Abstract:

Did you know that even when it seems like your are sitting or lying still, your are actually moving on top of a huge crusty plate? This investigation focuses on the concepts of plate tectonics, including: the causes of these motions; directions and rate of movement; understanding of the three types of plate boundaries and their consequences (e.g. convergent boundaries and the "Ring of Fire" ); and prediction of future locations of geographical features based upon past and present plate motion measurement. Learners will extract and analyze Internet data to ascertain these answers and will graph rates of movement to make rational predictions.

 

Background
Did you know that the coal that is mined in Pennsylvania was actually formed from tropical plant life near the Equator? How did it travel northward to Pennsylvania? Scientists believe that 200 million years ago, when the dinosaurs dined upon tropical ferns and tall tropical vegetation, what is now Pennsylvania was at a different location, namely the equatorial region. The term first coined for the "free ride" on large crustal plates was Continental Drift. Alfred Wegener, a German meteorologist, introduced the theory of Continental Drift in 1912. He proposed that the continents were once connected as a huge land mass which he named "Pangaea" (which means "all lands" in Greek). This land mass then broke apart 200 million years ago and drifted to the locations which we observe today. To read an excellent historical account of this theory with informative graphics, go now to the following Internet sites:

http://pubs.usgs.gov/publications/text/historical.html#anchor4833509

http://xray.geol.uni-erlangen.de/html/teaching/plate/pla_tec.html

As you have now read, Wegener's Continental Drift theory was not readily accepted by the science community of his day. It was difficult to conceive of large continents plowing through the sea floor to move to new locations. To understand how continents might move, it is important to review several concepts about the Earth's structure. Recall that the Earth is made up of several layers, each having different compositions and properties. From the center of the Earth outward, these layers are the: inner core (solid); outer core (molten); lower mantle; upper mantle; and crust. These are depicted in the following graphic:

The quest to further discover how continents might move led to the now accepted theory of plate tectonics. In the early 1960's, Harry Hess, a scientist from Princeton University, proposed that the upward motion of the less dense and very hot material in the mantle makes new crust at the mid-oceanic ridges. The following diagram shows the process of land formation at spreading zones and deformation at subduction zones.

Taken from:
http://xray.geol.uni-erlangen.de/html/teaching/plate/pla_tec.html

Now that you know what the Earth's various interior layers are composed of, and why and how heat from the center of the Earth is released, it is important to understand that plate tectonics theory says that the Earth's crust is divided into about 12 large plates upon which all of the Earth's continents and oceans ride. A tectonic plate is a massive slab of solid rock made of both continental and oceanic lithosphere. Ocean crust, made of basaltic rocks, is heavier and more dense than continental crust which is made of granitic rocks composed of quartz and feldspar. Ocean crust (about 5 km thick) is much less thick than continental crust (up to 100 km thick). Most of the boundaries between plates cannot be seen directly since they are beneath the oceans, but oceanic plates can be accurately mapped from space via the measurements from GEOSAT satellites. Click on these sites to see an incredible satellite image of the Earth's tectonic plate interfaces:
http://bang.lanl.gov/solarsys/raw/earth/plates.gif

http://www.geo.Arizona.EDU/saso --then click on "Earthquake information" and go to "Plate Tectonic Map"

You will note that as the plates move, they have three options--hence the three types of plate boundaries. The first, called convergent boundary, means that the plates are coming together or colliding. This collision may be between two ocean plates, two continental plates, or an ocean and a continental plate. Also collision may result in an uprising of continents, as is happening in the Himalaya Mountains today, or in one plate going beneath the other into a subduction zone or trench. In the latter case, the lithosphere will become hot, melt, and become a part of the asthenosphere once again. The three major types of plate boundaries are illustrated in the following pictures:

Notice that the ocean plate is subducting under the continental crust into the hot asthenosphere where it will melt and eventually become new lithosphere at a spreading zone.
Another type of plate boundary already mentioned is the divergent boundary, or spreading center where magma upwells, as at the Mid-Atlantic ridge.

Notice the long light blue ridge that is located between North/South America and Europe/Africa. This is the spreading zone known as the Mid-Atlantic ocean ridge. It is interesting to note that the tallest mountains in the world are beneath the oceans.
The last common plate boundary is known as the transform fault, where plates move in a sliding motion parallel to each other. Perhaps the most famous example of this boundary type is the San Andreas fault in California where the Pacific and Juan de Fuca plates crunch past each other.
The San Andreas Fault .....A transform Boundry.

It is the moving, banging, crunching, grinding, and occasional snagging or binding up of these plates which causes earthquakes and volcanic eruptions. It is no surprise then that more earthquakes and volcanoes occur in the Pacific Ocean regions where there are more convergent and transform fault plate boundaries. In contrast, the Atlantic Ocean region is fairly calm by comparison since its plates tend to diverge, creating new crust. One additional element of plate tectonics is hot spots. Some volcanoes occur within a plate and are called intra-plate volcanoes. These are formed when the plate passes slowly over a thin, very hot ocean crustal area, causing magma upwelling and formation of volcanic islands such as the islands of Hawaii, shown below:

It is apparent that planet Earth is a dynamic system which needs to continuously release internal heat. Plate tectonics has provided a reliable theory to explain the interactions which occur between the inside and outside of Earth's surface. The following diagrams depict the major tectonic plates of the world and the continents which ride on them. As you look at these plate boundaries, notice the jagged edges which define the plate boundaries. Those large "cracks" in the Earth's surface are indeed places where magma upwells or crust subducts and melts. Notice also which plates are the largest and which are the smallest. In the picture which provides the names of the plates, do most of Earth's continents have the same name as the plates upon which they ride? Does everyone in North America ride on the North American plate? How do these boundaries relate to earthquakes and volcanoes?

You have learned much about the theory of plate tectonics. This lesson is designed to put your knowledge into action. If you can know the rate of speed at which plates are actually moving, you may be able to predict how far they will have traveled in a defined period of time and what the world may look like one million or more years from now! If you still need a little research time to refine your knowledge of plate motion, please visit several of these excellent Internet sites listed in the Resources section below.

 

INVESTIGATION

Part I. Review of Plate Tectonics Background Information.

Procedure:

1. Complete the following plate tectonics challenge . When you have answered all 5 questions, you may go to the answer key in the Teacher's Resource section.
   
   
   1. The continental drift theory proposed by Wegener cited all of the following as evidence of the theory except:
      a) glossopteris fossils in Africa and South America
      b) the shapes of the coastlines of South America and Africa
      c) ancient Indian artifacts
      d) fossils of mesosaurus
      
      
   2. Which of the following does plate tectonics theory NOT say:
      a) the crust is divided into rigid plates
      b) the plates move only a few cm per year
      c) convection currents drive plate motion
      d) there are 21 major plates
      
      
   3. Which of the following is NOT a major type of plate boundary?
      a) gliding
      b) convergent
      c) divergent
      d) transform fault
      
      
   4. Which of the following does NOT occur at plate boundaries:
      a) new oceanic crust is made
      b) continental plates crash into each other
      c) oceanic plate is subducted under continental plate
      d) continental plate is subducted under oceanic plate
      
      
   5. An example of an island(s) formed over a "hot spot" is:
      a) Chincoteague Island
      b) Hawaiian Islands
      c) Gibson Island
      d) Assateague Island
      
      

CONGRATULATIONS, if you were correct most of the time. If not, you may wish to detour and revisit the Internet sites listed in the first portion of the investigation.


Part II. Sizing up the earth
Materials: A ruler
A large map and/or large globe with a distance scale
Printouts : #1 & #6 in Procedure
Procedure:

1. Go to http://denali.gsfc.nasa.gov/research/lowman/lowman.html. Print out a copy of this plate tectonic map.
2. Using the site,http://www.indo.com/distance/, you will be asked to choose one city in the Pacific Ocean region. You will be looking for its latitude and longitude. Find the latitude and longitude and record them on a piece of paper.
3. Using the NASA plate tectonics map which you printed, locate the tectonic plate upon which your chosen city rides. Write down the plate name on the paper you used to record the latitude and longitude.
4. Go to http://manbow.ori.u-tokyo.ac.jp/tamaki-html/plate_motion.html. Here you will be entering the latitude and longitude information which you found in number 2. When you have successfully done this you will be given a distance which your chosen city will travel on its plate in one Million years. Write down the following information which this site gives you:
   1. "Latitude inputted"--
   2. "Longitude inputted"--
   3. Velocity=
   4. Direction=
5. Your task is to calculate how far and in which direction the city will move in:
   
   
   1. 1,000,000 years
      
   2. 500,000 years
      
   3. 250,000 years
      
   4. 125,000 years
      
   5. 50,000 years
      
   6. 1000 years
      
   7. 100 years

    

6. Click here (wheel.pict) to print out a copy (teachers may wish to make transparencies to facilitate visual observation over designated cities chosen) of the worksheet, Geographic Direction Finder.
7. Using a large map (or globe), locate the city you chose. Place the center point of your Geographic Direction Finder (GDF) over the center dot designating your city (hint--center the eraser end of a pencil over your city with the point end of the pencil held straight up, vertically. You may then place the center of your GDF over the pencil point and gently pierce it and lower it down over your city.
   
   
8. Make sure that you have

   N

   on the GDF lined up with North on your map. Using the Direction value you copied down from the "plate motion calculator," begin at zero and move around the GDF counterclockwise until you come to the value that is closest to the Direction value. Make a light mark with pencil (or wax pencil on a laminated map).

9. Using a clean sheet of paper, line the left edge of the paper up with the scale on the map you are using. Make small dash marks on the edge of the paper to correspond with the scale intervals on your map. Record on the paper the value in kilometers of each interval.
   
10. Using the left edge of the paper, line the paper up so that the left edge passes through both points you have defined (center of your city and point you drew for "direction").
    
11. Calculate the distance your city will travel for each of the time measurements listed in number 12 using the velocity measurement from the "plate motion calculator." Mark the spot where your city will be in one million years. Place a small strip of paper next to the spot with the name of your city and the approximate year that it may be in that location.
    
12. Choose a second city to calculate. Repeat the steps for that city and locate and identify it on the world map.
    
13. If this activity is being done in a classroom, have other partner groups or cooperative learning groups also locate and identify their cities on the map in the locations they will occupy in one million years. Compare and contrast how the world looks today and how it may look one million years from now.
    
14. Prepare a bar graph to show the distance traveled by your cities (and those of your classmates) in: 1,000,000 years, 10,000 years, 1,000 years, 100 years.. .
    
15. Write a two paragraph story about how conditions in one million years will have changed from what they are like today in your selected cities. Would you rather live in that city now or in one million years? Explain.
    

CONGRATULATIONS! You are now a plate tectonics expert! You can now prove to folks that this is perhaps the greatest and latest free amusement park "ride" people could ever enjoy, compliments of natural forces, although it is a little SLOW. Hopefully you have learned that Earth is a dynamic system, which interacts with forces both under its crust and above its crust, in oceans and on continents. We need to understand our Earth in order to care for it, predict its natural phenomena, and plan for future generations.

Teacher Resources

Coding:

Maryland Core Learning Goals (Science): 1,2
National Standards (Science): A.1, A.2,A.3,A.8, B.2,B.3, D.1,D.2, E.1,E.2
National Standards (Geography): 1,3,7,17,18
National Standards (Mathematics): 4.2, 4.4,4.5,12.3,12.4,12.6,13.1,13.2,13.3,13.4,

13.5,13.6

Objectives /Indicators (Concepts to be learned):
At the conclusion of this lesson, learners will:

1. Demonstrate use of technology to acquire, explore, and analyze data images.
   
2. Conduct scientific inquiry using a variety of technical resources.
   
3. Use the Internet and World-Wide-Web resources to conduct scientific investigation.
   
4. Demonstrate use of graphing skills to analyze and present data.
   
5. Describe in scientific terminology the theory of plate tectonics.
   
6. Identify and describe the three major types of plate boundaries: convergent, divergent, and transform fault, and note where each occurs on a world map (via Internet).
   
7. Draw and explain the physics of convection currents as they relate to causation of plate tectonics.
8. Access and evaluate Internet data to determine past and present rate of plate movement.
   
9. Graph the rate of plate movement at various plate boundaries.
   
10. Predict the position of various plate boundaries (e.g. the African Rift Valley, moving approximately 2.1 cm/year)) in 1,000,000, 500,000, 250,000, 125,000, 50,000, 1000, and 100 years using present rate of motion data.

 

Extensions:

There are numerous extensions which may be investigated from this investigation. Some of these include the following:
a) Redo the investigation using a large globe. Would the location of these cites look the same on the globe as on a two dimensional map? Why?
b) Select cities on the Atlantic Ocean side of the world. Calculate the distances traveled and compare and contrast to findings on the Pacific Ocean side. Does this have anything to do with the frequency and magnitude of earthquakes occurring in those two geographical areas? Why do you think this is so?
c) With classmates, create a new world map for the year 1,001,997. Where would you like to live then? Explain why!
d) Use your investigation of plate tectonics as a launching place for a study of earthquakes. How do these topics relate?

Resources:

http://pubs.usgs.gov/publications/text/dynamic.html--This Dynamic Earth: the story of plate tectonics; excellent site describing the history, theory, understanding of plate motion, including pictures and graphics. Includes a discussion of "hot spots," "plate tectonics and people," and, "unanswered questions>"

http://pubs.usgs.gov/publications/text/historical.html#anchor4833509--describes historical development of the plate tectonics theory; includes graphics.

http://pubs.usgs.gov/publications/text/tectonic.html--What is a tectonic plate? history; graphics of Pangaea; definitions of plate, theory of plate tectonics, plate motions.

http://pubs.usgs.gov/publications/text/understanding.html#anchor4665685 --discusses the four types of plate boundaries: divergent; convergent; transform; and, plate boundary zones.

http://zebu.uoregon.edu/~soper/Earth/tectonics.html--super topographic map of Earth and good discussion of the theory of plate tectonics.

http://www.mpm.edu/exhibit/third/tp3.html--wonderful graphics show "ring of fire," subduction zones, transform fault zone.

http://www.seismo.unr.edu/ftp/pub/louie/class/100/plate-tectonics.html--Plate Tectonics, the Cause of Earthquakes. great topo maps from NASA, NOAA, USGS.

http://earthview.sdsu.edu/trees/tecqest.html--includes an outline listing of questions that can be answered by visiting sites listed.

http://cddis.gsfc.nasa.gov/926/slrtecto.html--good graphics drawn from index map for satellite laser ranging site velocity.

http://xray.geol.uni-erlangen.de/html/teaching/plate/pla_tec.html--Excellent site for graphics of earth layers, Pangaea evidence, Wegner's and Holmes models, major plates illustration, boundary types illustrated and discussed.

http://volcano.und.nodak.edu/vwdocs/vwlessons/activities/p_number9.html- Excellent site for locating plate boundaries; provides a blank map to draw plate boundaries.

http://volcano.und.nodak.edu/vwdocs/vwlessons/hot_spots/introduction.html- graphics and explanation for "hot spots."

http://volcano.und.nodak.edu/vwdocs/vwlessons/plate_tectonics/part12.html--great pictorials for location of plate boundaries and major tectonic plates of the world. "NEXT" leads to plate boundary types and diagrams.

http://hiris.anorg.chemie.tu-muenchen.de/AAL/otto/solarsystem/earthint.htm--provides an explanation on Earth's structure with relevant graphics.

http://wwwneic.cr.usgs.gov/neis/general/handouts --excellent article on relationship between plate tectonics and earthquakes, includes map of world with plate boundaries and schematic showing midocean spreading zones and subduction zones.

http://volcano.und.nodak.edu/vwdocs/vwlessons/plate_tectonics/part13.html --This site describes the types of plate boundaries and their motions.

http://volcano.und.nodak.edu/vwdocs/vwlessons/plate_tectonics/part3.html --this site has an introduction to plate tectonics including a graphic with distribution of fossil evidence across southern Pangaea.

http://wwwneic.cr.usgs.gov/neis/general handouts/rift_man.html --this is a U.S. Geological Survey site, National Earthquake Information Center depicting why Earth's earthquakes are not randomly distributed.

Feedback:

Credits:
Lynn Birdsong, Principal Investigator
Roy Avedon
Pat Keeney
Robert Swanson

Administrative/technical consultants: Steve Gilligan; Vern Smith;Luther Petry; Shane Keating; Kimmie Kiesgen; Farzad Mahootian; Eleanor Smith; Linda Spruill

NASA Scientist Advisors :: Dr. Paul Lowman ; Stephanie Stockman; Dr. Steve Cohen

Answers to Challenge Questions

Answers to Challenge: 1) C; 2) D; 3) A; 4) D; 5)

Printouts