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Date: For October 10th, 2003 submission

Lesson Title: Evidences on Sea Floor Spreading and Continental Drift

Author: Brian Wilson

Ohio Standards Connection:

Standard: Earth & Space Sciences: Grade Nine- Processes That Shape Earth

Benchmark E: Explain the processes that move and shape Earths surface.

Indicator 7: Explain sea-floor spreading and continental drift using scientific evidence (e.g., fossil distributions, magnetic reversals and radiometric dating).

Benchmark/Indicator Background. According to Continental Drift Theory, there was at one time a single continent, Pangaea, representing two major land masses sutured together: Gondwanaland, centered around the South Pole; and Laurentia, in the vicinity of the Equator. These masses gradually drifted northward, Laurentia splitting into North America and Eurasia, and Gondwanaland splitting up to form Africa, South America, Antarctica, and the Arabian and Indian peninsulas. The drifting was very slow and depended on the movement of plates under the continents. This drifting continues.

Associated Standards: Ideas in this lesson are also related to concepts found in:

Grade 9 Earth & Space Science, Benchmark E, Indicator 6

Grade 9 Earth & Space Science, Benchmark F, Indicator 8

Grade 9 Scientific Inquiry, Benchmark A, Indicator 6

Lesson Summary:

Most students will likely know some information about the planet Earth. In this lesson, students will build on this knowledge as they inquire and research scientific evidence on continental drift, and sea-floor spreading. Students will investigate further the processes that move and shape the Earths surface.

The lesson begins with a student activity/teacher demonstration on simulated magnetic reversals. This is then followed by an overhead visual aid listing several questions relating to sea floor spreading and continental drift. A teacher led discussion and answer session of these thought provoking questions ensues.

Then, using the provided scientific evidences of fossil distributions, magnetic reversals and radiometric dating as a starting point, the students will research further and present their findings on these scientific evidences by use of a poster board visual display. A follow-up gallery walk of the posters boards will next occur with the students writing in their journal key points of each poster board relating to scientific evidence on continental drift and sea floor spreading.

Estimated Duration:

3 to 5 classroom periods

Pre-Assessment:

Instructions to the Teacher:

To start Part 1A, a vocabulary sheet will be handed out and briefly discussed in class. Fig 1 will then be handed out which the students are requested to read.

Fig 1

Initial Introductory Reading by the Student

In the early 1910s Alfred Wegener proposed the hypothesis of Continental Drift. He proposed that the continents were once joined together into one giant continent called Pangaea meaning all Earth from which todays continents broke apart and drifted into their current locations. Wegener used the fit of the continents, the distribution of fossils, a similar sequence of rocks at numerous locations, ancient climates and the apparent wandering of the earths polar regions to support his idea.

In the early 1960s Harry Hess proposed the hypothesis of Sea-Floor Spreading, in which basaltic magma from the Earths mantel rises to create new ocean floor at mid ocean ridge. On each side of the ridge, sea floor moves from the ridge towards the deep-sea trenches where it is subducted and recycles back into the mantle.

The hypothesis of Continental Drift when combined with Sea Floor Spreading hypothesis led to the theory of Plate Tectonic which is based on several uniformitarian assumptions and precise radiometric and fossil dates.

END OF FIG 1

In Part 1B, a student activity on Sea Floor Spreading is first undertaken using Activity 1 (See Attachment 2). Alternately Attachment 2 could be used as a teacher demonstration.

Fig 2 will then be handed out which the students are requested to read. This information should solidify the information that the students just previously learned in Activity 1.

Fig 2

After Activity Reading by the Student

Worldwide it has been estimated that currently about 20 cubic kilometer of molten magma rises each year to create new oceanic crust. At the time of cooling, some of the rocks minerals acquire magnetism from the Earths magnetic field, recording the fields direction at that time. Evidence indicates that the Earths magnetic field has reversed many times in the past. So, during the cooling, some of the oceanic crust was magnetized in a reverse direction. If sea floor spreading is continuous the ocean floor should possess a smooth magnetic recording of reversals.

Indeed the zebra stripe pattern of linear magnetic anomalies parallel to the mid ocean ridge crest has been recorded in many areas. While the zebra stripe pattern has been confirmed in many areas, drilling through the basalt adjacent to the ridges has shown that the neat pattern recorded by dragging a magnetometer above the ridge is not always present when the rock is actually sampled. The magnetic polarity in some cases changes in patches down the holes, with no consistent pattern with depth. Thus additional factors may need to be taken into account. By determining the strength and polarity of the magnetic signature of particular land rocks that have been radiometrically dated, and by comparing the resulting patterns to sea-floor patterns, the marine rock can be roughly dated by a method known as paleomagnetism.

END OF FIG 2

Next In Part 1C, the teacher will then hand out and display on an overhead or other visual aid from 4 to 7 of the Fig 3 list of questions shown below. (Note: Suggested answers are given in bracketed italics.)

Fig 3

List of Pre-Assessment Questions (not inclusive) : [19,] [26], others

1. Give several reasons why you think the continental drift theory is correct.

[Standard answer is the scientific evidence on fossil distributions, magnetic reversals, and radiometric dating]

2. How does palaeomagnetism relate to both radiometric and geologic dating methods?

[Palaeomagnetism is not a dating technique but provides globally synchronous correlation planes, whose identification is possible by comparison with stratigraphic index fossils or radiometric data]

3. Define and explain the following: (1) earths fluid core; (2) a magnetic field; (3) earths geomagnetic field [GMF]; reversed polarity.

[Use the standard definitions that are given in typical Earth & space science textbooks]

4. Explain the concept behind geo-magnetic reversals (reversals in earths magnetic field).

[Evidence from cooled surface lava flow indicate that reversals of the earths geomagnetic field have occurred. This is generally thought to be caused by motion disturbances in the Earths outer core which is presumed to consist of highly conductive molten metals]

5. Potassium-argon is the primary dating method used to try to date reversals. From the evidence available is this technique always reliable?

[Anomalies in the data do exist which sometimes give contradictory or conflicting results]

6. Discuss the reliability of ocean core dating.

[As only a portion of the deep-sea cores are stratigraphically continuous and undisturbed, the method can never be precise thus consequently most of the dating of the deep-sea cores is actually done by simple curve matching of particular variables, especially oxygen isotope fluctuations to an assumed standard curve ]

7. Explain the facts discovered about the ocean floor, in relation to magnetic stripes and geologic fault lines.

[Towed magnetometer readings from surface ships has shown an apparent striped pattern of either: change in magnetic field direction (reversals); or change in magnetic field intensity (strength) over diverging areas such as Mid Atlantic Ridge, which contains fault lines]

END OF FIG 3

The students are to individually write an answer including a brief explanation for each of the questions. The teacher collects the students written answers to Figure 3 handout questions, and then provides the suggested answers on another overhead. Afterwards a teacher guided classroom discussion follows regarding any questions or comments that the students may have related to the questions shown in the figure. After the class is over, the teacher evaluates each students answers individually to gauge the students prior knowledge of the subject matter.

Scoring Guideline:

This is an informal evaluation of the students understanding and knowledge. Teachers should make informal notations and record anecdotal comments about the level of understanding of the students.

Post-Assessment:

Instructions to the Teacher:

Transition into Part 2- Scientific Evidence on Sea-Floor Spreading and Continental Drift shown in the outline below.

An evaluation is undertaken for the scientific evidences in each individually numbered line item listed in Fig 4. Have students break into groups of two. Ask for volunteers for each of the numbered line items listed in Fig 4. Note, other scientific evidences may be included or substituted from those shown at teachers discretion. The students will also demonstrate their ability to perform critical thinking skills by incorporating known scientific anomalies into the research activity. Each pair will research two scientific evidences and then create a visual presentation such as a poster board or tri-fold for each scientific evidence. See attachment 1- General Student Research and Reporting Guidelines for specifics. A gallery walk will then occur with students writing in their journal notebook key concepts of each poster board or tri-fold. The teacher will take a picture of each poster board or tri-fold and distribute copies to each student for their journal notebook.

Fig 4

Commonly Cited Scientific Evidences on Sea-Floor Spreading and Continental Drift

Modified from Ref [50],(Additional good sources of information include:[19], [22], [36], [5], [26])

Note: Ref [51] is a good summary source of information on Anomalies pertaining to these evidences

I. Shape of the coastline

(Similarity in shape of continent, as if they once fit together like the pieces of a jigsaw puzzle)

1. e.g. coastlines of Africa and South America

II. Fossil Evidence

(Implies once continuous land connections between now-separated areas)

1. Distribution of Glossopteris flora (plant fossils)

Late Paleozic seed ferns

Gondwanaland (India, Australia, S. America, Antartica)

2. Foraminifera & other microfossils found both in South America and Africa

3. Distribution of Mesosaurus (fish eating freshwater reptile)

4. Distribution of Lystrosaurus (plant eating freshwater reptile)

5. Distribution of Cynognathus (small carnivorous reptile transitional to mammals)

6. Distribution of Paleozoic fishes and amphibians

III. Geologic Similarities

1. Between South America, Africa, and India

a. Same stratigraphic sequence (i.e., same sequence of layered rocks of same ages in each

place)

b. Mountain belts and geologic structures (trends of folded and faulted rocks line up)

c. Precambrian basement rocks are similar in Gabon (Africa) and Brazil

2. Between Appalachian Mountains and Caledonian Mountains in British Isles and Scandinavia

IV. Paleoclimatic (ancient climate) Evidence

(Ancient climatic zones match up when continents are moved to their assumed past positions)

1. Layers of glacial deposits (tillites) are found at same place in sequence of rocks

Note directions of glacial ice movement as indicated by striations or grooves in the rock

2. Coal seams with logs from tropical (low latitude) trees found at high latitudes

3. Distribution of carbonate deposits (including reefs) and evaporate deposits

V. Magnetic Reversals

1. Zebra stripe pattern of parallel linear magnetic anomalies (alternating bands of slightly

higher and lower magnetic intensity measured by using ship towed magnetometers) is

commonly symmetrical about mid-ocean ridge crest. This is commonly interpreted to be

caused by sea floor spreading in combination with global geomagnetic field reversals [55].

2. The Sun reverses its magnetic field every eleven years [23]. Rapid field variation reversals have also been found in some locations on Earth [21], [23], [41]

3. Extraterrestrial magnetic reversals have been measured by the Mars Global Surveyor

spacecraft. These are a relic of a past era of spreading centers on Mars that are no longer

active and hence have since ceased movement [52]

VI. Radiometric Dating

1. Ocean core sample data are commonly reported in the literature to have Basalt rock K/Ar

radiometric dates of less than 200 million years (Jurassic Geologic Era) [14], [19]

2. Some investigators have reported the following factors can affect K/Ar radiometric dating:

Ar gas escapes from rock [46], [47]; K can leach out of rocks when exposed to water [48];

K decay rate variation [46]

END OF FIG 4

Scoring Guideline:

Rubric for Grading the Displays

CATEGORY

Level 4

Level 3

Level 2

Level 1

Depth of

Understanding

Scientific information and ideas are accurate, thoughtfully explained and accurately linked to the Item.

Scientific information and ideas are accurate and linked to the Item.

Scientific information has occasional inaccuracies or is simplified.

Scientific information has major inaccuracies or is overly simplified.

Evidence of

Inquiry

Evidence and explanations have a clear and logical relationship.

Evidence and explanations have a logical relationship.

Evidence and explanations have an implied relationship.

Evidence and explanations have no relationship

Communication

Scientific information is communicated clearly and precisely but may also include inventive/ expressive dimensions.

Scientific information is communicated clearly.

Scientific information has some clarity.

Scientific information is unclear.

Relevance to Society

Background information provides clear context for interpretation.

Background information provides context for interpretation.

Background information provides some context for interpretation.

Background information provides minimal context for interpretation.

Instructional Procedures:

Engagement

Instructions to the Teacher:

Part 1A, Initial Introductory Reading

1. If the teacher or their students want to do some preliminary research on the topic before the lesson go to the following internet sites: [19] [26]

2. A vocabulary sheet will be handed out and briefly discussed in class.

3. Fig 1- Initial Introductory Reading, will be handed out for the students to read.

Part 1B, Activity/Demonstration

4. An activity of simulated magnetic reversals is first undertaken by the students using Activity 1 (see Attachment 2). Alternatively Attachment 2 could be used as a teacher demonstration. Allow one half a class period for this activity.

5. Fig 2- After Activity Reading, will then be handed out for the students to read. This information should solidify the information that the students just previously learned in Activity 1.

Part 1C, Pre-Assessment Questions

6. Teacher will pre-select 4 to 7 questions that are listed in Fig 3.

7. Teacher will then hand out and also display the selected questions (without the suggested answers) from Fig 3 on an overhead or other visual aid.

8. During the display of the overhead, students are to individually write an answer including a brief explanation for each of the questions.

9. The teacher collects the students written answers to the Fig 3 handout questions, and then provides the suggested answers on another overhead.

10. Afterwards a teacher guided classroom discussion follows regarding any questions or comments that the students may have related to the questions shown on the figure.

11. After the class is over, the teacher evaluates each students answers individually to gauge the students prior knowledge of the subject matter.

Allow a total of one to one and one half class periods for Parts 1A,B,C

Instructions to the Student for Parts 1A,B,C:

Write down your questions and comments while you read the two handout readings and during the Activity/Demonstration.

What would you want to know or hope to learn about sea floor spreading and continental drift?

Be prepared to share your questions and comments with the class.

Development

Instructions to the Teacher:

Part 2, Scientific Evidence on Sea-Floor Spreading and Continental Drift

12. Hand out Fig 4 which contains individual line item numbered scientific evidences. State that research will be done by groups for the scientific evidence listed in each individually numbered line item. Note that other scientific evidences may be included or substituted from those shown at teachers discretion.

13. Have students break into groups of two. Ask for volunteers to research each of the individually numbered line items listed in Fig. 4. It should be noted that the students will also demonstrate their ability to perform critical thinking skills by incorporating known scientific anomalies into their research activity. Balance out the class so that a majority of the individually numbered line items are covered for each of the categories. Those not covered may be done as possible extra homework or extended learning assignments.

14. Each student pair will do joint research on two scientific evidence items. For information resources, students are to use standard Earth & Space Science textbooks, Library research and/or internet web sites to perform the research. The specifics listed in Attachment 1- General Student Research and Reporting Guidelines should be followed by the students.

15. The group should provide copies of all background information that was used, when they hand in their poster boards or tri-folds. One half class period should be allowed for the initial start of the research phase of both topics. It is understood that some additional out of classroom time will be needed by the student for them to finish and complete their presentation.

16. Each individual will then create a separate visual presentation such as a poster board or tri-fold for the one scientific evidence item that they have. One half class period should be allowed for the initial start of the presentation phase of both topics. It is understood that some additional out of classroom time will be needed by the student for them to finish and complete their presentation.

17. A gallery walk will then occur with students writing in their journal notebook key concepts of each poster board or tri-fold. One class period should be allowed for the gallery walk.

18. The teacher will take a picture of each poster board or tri-fold and distribute copies to each student for their individual journal notebook.

19. Up to one half a class period is taken by the class as a whole to answer any questions that the students may have regarding the poster board displays.

20. The teacher collects the students poster boards or tri-folds and then after the class is over evaluates each student based upon the Rubric, using both: the copies of the students research background information that was handed in; and also the students poster board or tri-fold graphic display.

Instructions to the Student:

Your teacher can help guide you on potential reference sources to use or suggest key words/phrases to try when using internet web search engines.

Follow Attachment 1 guidelines on researching and reporting.

If you have any questions regarding what format to use in your presentation, ask your teacher to help you in choosing an acceptable model to follow.

If there are still any questions after the poster board gallery walk presentation do not hesitate to ask for further help.

Differentiated Instructional Support:

Instruction is differentiated according to learner needs, to help all learners either meet the intent of the specified indicator(s) or, if the indicator is already met, to advance beyond the specified indicator(s).

For students who struggle with the material covered in this lesson plan, partner them with others that possess understanding. Use material from a textbook, internet site, or other lesson plan that contains similar subject material. Encourage the struggling student to work on the material, preferable with the helper partner whenever possible, outside of instructional time. This can take place prior to or after the daily lesson, during shared study hall periods, before or after school, etc.. Possible use of supplemental multi-media software.

Extension:

Part 3 Extended Learning

Instructions to the Teacher:

For extended learning each student has an option on researching a related topic that was not covered previously in this lesson cycle and write a report on the topic. Possible topics include the following topics:

Fig. 5

Possible Extended Learning Topics

I Paleoclimate Assumptions

1. Ancient overall climate similar to present time, with warmer local temperature variations

closer to the equator based on geographic latitude relative to the frigid geographic N & S

Poles. This is conventionally assumed in Uniformitarian fossil based paleodating analysis

2. Ancient overall climate warmer than present time (greenhouse effect, etc.), with less local

temperature variations based on geographic latitude relative to a warmer geographic N & S

Poles. This is typically not considered when using fossil based paleodating analysis.

II Palaeomagnetic Data

1. Apparent (Magnetic) Pole Wandering {APW}- Apparent movement of a stationary magnetic

pole relative to a moving continent palaeomagnetic measurement location, caused by continental drift. This is typically assumed in determining Palaeomagnetic Data [53]

2. True (Magnetic) Pole Wandering {TPW}- True movement of a moving magnetic pole

relative to a stationary continent palaeomagnetic measurement location, caused by asteroid

impact, volcanic or polar ice induced geostatic imbalance [38],[39],[40]. This can also

be associated with the actual shifting of the Earths axis of rotation,

3. Actual Magnetic Pole Shift (Pole shift)- Actual movement of the geomagnetic North Pole,

caused by turbulence to change in rotation . [9][10]

VIII Subduction Mechanism

1. Convection currents

A. Conventional Plate Tectonics Theory: Assumed, but not confirmed that convection

currents are the driving force behind plate movement. Modeled as gravity controlled

sinking of a cold, denser slab into the subduction zone [19].

B. Anomalies: Mechanical resistance to tractional transit of oceanic crust across an ocean

basin is significantly greater than the energy available from proposed motivating

mechanisms [26]. The question of what drives the plates remains unanswered [19].

2. Slab pull (subduction at trenches) & slab push (sea floor spreading at ridges) [7]

A. Anomalies: Energy requirements to drive subduction of oceanic crust is not available by

proposed push, drag and pull mechanisms [26].

END OF FIG 5

Copies of all references used by the student shall be presented along with the written report. After the reports are turned in the student shall prepare a brief presentation on their findings. The teacher will then conduct a teacher directed discussion on the topic. Allow 1 week non classroom time for the students to prepare the report as homework, and minimum 2 minutes, maximum 3 minutes for each student presentation, with a maximum 2 minute class discussion immediately following each presentation. Allow one half a class period.

Instructions to the Student:

Your teacher can help guide you on potential reference sources to use or suggest key words/phrases to try when using internet web search engines.

Follow Attachment 1 guidelines on research and reporting.

If you have any questions regarding what format to use in your presentation, ask your teacher to help you in choosing an acceptable model to follow.

Homework Options and Home Connections:

Instructions to the Teacher:

Research one or more of the physical measurements listed as an individually numbered line item in Fig. 6 below. Then write a brief one page paragraph on that physical measurement(s). Attach copies of all background information that was used. Assume one half a class period to discuss any questions relating to the homework.

Fig. 6

Physical Measurements

I. Continental Spreading Rate Measurement

1. Uniformitarian constant rate assumption. Published space GPS geodetic systems

measurements [36]: Present movement rate 2-3 cm/yr Mid Atlantic Ridge, East Pacific Rise

up to 15 cm/yr [15], Artic Ridge 2.5 cm/yr [19].

2. Drastic change in spreading rate and direction. Central Indian Ocean Ridge had rapid

decrease in spreading rate followed by a change in spreading direction [54].

II. North Magnetic Pole

1. Present movement rate 40 km/yr [10].

III. Earth shape

1. Obloid spheroid with equatorial bulge stabilizes rotational axis [38].

IV. Apollo Objects and potential Earth Collisions

1. 100 known Apollo objects ranging in size from 1 to 10 km with perihelions that lies within

the Earths orbit. [38].

2. Hypothesis: Estimated 1000 to 2000 Apollo objects fit above category [38].

V. Earth Craters

1. Present total count of the recognized terrestrial craters on Earth is 120 [34], [35].

2. Hypothesis: Estimated 4 collisions on Earth /1 MY for Asteroids 1 km or larger [38].

VI. Total Worldwide Trench and Ridge Lengths

1. The combined length of all sea trenches is ~30,000 km, the combined length of all spreading

ridges is ~60,000 km [26].

2. Anomaly: The combined length of all trenches (~30,000 km) is only about of that required

(Two times ~60,000 km = 120,000 km required) [26].

3. Anomaly: Global only balance of lithosphere. Mid Atlantic Ridge divergence must be

compensated by western Pacific trenches subduction [11].

END OF FIG 6

Instructions to the Student:

Your teacher can help guide you on potential reference sources to use or suggest key words/phrases to try when using internet web search engines.

Follow Attachment 1 guidelines on researching and reporting.

Interdisciplinary Connections:

Grade 9

Social Studies (Social Studies Skills and Methods- Thinking and Organizing Indicators 1,2,3)

English Language Arts (Reading Applications: Informational, Technical and Persuasive Text Indicators 2,4; Research Indicators 2,3,4)

Materials and Resources:

Science notebooks, Poster sized paper, Colored pencils or magic markers, Masking tape,

Textbook, Library and internet access by the Teacher and/or Student

Note for classrooms with only one computer-

An overhead, LCD or television screen can be used to project images from the computer onto a classroom screen. The lesson can be bookmarked or previously downloaded onto the computer or CD. This will facilitate a more organized and predictable large group presentation and minimize glitches.

Note for Classrooms that do not have computer access-

For teachers with school library or home computers with internet access selected parts of the lesson may be printed out on paper or transparencies.

If there are one or more computers located outside the classroom inside at the school or nearby at a local library, students may experience their research lesson individually or in small groups as a learning station.

For those students with home computer internet access, their research lesson may be done as homework or as an extension lesson.

Vocabulary:

Palaeo, palaeomagnetism, palaeoclimate, palaeozic, radiometric dating, magnetic reversals, magnetic stripes, geologic fault lines, microfossils, basaltic rock, fracture zone, rock deformation, tektites, magnetic dipole reversal, magnetic pole, pole inversions, magnetic field reversal, magnetometer, stratigraphic dating, discordant dates, decay rate, subduction, convection currents, slabs, plates, GPS geodetic systems, Apollo objects, lithosphere, divergence.

Technology Connections:

Internet web sites, multi-media computer downloads, analog photo copies or scanned digital images

Research Connections:

Inquiry strategies, theory on multiple intelligence, Marzano cooperative group learning,

Identifying similarities and differences, direct vocabulary instruction, writing answers more memory retention than oral answers

General Tips:

The indicator and the benchmark does not mandate any teaching requirement as to assigning any age to the Earth (whether absolute, relative, apparent, order of magnitude, etc.). Thus it is at the teachers discretion to omit or include any information (whether for or against) regarding the age of the Earth.

Attachments:

Attachment 1: General Student Research and Reporting Guidelines

Attachment 2: Activity 1 on simulated magnetic reversals entitled What can be learned from observations of polarity directions in the sea floor?

References:

The recommended references listed below are the minimum required for the basic core lesson to be used by all students. Each reference is keyed to one or more appropriate lesson topics by the use of a bracket containing a bold 2 digit number in italics. For example [15] is Reference 15.

RECOMMENDED REFERENCES for Core Basic Lesson

[19] http://pubs.usgs.gov/publications/text/dynamic.html Online edition of This Dynamic Earth: the Story of Plate Tectonics

[22] http://earthsciencesportal.gsfc.nasa.gov/Terrestrial_Physics/Geophysics/ Geomagnetism and plate boundary interactions

[26] www.geocities.com/CapeCanaveral/Launchpad/8098/1.htm General introduction to global expansion tectonics

[51] www.scientificexploration.org/jse/articles.html David Pratt, Plate Tectonics: A Paradigm Under Threat, JSE 14:3, 2000, pp. 307-352

[56] www.science-frontiers.com Online Reference for Scientific Anomalies

Note: no space between any letters of web page. Underscore _ exists between letters where there appears to be a space. The underscore _ exists but is obscured by the underline for link.

Also some sites use lower case L l which looks like the number one 1

Footnotes:

The optional suggested footnotes listed below are for the PreAssessment and PostAssessment assignments. Each footnote is keyed to one or more appropriate lesson topics by the use of a bracket containing a bold 2 digit number in italics. For example [15] is Reference 15.

FOOTNOTES for PreAssessment and PostAssessment Activities

[5] Wesson, P.S., 1972. Objections to continental drift and plate tectonics. Journal of Geology, vol. 80, pp. 185-197. (cited in www.cnt.ru.users.chas/tectonic.htm) 74 objections to gradualist plate tectonics

[14] http://lamar.colostate.edu/~gnelson/nazli.html Sea-floor spreading animation

[19] http://pubs.usgs.gov/publications/text/dynamic.html Online edition of This Dynamic Earth: the Story of Plate Tectonics

[21] Coe, Robert S., and Michel Prevot. 1989. Evidence supporting extremely rapid field variation reversal, Earth and Planetary Science Letters 92(3/4): 292-298.

[22] http://earthsciencesportal.gsfc.nasa.gov/Terrestrial_Physics/Geophysics/ Geomagnetism and plate boundary interactions

[23] Science News April 5, 1995 (Vol. 14) Nature article, Extremely-rapid field orientation shifts

[26] www.geocities.com/CapeCanaveral/Launchpad/8098/1.htm General introduction to global expansion tectonics

[36] http://kids.earth.nasa.gov/archive/pangaea/ Plate Tectonics Glossary and general overview

[41] Coe, R.S., M. Prevot, and P. Camps, 1995. New evidence for extraordinarily rapid changes during a reversal. Nature 374:687-692.

[46] G.W. Wetherill, Radioactivity of Potassium and Geologic Time, Science, September 20, 1957, p.545

[47] J.F. Evernden, et.al., K/A Dates and the Cenzoic Mammalian Chronology of North America, American Journal of Science, February 1964, p.154

[48] Rancitelli and Fisher, Planetary Science Abstracts, 48th Annual Meeting of the American Geophysical Union, 1967, p.167

[50] www.gpc.peachnet.edu/~pgore/geology/historical_lecture/chapter5notes.html Evidence in support of the Theory of Plate Tectonics

[51] www.scientificexploration.org/jse/articles.html David Pratt, Plate Tectonics: A Paradigm Under Threat, JSE 14:3, 2000, pp. 307-352

[52] www.sciencemag.org J.E.P. Connerney, et.al, Magnetic Lineations in the Ancient Crust of Mars, Science Vol 284, April 30, 1999, pp. 794-798

[55] http://beerfrdg.tamu.edu/~guinness/jqz.html Magnetic Reversal Model of Deep-Tow Magnetic Data from the Pacific Jurassic Quiet Zone

The optional additional footnotes listed below are suggested for use in the optional Extended Learning assignment. Each footnote is keyed to one or more appropriate lesson topics by the use of a bracket containing a bold 2 digit number in italics. For example [15] is Reference 15.

ADDITIONAL FOOTNOTES for Extended Learning Figure 5

[7] www.geotimes.org/dec02/NN_plates.html Fast and slow plates

[9] www.geotimes.org/jan03/feature_polar.html Deciphering Earths dicey dipole

[10] www.geotimes/org/may02/NN_pole.html Pursuing the North Magnetic Pole

[38] http://wwwesterni.unibg.it/siti_esterni/dmsia/dynamics/poles.html Asteroid impact causing geographical pole shift

[39] www.sciencemag.org/cgi/content/full/279/5347/9a Polar Wander and the Cambrian

[40] www.gps.caltech.edu/~devans/iitpw/science.html Cambrian True Polar Wander

[53] http://www1.ncdc.noaa.gov/pub/data/paleo/timescales/mead1995/readme_mead1995.txt Correlation of Geomagnetic Polarity Time Scales: An Internet Archive

The optional additional footnotes listed below are suggested for use in the optional Homework assignment. Each footnote is keyed to one or more appropriate lesson topics by the use of a bracket containing a bold 2 digit number in italics. For example [15] is Reference 15.

ADDITIONAL FOOTNOTES for Homework Figure 6

[11] http://vulcan.wr.usgs.gov/Glossary/PlateTectonics/framework.html Plate tectonics and sea-floor spreading

[15] www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/Lec12.html Sea-floor spreading and plate tectonics

[34] www.solarviews.com/eng/tercrate.htm Terrestrial impact craters photo gallery

[35] www.unb.ca/passc/ImpactDatabase/ Earth impact database

[54] www-sdt.univ-brest.fr/~jerome/magofond2_en.html The Magofond 2 cruise: a surface and deep tow survey on the past and present Central Indian Ridge

General Note for all Footnotes:

When more classroom time is available, or for advanced students as part of extended learning, all the References and Footnotes may be made available for use by the teacher and student.

ATTACHMENT 1

General Student Research and Reporting Guidelines:

1. Teacher is to provide topic and question.

2. Suggested reference source(s) and key word(s)/phrase(s) for web search engine will be provided by teacher.

3. Student is to evaluate the usefulness, and whenever possible the credibility, validity and possible bias/slant of data, information and sources (primary and secondary). Teacher is to act in a review capacity during this process.

4. The credentials and past reliability track record of both the author and publisher should be taken into consideration in evaluating the reference source. One should note though that some important paradigm shifts in the past were first discovered by investigators working outside of their specialty field of formal education, e.g. Charles Darwin was a divinity school graduate. Also, from 1903 until 1908 the two bicycle mechanics Wilbur and Orville Wright were rejected by Scientific American for their 1903 claim to have successfully built and flown a heavier than air flying machine.

5. Critical thinking skills should include a check by the student for potential errors in logical reasoning and/or extrapolation used in the reference source.

6. Where appropriate and available, contrary/anomalous information should also be evaluated in order to provide an intellectually honest and balanced perspective.

7. An attempt should be made to include some non-American references that provide written information available in the English language.

8. Student should utilize investigative inquiry methods appropriate to the type of question being researched.

9. Research should be linked to relevant scientific theory/knowledge, and be germane to the topic so as to stay on target with the indicator and benchmark.

10. The student should use and describe a logical, coherent and explicit line of reasoning.

11. Information from various resources should be organized, and the sources selected should be appropriate to support the central ideas, concepts and themes.

12. Students should produce reports that give proper credit for sources.

13. The findings communicated on the substance and processes should include using the proper modes and media appropriate to the nature and/or type of information.

Modified from Reference: Scientific Research in Education, Committee on Scientific Principles for Education Research, Richard J. Shavelson and Lisa Towne, Editors, National Research Council ISBN 0-309-08291-9

ATTACHMENT 2 (1 of 3)

Student Activity 1 or Teacher Demonstration 1

Sea Floor Spreading Activity

Purpose: What can be learned from observations of magnetic polarity directions in the sea floor?

Materials: Ruler

Background Summary: In this activity, you are going to act as marine geologists on a cruise. You will collect magnetic field strength data as you sail in a zig-zag pattern across the Mid-Atlantic Ridge just southwest of Iceland. Table 1 shows the data which were collected. Previously an ocean floor drilling expedition in the area collected cores samples of the sea floor at the same location were you collect the magnetic field strength data. These core samples were analyzed for oxygen isotope measurements and then compared with an assumed standard curve that correlates oxygen isotope concentration with stratigraphic index fossils or radiometric data. From this curve matching an assumed apparent age can be derived. The assumed apparent age is also given in Table 1 last column.

The magnetic field strength data provided in Table 1 is actual data collected during a magnetic study of the area. The scientists used an instrument called a magnetometer, carried aboard a U.S. Navy plane. Note the planes magnetometer measures sediment magnetism and not necessarily the sea floor basaltic rock magnetism. The magnetometer does not have a compass needle that really reverses. It measures the strength of the magnetic field. When the magnetometer is above reversely magnetized rock, it will show the field to be weaker than when it is over normally magnetized rock. It should be noted that the weaker field strength may also be caused by variations in intensity and not necessarily changes in direction. For the purposes of this exercise we will assume that all weaker field strength measurements are caused by magnetic field direction reversals

Procedure:

1) On the Worksheet C, mark an X or an O at the location of each station in Table 1. Note that the X indicates inferred reversed magnetism and O indicates inferred normal magnetism. Where each apparent age is given, write next to the symbol either the number 10 (for 10 million years) or the letter P (for Present, e.g. 0 million years). Note the example of station 2 already plotted on the map.

2) After you have marked all of the normal and reversed symbols and the apparent ages that are given for some locations, draw one straight line with your ruler that will connect all the stations where the rocks are of Present age (P). This will separate the groups of 10 million-year-old rocks. Draw one straight line though each group of 10 million-year-old rocks (10).

Procedure 2 questions:

A. Where do you think the Mid-Atlantic Ridge is located on your map? What is your reason?

B. What pattern do you see on your map?

C. How can you explain this pattern?

3) Draw arrows on your map to show in what direction the ocean floor on each side of the ridge is moving. How do you know this?

ATTACHMENT 2 Cont. (2 of 3)

4) If a car travels 100 kilometers in two hours, what is its average speed in (kilometers) per hour? How can you find out how fast the ocean floor is moving on each side of the ridge? This number is an average rate. Does this mean that it is always moving at the same average (Uniform) rate, or could if have moved faster or slower at different times in the past?

5) Find the average uniform rate (in centimeters per year) at which the ocean floor is moving in the area of Iceland. (Remember that 1 km equals 1000 m, and 1 m equals 100 cm. Therefore, to convert kilometers to centimeters, you must add 5 zeros to the number of kilometers.)

6) If the sea floor spreads at a constant uniform rate, what is the apparent age of the sea floor at station 14?

7) Now that you know the average uniform rate at which the ocean floor is moving, assuming Uniformitarian principles apply, use this figure to find out how fast the ocean floor is spreading apart on the two sides of the ridge

Table 1

Magnetic study data

Station

North

Latitude

(Degrees)

West

Longitude

(Degrees)

Inferred Magnetic Field Orientation

Symbol

Apparent Age

(Million Years)

1

58.0

28.0

Reversed

X

2

58.0

29.0

Normal

O

10

3

58.5

29.5

Reversed

X

4

58.5

31.0

Normal

O

Present

5

59.0

31.5

Reversed

X

6

60.0

32.0

Normal

O

10

7

61.0

33.0

Reversed

X

8

60.5

31.0

Normal

O

10

9

60.0

30.0

Reversed

X

10

60.0

29.0

Normal

O

Present

11

59.5

28.5

Reversed

X

12

59.0

27.5

Normal

O

10

13

58.5

26.0

Reversed

X

14

59.0

25.0

Reversed

X

15

60.0

24.0

Reversed

X

16

61.0

24.5

Normal

O

10

17

61.0

25.5

Reversed

X

18

61.5

26.0

Reversed

X

19

61.5

26.5

Normal

O

Present

20

62.0

27.5

Reversed

X

21

62.0

28.5

Reversed

X

22

62.0

29.0

Normal

O

10

23

62.5

30.5

Reversed

X

ATTACHMENT 2 Cont. (3 of 3)

Page 1 of 17 Lesson #3 GREEN BDW8/28/2005