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Plate Tectonics Real Time Data Analysis
Part 1: Use your computer to identify the three types of moving plate boundaries. Cut and paste your images in the
right location below to match the proper description.
Tectonic Plate Boundary 1:
Tectonic Plate Boundary 2:
Tectonic Plate Boundary 3:
When continental and oceanic plates
collide the thinner and more dense
oceanic plate is overridden by the thicker
and less dense continental plate. The
oceanic plate is forced down into the
mantle in a process known as
"subduction". As the oceanic plate
descends it is forced into higher
temperature environments. At a depth of
about 100 miles (160 km) materials in the
subducting plate begin to melt. This partial
melting produces magma chambers
above the subducting oceanic plate.
These magma chambers are less dense
than the surrounding mantle materials and
are buoyant. The buoyant magma
chambers begin a slow asscent through
the overlying materials, melting and
fracturing their way upwards. The size
and depth of these magma chambers can
be determined by mapping the
earthquake activity arround them. If a
magma chamber rises to the surface
without solidifying the magma will break
through in the form of a volcanic eruption.
These plate boundaries are locations
where plates are moving away from one
another. This occurs above rising
convection currents. The rising current
pushes up on the bottom of the
lithosphere, lifting it and flowing laterally
(side –ways) beneath it. This lateral flow
causes the plate material above to be
dragged along in the direction of flow. At
the highest point of the uplift, the
overlying plate is stretched thin, breaks
and pulls apart. When this boundary
occurs beneath oceanic lithosphere, the
rising convection current below lifts the
lithosphere producing a mid-ocean ridge.
Extensional forces stretch the lithosphere
and produce a deep fissure (crack) .
When the fissure opens, pressure is
reduced on the super-heated mantle
material below. It responds by melting
and the new magma flows into the
fissure. The magma then solidifies and
the process repeats itself.
These plate boundaries are locations
where two plates slide past one another.
The fracture zone that forms within this
type of boundary is known as a transform
fault. Most transform faults are found in the
ocean basin and connect mid-ocean
ridges. A smaller number connect midocean ridges and subduction zones. These
faults are also locations of recurring
earthquake activity and additional cracking.
The earthquakes are usually shallow
because they occur within and between
plates that are not involved in subduction.
Volcanic activity is normally not present
because the typical magma sources of an
upwelling convection current or a melting
subducting plate are not present. The most
famous example of this is the San Andreas
Fault Zone of western North America.
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Part 2: Fill in the answers to the questions using the ABC’s . Please use specific data from the website to support your
answers. (Hint use quantitative data: This means the use of measurement usually in numbers.)
Earthquake Expert:
Earthquake Data Questions: Examine the earthquake data plotted on the map and notice where earthquakes are located
as well as where they are not located.
A. How are earthquakes distributed? If there is a pattern, how would you describe it? Where are there no earthquakes?
Are they located near the edges of the continents, mid-continent, in the ocean?
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B. At what depth(s) do the earthquakes occur? (Hint: look at the legend)
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Volcano Expert:
Volcano Map Questions: Examine the volcano data plotted on the map and notice where volcanoes are located as well
as and where they are not located.
A. How are volcanoes distributed? Where are there no volcanoes? Are they located near the edges of the continents,
mid-continent, in the ocean?
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B. If there is a pattern, how would you describe it?
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Part 2 (continued)
Map your data
Using the “Insert” menu at the top of this document, choose “Shapes” to sketch the general locations of the majority of
the volcanoes/earthquakes on the map below. You do not need to make individual symbols. Lines or shading of the
correct color in the general areas will be sufficient.
A. What geographic features (mountains, plains, valleys, etc) are frequently found where there are only:
Earthquakes?
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Volcanoes?
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B. In which regions do you find earthquakes and volcanoes near each other? Describe the geographic features of these
regions.
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C. Summarize the relationships you discovered. Are the geologic events you looked at (earthquakes and volcanoes)
more commonly found together or separate?
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D. What explanation can you provide for the observed relationships?
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Part 3: Examine GPS Vector Data
1. Sketch some of the vector arrows on your map on Page 2; click on the map to zoom in and use the zoom out button
to zoom out. Pay special attention to what direction the arrows are pointing (e.g. the direction the ground is moving)
and the lengths of the vector arrows (velocity). Answer the questions and then join your teammate to discuss your
answers and come to a consensus on the answers.
A. What do you notice about the length of the vectors (the velocities) in the Pacific Northwest compared to those in
coastal California? What is the scale for the vectors on this map? What direction(s) do the vectors point in the Pacific
Northwest and California? What does this indicate?
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B. How does the velocity of each GPS station change from the coast to inland California? Why do you think there are
many GPS stations (lots of vectors) near the coast of California and not many GPS stations farther inland?
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More questions to think about:
Why does volcanism occur at convergent boundaries but not at transform boundaries?
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Do you observe a relationship between geographic features (shapes on the crust) and plate boundaries?
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Do the patterns that you observed in the Western United States occur worldwide? Support your answer from what you
know about plate tectonics, the lithosphere, the asthenosphere and what the earths is made up of…..
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