Igneous Rocks
Part 1 – Read the pages in your textbook and answer the following questions.
1. What characteristics do geologist observe when studying a rock sample?
2. List the three main families and describe each one.
a. _______________________=
b. ________________________=
c. ________________________=
3. What is the difference between magma and lava?
4. What is an intrusive rock? Give an example
5. What is an extrusive rock? Give an example
6. What are the four textures of an igneous rock?
7. Large crystals in an igneous rock would mean that magma cooled____________.
8. Magma that reaches the Earth’s surface as lava (extrusive rocks) would cool
(fast , slow) and contain (large , small) crystals
9. Define a porphyritic texture.
10. How might a porphyritic rock have formed?
11. Silica is formed from what two elements? (hint: they are the two must
abundant elements in the crust)
12. Magma low in silica usually forms ________________________ colored rocks
13. Magma high in silica usually forms _________________________colored rocks
14. List three uses of Igneous rocks
a. __________________
b. ___________________
c. ___________________
Part 2 – Identifying Igneous Rocks
1. Compare granite and obsidian. How are they similar? How are they
2. In what way is gabbro different from basalt? What can you infer from this
about how these two kinds of igneous rocks formed?
3. How is granite like gabbro?
4. Which rock has more silica in it, granite or basalt? How do you know?