Geo Chapter 4

16. Which type of magma has the greatest silica content? A. felsic B. intermediate C. mafic D. ultramafic

A. Felsic

Very early in Earth's history, it was so hot that the surface was likely entirely molten. A. True B. False

A. True

4. A sill is ____________ A. a sheetlike intrusion that lies parallel to surrounding layers of sedimentary rock B. a cooled layer of lava C. an intrusion formed within the magma chamber of a volcano D. a sheetlike intrusion that cuts across preexisting layers

A. a sheet like intrusion that lies parallel to surrounding layers of sedimentary rock

11. As compared to coarse-grained igneous rocks, all fine-grained igneous rocks ________ . A. cool and solidify more quickly B. cool and solidify more slowly

A. cool and solidify more quickly

10. If a body of magma becomes more felsic, its viscosity will . A. increase B. decrease C. stay the same

A. increase

When magma crystallizes,_________________ are formed. A. intrusive igneous rocks B. extrusive igneous rocks C. volatiles D. pyroclastic debris

A. intrusive igneous rocks

17. When rock is melted within Earth, typically the entire volume of rock is transformed from a solid state to a liquid. A. true B. false

B. False

2. A blob-like igneous rock body that has cooled beneath the surface of Earth is called a A. guyot B. pluton C. lava flow D. andesite

B. Pluton

14. Most commonly, felsic igneous rocks __________ A. contain more iron and magnesium than intermediate rocks B. are lighter in color than mafic rocks C. are darker in color than mafic rocks D. are found in oceanic crust

B. are lighter in color than mafic rocks

9. If the volatile content of magma is increased, its viscosity will . A. increase B. decrease C. stay the same

B. decrease

12. All other factors being equal, intrusive rocks that form deep within Earth _____________________ than intrusive rocks that cool near the surface. A. are more felsic B. contain a smaller proportion of volatiles C. cool more slowly D. cool more rapidly

C. cool more slowly

8. Volatiles refer to substances that ______ A. crystallize most rapidly out of a melt B. melt immediately upon contact with a hot body of magma C. have a tendency to evaporate and are stable as gases

C. have a tendency to evaporate and are stable as gases

1. The difference between lava and magma is that . A. magma is light in color and lava is dark B. magma usually has mafic composition and lava usually has felsic composition C. magma is found beneath the Earth's surface, whereas lava has reached the surface D. magma flows more quickly than lava

C. magma is found beneath the Earth's surface, whereas lava has reached the surface

15. Important volatiles in magmas include ____________ A. iron- and magnesium-rich minerals, such as olivine B. potassium and aluminum C. water and carbon dioxide D. trinitrotoluene and nitroglycerin

C. water and carbon dioxide

5. Igneous rocks ___________ A. are formed through the freezing of melt B. can be produced at the surface of the Earth as well as deep below the surface C. are the most common type of rocks within Earth D. all of the above

D. All of the above

A dike is ___________ A. a sheetlike intrusion that lies parallel to surrounding layers of sedimentary rock B. a cooled layer of lava C. an intrusion formed within the magma chamber of a volcano D. a sheetlike intrusion that cuts across preexisting layers

D. a sheet like intrusion that cuts across preexisting layers

13. Obsidian ______________ A. is volcanic glass B. possesses conchoidal fracture C. typically is felsic in composition D. all of the above

D. all of the above