Igneous Rocks

Question 1

What is the difference between lava and magma

Answer 1

Lava is molten rock that has reached the earth’s surface while magma is molten rock stored in the earths crust

Question 2

What causes magma to form

Answer 2

Decompression melting and a volatile

Question 3

Decompression melting

Answer 3

When rock in the mantle starts to move up toward the crust causing a large decrease in pressure which results in the rock partially melting

Question 4

Volatiles

Answer 4

A substance that evaporates easily and exists as a gas on earth’s surface

Question 5

What are assimilation and contamination, and how do they differ

Answer 5

The parts of rocks that are taken by magma rise and become magma as well. Assimilation is when large chunks of rock are incorporated into the magma, while contamination is a partial melt of the wall of the magma rise that slowly incorporates.

Question 6

Where does magma form

Answer 6

convergent boundaries, divergent boundaries, and hot spots

Question 7

What types of magmas exist

Answer 7

Felsic, intermediate, mafic, and ultramafic

Question 8

What changed in the different types of magma

Answer 8

Silica content

Question 9

What six factors control magma composition

Answer 9

Source rock, partial melting, crystal settling, magma mixing, assimilation, and contamination

Question 10

What generally happens to the composition of magma over time

Answer 10

Becomes more felsic because mafic minerals slowly extract

Question 11

What affects how fast molten is able to cool

Answer 11

Depth of the magma, size, and shape of the magma body, and presence of groundwater

Question 12

What are the two different types of igneous rock (one forms on the surface the other form under the surface)

Answer 12

Extrusive and intrusive

Question 13

What does texture describe in igneous rocks

Answer 13

Crystal size, porosity, and if it’s made up of fragments of volcanic debris

Question 14

What are the six common textures when talking about igneous rocks

Answer 14

Glassy, aphanitic, phaneritic, porphyritic, pyroclastic, and vesicular

Question 15

What is an igneous composed of

Answer 15

An igneous rock composition is inherited by the molten rock it came from

Question 16

What does Bowen’s Reaction Series tell us about the minerals on the table

Answer 16

It identifies at what temperature the minerals in the table crystalize

Question 17

What does Bowen’s Reaction table tell us about different igneous rocks types

Answer 17

It identifies generally what minerals are found in the different types of igneous rocks

Question 18

What are the two names for a felsic rock based on where it cooled and which is which

Answer 18

Rhyolite (extrusive) and Granite (intrusive)

Question 19

What are the two names for an intermediate rock based on where it cooled and which is which

Answer 19

Andesite (extrusive) and diorite (intrusive)

Question 20

What are the two names for an mafic rock based on where it cooled and which is which

Answer 20

Basalt (extrusive) and Gabbro (intrusive)

Question 21

What is it called when an ultramafic rock is cooled intrusively

Answer 21

Peridolite

Question 22

What tends to happen to rocks that cause them to become more and more felsic overtime

Answer 22

Partial melting (more felsic minerals melt first and rise from the more mafic minerals) and crystal settling

Question 23

What minerals are in felsic rocks? (6)

Answer 23

Orthoclase, Quartz, Plagioclase (Na-rich), Biotite, Muscovite, Amphibole (only a little bit)

Question 24

What minerals are in intermediate rocks? (5)

Answer 24

Biotite, Amphibole, Plagioclase, Pyroxene (only a little), Quartz (only a little)

Question 25

What minerals are in mafic rocks? (4)

Answer 25

Plagioclase (Ca-rich), Amphibole, Pyroxene, Olivine

Question 26

What minerals are in ultramafic rocks? (2)

Answer 26

Pyroxene, Olivine