Igneous Rocks

Question 1

What are igneous rocks?

Answer 1

Rocks are formed by the solidification of cooled magma, with or without crystallization, either below the surface or on the surface of the Earth.

Question 2

What is the difference between magma and lava?

Answer 2

Magma is below the surface and lava is above the surface.

Question 3

What are intrusive rocks?

Answer 3

Rocks that formed bellow the earth’s surface.
Granite

Question 4

What are extrusive rocks?

Answer 4

Rocks are formed at the earth’s surface.
Basalt

Question 5

What is classification based on?

Answer 5

Texture and composition

Question 6

What three components are in magma?

Answer 6

Solid, liquid, and gas

Question 7

What is the solid in magma?

Answer 7

Solidified mineral crystals

Question 8

What is the liquid part of magma?

Answer 8

Molten rock

Question 9

What is the gas part of magma?

Answer 9

Volatiles are dissolved in gases in the melt.

Question 10

What are the three ways to form magma?

Answer 10

Change the pressure
Change the ingredients
Turn up the temperature

Question 11

How does changing the pressure form magma?

Answer 11

Pressure release melting

Question 12

How does changing in the ingredients form magma?

Answer 12

add volatiles

Question 13

How does changing the temperature from magma?

Answer 13

Heat transfer

Question 14

What plate boundary would we find compressional melting?

Answer 14

Divergent settings

Question 15

Where does the addition of volatiles happen?

Answer 15

Subduction zones or convergent plate boundaries.

Question 16

What are the factors that affect crystal sizing?

Answer 16

Cooling time
Percentage of Silica
Dissolved gases

Question 17

What is cooling rate affected by?

Answer 17

depth, shape, and size of the igneous formation. (shape of the magma)

Question 18

What is phaneritic texture?

Answer 18

Magma has cooled slowly, and larger crystals have formed (can see individual crystals) Intrusive

Question 19

What is aphanitic texture?

Answer 19

Magma cooled quickly, so small crystals formed (sugary texture, can’t see individual crystals).Extrusive

Question 20

What is texture?

Answer 20

The size and arrangement of mineral grains.

Question 21

What is porphyritic texture?

Answer 21

Two distinct crystal sizes.

Question 22

What is pegmatitic texture?

Answer 22

Mineral grains are exceptionally large. The exception to the cooling rate trend; is usually due to dissolved water in the magma. This changes the cooling rates and allows larger crystals to form.

Question 23

What is pyroclastic texture?

Answer 23

Pre-existing rocks that were shattered by an eruption.

Question 24

What does pyroclastic mean?

Answer 24

broad category to describe material explosively ejected from volcanic vents.

Question 25

What is a tuff?

Answer 25

consolidated and cemented volcanic ash.

Question 26

What is breccia?

Answer 26

broken, angular fragments in a fine-grained matrix.

Question 27

What is pumice?

Answer 27

Texture formed from 'frothy' lava.

Question 28

What is glassy texture?

Answer 28

When molten rock quenches due to contact with water, it forms volcanic glass, with no crystals formed.

Question 29

What does magma composition control?

Answer 29

density, time, and velocity.

Question 30

What is silica-rich magma like?

Answer 30

Thick and viscous

Question 31

What is silica-poor magma like?

Answer 31

Thin and 'runny'

Question 32

What does a low viscosity volcanic eruption look like?

Answer 32

Passive eruption

Question 33

What does high viscosity volcanic eruption look like?

Answer 33

Explosive eruption

Question 34

Why are their different magma compositions?

Answer 34

1.)Different starting rocks 2.)Different ingredients

Question 35

What do mantel rocks produce?

Answer 35

Ultra mafic and mafic magmas

Question 36

What does mantel rock produce?

Answer 36

Ultra-mafic and mafic magmas

Question 37

What does crustal rock produce?

Answer 37

Mafic and intermediate, and felsic magmas

Question 38

How can you produce different magmas from the same source?

Answer 38

1.) Assimilation 2.)Magma mixing 3.)Partial melting 4.)Fractional crystallization

Question 39

What is assimilation of magma?

Answer 39

Magma melts the country rock it passes through and blocks the country rock fall into the magma.

Question 40

What is magma mixing?

Answer 40

Different magmas may blend in a magma chamber.

Question 41

What is partial melting?

Answer 41

The silica-rich minerals melt first causing the magma to be silica-rich even if it didn't start out that way.

Question 42

What is fractional crystallization?

Answer 42

As the magma cools, early crystals settle by gravity. Mafic minerals are removed making the magma more felsic.

Question 43

What is a magma chamber?

Answer 43

The open cavity or area of highly fractured rock in the upper crust contains large counties of magma.

Question 44

What is a dike?

Answer 44

Near vertical intrusion of igneous rocks

Question 45

What is a sill?

Answer 45

Near horizontal intrusion of igneous rock.