chapter 4 geo

a dike is

a sheetlike intrusion that lies parallel to preexisting layers

a sill is

a sheetline intrusion that lies parallel to surrounding layers

if a body of magma becomes more felsic, its viscosity will

increase

t/f: very early in earth's history, it was so hot that the surface was likely entirely motlen

true

igneous rocks a. are formed through the freezing of salt 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

all of the above

obsidian a. is a volcanic glass b. possesses conchoidal fracture c.typically is felsic in composition d. all of the above

all of the above

most commonly, felsic igneous rocks

are lighter in color than mafic rocks

all other factors being equal, intrusive rocks that form deep within earth __________ than intrusive rocks that cool near the surface

cool more slowly

if the volatile content of magma is increased, its viscosity will

decrease

t/f: when rock is melted within earth, typically the entire volume of rock is transformed from a solid to a liquid

false

which type of magma has the greatest silica content?

felsic

volatiles refer to substances that

have a tendency to evaporate and are stable as gases

when magma crystallizes, ____ are formed

intrusive igneous rocks

the difference between lava and magma is that

magma is found beneath earth's surface, whereas lava has reached the surface

a blob- like igneous rock body that has cooled beneath the surface of earth is called a

pluton

important volatiles in magmas include

water and carbon dioxide