Geology 1121- Quiz 3 (Ch.4)

What two things are used to identify igneous rocks?

grain size and color

What is another word for intrusive?

pluntonic

What is another word for extrusive?

volcanic

Where does the intrusive process occur?

unground in magma

Where does the extrusive process occur?

above ground in lava

What is the grain size of an intrusive rock?

large

Why is the grain size of an intrusive rock large?

there is no exposure to the atmosphere, so it takes a long time for rocks to cool giving crystals time to grow.

What is the grain size of an extrusive rock?

small

Why is the grain size of an extrusive rock small?

there is exposure to the atmosphere speeding up the cooling process

What does “texture” mean in terms of igneous rocks?

size of crystals (grain size)

What is the texture of a fine-grained rock?

aphanitic

What is the texture of a course-grained rock?

phaneritic

What is the texture of a mixed-grain rock?

porphyritic

What are the two components of a felsic rock?

feldspar and silica

What are the two components of a mafic rock?

magnesium and iron

What color are felsic rocks?

light colors (pink, white, light grey)

What color are intermediate rocks?

salt and peppered, medium grey, medium green

What color are mafic rocks?

dark colors (black, dark grey)

What color are ultramafic rocks?

olive green

Felsic, extrusive rock

rhyolite

felsic, intrusive rock

granite

intermediate, extrusive rock

andesite

intermediate, intrusive rock

diorite

mafic, extrusive rock

basalt

mafic, intrusive rock

gabbro

ultramafic, extrusive rock

komatiite

ultramafic, intrusive rock

peridotite

What is decompression melting?

downward pressure causes the rock to melt without temperature change

Where is the greatest volume of magma produced?

mantle plumes

What is a mid-ocean ridge?

underwater volcanic mountain chain

What is a rift valley?

linear belt where continental crust pulls apart

What is a mantle plume?

column of very hot rock rising through the mantle to the lithosphere

What is a volatile?

occurs in subduction zone where intermediate and felsic magma make mafic material

What is a subduction zone?

a place where one plate sinks below another into the mantle

Explain partial melting

felsic rocks melt at a lower temperature than mafic materials, so newly formed magma is going to be more felsic than the starting material

What does heat transfer mean?

hot magma melts surrounding rock next to the intrusion (underground magma body)

What is Bowens Reaction Series?

iron rich compounds melt last so they crystalize first while silica compounds melt first so they crystalize last in cooling

As magma temperature (increases, decreases), minerals crystallize in an ordered series

decreases