Chapter 4

1. Which of the following features would indicate an igneous rock cooled quickly? large mineral crystals small mineral crystals dark-colored minerals light-colored minerals

2. What distinguishes a felsic extrusive rock (rhyolite) from a felsic intrusive igneous rock (granite)? mineral composition crystal size both of these

3. Where is the most likely location for molten rock to cool and minerals to form quickly? in Earth’s crust at Earth’s surface in Earth’s core in Earth’s mantle

4. The presence of large amounts of igneous rocks composed of small mineral crystals is suggestive of what process occurring in the past? volcanic eruptions earthquakes floods landslides

5. What kind of cooling history do porphyritic textures indicate? slow fast instantaneous slow then fast fast then slow

6. Silica is abundant in most igneous rocks, meaning that the elements 6. Silica is abundant in most igneous rocks, meaning that the elements and make up a large percentage of their weight. iron and magnesium sodium and potassium silicon and oxygen calcium and aluminum

7. The primary difference between felsic and mafic igneous rocks is: crystal size. mineral composition. cooling rate. depth of formation.

8. Felsic igneous rocks contain more. and are 8. Felsic igneous rocks contain more and are in color compared to mafic igneous rocks. iron; darker iron; lighter silica; darker silica; lighter

9. Rocks of which composition will melt at the lowest temperature? mafic intermediate felsic All of these will melt at the same temperature.

10. Rocks of which composition will melt at the highest temperature? mafic intermediate felsic All of these will melt at the same temperature.

11. Which mineral will crystallize at the highest temperature? quartz muscovite olivine pyroxene All of these will crystallize at the same temperature.

12. Which mineral will crystallize at the lowest temperature? quartz muscovite olivine pyroxene All of these will crystallize at the same temperature.

13. Partial melting will cause minerals with a relatively 13. Partial melting will cause minerals with a relatively melting point to become a liquid. lower higher

14. Increased pressure will the melting temperature of a rock. decrease not change

15. The addition of water will the melting temperature of a rock. increase decrease not change

16. The body of igneous rock shown is composed of large mineral crystals and formed . slowly below the surface quickly below the surface slowly at the surface D. quickly at the

17. What type of igneous intrusion is shown? dike sill pluton

18. Which tectonic setting is most likely to have intermediate plutons? hot spot spreading center subduction zone

19. What is a major process of magma production at spreading centers? partial melting decompression melting fluid-induced melting

20. What is a major process of magma production at subduction zones? partial melting decompression melting fluid-induced melting