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GEOLOGY 12
STUDY GUIDE
CHAPTER 4 VOLCANOES
Name __________________
Major Concepts
1.
Volcanic activity produces several types of eruptions.
a. Fissure eruptions occur along mid-oceanic ridges and in a few continental
settings .
b. Several types of volcanic cones can be distinguished on the basis of size,.
shape, composition, and geologic setting.
c. The type of volcanic cone which is constructed depends largely upon the
composition of the lavas which are erupted.
d. Calderas may form when the top of a volcano collapses following the eruption
of magmas from within the cone.
2.
Types of volcanic activity strongly related to various plate tectonic settings.
a. Each tectonic setting produces certain compositions of magma which give rise,
in turn, to certain kinds of volcanic eruptions.
b. Divergent plate boundaries tend to produce mafic lavas in quiet, fissure eruptions.
c. Convergent plate boundaries accompanied by subduction tend to produce
more silicic lavas in violent, explosive eruptions.
d. The composition of lavas produced at a hot spot depends largely on the
compositions of the overlying lithosphere.
e. Changes in pressure and amount of water in rock material will affect the
melting temperatures of igneous rocks.
3.
Volcanic eruptions cause a variety of hazards to people and property.
a. Volcanic hazards include lava flows, pyroclastic debris, lahars, nueé ardentes,
toxic gases, steam explosions, and secondary effects on climate.
b. The direction of lava flows can be easily predicted and, in some cases, the
progress of a flow can be halted through clever engineering techniques.
c. Pyroclastic eruptions are more dangerous than lava flows because they may
erupt more suddenly, more explosively, and spread faster and farther.
d. Lahars and nueé ardentes are especially devastating because of their great
speed moving down the slopes of a volcano.
e. Climatic effects of volcanic eruptions can be dramatic and long lasting.
4.
Reducing loss of lives in the event of a volcanic eruption by predicting the
eruption is extremely difficult because of long periods of "dormancy"
common to many volcanoes and volcanic areas.
a. Monitoring precursor phenomena on and near volcanoes is the first step
toward predicting an eruption.
b. Precursor phenomena include seismic activity; bulging, tilt, or uplift of the
slopes of the volcano; possible changes in gases emitted by the volcano;
possible changes in surface temperature; and strange behavior in animals.
c. Geothermal activity, such as hot springs and geysers, may indicate that there
is magma or hot rock close to the surface.
d. Precautionary evacuation of people in the vicinity of a volcano is our best
means of saving lives in the event of eruption.
cont’d…
Terms and Phrases
•
Refer to the Terms to Remember at the end of Chapter 4, p.82.
Introductory Assignments
1.
2.
3.
4.
5.
Define or explain the terms and phrases listed above. (Highlighting DOES NOT count.)
Rewrite the Summary on page 81 in point form.
Review chapter by paying special attention to the diagrams, photos and their
captions. Read text for clarification.
Complete the Main Topic Questions below.
Highlight the main ideas on reading supplements (see handouts).
Main Topics (Refer to the Terms to Remember at the end of Chapter 4, p.82.)
1.
2.
3.
4.
Which terms describe different types of volcanic cone eruptions?
Which terms describe different types of volcanic rocks or rock features produced by
volcanic eruptions (of any type)?
Which terms represent hazards or are related to hazards caused by volcanic eruptions?
Which terms are related to predicting volcanic eruptions?
Assignments and Activities
1.
2.
3.
Complete the Terminology Review Exercise.
Complete the Chapter 4 WS.
Complete the Questions For Review #3-12 p.82.
Follow-Up and Evaluation
•
Chapter 4 Quiz
Chapter 4
Study Guide
Page 2