Juan de Fuca Plate, a High School Systems PCA
Juan de Fuca Plate
High School
Systems
Powerful Classroom Assessment (PCA)
Published by the Science Assessment Team of the Washington Office of the Superintendent of Public Instruction on January 2, 2009.
Copyright © 2009 by Washington Office of the Superintendent of Public Instruction (OSPI)
All rights reserved. Educational institutions within the State of Washington have permission to reproduce this document. All other individuals wishing to
reproduce this document must contact OSPI.
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January 2, 2009
Juan de Fuca Plate, a High School Systems PCA
Juan de Fuca Plate
Directions: Use the following information to answer questions 1 through 9.
Three tectonic plates are located in the Pacific Northwest. Two of the plates are oceanic, the Pacific and
the Juan de Fuca Plates. There is a spreading zone between these two oceanic plates. The third plate is the North
American Plate, a continental plate. There is a subduction zone between the Juan de Fuca Plate and North
American Plate. The diagram below, Plates of the Pacific Northwest (top view) shows these plates.
Another way to look at these plates is by a cross section. Below is a cross section of a line connecting Points A
and B in the diagram above.
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Juan de Fuca Plate, a High School Systems PCA
1 Why is the Juan de Fuca Plate being subducted under the North American Plate?
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A. The ocean water forces the Juan de Fuca Plate downward.
B. The Juan de Fuca Plate is the denser of the two plates.
C. The mantle pulls less on the North American Plate.
D. The North American Plate is moving northward.
2 What type of activity causes the Juan de Fuca Ridge to keep forming new crust?
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A. Oceanic plates moving against each other
B. Magma pushing up through the plates
C. Earthquakes occurring underwater
D. Weathering of the tectonic plates
3 What causes the movement of the Juan de Fuca Plate?
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A. Temperature differences between the ridge and continental plate
B. Magnetic forces between the North and South poles
C. Convection currents in the mantle
D. Earth’s spin and axial tilt
4 What is a main source of energy for the motion of these tectonic plates?
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A. Nuclear energy in Earth’s core
B. The Sun’s gravitational energy
C. Earth’s rotational energy
D. Heat energy in the Sun
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Juan de Fuca Plate, a High School Systems PCA
5 Subduction rates can change. Describe how the surface of Washington State might change if the subduction
rate of the Juan de Fuca Plate were to increase
In your description, be sure to:
 Identify two possible changes in the surface of Washington State.
 Describe why the surface might change due to the increased subduction rate
One possible change:
Why the surface might change:
Another possible change:
Why the surface might change:
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Juan de Fuca Plate, a High School Systems PCA
6 As the Juan de Fuca Plate is subducted deep under Washington State, energy is stored and periodically
released. How does this energy reach the surface of Washington State?
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A. Chemical energy traveling in magma
B. Light waves traveling in the Pacific Ocean
C. Seismic waves traveling through the North American Plate
D. Electromagnetic energy traveling through Earth’s tectonic plates
7 What are two ways the energy from an underwater earthquake centered at the Juan de Fuca Ridge can reach
coastal cities of Washington State?
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A. Seismic waves in the plates and tsunamis in the ocean
B. Volcanic eruptions and earthquakes in the plates
C. Earthquakes and changing weather patterns
D. Heating of the ocean and seismic sea waves
8 Mars, Jupiter, and Saturn are aligned in Earth’s sky about once every 57 years. Some people think this
alignment of planets can cause severe earthquakes along the Juan de Fuca subduction zone. Why is this
conclusion flawed?
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A. Data on earthquakes is difficult to collect.
B. Data on planetary positions indicate the 57 year cycle is changing.
C. The data can only be collected every 57 years when the alignment occurs.
D. The data collected does not indicate any severe earthquakes during an alignment.
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Juan de Fuca Plate, a High School Systems PCA
9 For many years, satellites have been orbiting Earth to determine the exact locations of tectonic plates.
Describe how this information can be used to benefit science and society.
In your description, be sure to:
 Describe how knowing the locations of tectonic plates over many years can improve our understanding
of the geology of Washington State.
 Describe how the understanding of geology can benefit the people of Washington State.
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