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8.1: Volcanic Activity

Difficulty Level: At Grade Created by: CK-12

Lesson 8.1: True or False

Name___________________ Class______________ Date________


_____ 1. Iceland consists of volcanoes that formed over a hot spot.

_____ 2. Volcanoes are scattered randomly across Earth’s surface.

_____ 3. Many volcanoes occur along the mid-Atlantic Ridge.

_____ 4. Volcanoes occur only in oceanic crust.

_____ 5. Chains of volcanoes form above hot spots because of plate tectonics.

_____ 6. The Hawaiian hot spot is no longer active.

_____ 7. Hot spots never occur under continental crust.

_____ 8. The majority of mantle plumes are found under the ocean basins.

_____ 9. All hot spots are in the middle of tectonic plates.

_____ 10. The molten rock of a volcano comes from Earth’s core.

Lesson 8.1: Critical Reading

Name___________________ Class______________ Date________

Read this passage based on the text and answer the questions that follow.

Volcanoes at Plate Boundaries

There is a lot of volcanic activity at divergent plate boundaries in the oceans. For example, many undersea volcanoes are found along the Mid-Atlantic Ridge. This is a divergent plate boundary that runs north-south through the middle of the Atlantic Ocean. As tectonic plates pull away from each other at a divergent plate boundary, they create deep fissures, or cracks, in the crust. Molten rock, called magma, erupts through these cracks onto Earth’s surface. At the surface, the molten rock is called lava. It cools and hardens, forming rock. Divergent plate boundaries also occur in continental crust. Volcanoes form at these boundaries, but less often than in ocean crust. That’s because continental crust is thicker than oceanic crust. This makes it more difficult for molten rock to push up through the crust.

Many volcanoes form along convergent plate boundaries where one tectonic plate is pulled down beneath another at a subduction zone. The leading edge of the plate melts as it is pulled into the mantle, forming magma that erupts as volcanoes. When a line of volcanoes forms along a subduction zone, they make up a volcanic arc. The edges of the Pacific plate are long subduction zones lined with volcanoes. This is why the Pacific rim is called the “Pacific Ring of Fire.”


  1. Explain how volcanoes form at divergent plate boundaries.
  2. Why are volcanoes less likely to form at continental than oceanic divergent plate boundaries?
  3. Explain how volcanoes form at convergent plate boundaries.

Lesson 8.1: Multiple Choice

Name___________________ Class______________ Date________

Circle the letter of the correct choice.

  1. The only place where the mid-Atlantic ridge is above sea level is
    1. Iceland.
    2. England.
    3. Greenland.
    4. none of the above
  2. Volcanoes form at
    1. hot spots.
    2. divergent plate boundaries.
    3. convergent plate boundaries.
    4. all of the above
  3. Many volcanoes are located
    1. within the Eurasian plate.
    2. at the edges of the Pacific plate.
    3. within the North American plate.
    4. at the edges of the Atlantic plate.
  4. Volcanoes form in a subduction zone where a tectonic plate
    1. is pulled down into the mantle.
    2. remains over a hot spot.
    3. pulls away from another plate.
    4. creates a rift valley.
  5. Examples of volcanic arcs that formed at convergent plate boundaries include the
    1. island nation of Japan.
    2. Cascade Range in Washington State.
    3. Andes Mountains of South America.
    4. all of the above
  6. About how many hot spots have scientists identified on Earth?
    1. 5
    2. 15
    3. 50
    4. 500
  7. Which U.S. state formed over a hot spot in an oceanic plate?
    1. Oregon
    2. California
    3. Florida
    4. Hawaii

Lesson 8.1: Matching

Name___________________ Class______________ Date________

Match each definition with the correct term.


_____ 1. column of hot rock that lies below a hot spot

_____ 2. crack in Earth’s crust where magma pushes up through the crust

_____ 3. feature that forms when magma flows onto Earth’s surface

_____ 4. location where most volcanoes occur

_____ 5. fixed spot where magma rises through the crust and creates volcanoes

_____ 6. name for melted rock under Earth’s surface

_____ 7. name for melted rock after it flows onto Earth surface


a. volcano

b. magma

c. lava

d. hot spot

e. mantle plume

f. plate boundary

g. fissure

Lesson 8.1: Fill in the Blank

Name___________________ Class______________ Date________

Fill in the blank with the appropriate term.

  1. Fissures occur at __________ plate boundaries.
  2. Subduction occurs at __________ plate boundaries.
  3. A hot spot lies directly above a(n) __________.
  4. At a hot spot, magma travels toward the crust through a(n) __________.
  5. As a tectonic plate moves over a hot spot, it creates an island __________.
  6. The Emperor Seamounts formed over a(n) __________.
  7. Iceland formed at a(n) __________ in the mid-Atlantic ridge.

Lesson 8.1: Critical Writing

Name___________________ Class______________ Date________


Explain how a hot spot chain of volcanoes forms. Why do the volcanoes in the chain have different ages?

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