Lab 3

Question 1

what are the three types of rock

Answer 1

Igneous, Sedimentary, Metamorphic

Question 2

Describe the rock cycle

Answer 2

Igneous rocks are uplifted, weathered and transported to become sediments
Metamorphic rocks are weathered+transported to become sediments
sediments are deposited and lithificated to form sedimentary rocks
Sedimentary rocks are turned into metamorphic rocks by heat and pressure
Sedimentary rocks or metamorphic rocks are melted into magma
Magma cools and crystallized into igneous rocks
Igneous rocks turn into metamorphic rocks from heat and pressure

Question 3

what is magma

Answer 3

molten rock underground, when it goes above ground it becomes lava

Question 4

when is an igneous rock intrusive or extrusive

Answer 4

intrusive if formed by magma, extrusive if formed by lava

Question 5

what does texture refer to in igneous rocks

Answer 5

both size of the mineral grains and the physical morphology of the rock

Question 6

what does composition mean

Answer 6

the types of minerals that make up a rock

Question 7

What determine grain size in igneous rocks

Answer 7

How fast the magma cools. Slow cooling often underground leads to large visible grains. Fast cooling on the surface leads to small grains

Question 8

What are felsic minerals

Answer 8

quartz, potassium feldspar, sodium feldspar, and muscovite. Light in colour, rich in Si, Al, Na, and K. Crystallize while magma is colder

Question 9

What are Mafic minerals

Answer 9

ferromagnesian - olivine, pyroxene, horneblende, biotite, calcium feldspar. Dar in colour, high in Fe, Mg, and Ca. crystallize when magma is hot

Question 10

describe Quartz

Answer 10

irregular, glassy grains which are usually smoky in colour in igneous rocks. Conchoidal fractures on some surfaces. Always transparent

Question 11

describe Muscovite

Answer 11

soft, brass-coloured flakes due to perfect cleavage in one direction. Sometimes glitter like small specks of pyrite.

Question 12

K-feldspar

Answer 12

has pearly to glassy lustre and is commonly, pink, white, or grey. Cleavage in two directions at 90º may be detected. Often appears milky under hand lens

Question 13

describe Plagioclase feldspar

Answer 13

usually grey or white in granite. a dark bluish colour in gabbro. Two cleavage at right angles may be detected. twinning striations are common

Question 14

Describe biotite

Answer 14

small, black, glassy flakes with hardness 2.5-3.5. perfect cleavage in one direction. distinguished from hornblende or pyroxene by scratching with steel probe.

Question 15

describe hornblende

Answer 15

long black glassy crystals. Two cleavage planes that intersect at 60 and 120 º

Question 16

describe pyroxene

Answer 16

short, greenish black minerals in darker rocks. Cleavage in two directions at 90º. Hard to differentiate between pyroxene and hornblende when grains are small.

Question 17

what are Phenocrysts

Answer 17

crystals that are larger than the surrounding matrix

Question 18

what is an andesite

Answer 18

a light coloured rock with hornblende phenocrysts

Question 19

what is basalt

Answer 19

a rock with pyroxene, olivine, or plagioclase phenocrysts

Question 20

what does porphyritic mean

Answer 20

an adjective added to the rock name that means the phenocrysts are conspicuous.

Question 21

what is viscosity

Answer 21

the resistance of a substance to change in form or the resistance to flow within a liquid. Ex honey has a higher viscosity than water

Question 22

what is viscosity important for magma

Answer 22

is determines how fast magma moves
it influences how fast crystals can rise or sink in magma
it helps volcanologists predict whether lava from a volcano will spread slowly or fast, and wether it will be prone to getting stuck and building up pressure
It helps determine how explosive an eruption will be
it helps determine the shape of the volcano made by magma

Question 23

how do you calculate viscosity

Answer 23

((gravitydensitysin(angle of slope)(thickness of flow)^2)/(3velocity)

Question 24

What is the Ultramafic rock

Answer 24

Peridotite

Question 25

What is the main Med+coarse grained mafic rock

Answer 25

Gabbro

Question 26

What is the main fine grained mafic rock

Answer 26

Basalt

Question 27

What is the main intermediate fine grained rock

Answer 27

Andesite

Question 28

What is the main intermediate medium/coarse grained rock

Answer 28

Diorite

Question 29

What is the main felsic fine grained rock

Answer 29

Rhyolite

Question 30

what is the main felsic med+coarse grained rock

Answer 30

Granite

Question 31

What is a smooth glassy Intermediate/felsic rock

Answer 31

Obsidian

Question 32

what is a frothed glassy felsic/intermediate rock

Answer 32

Pumice

Question 33

How does silica content affect magma viscosity

Answer 33

Higher silica content increases magma viscosity because silicon-oxygen tetrahedra link to form complex, stable chains, making the magma thicker and more resistant to flow. This polymerization slows the movement of magma and traps gases, leading to more explosive eruptions, in contrast to low-silica, low-viscosity magmas that flow easily and allow gases to escape gradually