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Name: _____________________________________Date: ________________
Earth Science
Mr. Herman
Exeter SHS
Chapter 10.1 Volcanoes and Plate Tectonics
Decompressing melting
Ring of fire
Intraplate volcanism
Hot spot
 Describe the origins of magma
 Explain the relationship between plate tectonics and volcanism, including
intraplate volcanism
Anticipatory Questions
1. How are the locations of volcanoes related to plate boundaries?
2. Where is the ring of fire and does it relate to the above question?
Origin of Magma
 Geologists conclude that magma originates when essentially solid rock,
located in the crust and upper mantle, partially melts.
 The most obvious way to generate magma from solid rock is to raise the
temperature above the level at which the rock begins to melt.
Role of Heat
 The geothermal gradient—Earth’s natural temperature increases with depth but
is not
sufficient to melt rock in the lower crust
and upper mantle
 Additional heat is generated by
o friction in subduction zones
o crustal rocks heated during subduction
o rising, hot mantle rocks
Role of Pressure
• Pressure Increases with depth inside the Earth increasing melting point
• When pressure decreases melting point decreases.
• Subducting plates reduce the pressure helping to melt the rock and form magma
Role of Water
• Causes rock to melt at a lower temperature
• Plays an important role in subducting ocean plates
Divergent Plate Boundaries
• The greatest volume of volcanic rock is produced along the oceanic ridge system.
• Lithosphere pulls apart.
• Less pressure on underlying rocks
• Partial melting occurs
• Large quantities of fluid basaltic magma are produced.
Convergent Plate Boundaries
• The basic connection between plate tectonics and volcanism is that plate
motions provide the mechanisms by which mantle rocks melt to generate
• Rising magma can form volcanic island arcs in an ocean (Aleutian Islands).
• Rising magma can form continental volcanic arcs
Intraplate Igneous Activity
• Intraplate volcanism is igneous activity that occurs within a tectonic plate
away from plate boundaries.
• Most intraplate volcanism occurs where a mass of hotter than normal mantle
material called a mantle plume rises toward the surface.
• The activity forms localized volcanic regions called hot spots.
o Examples include the Hawaiian Islands and the Columbia Plateau.