Lecture 7: Igneous Rocks

Question 1

What are Igneous rocks formed from?

Answer 1

The crystallization and cooling of magma

Question 2

What are igneous rocks classified by?

Answer 2

Their texture

Question 3

What are the Extrusive igneous rocks?

Answer 3

Basalt and Rhyolite

Question 4

What are the Intrusive igneous rocks?

Answer 4

Gabbro and Granite

Question 5

What are the Mafic igneous rocks?

Answer 5

Basalt and Gabbro

Question 6

What is the Felsic igneous rocks?

Answer 6

Rhyolite and Granite

Question 7

What are Mafic rocks composed of?

Answer 7

Iron and Magnesium and are dark colored

Question 8

What are Felsic rocks composed of?

Answer 8

Aluminium and Silicon and are Light colored

Question 9

What are the 3 types of Extrusive Pyroclasts?

Answer 9

• Volcanic ash
• Bomb
• Pumice

Question 10

What are large grains of rock called?

Answer 10

Phenocrysts or intrusive rocks

Question 11

What are Porphyritic crystals?

Answer 11

Crystals that start to grow beneath earth’s surface and then somehow get to above the earth’s surface and cool into smaller crystals

Question 12

What is Country Rock?

Answer 12

Rock that existed before igneous rock intruded

Question 13

What are Sills?

Answer 13

A sheet like formation of magma that grows horizontally

Question 14

What are Dikes?

Answer 14

A dike is an intrusion of magma but more vertically

Question 15

What are Batholiths?

Answer 15

Large intrusions of magma that form long rocks

Question 16

What are Plutons?

Answer 16

Large intrusions of magma that kind of look like mountains

Question 17

What are Veins?

Answer 17

Deposits of minerals found within a rock fracture

Question 18

What do flood basalts originate from?

Answer 18

Continental rifts

Question 19

What is the difference between volcanic ash and volcanic bombs?

Answer 19

Volcanic ash is more fine while Volcanic bombs are more house sized

Question 20

What is a Pyroclast?

Answer 20

Any volcanic rock that is ejected into the air

Question 21

What are the characteristics of mafic magma?

Answer 21

They tend to be more runny

Question 22

What are the characteristics of Silica rich magma?

Answer 22

They tend to be more explosive and viscous, giving more pyroclastic material

Question 23

What is Tephra?

Answer 23

When pyroclasts fall and are often lithified together upon cooling forming rocks

Question 24

What are Volcanic tuffs and Volcanic breccias?

Answer 24

Volcanic Tuffs have smaller pyroclastic fragments

Volcanic Breccias have larger fragments

Question 25

What is Porphyry?

Answer 25

Rocks that form when rocks crystalize below ground and then are subject to rapid cooling

Question 26

Which igneous rocks are the same composition different texture?

Answer 26

Basalt/Gabbro | Rhyolite/Granite

Question 27

What are the main Felsic minerals?

Answer 27

* Quartz * Orthoclase feldspar * Plagioclase feldspar * Muscovite (mica)

Question 28

What are the Mafic Minerals?

Answer 28

* Biotite (mica) * Amphibole group * Pyroxene group * Olivine

Question 29

What is the Intrusive Felsic rock?

Answer 29

Granite

Question 30

What is the Extrusive Felsic Rock?

Answer 30

Rhyolite

Question 31

What is the Extrusive intermediate rock?

Answer 31

Andesite

Question 32

What is the Mafic Intrusive rock?

Answer 32

Gabbro

Question 33

What is the Mafic Extrusive rock?

Answer 33

Basalt

Question 34

What is the Ultramafic Intrusive rock?

Answer 34

Peridotite

Question 35

What are the characteristics of Basaltic lava?

Answer 35

* Mafic | * Highly fluid

Question 36

What are pillow lavas?

Answer 36

Underwater Basalt

Question 37

What is the composition of Intermediate lavas?

Answer 37

* Andesitic | * They have a composition of Basalt and Rhyolite

Question 38

What is the composition Rhyolitic lavas?

Answer 38

* Felsic * highly viscous * Forms pumice

Question 39

What is the composition of magma starting off?

Answer 39

It starts off as Basalt but as the country rocks melt into it, it becomes more intermediate

Question 40

What is Decompressional melting?

Answer 40

When the mantle rises and pressure decreases below a critical point, solid rock begins to melt without the introduction of additional heat

Question 41

What is Magmatic Differentiation?

Answer 41

When different minerals crystalize at different temperatures and during the crystallization process, the composition of the parent magma changes from ultramafic as it becomes depleted of the chemical elements that compose crystals

Question 42

Which type of rock crystalized out of magma first?

Answer 42

Mafic

Question 43

What is the order of rocks crystallization of magma?

Answer 43

``` Olivine Pyroxene Amphibole Biotite mica Quartz Muscovite mica Orthoclase feldspar ```

Question 44

How does the Magma composition change as it cools?

Answer 44

It goes from ultramafic to intermediate