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Global Volcanoes
http://earthref.org/SCC
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Volcanoes occur at:
1. Hotspots
2. Plate Boundaries
-Convergent (subduction
zones)
-Divergent
Where do volcanoes occur?
http://earthref.org/SCC
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Hotspots
Spot on Earth with
volcanism
Hawaii
Can occur in the middle
of tectonic plates
Hotspots don’t move
Tectonic plates move over
hotspots
Makes a chain of volcanoes,
like Hawaii
What are hotspots?
http://earthref.org/SCC
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Ocean Hotspots
Shield volcanoes,
Hawaiiian Islands
Fast moving, basaltic lava
Effusive
Stratovolcanoes, Canary
Islands
Alternating lava and ash
Explosive
Continental hotspots
Explosive
Yellowstone Caldera,
Wyoming
http://earthref.org/SCC
Hotspot volcanoes
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Subduction Zone
Volcanoes

Most major
volcanoes found
near subduction
zones

Stratovolcanoes

Most dangerous
Two different types:
1.
Ocean-Ocean
2.
Ocean-Continent
http://earthref.org/SCC
Subduction Zones
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Ocean-Ocean
Island Volcanic Arcs
Japan
Aleutian Islands, Alaska
Ocean-Ocean Subduction Volcanoes
http://earthref.org/SCC
Scripps Classroom Connection
Ocean-Continent
Continental Volcanic
Arcs
Andes Mountains,
South America
Cascades, N.W. United
States
Ocean-Continent Subduction
Volcanoes
http://earthref.org/SCC
Scripps Classroom Connection
Tectonic Spreading
Centers
● Under the ocean
Mid-ocean ridges
● On Land
Continental rifts
● Almost continuous
volcanism
● Create new oceanic
crust
http://earthref.org/SCC
Spreading Centers
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Mid-Ocean Ridge
Volcanoes
Volcanoes form on
fissures parallel to the
ridge axis
Hundreds of volcanoes
along each ridge, nearcontinuous volcanism
Erupt basalt
Create new oceanic
crust
Mid-Ocean Ridge Volcanoes
http://earthref.org/SCC
Scripps Classroom Connection
Global Volcano Conclusions
●
Most volcanoes occur at plate boundaries:
1. Subduction zones
2. Mid-ocean ridges
●
Some volcanoes occur at hotspots:
1. Ocean floor
2. Continental
http://earthref.org/SCC
Scripps Classroom Connection