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geology > midterm > Flashcards

midterm Flashcards

1
Q

geology

A

evidence collected on every imaginable material to test hypotheses and develop theories on how the earth works

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2
Q

doppler effect and why is it important

A

the change in wave frequency during the relative motion between a wave source and its observer, important bc it explains red shift

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3
Q

theory vs law

A

theory: idea supported by lots of evidence
law: precise statement that always applies

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4
Q

star “fingerprint”? why are they significant?

A

Na, Mg, H, and Ca in stars can block certain wavelenghts of light, so they can be used to make a fingerprint

=> red shift = stationary stars have these bands shifted towards red, using doppler effect shows that distant stars moving farther away (universe ever expanding)

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5
Q

how old is the universe approximately?

A

15 billion

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6
Q

singularity theory?

A

everything in the universe used to be in one dot = Singularity, before big bang 13.8 bil years ago

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7
Q

what did the Big Bang form? (right after)

A

nebula separated by space => [98% H, 2% He, trace Li trace Be, trace B]

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8
Q

why do nebulas collapse and what happens?

A

particles have gravity so they are pulled towards each other, forms stars and galaxies

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9
Q

why are stars called “elements factory” and what happens when they “run out”

A

factory => nuclear fusion inside the stars gives us more elements (up until iron, nucleus is too strong can only be fused in a supernova)
runs out => when all the smaller elements (H, He) are used up, the star may collapse into a supernova (1/3 times)

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10
Q

nebular theory?

A

explains formation of our galaxy
1. nebula left over from supernova
2. nebula collapses & makes a new star
3. orbiting debris flattens into disc
4. planets formed from collisions of smaller debris, clumps form & get bigger n’ bigger (gravity UP)

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11
Q

why are the farther 4 planets gas giants?

A

volatile elements (evaporate easily) like carbon, nitrogen, hydrogen, and helium freeze when they are too far from the sun

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12
Q

what is the elemental composition of the universe vs earth (roughly)?

A

universe => hydrogen & helium
earth => silicon, oxygen, & iron

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13
Q

felsic vs mafic

A

felsic => high Al, Si
mafic => high Mg, Fe

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14
Q

lithosphere

A

crust + uppermantle
- felsic/mafic depending on crust on top
- brittle

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15
Q

aesthenosphere

A

upper mantle under lithos that convects
- ultramafic
- ductile

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16
Q

convection (geology)

A

density driven flow because of Hadley cells => as rock heats up & expands, it rises. when it hits the surface, it cools, gets denser, and sinks

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17
Q

continental crust

A

felsic, brittle, light (won’t submerge)

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18
Q

oceanic crust

A

mafic, brittle, heavy (will always submerge)

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19
Q

plate tectonic theory

A

Lithosphere split into 12 major plates

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20
Q

geothermal gradient & why

A

crust gets 20-30C warmer per km down
why => high pressure, residual heat from accretion (formation), radioactive decay (U, Th, K)

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21
Q

why is the earth a bar magnet?

A

the core has swirling Fe, Ni => generates electric currents
- dipole, field lines from south to north, which have REVERSED b4

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22
Q

alfred wegener

A

continental drift
- continental fit
- related rocks along cont. borders
- matching geology (mnts)
- fossil records
- NO ONE BELIEVED HIM BC HE WASNT A GEOLOGIST bc he was j a guy

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23
Q

midatlantic ridge & how was it discovered

A

divergent boundary (heart) found bc US wanted to hide nuclear subs (heart eyes) so they mapped the ocean
evidence:
- drilling in 60’s revealed no sediment on ridge but thicker towards continents
- rock dating revealed ridge is super young, older towards continents
- magnetism - rocks w/ Fe show poles reversing (same on each side)

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24
Q

marine magnetic anomalies

A

magnetometer measures magnetism as ship crosses ocean, its weird b/c of earth’s magnetic field and iron in rocks showing poles reversal

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25
Q

divergent boundary

A

constructive, 2 plates move away from mid-ocean ridge, shallow earthquakes

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26
Q

convergent boundary

A

destructive, 2 plates move towwards each other, denser oceanic subducts
=> mountains & volcanoes on the top plate form because the plate lifts up
=> OC-OC forms deep trenches bc both want to subduct

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27
Q

accretionary prism

A

sediment build up at a convergent boundary

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28
Q

transform boundary

A

2 plates slide past each other at a verticle fault
=> offset drain - when a stream’s flow is broken by transform boundary

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29
Q

continental rift

A
  1. continental crust stretches & thins
  2. breaks & forms faults
  3. parts of crust break & fall into rift valleys (low areas)
  4. aesthenosphere melts & rises, magma erupts out of volcanoes
    5a. continues: plate splits in 2
    5b. stops: rift fills w/ sediment
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30
Q

3 forces that cause lithosphere to move

A
  • convection: rising & sinking currents in the mantle
  • ridge-pull force: slope of lithosphere near ridge pushes outward from ridge
  • slab-pull force: heavy lithosphere pulls down the rest of the plate in subduction
31
Q

continental collision

A

OC-CC, when the oceanic part of OC all subducts, the land part of the OC crashes into the CC => forms a HUGE mountain range

32
Q

where in the earth’s layers and what type of boundary are these earthquakes [33-70km, 70-700km] at?

A
  • 33-70km: crust, divergent or transform
  • 70-700km: mantle, convergent
33
Q

hot spots & island chains

A

heat rising from the core rises through the mantle and melts the rock => crust is pierced and erupts w/ magma; island chains form from hotspots bc the crust moves but the hotspot still erupts, creating an island chain

33
Q

how were the himalayas formed?

A

India (CC) crashed into asia (CC)

34
Q

why does the pacific ocean grow faster than the atlantic ocean?

A

slab-pull from subduction

35
Q

minerals

A

naturally occuring solid w/ orderly structural arrangement & definite chemical composition

36
Q

magma & formation

A
  • liquid rock below the surface,
  • formation: decompressional melting - when hot mantle rock rises as pressure decreases, it melts
  • can cool at depth in lithosphere ex: granite
37
Q

lava

A
  • liquid rock above the surface
  • can cool quickly at earth’s surface ex: basalt
38
Q

how can you melt rock?

A
  • water (liquifies minerals)
  • heat
  • decreasing pressure
39
Q

why is the mantle solid (even tho it’s super hot)?

A

PRESSURE

40
Q

types of mineral structures

A

in chronological order (as magma cools)
- independent/isolated: ionic
- single chain: mix
- double chain: mix
- sheet: mix
- framework: covalent (but it can also form first idfk)

41
Q

bowen’s reaction sequence w/ strucutrew/ mafic/felsic

A
  • mafic: olivine (isolated), pyroxene (single chain), Ca-rich plagioclase (framework)
  • intermediate: amphibole (double chain), micas (sheet), Na-rich plagioclase (framework)
  • felsic: K-rich feldspar (framework), muscovite mica (sheet), quartz (framework)
42
Q

fractionalized crystallization

A

minerals will cool & fall out of liquid rock

43
Q

igneous rocks (intrusive)

A
  • intrusive: magma, large & coarse grain from slow cooling
    > felsic: pink & light grey
    >mafic: dark grey & black

in mafic => felsic order…
gabbro, diorite, granite

44
Q

why are igneous rocks geologically constructive?

A

they are always found where new rock is being formed (hot spots, divergent boundaries, convergent boundaries, continental rifts), crust is being built w these

45
Q

where are volcanoes

A

hotspots, divergent boundaries, convergent boundaries, continental rifts

46
Q

why is the Seirra Nevada mnt range felsic even tho its a OC-CC boundary (mafic lithosphere melted to form it)?

A
  • partial melting (bottom of BRS aka felsic melts first)
  • felsic sediments (sand) from OC melts
  • crustal assimilation (felsic parts of crust melt first)
47
Q

why do mafic rocks make up the sea floor?

A

oceanic crust is mafic durr

48
Q

andesites

A

volcanoes make of intermediate rocks, lots of them at subduction zones (around the pacific)

49
Q

how does glass form :D

A

lava cools SUPA quickly

50
Q

divergent igneous composition

A

mafic, basalt over gabbro

51
Q

convergent igneous composition

A

intermediate/felsic, andesite & diorite and/or rhyolite & granite

52
Q

hot spot igneous composition

A

OC: basalt
CC: any

53
Q

continental rift igneous composition

A

any :D

54
Q

regolith

A

rubble/break down from erosion

55
Q

what are joints in rocks

A

cracks from change in pressure

56
Q

physical weathering

A
  • frost wedging
  • root wedging
  • thermal expansion
  • animal attack
57
Q

chemical weathering

A
  • dissolution: water molecules surround ions in minerals
  • hydrolysis: reaction with water changes minerals into new ones
  • oxidation: oxygen combines with iron in minerals to form weak, rusty minerals ew
  • hydration: minerals expand when absorbing water
58
Q

igneous structure vs sedimentary structure

A
  • igneous: form when melt cools, chrystalline (interlocking grains)
  • sedimentary: form when grains of preexisting rock stick together, clastic (cementic rocks)
59
Q

sedimentary rocks (near to source)

A

conglomerate:
- grains 2mm+
- fragments rounded
- mix of quartz, feldspar
- mountains
breccia:
- grains 2mm+
- angular clasts
* gravity driven transport
- landslides

60
Q

sedimentary rocks (far from source) (sandstones)

A

> 0.0063-2mm grains
well sorted
moderate energy environments (beaches, dunes, rivers)
arenite:
- grains rounded
- 90% quartz
* long distance transport
lithic sandstone:
- quatz, feldspar, rock fragments
* short distant transport
arkose sandstone:
- 25% orthoclase feldspar
* short distance transport

61
Q

sedimentary rocks (far from source)
(non-sandstones)

A

> well sorted
low energy environment
siltstone:
- 0.004-0.0063 grains
- feels gritty
- typically quartz
- lakes, delta, beaches
mudstone & shale:
- <0.004mm grains
- mostly clay
- deep water
- shale is LAMINATED
- mudstone breaks up into blocks
- shale breaks into thin sheets

62
Q

igneous rocks (extrusive)

A
  • lava, fine grain from fast cooling
    > felsic: pink & light grey
    >mafic: dark grey & black

in mafic => felsic order…
basalt, andesite, rhyolite

63
Q

sedimentary (biochemical)

A

fossiliferous limestone:
- CaCO2
- wam, shallow seas
coal:
- carbon rich
- oxygen poor environments ex: swamps

64
Q

cross beds

A

formed when currents change (sediments fall at different angles over time)

65
Q

pitted grains

A

grains with indentations formed from grains crashing into each other in wind

66
Q

how and where are metamorphic rocks formed?

A
  • how: add heat and/or pressure to a rock
  • where: subduction zones (H), hot spots (H), plate collision (H+P), bottom of sedimentary basin (H+P)
67
Q

how does metamorphism change a rock?

A

texture:
- rechrystallization: clastic to bigger, interlocking grains
- plastic deformation: grains get squished
- foliation: minerals align perpendicular to stress (lots can lead to compositional banding) only when there is pressure
minerology:
- minerals like garnets can grow

68
Q

shields (metamorphic rocks)

A

continental interiors where ancient high grade metamorphic rocks are exposed

69
Q

what type of rock are the oldest rocks?

A

metamorphic

70
Q

metamorphic rocks (foliated)

A

in order of increasing heat&pressure

slate:
- fine grains
- some foliation
> shale + HP
phyllite
- fine grains
- some foliation
- bigga grains than ^^
schist
- coarse grains
- foliated
- bigga grains than ^^
gneiss
- coarse grains + garnets
- foliated => comp. bonding
- granite is often protolith

71
Q

dropping shale vs slate on the table?

A

shale: thud, solid sounding
slate: pang, hollow sounding

72
Q

metamorphic rocks (non foliated)

A

marble:
- calcite (CaO3)
> limestone + HP
quartzite:
- arenite +HP
greenstone:
- mafic minerals
> basalt + HP

73
Q

where does metamorphism occur?

A
  • mid ocean ridge (hydrothermal vents give heat)
  • igneous intrusion (under volcano, rising plutons)
  • subduction zone (pressure = foliation)

geology (3 decks)

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