Geology 15                                                                                          West Valley College                                                                                                                 R. Lopez


Study Questions 5



1)      Read Harden p. 70-75.

2)      What is the difference between “active”, “potentially active”, and “inactive” volcanoes?

3)      Approximately how many active and potentially active vents are there in California, and in what geomorphic regions do they occur?  Be able to sketch a map of California and locate these areas.  Where is the “Eastern Sierra Nevada”?

4)      What are silica tetrahedra?  What is the relationship between silica content, polymerization, and viscosity?

5)      What drives volcanic explosions?

6)      Contrast the eruptive styles (i.e. explosivity, distance lavas flow from vents) or mafic, intermediate, and silicic magmas.  (see Harden Table 5-1, p. 71).

7)      Why is Mt. Shasta high and the Modoc Plateau flat?

8)      Define and use the following terms:









Fall Out

Pyroclastic flow (nuee ardente)

Shield volcano

Cinder cones

Stratocones or stratovolcanoes

Lava dome


9)      Sketch and very briefly discuss the two stages that are typical in the development of a lava dome (Plinian Eruption); part 3 deals with the formation of a coulee, a short, stubby rhyolite lava flow, but you don’t need to know that term.

10)  Be able to recognize the following volcanic features in slides:


a) Pyroclastic flows/nuees ardents

b) Shield volcanoes

c) Stratocones/stratovolcanoes

d) Cinder cones

e) Lava domes

f) From a picture of a lava flow, be able to make a reasonable statement regarding the viscosity and composition of the lava.