Chemistry courses where the lyrics of popular songs are changed to fit the chemistry topic at

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hand and then performed a cappella by the instructor in front of the class. The observation was made that student attendance increased significantly by doing this (Pye, 2004).

Conclusions There are many ways instructors can work music into the geoscience class: a listening comprehension exercise such as “Volcano,” having students create their own lyrics to fit popular tunes, finding song titles that fit a discussion topic and even using aural comprehension skills to understand how the mood or feel of the music fits in with the topic. Since the incorporation of such activities can benefit students in more areas than just science, it is a worthwhile activity to include. Also, it is a lot of fun for both the students as well as their instructor!

References Nierman, G.E. (1995). Does Music Instruction Affect Reading Development? Nebraska Music Educator. Nierman, G.E. (1996). Music Instruction and Language Skill Development. Nebraska Music Educator. Pellegrino, C. (2004). Ghosts of Vesuvius. New York: HarperCollins Publishers, 489 p. Pliny. Letters of Pliny. Translated by William Melmoth (revised by F.C.T. Bosanquet, 1878). London: George Bell & Sons, 415 p. Plummer, C.C. (1988). Music to soothe the savage physical-geology student. Journal of Geological Education, 36, p. 88-89. Plummer, C.C., Carlson, D.H, & McGeary, D. (2006). Physical Geology, Eleventh Edition. Boston: The McGraw-Hill Companies, Inc., 580 p. Pye, C.C. (2004). Chemistry and song: A Novel way to education and entertain. Journal of Chemical Education, 81, no. 4, p. 507-508. Rauscher, F.H, Shaw, G.L., Levine, L.J., Ky, K.N, & Wright, E.L. (1994). Music and Spatial Task Performance: A Causal Relationship. Paper presented at American De Boer, J.Z. & Sanders, D.T. (2002). Volcanoes in Human History. Princeton: Princeton University Press, 295 p. Fisher, R.V., Heiken, G., & Hulen, J.B. (1997). Volcanoes: Crucibles of Change. Princeton: Princeton University Press, 317 p. Hanshumaker, J. (1980). The Effects of arts education on intellectual and social development: A Review of selected research. Bulletin of the Council for Research in Music Education, 61, p. 10-28. MENC, 1999. Scores improve with increase in music instruction. Teaching Music, 6, issue 4, 1 p. Psychological Association 102nd Annual Convention, 26 p. Rauscher, F.H., Shaw, G.L., Levine, L.J., Wright, E.L., Dennis, W.R., & Newcomb, R.L. (1997). Music training causes long-term enhancement of preschool children’s spatial-temporal reasoning. Neurological Research, 19, p. 2-8. Tracy, L. (2000). It Takes a Whole Village: Music and Florida Writes! Florida Music Director. Waleson, H. (1995). Mozart makes you smarter? Billboard, 107, issue 23, p. 35.

Volume XXII, Issue 2

Rock Music—Teachers Guide and Student Handout (next page) This is a general list of lyrics and their accompanying interpretations based on the list of volcanic hazards provided in the main body of “Rock” Music in the Geoscience Classroom. The handout sheet for the students to complete follows this guide. This activity should be completed using “Volcano” from Jimmy Buffett’s album of the same title.

Volcano Written by Jimmy Buffet, Keith Sykes, and Harry Dailey Recorded by Jimmy Buffett Now, I don’t know. I don’t know. I don’t know where I’m gonna go when the volcano blows. (The eruption itself.) Let me say now I don’t know. I don’t know. I don’t know where I’m gonna go when the volcano blows. Ground, she’s movin’ under me. (Earthquake, Lahar, Landslide) Tidal wave’s out on the sea. (Volcanic Tsunami) Sulfur smoke up in the sky. (Volcanic Gases) Pretty soon we learn to fly. (Eruption Column in an Ash Fall à ash has to be ejected into the atmosphere before it can fall.) Let me hear you now. I don’t know. I don’t know. I don’t know where I’m gonna go when the volcano blows. Now my girl quickly said to me Man, you better watch your feet. (Lahar, Landslide) Lava come down soft and hot. (Lava Flow) You better love me now or love me not. Let me say now I don’t know. I don’t know. I don’t know where I’m gonna go when the volcano blows. No time to count what I’m worth. Cause I just left the planet Earth. (A bit of a stretch, but an Eruption Column leading to an Ash Fall works here.) Where I go, I hope there’s rum And not to worry, monsoon come. (Volcanic Gases leading to climate change.)

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“Rock” Music!

Name: ___________________________

Instructions: Let’s have some fun with volcanoes! Below are the lyrics to a song called “Volcano.” Listen to the song. While the song is playing, follow along with the lyrics and find the places where the artist sings about a volcanic hazard. Then, read the lyric carefully and decide which hazard the artist is singing about. Write the name of that hazard after the lyric that contains it. Find five hazards that are hidden in the song!

Volcano Sung by Jimmy Buffet Now, I don’t know. I don’t know. I don’t know where I’m gonna go when the volcano blows. Let me say now I don’t know. I don’t know. I don’t know where I’m gonna go when the volcano blows. Ground, she’s movin’ under me. Tidal wave’s out on the sea. Sulfur smoke up in the sky. Pretty soon we learn to fly. Let me hear you now. I don’t know. I don’t know. I don’t know where I’m gonna go when the volcano blows. Now my girl quickly said to me Man, you better watch your feet. Lava come down soft and hot. You better love me now or love me not. Let me say now I don’t know. I don’t know. I don’t know where I’m gonna go when the volcano blows. No time to count what I’m worth. ‘Cause I just left the planet Earth. Where I go, I hope there’s rum And not to worry, monsoon come.

Volume XXII, Issue 2

STATISTICAL ANALYSIS OF FOCI DATA Jason Petula Tunkhannock Area High School, Tunkhannock, Pennsylvania, [email protected]

Introduction A common model representing Earth’s interior comprises a crust, mantle, and a core. As students acquire more understanding, their conceptual models of Earth’s interior can become more complex. These models may include such layers as the lithosphere, asthenosphere, and even the often mispronounced Mohorovičić discontinuity – thankfully abbreviated to Moho. Sometimes differentiating between these layers is a challenge. How do we even know the Earth contains these layers? After all, the deepest hole ever drilled barely exceeds 12 kilometers (~40,000 feet). In other words, we have yet to drill through the crust in order to make direct observations of what lies beneath. Fortunately, Earth’s interior can be inferred using seismic data. Seismic data is readily available (e.g., earthquake.usgs.gov) on the Internet and can be used for a variety of inquiries. One inquiry, appropriate for upper-middle and high school students, explores patterns of foci depths. The activity highlighted in this article demonstrates how statistical analysis of foci data reveals Earth’s hidden structure, such as the interface between the upper mantle and lower mantle. This activity supports a deeper understanding of Earth’s interior because students must use data to support the conclusions they construct.

Teachers Guide Students must be familiar with basic statistical strategies for interpreting data. For instance, two strategies I use often are stem-and-leaf plots and box-and-whisker plots. It may be beneficial to review how these graphs are constructed even if students had prior exposure. The progression I use for this activity is outlined below. 1. Obtain or create a small data set (n = 30). The letter n represents the amount of data. Ex:

33 62 97 30 23

12 25 22 57 30

33 54 31 33 33

61 113 77 17 41

110 22 43 37 5

3 33 82 27 19

2. Create an Unsorted Stem-and-Leaf Plot. The stem represents a vertical number line comprising numbers from the data that exclude the one’s place (i.e. - the right most digit). The leaf represents the one’s place of each datum and is plotted on this number line horizontally. Ex: 0|3 5 (n = 30) 1|2 2 7 9 2|5 2 7 3 3|3 3 3 1 0 3 7 0 3 4|3 1 5|4 7 6|1 2 7|7 KEY 3|3 = 33 8|2 11|2 = 112 9|7 10| 11|0 3

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Note that the Stem-and-Leaf Plot organizes the data into a simplified bar graph. Also, the n- value is rechecked to ensure no data was accidentally omitted. 3. Organize the Unsorted Stem-and-Leaf Plot into a Sorted Stem-and-Leaf Plot, i.e. arrange the leaves in numeric order. Ex: 0|3 5 (n = 30) 1|2 2 7 9 2|2 3 5 7 3|0 0 13 3 3 3 3 7 4|1 3 5|4 7 6|1 2 7|7 KEY 3|3 = 33 8|2 11|2 = 112 9|7 10| 11|0 3 4. Obtain the following statistical points from the Sorted Stem-and-Leaf Plot: Lower Extreme: The lowest number in the data set. Upper Extreme: The highest number in the data set. Median: The middle point of your data. In other words, an equal amount of data is above and below this number. Lower Quartile: The median of the lower half of the data Upper Quartile: The median of the upper half of the data. Ex:

0|3 5 1|2 2 7 9 2|2 3 5 7 3|0 0 1 3 3 ‡ 3 3 3 7 4|1 3 5|4 7 6|1 2 7|7 8|2 9|7 10| 11|0 3

n = 30

KEY ‡ = median 3 = quartile 3 = extreme

Notice that the statistical points divide the data into quartiles each containing the same amount of data. In this example, each quartile contains seven numbers. For instance, the upper quartile comprises the numbers 61, 62, 77, 82, 97, 110, and 113. 5. Use the statistical points to generate a Box-and-Whisker Plot above an appropriate number line: lower extreme = 03 lower quartile = 23 median

= 33

upper quartile = 57 upper extreme = 113

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EARTHQUAKE FOCI 0

10

20

30

40

50

60

70

80

90

100

110

120

depths (km) Interpreting the box-and-whisker plot involves recognizing that the data are broken into quartiles. For instance, this data indicates twenty-five percent of earthquake foci are located at depths between 3 km and 23 km. Analysis of the data can provide insight into Earth’s interior. Why is the majority of the foci (i.e. – seventy-five percent) found 57 km or less in depth? Why is there no data for foci at depths greater than 113 km? Is this value for the upper extreme a manifestation of too little data? Would analysis of a larger data set significantly change the box-and-whisker plot? Teachers can use the curiosity generated from these questions to introduce more complex models of Earth’s interior that are grounded in data.

Interpreting the Data When larger data sets of earthquake foci (e.g. - neic.usgs.gov/neis/gis/qed.asc) are analyzed, the upper extreme increases to almost 700 km, where as the other statistical points remain relatively unchanged. Interestingly, the interface between the upper mantle and lower mantle occur at an average depth of 650 km. The majority of the data correlates with earthquakes that occur in the lithosphere, the rigid outermost portion of Earth with an average thickness of 100km. Allowing students to develop more sophisticated models of Earth’s interior can facilitate teaching plate tectonics. The Mohorovičić discontinuity reveals the boundary between crust and mantle material. Yet, including the Moho boundary in a conceptual model of Earth’s interior is not necessary for understanding plate tectonics. Of greater importance is recognizing that a plate comprises oceanic crust and/or continental crust and the rigid portion of the upper mantle. Beneath the plate (i.e. the lithosphere) is the asthenosphere, a portion of the upper mantle that is weak and capable of flow.

Conclusions Working with authentic data provides many opportunities for student learning. Some past spin-offs from the initial activity outlined above are: •

Investigating the relationship between earthquake depth and magnitude

•

Debating how much data is needed

•

Comparing earthquake foci distribution between oceanic and continental crust

The teacher and students determine the ultimate direction of the activity. The emphasis of this type of inquiry is to have students support their ideas about Earth’s interior with data. Furthermore, this type of inquiry facilitates the development of more sophisticated conceptual models of Earth’s interior.

Figure 1. A sophisticated model of Earth’s interior. Tarbuck/ Lutgens, EARTH SCIENCE 11/E, ©2006, p. 208. Reprinted by permission of Pearson Education, Inc., Upper Saddle River, New Jersey.

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INVESTIGATING LAVA FLOWS Michael J. Smith1 and John B. Southard 1Wilmington Friends School, 101 School Road, Wilmington, DE 19803, [email protected]

Using simple fluids and materials, students explore factors that affect volcanic flows (viscosity, slope, magma temperature, and channelization). They explore the relationship between volume and surface area of a flow. The activity helps them to develop an understanding of the nature and hazards of lava flows, pyroclastic flows, and lahars. Students also design a controlled experiment, and learn how knowledge of Earth science contributes to wise planning.

Background Information Fluids, in contrast to solids, are substances or materials that continue to change in shape for as long as they are acted upon by a deforming force. Fluids are of two kinds: liquids and gases. Liquids maintain a definite volume, whereas gases expand to fill their container. Mixtures of liquid or solid particles in a gas, and mixtures of solid particles in a liquid, also behave as fluids, unless the particles are so numerous that they form an interlocking network. Magmas (molten rock) are liquids. Magmas commonly contain solid particles in the form of crystals that grow suspended in the magma as it cools. Magmas, especially when they approach the Earth’s surface, can contain gas bubbles as well, which rise slowly upward through the magma.

Figure 1. Map of Mauna Ulu lava flows in Hawaii Volcanoes National Park from 19691974 Credit: R. I. Tilling, USGS Hawaiian Volcano Observatory .

The two most significant physical properties of a fluid are its density and its viscosity. These two properties are not directly related. The density of a fluid is its mass per unit volume. The viscosity of a fluid describes its resistance to deformation. Here’s a good “thought experiment” to give you a better understanding of the concept of viscosity. Lay a plate of glass horizontally on a table, smear it with a thick layer of a viscous liquid like honey, molasses, corn syrup, or motor oil, and then cover the layer of liquid with another plate of glass. Attach suctioncup handles to the top of the upper plate, and slide the upper plate horizontally, parallel to the lower plate. The layer of liquid between the plates undergoes a shearing motion. The greater the viscosity of the liquid, the more force you have to exert to keep the upper plate moving at a given speed. Magmas and lavas, although they are liquids, have very high viscosities, much higher even than everyday viscous liquids like those mentioned above. Students should not have the impression that magmas and lavas are as “flowy” as the liquids that are part of their everyday experience. Silica-rich magmas are of higher viscosity than silica-poor magmas. As with any liquid, lavas flow downslope in response to the pull of gravity. A given volume of lava in a flow is acted upon by the downslope component of the force of gravity. Newton’s second law of motion would tell you that the fluid should be accelerated in its downslope motion. The reason it instead flows at an almost constant speed is that a friction force develops at the bottom of the flow, which counterbalances the downslope driving force of gravity. Lavas flow faster on steeper slopes because the downslope force of gravity is greater. Lavas that flow in channels tend to move faster than lavas that flow as wide sheets, because the area of the base of the flow, where the retarding force of friction is generated, is less in relation to the volume of the flow, to which the force of gravity is proportional. For the same reason, thicker flows of lava tend to move faster than thinner flows. Pyroclastic flows are a very different kind of flow that is sometimes caused by an explosive eruption. If the volcano emits a large volume of a concentrated mixture of gases, liquid droplets, and solid par-

Volume XXII, Issue 2

ticles, the mixture can flow downslope like a dense liquid. The effective viscosity of such a mixture is much less than the viscosity of a lava, so the speed of movement is much greater. Speeds of pyroclastic flows can be over a hundred meters per second, which is even faster than racing cars! The potential for destruction of plant and animal life, and human habitation, is staggering. When pyroclastic flows finally stop, they sometimes become welded into solid rock as the still-hot material cools. Lahars are a kind of debris flow whose solid materials are mainly or entirely volcanic ash. Debris flows are downslope-flowing mixtures of water and solid particles. If the concentration of solid particles is sufficiently high, greater than forty to fifty percent by volume, the mixture of water and particles tends to flow like a viscous liquid. Because of the high concentration of solid particles, they cannot readily settle out to the bottom of the flow, as would be the case in an ordinary river flow, so the mixture can flow for long distances. If any of your students have had experience with concrete, they could appreciate that debris flows have a consistency something like that of fresh concrete that has just a bit too much water. Speeds of debris flows vary from very slow, no faster than a walk, to very fast, tens of meters per second. Areas susceptible to debris flows are those where slopes are steep and loose sediment containing fine as well as coarse materials are common. Land surfaces with steep slopes and a mantle of weathered volcanic ash are particularly susceptible to debris flows. Debris flows whose solid materials are mainly or entirely volcanic ash are called lahars. Lahars commonly develop during heavy rains some time (often a long time) after an explosive eruption has covered the land with a thick layer of volcanic ash. Lahars are especially common after weathering of the ash in a warm, humid climate has produced abundant fine clay material in the layer. Debris flows can start in various ways: runoff down slopes during and after especially heavy rainfall; collapse and sliding of steep, water-saturated slopes; or breakout of temporary lakes in terrain covered by volcanic ash. Debris flows, including lahars, tend to find their way into preexisting stream or river valleys, and when they finally come to a stop, the valley is filled with a deep layer of watery sediment. Entire villages can be buried almost instantly in this way. The village of Herculaneum, near the modern city of Naples in Italy, was deeply buried by a lahar that resulted from an eruption of Vesuvius two millennia ago. In this activity, the students are asked to develop hypotheses and then design experiments to test those hypotheses. Commonly, science really works that way. Hypotheses come about by virtue of scientists’ previous understanding, which might be based on an existing theory or on observational evidence already at hand. Sometimes, however, scientists just have a hunch or intuition that a certain new kind of experiment will reveal some information that opens up a new area of thought and research. Then the theoreticians have to scramble to develop new theories based on the new observational evidence, rather than the other way around! Good design of an experiment is of critical importance in science. The experimenter needs to vary each of the variables or parameters that might have an effect on the process or phenomenon, or at least take them into account by making sure they are held constant. The values of each of those variables or parameters have to be chosen to cover the range of interest, and the number of values has to be chosen so that the “experimental matrix” (number of variables vs. numbers of values of each variable) stays within workable limits. You might impress your students with the idea that, for example, with three or four variables and four or five values of each variable, they would end up having to perform anywhere from twelve (3 x 4) to twenty (4 x 5) individual experiments!

The Activity Goals—In this activity students will: • Measure and understand how volume, temperature, slope, and channelization affect the flow of fluid. • Apply an understanding of factors that control lava flows, pyroclastic flows, and lahars (mud flows). • Apply understanding of topographic maps to predict lahar flow (mud flow) patterns from a given set of data.

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• •

Describe volcanic hazards associated with various kinds of flows. Become aware of the benefits of Earth science information in planning evacuations and making decisions.

•

Show understanding of the nature of scientific evidence and the concept of a controlled experiment.

Materials Needed, Preparation, and Teaching Tips • • • • • • • •

Liquid soap (or a similarly viscous liquid; see below) Eye dropper (with rubber top - 1 ml or 1 cc volume) Ice (to cool the liquid soap) Hot water or heat source (to warm the liquid soap - you do not have to boil it) Transparency (onto which you photocopy a sheet of square centimeter graph paper – this provides a grid for estimating surface area of flows) Metric ruler (30 cm) Graph paper Calculator (or computer with spreadsheet program to enter, plot, and print data and graphs).

Spend most of one class period with the opener (to reveal student’s initial conceptions) and the first stages of part A. This will allow students to become familiar with the materials and brainstorm about possible experiments. You could review their designs that day and provide feedback the next time the class meets. Encourage the students to think carefully about the design of the experiment to test their hypothesis. This includes the experimental setup or arrangement, the variables or phenomena to be observed, and the values of the variables to be used. You will need a liter of a viscous (slow flowing) fluid. The fluid should be one that changes its viscosity greatly when heated or cooled. Liquid soap works well and cleans up easily. Alternatives include molasses, corn syrup, shampoo, and glycerin. Photocopy a piece of graph paper with centimeter grids onto overhead transparencies. Affix the transparencies to a manila folder. If you want a larger surface area with which to work, tape two transparency grids together and affix them to an opened manila folder. The folder provides support for some experiments. In lieu of overhead transparencies, laminate sheets of graph paper that have been affixed to manila folders are suitable. Eye droppers usually have a capacity of 1 milliliter or 1 cubic centimeter. Students will need books to create various slopes, and a source of hot water and ice to conduct experiments on the effects of temperature on viscosity. As students work, circulate and review their hypotheses, data tables, experimental designs, and the records they keep of their observations. The investigation presents many opportunities to discuss the nature of scientific inquiry. For example, students will have to determine what to do about bubbles that appear in the liquid soap (should they pop them or not?), how to measure the area covered by the flows, when to stop measuring, and so on. Students are asked to record their results in a data table. They are not specifically asked to graph their results. As you review student work, ask them whether or not a graph of the data might help to reveal patterns in the data. You can prepare an Excel spreadsheet ahead of time, you can plot the results obtained by each group for steps 1-7 in such a way that a graph of each group’s results is made. This often reveals anomalous data and provides an opportunity to discuss how to resolve and/or deal with discrepancies, or whether or not to average the data to produce a “class average result”. Some students may need help in calculating or determining area and remembering that area is in units of length or distance squared, whereas volume is in units of length or distance cubed. The investigation provides an excellent opportunity to conduct formative performance assessments of science process skills. Part B provides a link to technology applications. Have students use graphing calculators or spreadsheet software to plot lahar travel times. Alternatively, have them develop their graphing skills with graph paper.

Volume XXII, Issue 2

Warm-up Material that erupts from a volcano and flows down its slope is a major concern for people who live near volcanoes. Suppose you live near a volcano and you have just been told that it has erupted. • What do you think would affect the amount of time you and your family have to evacuate to escape from a volcanic flow? What might control the speed of the flow? What do you think? Record your ideas about this question in your notebook. Be prepared to discuss your responses with your small group and the class.

Investigation Part A: Area of Lava Flows 1. Suppose a volcano produces twice the amount of lava than in a prior eruption. Write a hypothesis based upon the following question: What is the relationship between the volume of an eruption and the size of the area it covers? Record your hypothesis in your notebook. 2. Check your hypothesis to see if it could be disproved. A hypothesis must be a prediction that can be falsified. The statement "Some stars will never be discovered," cannot be disproved. Therefore, it is not a hypothesis. 3. In this investigation, you will use liquid soap to simulate flow during a volcanic eruption. Volcanic flows include lava, gases, and mixtures of solid particles and gases. In your notebook, set up a data table. The table should help you record the relationship between volume of liquid soap and the surface area that the soap covers. You will do trials with 0.5, 1, 2, 4, 8, and 16 cm3 (cubic centimeters) of liquid soap. 4. Place an overhead transparency of a square grid on a flat surface. 5. Pour 0.5 cm3 of liquid soap onto the transparent graph paper. 6. When the soap stops flowing, measure the area of the flow. Record the area of the flow in your data table. 7. Wipe the surface clean. Repeat the trials using 1, 2, 4, 8, and 16 cm3 of liquid soap. Record your data in your table. Look for patterns. Discuss your hypothesis in light of your results and possible sources of experimental error. 8. Develop a hypothesis and design a test for one of the following questions related to the flow of fluids. Remember that during scientific inquiry, you can return to the materials or your data and revise your procedures as needed. • What effect does temperature have on resistance to flow (viscosity)? • What happens to fluid when slope changes from steep to gentle? • What effects would you see if fluids moved through narrow channels? a) Write down your research question and your hypothesis. b) Record your procedure in your notebook. c) Describe the variables you wish to investigate and any controls on your experiment. 9. Present your procedure to your teacher for approval. Then run your test and record your data. 10. Summarize your conclusions. Was your hypothesis correct? What are the possible sources of experimental error? How might an emergency planning commission apply your results to an evacuation plan for volcanic eruptions? 11. Obtain results from groups in your class that investigated other questions. Record their conclusions in your notebook.

Investigation Part B: Travel Time of Lahars 1. Examine the table of expected travel times of lahars (mudflows) triggered by a large eruption of Mt. St. Helens (see Table 1). The values in the table come from computer simulations and actual

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behavior of mudflows in the 1980 eruption. Table 1. Expected Travel Times for Lahars Triggered by a Large Eruption of Mount St. Helens. (USGS) Distance (via river channels) from Mount St. Helens (km) 10

Estimated Travel Time (minutes) South Fork Toutle River, Pine North Fork Toutle River Creek, Muddy River, Kalama River 37 11

20

68

30

30

97

54

40

136

81

50

173

109

60

207

140

70

228

173

80

283

211

90

336

258

100

530

312

2. Make a graph of travel time (in minutes on the vertical axis) versus distance (in kilometers on the horizontal axis) for both data sets. a) Plot both data sets on the same graph. b) Connect the data points so that you can compare the data. c) Calculate an average velocity for mudflows along each fork of the Toutle River. 3. Answer the following questions in your notebook. a) Which area (North Fork or South Fork) is more likely to have a steeper gradient? Use the results of investigations from Part A to support your answer. b) What evidence in your graphs suggests that the gradient on either river is not constant? Explain. c) Based on the information in the table, explain whether or not you think that a community located 50 km from Mt. St. Helens along either of these river valleys would have time to evacuate in the event of an unexpected massive eruption.

Reflecting on the Activity In this activity, you found that temperature, volume, channels, and slope affect the flow of liquids. Analyzing data from a computer model you predicted the flow of volcanic fluids down river valleys near Mt. St. Helens. You can now describe the volcanic hazards associated with various kinds of flows and factors which affect the flows. You can also understand how the flows might affect surrounding communities.

Inquiring Further 1. Research a famous lava flow. Search the web for information about the Columbia River Basalt group in the northwest. Prepare a report to the class about the members of this famous basalt group in relation to largest, longest, thickest, cooling characteristics, effects on ancient topography, and cause. 2. Lava and the biosphere. How have lava flows at Mauna Loa and Kilauea Volcanoes affected Hawaiian communities? How does the lava that enters the Pacific Ocean in Hawaii affect coastal ecosystems? What kinds of organisms develop and thrive at the "black smokers" along mid-ocean

Volume XXII, Issue 2

ridges? Research the 1783 Laki fissure flow in Iceland. It was 40 km long and covered 500 km2. How did it affect vegetation and livestock? 3. Lava and the cryosphere. What happens when lava erupts from an ice or snow-capped volcano? This is an issue in the Cascade volcanoes. Mt. Rainier, which overlooks Seattle, has 27 glaciers. Some insights might be gained from exploring the recent eruption at Grimsvotn in Iceland.

References and Resources Decker, R.W., and Decker, B.B. (1998) Volcanoes (3rd edition). W.H. Freeman, New York, NY. 320 p. Francis, P., and Oppenheimer, C. (2004). Volcanoes. Oxford University Press, New York, NY. 521 p. Sigurdsson, H., Houghton, B., McNutt, S.R., Rymer, H. and Stix, J. (Eds.). (2000). Encyclopedia of volcanoes. Academic Press, San Diego, CA. 1417 p. Smith, M.J., Southard, J.B., and Demery, R. (2002). EarthComm: Earth’s Dynamic Geosphere. It’s About Time Publishing Company, Armonk, NY. 80 p. Smithsonian Global Volcanism Web Site. Available at http://www.volcano.si.edu/index.cfm. Williams, Stanley. (2001). Surviving Galeras. Houghton Mifflin Company, Boston & New York. 270 p. Winchester, S. (2003). Krakatoa. The day the world exploded: August 27, 1883. Harper Collins, New York, NY. 416 p. Wolfe, E. W. & Pierson, T. C. (1995). Volcanic-hazard zonation for Mount St. Helens, Washington, 1995. Retrieved May 7, 2006, from USGS/Cascades Volcano Observatory, Vancouver, Washington Web site: http://vulcan.wr.usgs.gov/Volcanoes/MSH/Hazards/OFR95-497/OFR95497_inlined.html Wood, C.A. and Kienle, J. (1990). Volcanoes of North America: United States and Canada. Cambridge University Press, New York, NY.

Acknowledgements This article was based upon material developed for the EarthComm curriculum program of the American Geological Institute.

THE EARTH SCIENTIST ARTICLE SUBMISSION GUIDELINES • • • •

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Mail to: Michael J. Smith 403 West Chestnut Hill Road Newark, DE 19713-1121 [email protected]

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