KEY
1. Be able to define the following words: vent Ring of Fire crater geysers silica dormant pyroclastic flow extinct caldera basin
2. Where are volcanic belts found?
Volcanic belts are most found at converging (colliding) and diverging (spreading) plate boundaries. The biggest is the Ring of Fire at the colliding boundaries along the
Pacific Plate.
3. Explain what plate boundaries form an island arc. Be specific.
An island arc forms where two oceanic plates collide (p218).
4. Give examples of hot spot volcanoes.
Hawaiian Islands, Yellowstone National Park (p 219)
New hot spot volcanoes form as the plate drifts over the hot spot.
5. What causes magma to erupt to the surface?
The force of expanding gases pushes magma from the magma chamber through the pipe to erupt to the surface (p223).
6. How does the amount of silica affect how a volcano will erupt?
Low silica content magma will erupt quietly while high silica content magma will erupt explosively. (p224-225)
7. List the hazards from quiet and explosive volcanic eruptions.
A quiet volcanic eruption is hazardous because lava flows from vents setting fire to and burying everything in its path. A thick layer of lava can cover large areas with a quiet eruption. (p 226)
An explosive eruption is hazardous because hot clouds of deadly gases and ash, cinders, and bombs can cover entire cities. Also, landslides and avalanches can occur.
8. How do geologists monitor volcanic activity?
Geologists cannot be certain about the type of eruption or how powerful it will be but they can monitor earthquakes occurring around a volcano to predict possible eruptions. Magma moving upwards will trigger small quakes. (p 228)
9. Explain how a hot spot in the ocean floor can gradually form a series of volcanic mountains.
A series of volcanic mountains can form due to a hot spot in the ocean floor because material from deep within the mantle rises and melts forming magma. This magma erupts through the crust and reaches the surface but since the plates drift, the newly

formed land drifts with the plate. Additional magma that reaches the surface will create a new mountain. (p 219)
10. Draw a cinder cone volcano, a shield volcano, and a composite volcano. Indicate the type of eruption you would expect from each type of volcanoes.
Volcano type
Cinder cone
Shield
Composite
Description layers of cinders, easy to erode layers of lava flows; broad base, wide layers of cinders/ash and lava flows
Tall and broad base
Eruption type explosive eruption quiet eruption either type of eruption