Ocean-Continent Convergent
Plate Boundaries
Dana Desonie, Ph.D.
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Printed: January 4, 2016
AUTHOR
Dana Desonie, Ph.D.
www.ck12.org
C HAPTER
Chapter 1. Ocean-Continent Convergent Plate Boundaries
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Ocean-Continent
Convergent Plate Boundaries
• Explain a convergence plate boundary.
• Describe ocean-continent convergence and ocean-ocean convergence.
What do you see when oceanic lithosphere subducts?
At a convergent plate boundary, when one plate is oceanic, there are large volcanoes. These volcanoes are found
in lines that outline the subduction zone. Earthquakes also happen in these zones. The Aleutian Islands that border
southern Alaska are an island arc. In this winter image from space, the volcanoes are covered with snow.
Convergent Plate Boundaries
A convergent plate boundary forms where two plates collide. That collision can happen between a continent and
oceanic crust, between two oceanic plates, or between two continents. Oceanic crust is always destroyed in these
collisions.
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Ocean-Continent Convergence
Oceanic crust may collide with a continent. The oceanic plate is denser, so it undergoes subduction. This means
that the oceanic plate sinks beneath the continent. This occurs at an ocean trench ( Figure 1.1). Subduction zones
are where subduction takes place.
FIGURE 1.1
Subduction of an oceanic plate beneath a
continental plate forms a line of volcanoes
known as a continental arc and causes
earthquakes.
As you would expect, where plates collide there are lots of intense earthquakes and volcanic eruptions. The
subducting oceanic plate melts as it reenters the mantle. The magma rises and erupts. This creates a volcanic
mountain range near the coast of the continent. This range is called a continental arc. The Andes Mountains, along
the western edge of South America, are a volcanic arc ( Figure 1.2).
Ocean-Ocean Convergence
Two oceanic plates may collide. In this case, the older plate is denser. This plate subducts beneath the younger plate.
As the subducting plate is pushed deeper into the mantle, it melts. The magma this creates rises and erupts. This
forms a line of volcanoes, known as an island arc ( Figure 1.3). Japan, Indonesia, the Philippine Islands, and the
Aleutian Islands of Alaska are examples of island arcs ( Figure 1.4).
Summary
•
•
•
•
When two plates come toward each other, they create a convergent plate boundary.
If at least one plate is oceanic, there will be subduction.
Subduction of a plate leads to melting and volcanism.
An island arc is a line of volcanoes on an oceanic plate. A continental arc is a line of volcanoes on a continental
plate.
Explore More
Use the resources below to answer the questions that follow.
• Continent-Ocean Convergent Boundary at
1. Why does the oceanic plate subduct beneath the continental plate?
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Chapter 1. Ocean-Continent Convergent Plate Boundaries
FIGURE 1.2
A relief map of South America shows the trench west of the continent. The
Andes Mountains line the western edge of South America.
FIGURE 1.3
A convergent plate boundary subduction zone between two plates of oceanic
lithosphere.
Melting of the subducting
plate causes volcanic activity and earthquakes.
2. What is an example of this? In what states does this occur?
3. What is the deepest location off of this area?
4. Why are there volcanoes in this region?
• Ocean-Ocean Convergent Boundary at
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FIGURE 1.4
The country of Japan is an island arc
that lies at the intersection of the North
American, Filipino, and Eurasian plates.
Colors in this picture indicate elevation.
5.
6.
7.
8.
What is the relative density of the two oceanic plates?
What are some examples of this type of plate boundary?
Where is the trench relative to the two plates?
What is the result of these plates coming together?
Review
1. What is the direction of plate motion at a convergent plate boundary?
2. What creates an island arc?
3. How is a continental arc different from an island arc?
References
1. User:Booyabazooka/Wikipedia. Subduction of an oceanic plate beneath a continental plate causes earthquake
s and forms a line of volcanoes known as a continental arc . Public Domain
2. Courtesy of the National Oceanic and Atmospheric Administration. Relief map of South America and the
Andes Mountains . Public Domain
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Chapter 1. Ocean-Continent Convergent Plate Boundaries
3. Courtesy of the US Geological Survey. Diagram of a convergent plate boundary between two ocean plates .
Public Domain
4. Image copyright AridOcean, 2013. Japan is an island arc that lies at the intersection of the North American,
Filipino, and Eurasian plates . Used under license from Shutterstock.com
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