VOLCANIC ERUPTIONS – CHAPTER 3.3 (pp. 91-98)
This section explains what happens when a volcano erupts and two types of volcanic eruptions. You will
also identify a volcano’s stage of activity.
What are Volcanic Rocks Like? (p. 91 Lab Activity)
Volcanoes produce lava, which hardens into rock. Two types of rock are pumice and obsidian.
1. Watch the Discovery Education video and observe the differences between pumice and obsidian.
https://app.discoveryeducation.com/player/view/assetGuid/53310167-3f60-44c4-a743-643d6a99653c
2. Draw and describe the texture of pumice. What would have caused this texture?
DESCRIBE Pumice Rock:
DRAW Pumice
The texture of pumice is rough and porous.
Pumice formed when the lava had more gas in it; and created
air bubbles in the rock.
3. Draw and Describe the surface of obsidian.
DESCRIBE Obsidian Rock:
DRAW Obsidian
The surface of obsidian is smooth and glossy
Obsidian formed when lava cooled very quickly
Magma Reaches Earth’s Surface (p. 91-93)
4. Where does lava come from?
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Lava begins as magma, which forms in the asthenosphere.
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The materials in the asthenosphere are under great pressure.
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As magma rises, it flows upward into cracks in the rock above.
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But, if an opening in weak rock allow the magma to reach the surface, a volcano forms.
5. Label the drawing with the following terms:

Magma chamber – magma collects in this pocket
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Pipe – a long tube in the ground that connects the magma chamber to Earth’s surface
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Vent –molten rock and gas leave the volcano through this opening
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Crater – a bowl shaped area at the top of the volcano that may form around the vent
6. What is lava flow?

The area covered by lava as it pours out of a vent.