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EARTHSCI 1089G > Igneous Rocks (L7) > Flashcards

Igneous Rocks (L7) Flashcards

1
Q

Simply put, what are ROCKS?

A

rocks aer solid aggregates of minerals and mineral-like materials

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2
Q

Where does the term Igneous come from?

A

Igneous is from the Latin ignis meaning fire, the same root as the word “ignite”

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3
Q

How is Magma created?

A

from the melting of rock in the mantle or crust, or both

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4
Q

What does magma contain?

A

mostly liquid, but can contain gases such as water vapour and carbon dioxide, and mineral crystals

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5
Q

How does magma become lava?

A

when it reaches the surface and loses its gases (changing in composition)

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6
Q

As a general rule, temperature and pressure ____

A

increases with depth in Earth’s lithosphere

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7
Q

What are the 2 ways rocks can melt?

A

Decompression Melting and Subduction

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8
Q

Decompression Melting

A

is the reduction of pressure on, which allows the mateial of the asthenosphere part of the mantle to (whichis already very hot, near liquid) to completely molten into magma

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9
Q

Where does Decompression melting occur?

A

in places where plates of lithosphere are moving apart

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10
Q

Subduction

A

the formation of magma through one lithospheric plate being pushed under another (in the oceanic crust) and is heated and releases water in the form of vapour and the vapour hydrates the rock in the mantle

this lowers the melting point and the wet rocks become magma

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11
Q

Wet rocks tend to melt at lower temp than dry rocks. T or F

A

T

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12
Q

What happens in both cases of magma formation?

A

the magma is less than the rock surrounding it so = rise towards the surface

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13
Q

When magma rises, where can it collect?

A

Large pockets called “magma chambers”

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14
Q

What 2 things can happen to the magma that arose?

A

It can remain trapped in a magma chamber, or can escape to the surface and erupt from volcanoes

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15
Q

What happens when magma ascends towards the surface and starts to cool?

A

it allows minerals to crystalize from chemical components of the magma melt

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16
Q

What happens when magma remains trapped in a magma chamber?

A

it cools very slowly, allowing the crystals to grow to large sizes

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17
Q

What are Plutonic Igneous rocks?

A

rocks that form from the cooling of magma below the surface

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18
Q

what are plutonic igneous rocks AKA? and Why?

A

Intrsuive Igneous Rocks, b/c they are formed from magma intruded into pre-existing rocks of the crust

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19
Q

What is a Batholith?

A

a very large mass of igneous rock formed from cooling of a major magma chamber

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20
Q

A Dyke?

A

a tabular-shaped igneous body oriented at a significant angle to layers of pre-existing rocks

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21
Q

A Sill?

A

a tabular-shaped igneous body intruded parallel to layers of pre-existing rocks

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22
Q

Laccolith

A

blister like bodies which aer the overlying layers where magma is pushed through in between

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23
Q

Volcanic Neck?

A

Igneous material that once occupied the vent of a volcano

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24
Q

Why are crystals in most rocks shaped imperfectly? and what is this texture called

A

because intrsuive igenous rocks cool from magma below Earth’s surface and mineral crystals have ample time to grow

phaneritic texture

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25
Q

What is the extrued liquid material that escapes a magma chamber and erupts from a volcanic centre?

A

Lava

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26
Q

Why is lava extruded?

A

extruded from a volcanic vent due to the expansion of volatilies as they escape to the surface in response to a decrease in pressure

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27
Q

Why is lava not the exact same as magma?

A

because lava has lost much of its gas content

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28
Q

What is the name of the texture where the rocks are too small to be ovserved with the unaided eye?

A

Aphanitic Texture

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29
Q

the texture of igenous rocks that show large mineral crystals inbedded in a “groundmass” of much smaller crystals

A

porphyritic texture

30
Q

how is a porphyritic texture produced?

A

produced when the magma initially cools very slowly, but later moves closer to the surface, cooling more quickly and producing smaller crystals

a 2-step cooling history

31
Q

How is a glassy texture created?

A

when lava solidifes too quickly for any significant crystalization to occur

32
Q

What is an example of a glassy texture?

A

Obsidian

33
Q

What is a pyroclastic texture?

A

rocks that have dust particles of molten material made from volcano eruptions within them

34
Q

What are most igneous rocks principally made of?

A

silicate materials

35
Q

What do all silicate materials contain?

A

the substance silica

36
Q

What is the makeup of Silica?

A

a complex ion made of 1 silicon atom bonded to 4 oxygen atoms

37
Q

what is silicon atom’s overall charge?

A

-4

38
Q

What are Ferromagnesian silicate minerals?

A

the most important silicate minerals used in the identification of igneous rocks

basicallly iron and/or magnesium ions ionically bonded with silica units

39
Q

Planes of weakness are represented by ___

A

planes of ionic bonding

40
Q

What are all ferromagnesian silicate minerals made of?

A

iron, magnesium, and silica, with only minor additional metals

41
Q

What difference is found between the ferromagnesian silicate minerals?

A

the main diff lies in their structure

42
Q

Why do biotite mica break cleanly into thin sheets?

A

because the intermolecular bonds that hold the sheets together are weaker than the ionic bonds

43
Q

What does Quartz consists of?

A

only silica

44
Q

How are all of the bonds in quartz equally strong?

A

because of the complete sharing of oxygen by adjacent silicon atoms

45
Q

what kind of cleavage and fracture do Quartz generally show?

A

quartz doesn’t have cleavage and generally shows a conchoidal fracture

46
Q

What is the most common mineral group

A

Feldspar

47
Q

What are the 2 most common types of feldspar?

A

Plagioclase and Potassium Feldspar

48
Q

Plagioclase? Contain? Color?

A

contains ions of sodium and calcium. Color ranges usually from white to bluish grey

49
Q

Potassium Feldspar? Contains? Color?

A

contains ions of potassium, and the color ranges from creamy white to salmon pink

50
Q

Why aren’t all igneous rocks made of just one mineral with one composition?

A

the reason is that diff minerals crystalize at diff temperatures

51
Q

Bowen’s Reaction Series

A

The sequence of crystalization when magma cools, minerals crystalize in a distinct sequence

52
Q

how odes paglioclase feldspar crystalize?

A

In the continuous series.
where the mineral composition gradually changes

53
Q

What is the shorthand way of describing composition?

A

Based on the color or tone of an igneous rock

54
Q

Mafic igneous rocks

A

igneous rocks with high concentrations of dark-colored minerals

55
Q

Felsic Rocks

A

Igneous rocks containing high concentrations of light-colored minerals with only minor amounts of dark minerals

56
Q

Intermediate Rocks

A

rocks with intermediate composition and a color in-between mafic and felsic

57
Q

What does the rock name tell us and why is it important?

A

it tells us something about the rock’s composition and texture

58
Q

Gabbro

A

Phaneritic texture and Mafic Composition

59
Q

Diorite

A

Phaneritic Texture and Intermediate composition

60
Q

Granite

A

Phaneritic texture and Felsic Composition

61
Q

Basalt

A

Aphanitic texture and mafic composition

62
Q

Andesite

A

Aphanitic texture and intermediate composition

63
Q

Rhyolite

A

Aphanitic texture and Felsic Composition

64
Q

Gabbro is a ___ igneous rock (decompression melting)

A

Intrusive

65
Q

Basalt is a ___ igneous rock (decompression melting)

A

extrusive

66
Q

Granite is a ___ rock (hydration melting)

A

Intrusive

67
Q

Rhyolite is a ___ rock (hydration melting)

A

Extrusive

68
Q

Diorite is a ___ rock (hydration melting)

A

Intrusive

69
Q

Andesite is a ___ rock (hydration melting)

A

extrusive

70
Q

aside from aesthetic value, what is the main reason igneous rocks are used

A

durability

71
Q

What are the 3 components that play a role in the durability of an igneous rock being helpful

A

Naturally resistant to chemical damage

The Silicate minerals that make up most igneous rocks have high hardness values

composed of tightly interlocking crystals and is very tough

72
Q

3 disadvantages of using igneous rocks?

A

expensive

difficult to cut and polish

heavier (transportation costs)

EARTHSCI 1089G (33 decks)

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