Epsc 221: Igneous Rocks

Front 1

Igneous rocks form from the cooling and crystallization of ___________. Once it reaches the surface it is called lava.

Back 1

Magma

Front 2

Magma forms through ________ _________, during which mafic and felsic magmas differentiate.

Back 2

Partial Melting

Front 3

Magma can form at 1200 degrees in 3 environments:

1. ________________

2. ________________

3. ________________

Back 3

Spreading Centers, Subduction zones and Mantle plumes.

Front 4

The __________ _____________ causes temperature to increase with depth. In the lower crust and upper mantle temperatures are high enough and pressures are low enough.

Back 4

geothermal gradient

Front 5

Pressure drops can cause ____________ melting, causing magma to form.

Back 5

Decrompression

Front 6

______________ are water and gases which allow melting to occur at lower temperatures.

Back 6

Volatiles

Front 7

Magma melt is in the ___________ state and composed of mobile ions.

Back 7

liquid

Front 8

Magma _________ are silicate minerals that have already crystallized.

Back 8

crystals

Front 9

Magma _________ are gases already dissolved in the melt.

Back 9

volatiles

Front 10

Magma has three main components:

1._______________

2._______________

3._______________

Back 10

Melt, Volatiles and Crystals.

Front 11

Mafic magma tends to have a ________ silica content and a darker colour. Most of it is formed from the partial melting of ___________.

Back 11

1. low

2. Peridotite

Front 12

Felsic magma has a ________ silica content, as well as a light colour and high viscosity.

Back 12

high

Front 13

______________ igneous rocks are formed from the rapid crystallization of magma after an eruption. Crystals are much smaller.

Back 13

Extrusive

Front 14

_____________ igneous rocks are formed slowly at depths, allowing complete crystal formations.

Back 14

Intrusive

Front 15

The mineral composition of igneous rocks is determined by the ______________ _______________ of the magma from which it crystallizes.

Back 15

Chemical Composition

Front 16

In Bowen's reaction series, the _____________ branch shows plagioclase feldspar shifting from calcium-rich to sodium-rich

Back 16

Continuous

Front 17

In Bowen's reaction series, the minerals in the discontinuous branch go, from high T to low T:

1. ________

2. ________

3. ________

4. ________

Back 17

1. Olivine

2. Pyroxene

3. Amphibole

4. Biotite Mica

Front 18

In Bowen's reaction series, the felsic minerals at low temperatures are ____________, ___________ and _______________.

Back 18

Orthoclase feldspar, Muscovite Mica and Quartz.

Front 19

The factors that affect igneous crystal texture/size are ___________, _____________ and __________.

Back 19

Magma cooling rate, Silica content and volatile volume.

Front 20

An _____________ texture is due to rapid cooling and is composed of microscopic crystals.

Back 20

Aphinitic

Front 21

In aphinitic rocks, gas bubbles can sometimes become trapped, forming vesicles. This is called a ________________ texture.

Back 21

Vesicular

Front 22

A _____________ texture is due to slow cooling at depth, leading to large crystals forming. Grains are described as fine, medium or coarse.

Back 22

Phaneritic

Front 23

A ______________ texture is composed of large central phenocryst crystals surrounding by a groundmass of tiny crystals, or matrix. Indicates two cooling histories.

Back 23

Porphyritic

Front 24

A _________ texture is due to magma that was quickly quenched, forming an amorphous mass.

Back 24

Glassy

Front 25

A __________ texture is composed of angular volcanic fragments embedded in ash.

Back 25

Pyroclastic

Front 26

Igneous intrusion, also known as ____________, are subsurface features formed from the solidification of magma.

Back 26

Plutons

Front 27

___________ are tabular, discordant bodies that often look like walls.

Back 27

Dykes

Front 28

________ are concordant tabular bodies formed from magma injected in sedimentary bedding.

Back 28

Sills

Front 29

__________ are similar to sills but form a lens-shaped mass that is much less fluid.

Back 29

Laccoliths

Front 30

________ are the largest intrusive bodies, and are always discordant. Stocks are smaller versions of these.

Back 30

Batholiths

Front 31

Scoria is the mafic version of ________. Both are extrusive igneous rocks.

Back 31

Pumice

Front 32

Welded stuff and Obsidian are examples of _________ igneous rocks. Obsidian is glassy while welded stuff is pyroclastic.

Back 32

Extrusive

Front 33

Rhyolite and Granite are examples of ________ igneous rocks.

Back 33

Felsic

Front 34

Basalt and Gabbro are examples of ___________ igneous rocks.

Back 34

Mafic