Download Using Student-Generated Models to Understand Plate Tectonics

Using Student-Generated Models to
Understand Plate Tectonics
BY RON GRAY, ALLYSON ROGAN-KLYVE,
AND BRITTEN CLARK-HUYCK
T
he importance of engaging students in scientific modeling has been well established
and features prominently in the Next Generation Science Standards (NGSS Lead States 2013).
Engaging students in this practice provides an
authentic science experience; it also helps students make sense of the world around them (Krajick and Merritt 2012). We view scientific models
as more than just representations of a natural
phenomenon; they are tools with which students
make sense of phenomena (Passmore, Svoboda,
and Giere 2014). In this unit, we wanted students
to be able to use their own models as tools for
constructing a scientific explanation of a particu-
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lar phenomenon, rather than as simple representations of the phenomenon.
A key step in designing these learning experiences
was selecting an appropriate natural event that could
serve as the anchoring phenomenon for the unit. We
selected a puzzling phenomenon that would necessitate students gaining a strong understanding of the
theory of plate tectonics and associated concepts and
that would be engaging and relevant to their lives.
Our location in the Pacific Northwest and proximity
to the “ring of fire” gave us a number of options to
consider. However, in an effort to connect with ongoing and current scientific work, we selected Axial
Seamount as our anchoring phenomenon.
CONTENT AREA
Earth science; integrated
science
GRADE LEVEL
6–8
BIG IDEA/UNIT
Plate tectonics
ESSENTIAL PRE-EXISTING
KNOWLEDGE
Continental drift
TIME REQUIRED
11 (55-minute) class
periods
COST
None
S e p t e m b e r 2 016
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Scientific background
| FIGURE 1: Position of Axial Seamount
WIKIMEDIA COMMONS
Axial Seamount is an underwater volcano located on
the boundary of the Juan de Fuca and Pacific plates,
about 300 miles off the coast of Oregon (see Figure 1).
It is very active and well-studied, with documented
eruptions in 1998, 2011, and 2015. Axial Seamount is
located along a divergent boundary, which is why the
volcano is so active. Given Axial’s proximity to our
geographic location, the availability of rich and current scientific content about the volcano, and the likely interest of our students in this phenomenon, Axial
seemed to be an excellent topic to anchor our unit.
Lesson sequence
The main goal of this unit was to engage students
in the practice of modeling to construct a valid
scientific explanation of the existence of Axial Seamount through the theory of plate tectonics. We
introduced Axial Seamount through a video news
clip about the recent eruption and a series of datarich activities developed by the New Millennium
Observatory (NeMO) project, which reveal the
volcanic nature of the seamount (see Resources).
The four NeMO activities were conducted using
a group jigsaw approach over two class periods.
Although these activities are engaging, it is possible to begin the unit as we do below without using them by simply starting with the concept that
Axial is a volcano. After completing these activities, students were ready to begin creating explanatory models that would help them make sense of
this natural phenomenon. The following provides
a day-by-day overview of the activities we used
with students to help them co-construct models
with their peers to understand the cause of the
underwater volcano.
Day 1
Having introduced Axial, we began by
asking the driving question: How
did Axial Seamount come to be
where it is today? Through facilitated discussion, we elic-
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ited students’ initial ideas (e.g., “What do you see
going on here?” and “What do you think caused
the volcano to form here?”) on poster paper in the
front of the room. We then broke students into small
groups of three or four to co-construct initial conceptual models to answer the driving question. Each
Exaggerated swatch
bathymetry of Axial
Seamount.
NOAA
INVESTIGATING AXIAL SEAMOUNT
group drew a conceptual model on poster paper and
presented its model to the class through a facilitated
share-out session (see Figure 2a for an example of a
student group’s initial model). By the end of the first
day, students’ ideas had been elicited and were active resources (Campbell, Schwarz, and Windschitl
2015) for the class to reason with as we transitioned
to the data-rich activities that would build their understanding of plate tectonics in relation to Axial
Seamount.
examining patterns in earthquake data, groups were
able to outline Earth’s tectonic plates and look specifically at the area of Axial Seamount to discover
that it sits on a plate boundary. We then examined
the various types of plate boundaries that exist and
their associated geologic effects. Building on the previous earthquake map, groups added major mountain ranges and volcanoes to their world maps and
placed arrows along boundary lines to predict the
direction of plate motion.
Days 2 and 3
Days 4 and 5
After reviewing their initial models and the driving
question, student groups investigated the relationship between earthquakes and plate boundaries by
mapping recent data on a world-map handout (see
Resources for source of recent earthquakes). Through
To determine the type of fault at Axial Seamount,
we discussed Earth’s magnetic-field reversals
and the ways in which they affected seafloor rock
formation. We also talked about the role of radiometric dating. Students examined paleomagnetic
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| FIGURE 2: Examples of initial (a), revised (b), and final (c) student models
a
b
c
data sets (see Resources) across the globe
and then specifically at the Juan de Fuca
and Pacific plate boundary. By examining
these data, students were able to uncover
patterns of geologic features based on the
plate boundary type (e.g., terrestrial volcanic ranges occur at convergent boundaries). Most importantly, the ages of rocks
increase as they move away from the boundary,
revealing that Axial Seamount lies at a divergent
plate boundary. Using their previous understandings of plate boundary types, students were able
to label the boundary as divergent.)
Days 6 and 7
To provide students with a more complete understanding of plate tectonics, we asked groups to zoom
out from our focus on Axial Seamount and investigate the boundary on the other side of the Juan
de Fuca plate, where it meets the North American
plate. To investigate the boundary, we provided paleomagnetic data (see Resources) and earthquake
depth data. Using their previous understandings
of plate boundary types, students were able to label
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the boundary as convergent (student’s notes available with this article’s online supplements; see Resources). Further, the earthquake depth data (available with this article’s online supplements), when
graphed by students with longitude on the x axis and
depth on the y axis, revealed the angle of subduction
at the continental margin, or the Cascadia subduction zone. After this series of activities, groups were
able to complete their first model revision with their
new understanding: Axial is at a divergent plate
boundary (see Figure 2b).
Days 8 and 9
Through a discussion reviewing the evidence so far,
students realized that they still lacked a sufficient
mechanism to explain plate movements. During a
INVESTIGATING AXIAL SEAMOUNT
class brainstorming session, we
collected a number of possible
causes for plate movement,
which we used as keywords to
guide student internet research
to support or refute these explanations. Through this activity
and facilitated small- and wholegroup discussion, students were
able to identify the process of
convection, driven by energy from
radioactive decay of elements
in the Earth’s core, as a primary
mechanism. Students further revised their previous models to
include their new understandings of subduction and convection (see Figure 2c).
Days 10 and 11
| FIGURE 3: Checklist for final explanation
Evidence
Checklist
NeMo data
Axial is a volcano.
Earthquake data and
magnetic data
It’s at a divergent plate boundary (Juan de
Fuca and Pacific).
Earthquake depth data
There is a subduction zone on the other side
of the plate.
Earthquake data
Subduction zone causes earthquakes and
volcanoes (e.g., Mt. St. Helens).
Cascade volcanoes
Earthquake data
Earth’s crust is broken into plates that
“float” on magma.
Web hunt
Web hunt
Decay of radioactive material in the core
causes convection currents to move the
plates.
Students now had a complete
model that helped them underincluded in the final explanation and the evidence
stand why Axial Seamount is located where it is.
supporting it (see Figure 3). With this support, most
We facilitated groups in devising a testable hystudents were able to create a final, written explapothesis based on their model, and they searched
nation that drew upon their understanding of plate
for evidence to support or refute their hypothesis.
tectonics to account for the presence and location of
For example, some students thought, “If Axial SeaAxial Seamount (an explanation rubric is available
mount is formed at a divergent boundary, then we
with this article’s online supplements) with some
should see the same pattern of rock ages and magsupport (as described below).
netic reversals at other underwater seamounts.”
This hypothesis can be tested using the available
evidence and by examining the
Supporting student
geologic features of other seasense-making
mounts in Google Earth.
throughout the unit
We concluded this unit by reThe sequence of activities
quiring that each student write
From the variety of initial stuwas designed
a final, evidence-based expladent models, it was clear that
to help students develop
nation for why Axial is located
students had a number of difa more robust scientific
where it is, based on the final
ferent explanations for why
explanation that
models their groups had creatAxial is in its current location.
they could support
ed (see an example explanation
The sequence of activities was
with multiple types of
with this article’s online suppledesigned to help students dements). We chose first to cogenvelop a more robust scientific
evidence.
erate with students a checklist
explanation that they could
with the key elements to be
support with multiple types of
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| FIGURE 4: Summary table, formed intermittently during the unit
Activity
What we learned
Mapping earthquakes
The crust is broken into plates. Earthquakes occur at the edges of the plates
and show us where they are.
Axial is on a plate boundary!
Magnetic and
radiometric data
The Earth’s magnetic field reverses, which
affects rocks that are newly formed. By
looking at the ages and magnetic direction
of the rocks at a plate boundary, we can
tell which way they are moving (divergent,
convergent, transform).
Axial is at the boundary of the Pacific
and Juan de Fuca plates. Data shows
they are diverging (moving apart),
lifting magma up to the surface to
form Axial.
Earthquake depths activity
Juan de Fuca plate is converging with
the North American plate. Juan de Fuca
is subducting under the North American
plate, causing earthquakes and volcanoes
on land. The subducting plate is melted in
the mantle.
The seafloor created at Axial is
eventually “recycled” at the Cascadia
subduction zone.
Mechanism web hunt
The magma in the mantle slowly flows
in convection currents under the plates,
causing them to move. The energy for this
is from the decay of radioactive elements
in the core.
Convection currents are causing the
Juan de Fuca and Pacific plates to
diverge, releasing the magma that
formed Axial.
evidence. This proved to be a fairly complex task
for most students, and we found that a number
of strategies to support them in this work were
needed.
A key strategy was having students work together in small groups of three or four. Such
groups allowed students to negotiate ideas with
their peers and provided an opportunity to use
new information to revise their previous models.
This led to a general class structure of working
on activities or problems in small groups before
coming back to whole-group discussions for consensus building. We found this pattern helpful
for promoting student understanding. Working
in small groups also allowed us to better under-
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How it helps us explain Axial
Seamount
stand what sense students were making of the
phenomenon. Throughout the unit, the scientific
models were developed, revised, and tested in
these small groups. They were readily available to
groups each day of the unit and were often referenced by the teacher. This allowed the models to
be used as tools for group sense-making about the
phenomenon. Once the model was revised and
tested, they were vital resources for students as
they constructed their individual evidence-based
explanations.
Additionally, class share-out sessions, during
which we facilitated small groups’ presentation of
their models and follow-up questions and discussion, were fruitful for students’ learning from each
INVESTIGATING AXIAL SEAMOUNT
other and our ongoing formative assessment of student understanding. We also used these sessions to
talk explicitly about scientific modeling and the role
it plays in science, further helping students understand the work they were doing and why it is an authentic practice of science.
Although making use of small groups was
helpful, we also found it necessary to create
a number of scaffolds for students to successfully engage in this complex task. For example,
we used a whole-class summary table after each
activity (see Figure 4). This allowed the class to
come to a consensus on what they learned and
how their new knowledge added to their explanation of the Axial Seamount phenomenon. As a
whole-class public record, the summary table remained visible throughout the unit as a resource
for students. These scaffolds, along with probing
questions, and exit passes, served as formative
assessments throughout the unit.
Additionally, scaffolding students’ final, written
explanations was essential. Precisely how you go
about scaffolding your students’ writing depends on
their familiarity with writing evidence-based explanations. We also supported their writing by examining with students examples of other evidence-based
explanations we had created about topics of previous units.
Conclusion
Using a local geological feature likely to be of interest to our students allowed us to introduce a
puzzling phenomenon that could be the basis of
the construction of explanatory models. We suggest finding a local geologic phenomenon (e.g., the
Hawaiian archipelago, the Yellowstone caldera)
to increase this unit’s relevance to your students.
By engaging students in scientific modeling, we
helped students not only make sense of the specific
phenomenon of Axial Seamount but also develop a
robust understanding of the theory of plate tectonics and its related concepts.
•
REFERENCES
Campbell, T., C. Schwarz, and M. Windschitl. 2016. What we
call misconceptions may be necessary stepping-stones on
a path toward making sense of the world. Science Scope
39 (7): 19–24.
Krajcik, J., and J. Merritt. 2012. Engaging students in
scientific practices: What does constructing and revising
models look like in the science classroom? Science Scope
35 (7): 6–10.
National Governors Association Center for Best Practices and
Council of Chief State School Officers (NGAC and CCSSO).
2010. Common core state standards. Washington, DC:
NGAC and CCSSO.
NGSS Lead States. 2013. Next Generation Science Standards:
For states, by states. Washington, DC: National Academies
Press.
Passmore, C., J.S. Gouvea, and R. Giere. 2014. Models in
science and in learning science: Focusing scientific
practice on sense-making. In International Handbook of
Research in History, Philosophy and Science Teaching,
ed. M.R. Matthews, 1171–202. Netherlands: Springer.
RESOURCES
Axial Seamount blog—http://bit.ly/1JfAgVo
Cosmos News report on Axial Seamount eruption—http://bit.
ly/295IUcL
New Millennium Observatory (NeMO)—http://bit.ly/2agm5J3
New Millennium Observatory (NeMO) Curriculum—http://bit.
ly/29Tvenv
NOAA: Axial Seamount—http://bit.ly/29Tw1Vi
Online supplemental files for this article—www.nsta.org/
scope1609
Paleomagnetic data—http://bit.ly/29THOXI
Subduction zone earthquake data—http://bit.ly/29efvRo
USGS Earthquake Hazards Program: Recent Earthquakes
(change settings to: 30 Days, Magnitude 2.5+
Worldwide)—http://on.doi.gov/1GhKUIj
Ron Gray ([email protected]) is an assistant professor of science education in the Center for Science Teaching and Learning
at Northern Arizona University in Flagstaff, Arizona. Allyson Rogan-Klyve is an assistant professor of science education in the
Department of Science Education at Central Washington University in Ellensburg, Washington. Britten Clark-Huyck is a science
teacher at Corvallis High School in Corvallis, Oregon.
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INVESTIGATING AXIAL SEAMOUNT
Connecting to the Next Generation Science Standards (NGSS Lead States 2013)
• The chart below makes one set of connections between the instruction outlined in this article and the NGSS. Other valid
connections are likely; however, space restrictions prevent us from listing all possibilities.
• The materials, lessons, and activities outlined in the article are just one step toward reaching the performance expectations
listed below.
Standard
MS-ESS2: Earth’s Systems
www.nextgenscience.org/dci-arrangement/ms-ess2-earths-systems
Performance Expectation
MS-ESS2-2. Construct an explanation based on evidence for how geoscience processes have changed Earth’s surface at varying
time and spatial scales.
DIMENSIONS
CLASSROOM CONNECTIONS
Science and Engineering Practices
Developing and Using Models
Students construct initial, revised, and final models to show
how Axial Seamount was formed.
Analyzing and Interpreting Data
Students analyze and interpret multiple data sets, including
earthquake and radiometric data. They also determine which
data to collect and analyze as they test their final models.
Disciplinary Core Idea
ESS2-A. Earth Materials and Systems
• The planet’s systems interact over scales that range
from microscopic to global in size, and they operate over
fractions of a second to billions of years. These interactions
have shaped Earth’s history and will determine its future.
Students discover the cycling of oceanic crust through
mapping the Cascadia subduction zone and examining
patterns in radiometric dating of the seafloor.
Crosscutting Concept
Patterns
Students discover plate boundaries through mapping recent
earthquakes.
Connections to the Common Core State Standards (NGAC and CCSSO 2010)
ELA
CCSS.ELA-LITERACY.WHST.6-8.2: Write informative/explanatory texts, including the narration of historical events, scientific
procedures/experiments, or technical processes.
Mathematics
CCSS.Math.MP.2: Reason abstractly and quantitatively.
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