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Volcanoes (Geology 115) – Exam #1 Review

Lecture 3: Rocks

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Exam #1 will cover all materials from weeks 1 – 6. Exam topics will be from lectures 1 – 5. Exam questions will include multiple choice, true/false, matching, and short answer. Below is a list of questions that outline topics that I may test you on. These questions are intended to help you study, but are not intended to be fully encompassing. However, if you can answer these questions, you should be well prepared. Please note that exam questions will be based on lecture material, homework, and in-class assignments.


1. What is a rock? What are the three rock types? Why are studying rocks in a volcanoes class important?

2. What is magma? What is lava?

3. How do igneous rocks form? Describe the process.

a. In general, what is happening when magmas crystallize?

4. What are the two types of igneous rocks? What are the characteristics (cooling rate, crystal size, where crystallization takes place) of each.

5. How are igneous rocks identified/ classified?

a. What is texture? What does it indicate?

b. What does the composition of an igneous rock refer to? Why are general terms used to describe the composition of a rock?

6. What does a fine grained texture indicate about how the igneous rock formed? A coarse grained rock?

7. What does a porphyritic texture indicate? Glassy? Vesicular? Frothy?

8. Does a fragmental texture indicate an igneous rock formed from cooling of lava? How does it form? What does it indicate about the eruption?

a. How does this texture form?

b. What is pyroclastic material?

c. What are the sizes of pyroclasts in order from smallest to largest?

i. What is the difference between a block and bomb? Be specific.

9. Define the following compositions: Ultramafic, mafic, intermediate, and felsic. Be sure to include general statements about silica, sodium (Na)/ potassium (K), iron (Fe)/ magnesium (Mg)/ calcium (Ca) concentrations:

10. Know the following rocks where these rocks can be found/ importance of these rocks:

a. Peridotite

b. Gabbro

c. Granite

d. Basalt

e. Andesite

f. Rhyolite

g. Pumice

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