Geology 104 Midterm

Front 1

Uniformitarianism

Back 1

the physical, chemical and biological laws that operate today also operated in the past

Front 2

law of superposition

Back 2

the youngest layer of rock is on top and the oldest is on the bottom

Front 3

relative dating

Back 3

events are placed in their proper sequence

Front 4

layers of the earth by composition

Back 4

core: iron rich and nickel rich with minor oxygen, silicon and sulfur

mantle: most of earth's volume, the dominant rock is peridotite

crust: divided into oceanic and continental, mostly made up of basalt

Front 5

divergent boundary

Back 5

plates move away from eachother

Front 6

convergent boundary

Back 6

plates move into eachother

Front 7

transform fault boundaries

Back 7

plates slide past eachother

Front 8

layers of the earth by physical properties(8)

Back 8

lithosphere and asthenosphere: crust and upper mantle
mesosphere: lower mantle
outer core: liquid layers of flowing iron
inner core: behaves like a solid because of pressure
hydrosphere: dynamic mass of water
atmosphere: gaseous envelope around the earth
biosphere: all life on earth
geosphere: lies beneath atmosphere and oceans

Front 9

rock cycle (6)

Back 9

1. magma migrates to the earth's surface and cools
2. igneous rock formed by crystallized magma
3. weathering and transportation
4. particles deposited as sediment
5. sediment is cemented and compacted by heavy weight
6. pressure and heat change the rock into metamorphic, if subjected to more heat and pressure, it goes back into magma

Front 10

what is a mineral

Back 10

it is the building block of rocks and is an inorganic solid that possesses an orderly internal structure and a definite chemical composition

Front 11

what are the 5 mineral characterisitics

Back 11

1. must occur naturally
2. must be solid at surface temperature and pressure
3. must have a definite chemical composition
4. usually inorganic

Front 12

polymorph

Back 12

minerals that join together in more than 1 possible arrangement. ex. coal and diamond

Front 13

what is an igneous rock

Back 13

formed by the cooling and solidification of magma

Front 14

magma

Back 14

a silicate melt which may contain early formed crystals or inclusions/xenoliths

Front 15

intrusive

Back 15

plutonic or under ground

Front 16

extrusive

Back 16

volcanic or above ground

Front 17

factors affecting magma viscosity

Back 17

silica content: higher silica means more viscous
volatiles: higher volatiles means less visous

Front 18

factors affecting crystal size

Back 18

rate of cooling: faster cooling means smaller crystals
viscosity: higher viscosity means bigger crystals

Front 19

factors affecting cooling rate of magma

Back 19

location: intrusive means slower cooling
size of magma body: large means slower cooling

Front 20

porphyritic texture

Back 20

crystals are not uniform in size, large crystals called phenocrysts form first and are then surrounded by smaller crystals called the matrix/groundmass

Front 21

equigranular texture

Back 21

cooling rate is constant, so the crystals are the same size

Front 22

glassy texture

Back 22

disordered and no crystals

Front 23

aphanitic texture

Back 23

small microscopic crystals

Front 24

phaneritic texture

Back 24

visible crystals

Front 25

pegmatitic crystals

Back 25

very large crystals, and high volatile content

Front 26

Name 6 textures occuring in volcanic rocks

Back 26

aphanitic, prophyritic, glassy, vesicular, pyroclastic, amygdular

Front 27

name 2 intrusive rock textures (plutonic)

Back 27

aphanitic, and porphyritic

Front 28

what are the four main igneous compositional groups

Back 28

felsic: light coloured silicates, part of the conitinental crust, usually intrusive
intermediate: 20-40% dark minerals from explosive volcanic activity
mafic: dark silicates, oceanic crust and calcium rich feldspar
ultra mafic: very rare almost 100% ferromagnesian and is a major part of the mantle

Front 29

role of heat in making magma

Back 29

temperature increases with depth with the geothermal gradient between 20-30 degrees per km

Front 30

role of pressure in making magma

Back 30

increase in confining pressure increases a rock's melting temperature and when confining pressure drops, we get decompression melting

Front 31

role of volatiles in making magma

Back 31

volatiles cause rocks to melt at lower temperatures

Front 32

stratification

Back 32

a structure developed when fine grained pyroclastics like cinders, ashes and dust settle through water or air and are deposited in consecutive layers. this rock is termed tuff

Front 33

what is bowen's reaction series

Back 33

as magma cools, minerals crystallizw in a systematic fashion based on their melting points. the silica content becomes greater as crystallization proceeds

Front 34

proof supporting bowen's reaction (3)

Back 34

zoning in plagioclase, reaction rims in ferromagnesian minerals, and mineral associations and antipathies.

Front 35

list bowen's reaction series

Back 35

discontinuous: continuous:
olivine calcic plagioclase
pyrocene
amphibole
biotite sodic plagioclase


kspar
muscovite
quartz

Front 36

explain how igenous rocks are diverse (3)

Back 36

1. magmatic differentiation: rocks of different composition form from the same magma by crystal settling, filter press action,
2. magmas of different composition
3. magma mixing: more buoyant magma overtakes magma that rises more slowly and the mixed magma will be different from the other two original magmas

Front 37

magmatic stoping

Back 37

detaching and engulfing blocks of country rock. the engulfed rock may become assimilated, be an inclusion or be a xenolith

Front 38

volcanic neck/plug

Back 38

solidified lava in the throat of a volcano

Front 39

fissure flow

Back 39

fluid basaltic lava pouring out from fissures and are very rare and form vast sheets

Front 40

plutons

Back 40

an intrusive body of rock

Front 41

batholith

Back 41

largest of igneous intrusions. it is massive and discordant

Front 42

laccolith

Back 42

a massive intrusion bowing up the strata and concordant

Front 43

sill

Back 43

a thin extensive tabular and concordant intrusion with strata

Front 44

dike

Back 44

a tabular discordant intrusion to the strata

Front 45

stock

Back 45

a massive, discordant pluton similar to but smaller than a batholith

Front 46

pyroclastic flows

Back 46

nuee ardente. glowing avalanche. there is a cloud of incandescent gas that is released forming tuff and welded tuff. ex. mt. pelee

Front 47

lahar

Back 47

volcanic mud flow ex. nevado del ruiz

Front 48

what are the different types of lava flows (3)

Back 48

pahoehoe: formed by fluid lava. are smooth and ropy
aa: formed by thicker lava, has rough jagged blocks
pillow lava: formed in oceans as lava cools under water

Front 49

lava dome

Back 49

a viscous, silica rich lava that builds up in bulbous masses

Front 50

columnar jointing

Back 50

due to lava cooling and contracting. this causes cracks in the lava

Front 51

where are most active volcanoes found

Back 51

pacific rim of fire, mediterranean, african rift valley, and oceanic ridge belt

Front 52

fissure eruption

Back 52

ex. laki fissure in iceland, which covered a huge area. we do not usually see these eruptions

Front 53

central vent eruption and types of volcanoes

Back 53

1 central location of the eruption.

1. shield volcano: large gentle slopes, ex mauna loa
2. composite cone: medium, steep slopes near summit and gentle slopes at base. both pyroclastic and lava flows. ex. vesuvius
3. cinder cone: small steep slopes, often found in the caldera of large volcanoes, mostly pyroclastics. ex. sunset crater arizona

Front 54

caldera eruptions

Back 54

very rare and extremely violent eruptions. different from calderas inside volcanoes. yellowstone is a resurgent caldera because its floor has slowly been rising and doming up since its last eruption. they leave us with volcanic activity like geysers and hot springs

Front 55

what are sedimentary rocks

Back 55

form at or near the earth's surface due to accumulation and consolidation of sediments

Front 56

what are clastic sediments

Back 56

composed of products of physical weathering

Front 57

stratification

Back 57

bedding or layering

Front 58

lithification

Back 58

transformation into solid rock

Front 59

name the wentworth size scale (4)

Back 59

-conglomerate: gravel size 2mm
-sandstone: sand size 1/16 mm
-siltstone: silt size 1/256 mm
claystone: clay size finer than 1/256 mm

Front 60

how do we describe clastic sediments (6)

Back 60

-sorting: poorly or well sorted
-shape: equant, tabular or rod shaped
-roundness: means no sharp edges
-sphericity: means the particle is shaped like a sphere
-angularity: how sharp the edges are
-fissile or blocky

Front 61

biochemical and chemical rocks

Back 61

natural precipitates of aqueous solutions deposited through organic life or evaporated oceans

Front 62

evaporites

Back 62

rock salt and gypsum: may form a play which is a land locked basing

Front 63

carbonates

Back 63

dominantly calcite form limestone.

Front 64

travertine/dripstone

Back 64

formed from calcite deposits in caves. stalactites grow on the ceiling and stalagmites grow on the gorund

Front 65

dolostone formation

Back 65

form with dolomite mineral. form from limestone by replacement from magnesium bearing waters

Front 66

ripple marks

Back 66

these occur on the surface of sand deposits when wind or water currents move sand size particles, forming ridges and troughs perpendicular to the current direction
we have current ripple marks and ossilation ripple marks

Front 67

cross bedding

Back 67

sand grains are deposited at an inclination to the horizontal and will indicate the direction of current flow

Front 68

graded bed

Back 68

when a sediment laden current slows down and deposits particles coursest at the bottom and finest at the top due to a short lived turbidity current

Front 69

mudcracks

Back 69

when clay or mud dries out, it contracts and causes cracks to form

Front 70

diagenesis

Back 70

the physical, chemical, and biological processes that take place after sediment is deposited but before metamorphism occurs

Front 71

sedimentary facies

Back 71

sedimentary rocks characterized by chemical, physical or biological features that reflect a specific environment of deposition

Front 72

what is metamorphism

Back 72

a solid state transformation of pre existing rocks occuring well below the earth surface in response to heat, pressure and chemically active fluids.. there is a change in mineralogy, texture and structure

Front 73

heat and metamorphism

Back 73

about 100 to about 800 degrees. the geothermal gradient is about 25 degrees per km

Front 74

pressure and metamorphism

Back 74

about 1 k bar up to about 12 k bar. confining pressure increases with depth at about 250 bars per km. we also get directed pressure from things like plate tectonics with uneven direction

Front 75

fluids and metamorphism

Back 75

may be in pore spaces,, released by chemical reactions, in volatiles in magma, or migrating ions. fluids facilitate the growth of minerals because they increase the exchange of ions inducing chemical reactions. it is isochemical meaning that the net chemical composition of the rock does not change. h2o and co2 are usually present in metamorphic reactions

Front 76

classification of foliated metamorphic rocks (3)

Back 76

slaty: very fine foliations and parallel planes of splitting du to parallel minerals like mica and graphite
schistose: foliation in coursely grained rocks due to well developed parallelism of more than half of the minerals
gneissic: rocks are coarsely foliated and is more widely spaced. bands may be uniform or wavy

Front 77

classification of non foliated metamorphic rocks (2)

Back 77

granoblastic: a granular texture where recrystallization of minerals forms equidimensional crystals
hornfelsic: dense

Front 78

types of metamorphism (2)

Back 78

contact: due to heat from plutons. depth is < 8km and causes a halo or aureole, new minerals may form, intensity decreases away from the plutons and rocks are massive and non foliated

regional metamorphism: affects a large area, due o both heat and pressure, occurs at depth, rocks are compressed and deformed, there is directed pressure and this causes foliation. there is gradation in intensity of metamorphism

Front 79

index mineral

Back 79

characterizes a given intensity of metamorphism and has developed under a specific range of temperature and pressure conditions

Front 80

metamorphic zones

Back 80

an area of equal metamorphic intensity between isograds in which the mineral content in rocks remains constant

Front 81

isograd

Back 81

a line on a map connecting points of equal metamorphic intensity, usually indicated by the first appearance of a given index mineral

Front 82

metamorphic facies

Back 82

metamorphic rocks characterized by mineral assemblages that have formed within specific pressure-temperature conditions

Front 83

migmatite

Back 83

high-grade regional metamorphism. light coloured silicates will melt faster than dark ferromagnesians, so light bands of igenous rock will crosscut or parallel the foliation of the older darker rock. this is a mixed rock

Front 84

paired metamorphic belts

Back 84

in some regions, blueschist facies were found close to amphibolite or granulite facies rocks. these paired belts were difficult to explain until the advent of plate tectonic theory and the process of subduction.

Front 85

what is weathering

Back 85

an in situ change in rocks and minerals with little or no transport of particles occuring at or near the surface due to the atmosphere, water and living organisms

Front 86

physical weathering and its types

Back 86

Disintegration of rocks and minerals into smaller pieces

1. frost action, exfoliation(due to unloading), temperature changes, living organisms

Front 87

chemical weathering, its types, and its products

Back 87

decomposition or transformation of rocks and minerals as they are chemically altered

1. types: solution, hydration, oxidation and hydrolysis
2. products of chemical weathering are salts in solution, iron oxide, silica in solution and clay minerals

Front 88

factors influencing rates of weathering (6)

Back 88

-joints: more fractures = more surface area
-particle size: more surface area with wider particles
-depth: more rapid weathering at surface
-slope: weathered products move down slope
-composition: minerals weather in the same order as in bowen's reaction series, quartz is quite resistant
-climate: humid and tropical climates have rapid chemical weathering as well as climates with frost thaw cycles (frost action)

Front 89

differential weatheirng

Back 89

variations in rate of weathering creating land forms

Front 90

regolith

Back 90

discontinuous cover of unconsolidated weathered rock debris overlying solid bed rock

Front 91

soil

Back 91

upper part of the regolith

Front 92

erosion

Back 92

a process where rock and mineral particles are picked up and transported from 1 place to another

Front 93

deposition (7 types)

Back 93

when an erosional agent can no longer transport sediment, deposits are formed
-fluvial: streams
-marine: salt water
-glacial: ice
-Aeolian: wind
lacustrine: lakes

Front 94

spheroidal weathering

Back 94

chemical weather attacks the edges and corners first. as the outer layers of rounded blocks undergo chemical weathering, newly formed clay minerals take up more volume than previous minerals and the volume expansion causes cracks and the outer shells fall of creating boulders