Week 3

Question 1

Igneous Rocks

Answer 1

formed from hot material

Question 2

Magma is composed of…

Answer 2

1. A liquid component (called “melt” ).
2. Gases (called “volatiles” ), including water vapor and carbon dioxide.

Question 3

Where does magma come from?

Answer 3

Most magma is generated by the partial mantle. Temperature and pressure increase with depth in Earth’s lithosphere
Increased temperature acts to melt rock, increased pressure acts to drive the material toward a solid state.

Question 4

Decompression Melting

Answer 4

In places where hot, near-liquid, material of the asthenosphere is allowed to rise toward the surface, the pressure acting on this material is lowered.
Reduction of pressure on allows the material to be completely molten into magma.
Occurs in places where lithospheric plates are moving apart.

Question 5

Hydration-Related Melting

Answer 5

Subduction: in some places on Earth, one lithospheric plate is pushed under another.
As the plate descends, it is heated, and releases the water in the form of vapour.
The vapour therefore hydrates the rock in the asthenosphere
Water vapour lowers the melting point of rock, allowing it to melt into magma
In this way, “wet” rocks tend to melt at LOWER temperatures than “dry” rocks

Question 6

Plutonic/Intrusive Igneous Rocks

Answer 6

Rocks that form from the cooling of magma below the surface are commonly called plutonic igneous rocks
Because they are formed from magma intruded into pre-existing rocks of the crust, they are also called intrusive igneous rocks

Question 7

Igneous Intrusions

Answer 7

The magma in a magma chamber and smaller offshoots intruded into pre-existing layered rocks through fractures and contacts between sedimentary rock layers.

Question 8

Batholith

Answer 8

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

Question 9

Dyke

Answer 9

A tabular-shaped igneous body oriented at a significant ANGLE to layers of pre-existing rocks.

Question 10

Sill

Answer 10

A tabular-shaped igneous body intruded PARALLEL to layers of preexisting rocks.

Question 11

Laccolith

Answer 11

A blister-like igneous body intruded parallel to layers of pre-existing rocks (but involving some upwarping of overlying layers)

Question 12

Volcanic Neck

Answer 12

The remnant of igneous material that once occupied the vent of a volcano.

Question 13

Phaneritic texture of plutonic/intrusive igneous rocks

Answer 13

mineral crystals of intrusive igneous rocks are large enough to be observed with the unaided eye

Question 14

Extrusive Igneous Rocks

Answer 14

Rocks that form from the cooling of magma ABOVE the surface. Formed from magma EXTRUDED from the ground

Question 15

Lava

Answer 15

Magma that escapes a magma chamber and reaches Earth’s surface can erupt from a volcanic centre

Question 16

How is lava extruded

Answer 16

From a volcanic vent due to the expansion of volatiles (gases) as they escape to the surface in response to a decrease in pressure

Question 17

Aphanitic

Answer 17

Because extrusive igneous rocks cool above Earth’s surface, mineral crystals have little time to grow. As a result, the mineral crystals of extrusive igneous rocks are TOO SMALL to be observed with the unaided eye.

Question 18

Porphyritic

Answer 18

When a magma cools slowly underground in its early stages, then travels rapidly toward the surface where it can cool at a faster rate. This two-stage cooling can result in a rock that is essentially aphanitic (from quick cooling phase), but contains a few large crystals called phenocrysts (from slow cooling phase)

Question 19

Glassy

Answer 19

When lava solidifies too quickly for any significant crystallization to occur. Unordered ions remain essentially “frozen” before they can unite to form crystals. Obsidian is a common rock exhibiting such a texture.

Question 20

Pyroclastic

Answer 20

Eruptions that are exceptionally violent can eject particles containing blobs of molten material and pulverized bits of rock.

Question 21

Ferromagnesian Minerals

Answer 21

Those silicate minerals containing iron and magnesium.
Due to their iron/magnesium content, they are dark in colour (green, brown or black).
EX. Olivine, Pyroxene, Amphibole, Biotite Mica

Question 22

Feldspar Minerals

Answer 22

most common mineral group, forming under a very wide range of temperatures and pressures.
Like quartz, the structure of feldspar minerals is a three dimensional framework of silica, but also contains very light metals
Bonds are less uniform in strength than in quartz.

Question 23

Bowen’s Reaction Series

Answer 23

describes the order in which minerals crystallize from cooling magma

Question 24

Mafic Rocks

Answer 24

Igneous rocks containing a high concentrations of dark minerals (especially ferromagnesian minerals). Generally very dark in colour.

Question 25

Felsic Rocks

Answer 25

Igneous rocks that contain small amounts of dark minerals. Generally light in colour

Question 26

Intermediate Rocks

Answer 26

These are rocks that have a colour in-between mafic and felsic.

Question 27

Sedimentary Rocks

Answer 27

formed by the accumulation and hardening of sediment.

Question 28

Classic Sediment

Answer 28

consisting of particles derived from pre-existing rocks (e.g. sand)

Question 29

Chemical Sediment

Answer 29

consisting of mineral matter precipitated from a solution (e.g. salt)

Question 30

Biochemical Sediment

Answer 30

consisting of materials produced by organisms (e.g. shells, bone, teeth, leaves, wood, etc.)

Question 31

Mechanical/Physical Weathering

Answer 31

physical breakup of rocks and minerals without changes in their composition

Question 32

Chemical Weathering

Answer 32

breakdown of minerals due to chemical reaction of minerals with water or gases in the air.

Question 33

Classic Sediment Transportation

Answer 33

Sedimentary particles can be transported away from their source by: - wind or water (lighter particles), sorted well - mudflows end up poorly sorted

Question 34

Evaporites

Answer 34

Dissolved ions can become too concentrated for the water to hold, so positive and negative ions join together and precipitate as minerals Evaporite deposits accumulate in basins isolated from main sea seawater flows, becomes concentrated in dissolved ions and sinks EX. Gypsum and Halite

Question 35

Biogenic/Biochemical Sediment

Answer 35

Chemical sediment formed through biological activities EX. bones, shells, teeth, plant remains

Question 36

Metamorphism

Answer 36

Formed by the transformation of pre-existing rocks under the influence of high temperatures and pressures and chemically active fluids

Question 37

Three types of metamorphism

Answer 37

1) Contact metamorphism 2) Regional metamorphism 3) Metasomatism

Question 38

Contact Metamorphism

Answer 38

Pre-existing rock is “baked” under relatively low pressures. Commonly occurs when rock is heated by igneous intrusion, forming a metamorphic halo in the adjacent rock. Mineral grains recrystallize in random orientations (due to uniform pressure). Overall composition of the rock basically remains the same.

Question 39

Regional Metamorphism

Answer 39

Pre-existing rock subjected to heat and pressure on a regional scale. Commonly associated with mountain building events in which rocks are lowered to great depths and squeezed by compressive forces

Question 40

Metasomatism

Answer 40

Occurs when fluids (generally water or carbon dioxide) react with a pre-existing rock and alter the chemical composition of minerals within the rock

Question 41

Foliation

Answer 41

Regional metamorphism generally occurs in areas where two lithospheric plates are pressing against one another, and rocks are subjected to differential stress In response to this stress, platy/elongate minerals line up to produce a foliated texture

Question 42

Jade

Answer 42

Formed by metasomatism... Due to its extreme toughness, jade can be carved into intricate designs