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Lesson 5.1: Volcanoes and Plate Tectonics
Study Guide
Volcano A weak spot in the crust where magma has come to the surface
Magma The molten mixture of rock-forming substances, gases, and water from the
mantle
Lava
Liquid magma that reaches the surface
Ring of A major belt of volcanoes that rims the Pacific Ocean
Fire
Island
A string of volcanoes that form as the result of subduction of one oceanic
Arc
plate beneath another oceanic plate
Hot
An area where magma from deep within the mantle melts through the
Spot
crust above it
Key Idea: Volcanoes often form along plate boundaries.
Divergent Boundaries- plates pull apart
 Crust breaks and magma rises to the surface
 Magma rises through rift valleys
both on land and at deep-ocean trenches
Convergent Boundaries- plates come together
 Oceanic Plate and Oceanic Plate
o The denser plate subducts and pushes up the less dense plate
o Sometimes forms island arcs, such as Japan and the Caribbean Islands
 Oceanic Plate and Continental Plate
o The oceanic plate subducts at a deep ocean trench.
o The mantle melts and molten rock rises.
o Can produce volcanoes,
such as those in the Andes Mountains and at Mt. Saint Helens
Key Idea: The “Ring of Fire” is a major belt of volcanoes.
 Surrounds the Pacific Ocean
 Includes North and South America, as well as Japan, New Zealand, and the
Phillippines
Lesson 5.1: Volcanoes and Plate Tectonics
Study Guide
Key Idea: Not all volcanoes form along plate boundaries.
A volcano can occur above hot spots when magma breaks through the crust and
rises to the surface.
Hot Spot- an area where molten material rises from the mantle through crust and
forms magma
 Hot spots stay in one place while the plate moves over them.
 Examples: Yellowstone National Park, Hawaiian Islands