LESSON 24 EFFECTS OF ASH FALL
Name: Tommy Heffernan Class: Period 6 Date: 2/5/08
Student Sheet 24.1c Volcanoes Review
Directions The assessment for Part 3: Volcanoes will be held during Lesson 25. It follows the
format of previous assessments in the module. Complete the following questions to prepare for
the assessment.
1. What is the difference between lava and magma?
Lava is molten rock that has erupted from a volcano, and magma is the liquid like substance
inside of a volcano.
2. What causes magma to rise to the earth's surface?
Magma is buoyont, and lighter than the solid rock that surrounds it, which is why it rises.
3. Describe how rising magma and flowing lava create the following land formations:
a. Underwater pillow lava
When a volcano forms underwater and erupts, the lava that comes out can form pillow
lava.
b. Volcanic islands
These are not formed by lava and magma, but rather the subduction of one plate over
another that causes an underwater volcano to raise above the surface.
c. Bulges in the earth's surface
4. Which lava is more viscous: slow-moving lava or runny lava? Name one other liquid that you
consider very viscous.
Slow-moving lava is more viscous, because viscous means sticky and stickier substances move
slower.
(continued)
342 STC/MS™ CATASTROPHIC EVENTS
LESSON
© 2000 National Academy of Sciences
24 EFFECTS OF ASH FALL
Student Sheet 24.1c (continued)
5. Identify these two drawings of volcanoes by type. (Choose from composite volcano, cinder
cone, or shield volcano).
a. Shield Volcano
b. Cinder cone
6. Describe how each volcano type forms. Then name one volcano on the earth that is an
example of each type.
a. Composite volcano
Composite volcanoes are formed by subduction zones, and are usually found in chains or arcs.
An example of a composite volcano is Mt. St. Helens.
b. Cinder cone
Cinder cones are formed by fragments being thrown up from volcanic vents and piling up into a
cone shape. An example of a cinder cone is Parícutin.
c. Shield volcano
7. How does the heat content of a substance affect the way it flows? (Think about what
happened when you heated the corn syrup.)
8. Describe in a paragraph some of the challenges scientists face in deciding whether or not to
issue an alert when they are monitoring a potentially active volcano. You can use Mt. Pinatubo
or Mt. St. Helens as an example.
(continued)
STC/MS™
© 2000 National Academy of Sciences
EVENTS 343
CATASTROPHIC
LESSON 24 EFFECTS OF ASH FALL
Student Sheet 24.1c
(continued)
9. Complete Table 1 by describing the rock samples you observed in this module. If you draw a picture of
the rock, label it. Then tell everything you know about the rock. For example, did it form inside the earth
or on the earth's surface? How fast did it cool? If it has crystals, are they large or small? What color are
the crystals?
Table 1 : Igneous Rock Descriptions
Igneous
Rock
Description and/or
Drawing
How and Where it
Formed
Evidence I usedto know how
it Formed
Granite
Basalt
Pumice
Tuff
(continued)
344 STC/MS™ CATASTROPHIC EVENTS © 2000 National Academy of Sciences
LESSON 24 EFFECTS OF ASH FALL
Student Sheet 24.1c
(continued)
10. What type of rock is gneiss? How did it form?
11. Describe the constructive and destructive effects of volcanic eruptions. Include what you
know about lava and ash. Name as many effects as you can.
a. Constructive effects of volcanic eruptions:
b. Destructive effects of volcanic eruptions:
12. In Lesson 24, you discovered that ash and larger fragments of volcanic materials can erupt
violently into the atmosphere. Knowing this, answer these two questions:
a. Which would be carried farther into the atmosphere: 2-mm ash or 64-mm lava bombs?
Describe why you think this.
b. How can a volcanic eruption affect weather conditions locally and globally?
© 2000 National Academy of Sciences STC/MS™ CATASTROPHIC EVENTS
(continued)
345
LESSON 24 EFFECTS OF ASH FALL
Student Sheet 24.1c (continued)
13. This map shows where geologists discovered deep layers of ash in the soil around Mt. Hekia,
an active volcano in Iceland. The numbers represent different thicknesses (in meters) of ash
deposited around the volcano. Geologists believe the ash deposits formed when Mt. Hekia
erupted about 4000 years ago. They can use information from the ash deposits to learn more
about how winds blew during ancient times. Look at the illustration. Which direction was the
wind blowing when the volcano erupted ash? Answers _________________
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Mt. Hekia
14. Why do earthquakes almost always occur before a volcano erupts?
15. On a separate sheet of paper, write down all that you know about where tornadoes,
hurricanes, earthquakes, and volcanoes occur and why they occur there. You may want to create
a table to organize your lists.
346 STC/MS™ CATASTROPHIC EVENTS
© 2000 National Academy of Science