Review Questions - Igneous Rocks

1. Molten rock beneath the Earth's surface is called ______________.

2. Molten rock on or above the Earth's surface is called _____________.

3. __________ igneous rocks undergo final crystallization beneath the Earth's surface.

4. __________ igneous rocks undergo final crystallization on or above the Earth's surface.

5. Due to fast crystallization rates, extrusive igneous rocks typically exhibit __________ texture.

6. Due to slow cooling rates, intrusive igneous rocks typically exhibit ____________ texture.

7. An igneous rock with two distinctly different grain sizes is said to exhibit __________ texture.

8. Obsidian exhibits _____________ texture.

9. An extrusive igneous rock that forms during an explosive volcanic eruption is called a __________ rock.

10. An igneous rock that contains many gas vesicles is said to exhibit ____________ texture.

11. What is the name of a pyroclastic rock that exhibits a vesicular texture?

12. To which igneous rock compositional group do andesite and diorite belong?

13. Which igneous rock compositional group contains the greatest amount of Si?

14. Which igneous rock compositional group contains the greatest amount of Fe and Mg?

15. Which igneous rock compositional group is most likely to contain the mineral quartz?

16. Which igneous rock compositional group consists of rocks typically light in color?

17. What is the extrusive compositional equivalent of granite?

18. What do minerals on the 'continuous' side of Bowen's Reaction Series have in common?

19. What two minerals crystallize at lowest temperature as part of Bowen's Reaction Series?

20. The mineral ____________ crystallizes at highest temperature on the 'discontinuous' side of Bowen's reaction series.

21. According to Bowen's Reaction series, igneous rocks of the ____________compositional group crystallize at highest temperatures.

22. According to Bowen's Reaction series, pyroxene reacts with surrounding melt to form __________.

23. As the temperature of a magma decreases and crystallization of silicate minerals progresses, the Si content of the remaining melt _________________.

24. According to Bowen's Reaction Series, what common intrusive igneous rock crystallizes at lowest temperatures?

25. The progressive change in chemical composition of a magma during crystallization is called _____________.


Questions 26-32 refer to the following:

While conducting field research in an area characterized by igneous rock, you find a rock that is very dark in color. Using your hand lens, you determine that the rock contains microcrystalline plagioclase and pyroxene. Much larger crystals appear to be olivine.

26. How would you describe the texture of this rock?

27. Is this rock intrusive or extrusive?

28. To which igneous rock compositional group does this rock most likely belong?

29. With respect to Bowen's reaction series, does this rock represent high, intermediate or low temperatures of crystallization?

30. Does the rock contain relatively high or low Si, K, Na ?

31. Does the rock contain relatively high or low Fe, Mg, Ca?

32. What is the best name for this rock?