Chapter 3 - Igneous Rocks

Question 1

Igneous rock

Answer 1

Formed from the cooling and crystallization of magma.

Question 2

Sedimentary rock

Answer 2

Formed when weathered fragments of other rocks are buried, compressed, and cemented together, or when minerals precipitate directly from solution.

Question 3

Metamorphic rock

Answer 3

Formed by alteration (due to heat, pressure and/or chemical action) of a pre-existing igneous or sedimentary rock

Question 4

Rock cycle

Answer 4

Shows how the 3 rock types transform into one another.

There are two forces:
1. Earth’s internal heat engine, which moves material around in the core and the mantle, and leads to clow but significant changes within the crust.
2. The hydrological cycle, which is the movement of water, ice and are at the surface, and is powered by the sun.

Question 5

Intrusive igneous rock

Answer 5

When magma cools slowly within the crust over centuries to hundreds of years.x

Question 6

Extrusive igneous rock

Answer 6

Erupts to the surface and cools quickly, in seconds to years.

Question 7

Sediments

Answer 7

The weathered material (small rocks and mineral fragments) that are eroded, transported and deposited.

Question 8

Partial Melting

Answer 8

When only part of a rock melts - this happens because rocks are not pure. Most rocks are made of several minerals, each having a different melting point.

Question 9

Decompression Melting

Answer 9

Takes place within Earth when a body of rock is held at same temperature, but pressure is reduced. If a rock is hot enough to be close to melting point and is moved towards the surface, the pressure is reduced, and the rock can move to the liquid side of its melting curve.

Question 10

Flux Melting

Answer 10

If a rock is close to its melting point and water is added, the melting point is reduced and partial melting occurs.

Question 11

Polymerize

Answer 11

Si and O combine to form silica tetrahedra and as cooling continues, they link together to form chains.

Question 12

Bowen Reaction Series

Answer 12

The sequence in which minerals crystallize from magma.

Created by Canadian petrologist Normal L. Bowen.

Question 13

Gabbro

Answer 13

Magma becomes Gabbro when cooling slowly underground.

Question 14

Basalt

Answer 14

Magma becomes Basalt when cooling quickly at the surface.

Question 15

Fractional Crystallization

Answer 15

When crystals form and settle in the magma chamber, making the mafic magma more of a felsic magma due to the loss of iron and magnesium to the crystals.

Question 16

Porphyritic

Answer 16

A texture of rock when there is significant different in crystal size, where larger crystals are at least 10x bigger than the average smaller crystals.

Question 17

Phaneritic

Answer 17

Having crystals that are large enough to see by eye - >0.5mm

(From Greek: “visible”)

Question 18

Aphanitic

Answer 18

Crystals too small to distinguish.

(From Greek: “unseen”)

Question 19

Country rock

Answer 19

A native rock to a region in contrast to any intrusion of viscous geological material (magma).

Question 20

Stoping

Answer 20

When a fragment of country rock breaks and falls into magma. The resulting fragments of this event are called XENOLITHS. (From Greek: “strange rock”)

Question 21

Xenolith

Answer 21

The resulting rock formation when a country rock fragment falls into magma.

Question 22

Pluton

Answer 22

When upward moving magma cools within the crust.

Question 23

Stocks

Answer 23

Large irregular shaped pluton, exposure to surface is < 100 km sq.

Question 24

Batholiths

Answer 24

Large irregular shaped pluton, exposure to surface is > 100 km sq.

Question 25

Concordant

Answer 25

Being parallel to the existing layering surrounding said material.

Question 26

Sill

Answer 26

Rock that is concordant to layering surrounding it.

Question 27

Dyke

Answer 27

Rock layer that is discordant to layering surrounding it.

Question 28

Laccolith

Answer 28

A sill-like body that expanded upward by deforming the overlaying rock.

Question 29

Pipe

Answer 29

A cylindrical body that served as a conduit for movement of magma.

Question 30

Felsic

Answer 30

Term used for light-colored igneous minerals and igneous rocks rich in feldspar and silica.

Example: Granite, rhyolite

Question 31

Mafic

Answer 31

An igneous rock with high proportion of pyroxene and olivine (which form from magnesium and ferric (iron) minerals.

Example: Gabbro (intrusive), basalt (extrusive)

Question 32

Ultramafic

Answer 32

Igneous rock that consists of mostly ferromagnesian minerals, no quartz, and <45% SiO2

Question 33

Intermediate rocks

Answer 33

Cooling behavior lies between felsic and mafic.

Example: Diorite, andesite

Question 34

Continuous Series

(re: Bowen series)

Answer 34

The continuous, recurring change in composition of a mineral within a magma chamber. The mineral changes its composition by continuously exchanging cations with the magma to reach equilibrium.

Question 35

Discontinuous Series

(re: Bowen series)

Answer 35

A sequence of mineral reactions which takes place at specific temperatures of cooling magma. A mineral will remain in equilibrium until it reaches its reaction temperature. The mineral will react and form a new mineral. This mineral will maintain equilibrium until the next reaction temperature.

These minerals are:

Olivine > Pyroxene > Amphibole > Biotite