Evidence for Plate Movement Names ______
My World GIS Activity
Purpose Investigate how earthquake and volcanic activity provide evidence for plate boundaries.
Prelab - Biozone Pages 16,7 will have been assigned for homework. Answer additional questions on the student answer sheet Data Chart page before starting this activity
Geographic Clues
Plate tectonics is a relatively new scientific concept, introduced some 30 years ago, but it has revolutionized our understanding of the dynamic planet upon which we live. It drew together many branches of the earth sciences, from paleontology (the study of fossils) to seismology (earthquake study). It has provided explanations to questions why earthquakes and volcanic eruptions occur in very specific areas around the world, and how and why great mountain ranges like the Alps and Himalayas formed.
The theory of plate tectonics states that the Earth's outermost layer is fragmented into a dozen or more large and small plates that are moving relative to one another as they ride atop hotter, more mobile material. Before the advent of plate tectonics, however, some people already believed that the present-day continents were the fragmented pieces of pre-existing larger landmasses ("supercontinents").
The belief that continents have not always been fixed in their present positions was suggested in 1596 by the Dutch map maker Abraham Ortelius. In 1912 that the idea of moving continents -- called Continental Drift -- introduced by German meteorologist Alfred Wegener. He contended that, 200 million years ago, a supercontinent called Pangaea began to split apart.
Source: USGS http://pubs.usgs.gov/gip/dynamic/historical.html
1) Open My Documents, MyWorld GIS, plate tectonics.m3vz
Part 1: Geographic Evidence that Pangaea once existed
1) In 1596 Abraham Ortelius suggested the Americas were "torn away from Europe and Africa . . . by earthquakes and floods.” What visual evidence from the map you are viewing supports this statement?
______
2) To see what Pangaea looked like, turn on the “Linked Images” layer. Click the check mark to the left of the layer name.
Now click the link tool to show link flags. The image of Pangaea is linked to the easternmost point in Antarctica. Click the point below the flag to show the image link, and then click the image link to open the image.
NOTE mya means Million Years Ago
The upper left figure is Pangaea, and the remaining figures show transition to modern times. Examine the figures and answer
1. India broke away from Pangea approx ______
2. India crossed the equator approx ______
Close the image .
3. South America and Africa separated approx. ______
Part 2: Fossil Distribution
Wegener was also intrigued by geologic structures and plant and animal fossils found on the matching coastlines of South America and Africa. He reasoned that it was physically impossible for these organisms to have swum or have been transported across the vast oceans. The presence of identical fossil species along the coastal parts of Africa and South America was the most compelling evidence that they were once joined.
This also explained the evidence of dramatic climate changes on some continents. For example, fossils of tropical plants (as coal deposits) in Antarctica implied that this frozen land previously must have been closer to the equator. Other mismatches included fossil ferns (Glossopteris) in now-polar regions, and glacial deposits in present-day arid Africa.
When Wegener introduced his theory, the scientific community firmly believed the continents and oceans to be permanent features on the Earth's surface. Not surprisingly, his proposal was not well received
1) Turn OFF the “Linked Images” layer, turn on the “Fossil Distribution” layer. This shows fossils of the same type of plants and animals found on different continents. The name of each organism is in the upper right corner of the screen, and fossil type is color coded. The map represents the theoretical position of the plates soon after the breakup of Pangaea, and a representation of each organism.
2) “Fossil Distribution” layer, click radio button Glossopteris to show only Glossopteris.
Change the view
Click the pull down arrow next to “Map View:” and select “Stereographic.”
On the map mark the computer displayed positions of Glossopteris on the appropriate land mass with an “G.”
3) Study the maps
Glossopteris indicates prior connections of continents ______
Change the projection back to Geographic before proceeding.
4) ON “Linked Images” layer - click the point next to the westernmost flag in Antarctica. This will bring up an image showing “bands” corresponding to fossil ranges.
Add the bands to the map above - USE colored pencils!
Which fossil is found in Africa, India and Antarctica ?
______
Close the image .
Part 3: Glacial Evidence
As mentioned above, glacial deposits also provide important evidence for the existence of Pangaea.
1. OFF “Fossil Distribution” layer. Open the image of Pangaea again (the easternmost flag in Antarctica) - see above. Click the point below the flag to show the image link, and then click the link to open the image. Identify the sections of each land mass in the southern polar area 225 million years ago. (therefore likely to have glacial deposits)
ON “Glacial Deposits” layer and compare to your predictions (note: the glacial deposits in Antarctica not shown).
Explain how this distribution makes sense______
During which time era would you expect that the glaciation occurred? ______
Close the image.
Part 4: Evidence of Plate Boundaries
Wegner’s theory of continental drift was hotly debated off and on before it was largely dismissed, but beginning in the 1950s, a wealth of new evidence emerged. By 1968 a new theory replaced continental drift – plate tectonics.
A: Transform Plate Boundaries
1) ON the “plate boundaries” layer.
The transform type is color______Select “Transform” radio button - transform boundaries are now color ______
One of the best examples of a transform plate boundary is the San Andreas Fault, which runs the entire length of California
2) Use the zoom in tool to zoom into the west coast of the United States - the region around Oregon and Washington.
3) ON “Linked Images” layer click link tool. Click under the flag in North America to open the Transform Plate Boundary image.
4) With the image open, focus on the region around the Mendocino Fracture Zone, and think about
Will the earthquakes to be deep or relatively shallow?
Will there be volcanoes?
5) Investigate these questions
ON “Earthquakes medium m4.0-5.9 (2001-03)” layer.
This dataset shows the epicenter of over 28,000 earthquakes around the world, and the points are color coded according to the depth of the focus.
Toggle between the pre-selected depths to verify the depths of the earthquakes around the transform plate boundary.
Record the results in your Data Chart
6) ON the “Volcanoes” layer and record the results in your Data Chart
B: Divergent Plate Boundaries
OFF Volcanoes and Earthquakes layers.
ON “Linked Images” and “Plate Boundary Types” layers.
Click radio button in
“Plate Boundary Types” layer to highlight the divergent plate boundaries.
1) Zoom into the region around the Mid-Atlantic Ridge with Iceland in the view
2) ON “Linked Images” layer and click the link tool. Click the point under the flag in the Atlantic Ocean to open the divergent plate boundary image. Check the cross section you drew for HW
3) ON “Earthquakes medium m4.0-5.9 (2001-03)” layer.
Use the pre-selected depths to verify the depths of earthquakes around the plate boundary.
Toggle between deep and shallow earthquakes and record the results
4) ON “Volcanoes” layer enter results in data table
5) ON the “Sea-floor age (m.y.)” layer. This layer shows the age of the sea-floor in millions of years before present and age ranges are color coded. Toggle the different pre-selected age ranges ANSWER
1. Sea floor age closest to N. America and Africa? ______
2. Sea floor age closest to Greenland? ______
3. How does the age change between the Mid Atlantic ridge and the continents? ______
8) OFF “Sea-floor age (m.y.)”
ON “4' World Shaded Relief” “Elevation & Bathymetry” layers. These layers will give you a sense of the change in elevation along the sea-floor. Click the vertical profile tool draw a vertical profile.
Change the “Sample Every:” box from 60 to 10 to increase the resolution. Click “OK”
The vertical profile function works by clicking and drawing a line across the area you want to profile. Click once to start the line, double click to stop the line.
Draw the profile across the ridge at approximately a right angle.
Explain what is happening at the highest point on your profile
______
C: Convergent Plate Boundaries
1) OFF the layers from the previous activity
“Zoom To All” tool button to zoom out to the full extent. Click the radio button in the plate boundaries layer to highlight convergent plate boundaries..
Zoom to the region west of South America.
2) On the “Linked Images” layer and click the link tool Click the point under the flag in South America to open the convergent plate boundary image.
The process where one plate goes UNDER another is called SUBDUCTION
Check the cross section in your data sheet
3) As for divergent boundaries investigate
earthquake depth
volcanoes
and complete your Data Chart
4. Using the profile method check your cross section drawing and make sure the trench is accurately labeled. Teacher sig ______
The trench depth is ______m below sea level; the mountain peaks are ______m above sea level.
The mountains range is called ______
Where are the earthquakes located relative to the mountain range
a) Shallow quakes b) Deeper quakes
D. Investigate
a) Find the Himalayas, -Investigate boundary type This is a ______boundary
But without subduction. Since both plates are continents they are approximately equal density so neither sinks
Investigate Earthquakes , volcanoes and profile . Complete your data chart
Note the Alps in Europe are similar
E. Extra - Investigate
a) African Rift Valley Divergent b) Japan or Indonesia
Summary Questions - use the activity and HW (Biozone) to answer
1. According to the theory of plate tectonics, the lithosphere is broken into large segments called plates. These plates “float” on a more fluid layer called the ______,. The plates continuously move and gradually change shape and size.
2. Describe the movement at different types of plate boundaries on your chart
3. Describe one of the early evidences that led to the theory of plate tectonics.
4. Explain why deep ocean trenches are close to continents and not in the middle of oceans.
5. What is occurring in the ocean region between North America and Europe?
6. How do you account for mid-plate volcanoes such as Hawaii ?
7. Why are volcanoes not common at a transform plate boundary?
8. What geographic formations are found at divergent plate boundaries?
9. Describe the difference in sea floor age at a convergent and divergent plate boundary, and explain why there is a difference.
10. Explain the differences and similarities between the Andes in S.America and the Himalayas
11. How did using GIS help you to understand plate tectonics
This activity is modified from the free plate tectonics activities provided by Northwestern University and Pasco .
http://myworldgis.org/myworld/activities/
PlateTechGISnew.doc 5 8/13/09