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EAS 206 > Geological Processes > Flashcards

Geological Processes Flashcards

1
Q

Geology

A

“geo” = Earth, “logos’ = study
- Basis to which we can compare other planets

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2
Q

3 Main Rock Types

A
  1. Igneous = solidified from molten rock (magma = in Earth, lava = on surface)
  2. Sedimentary = composed of layers
  3. Metamorphic = igneous/sedimentary rocks are changed by environmental factors (heat, pressure, etc)
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3
Q

Geology Principle: Law of Original Horizontality

A

Sedimentary layers are deposited horizontally and continuous

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4
Q

Geology Principle: Law of Superposition

A

In sedimentary rock, layers are ordered oldest (bottom) to youngest (top)

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5
Q

Geology Principle: Law of Cross-Cutting Relationships

A

If an impact crater or rock body cuts through another rock, the ‘cutting’ rock must be younger in age

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6
Q

Geology Principle: Law of Inclusion

A

A rock included in another is older than the rock that includes it

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7
Q

Crust

A

Outermost layer (top of mantle)
- Composition varied

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8
Q

Mantle

A

Layer beneath crust; includes asthenosphere
- Composition is iron, magnesium and silicate minerals

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9
Q

Core

A

Solid inner layer; liquid outer layer
- Composition is iron (dense)

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10
Q

***Asthenosphere

A

Part of mantle, exists close to melting point (flows, close to melting point)
- Not all magma, but SOURCE of magma

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11
Q

***Lithosphere

A

Uppermost part of mantle, part mantle and part crust
- Rides on ‘plastic’ asthenosphere
- Plate tectonic movement, but does NOT include continental crust

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12
Q

Moho (Crust and Mantle Boundary)

A

After Andrija Mohorovicic, detected by examining seismic waves moving through Earth

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13
Q

Evidence of the Earth’s Interior: Density

A

Water density = 1.0g/cm3, rocks at surface = 2.0-3.5g/cm3, but bulk density of Earth = 5.5g/cm3
- Therefore interior must be more dense

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14
Q

Evidence of Earth’s Interior: Seismic Waves

A

Velocities of (earthquake) energy waves change according to density they pass through
- S(econdary) waves transmitted in liquid, p(ressure) waves are not
- Both waves SLOW in the asthenosphere

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15
Q

Evidence of Earth’s Interior: Meteorites

A

Iron meteorites = fragments of core; Stony meteorites = fragments of mantle (of a now disrupted planetary body)

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16
Q

Evolution of Earth’s Surface

A

***Supercontinents –> Columbia, Rodina, Pannotia, Pangea
- Breakup of Pangea contributed to Permian extinction event (biggest in history)

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17
Q

Current Geological Processes on Earth

A

Vulcanism (due to plate tectonics), rock ‘folding’ (due to plate tectonics), plate drifting, dendritic (water) drainage, sediment deposits (from water), dust storms & dune fields (wind), glaciers, impact craters (in turn undergo erosion),

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18
Q

***The Geological History of the Earth

A

IMAGE

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19
Q

The Hadean (Hades = Hell)

A

Accretion of millions of planetesimals/heavy bombardment
- Extremely hot
- Differentiation of iron to core, silicates to mantle, gases to atmosphere & magma ocean
- Moon-forming event

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20
Q

The Archean (“Ancient”)

A

Formation of continental nuclei and origin of primitive life/production of oxygen
- Condensation of oceans, removal of water vapor??

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21
Q

The Proterozoic (“Proto-life”)

A

Stabilization of continents (stronger lithosphere = shift towards modern plate tectonics)
- Removal of CO2 via chemical weathering
- Global increase in O2 (resulted in banded iron formation)

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22
Q

The Phanerozoic (“Evident Life”)

A

Formation and breakup of Pangea; results in:
- Expansion of life in oceans onto land
- Glaciation
- Sedimentary rock formation

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23
Q

Galaxy

A

Collection of a few hundred million to trillion stars (solar systems)
- Ex. Milky Way Galaxy (formed ~10 BYA, while our solar system formed 4.5 BYA → 4.567 +/- 0.0001)

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24
Q

Galaxy Supercluster

A

Tightly packed chain/sheets of galaxies

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25
Q

Fusion

A

Combination of two or more nuclei; byproduct is radiation (heat, light)
Responsible for the formation of elements

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26
Q

***Example of Fusion: Hydrogen Burning

A

Occurs at ~10 million K

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27
Q

Hydrostatic Equilibrium

A

The state in which a star exists where the inside pressure force (resulting from the heat/hot gas of fusion) matches the outside force of gravity
- Without fusion occurring, star will collapse!

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28
Q

Star Collapse (ex. For Hydrogen Burning)

A

Run out of hydrogen at the core → fusion stops → pressure from hot gas lost → collapse (star transitions to ‘dying phase’)

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29
Q

Evolution Rate in Stars: Low-Mass VS High-Mass

A

Low-Mass:
- Evolution slow = dramatic change at each stage
High-Mass:
- Evolution fast = stages blur together

30
Q

Low-Mass Star Evolution

A
  1. Star begins ‘dying’ when helium core collapses = hydrogen burning stops, helium burning begins
  2. Hot, high pressure of the core’s collapse makes the shell (of burning hydrogen) expand → Red Giant
31
Q

Red Giant (Low-Mass Stars)

A

As core increases in heat/pressure (star gets BRIGHTER), shell of burning hydrogen expands to 100 times the star’s initial radius
Since the shell is the coolest = red in color

32
Q

High-Mass Star Evolution
***For stars at more than 8 solar masses

A
  1. Star begins ‘dying’ when the helium core collapses = hydrogen burning stops, helium burning begins…C, O, Ne, etc.
  2. Hot, high pressure of the core’s collapse makes the shell (of burning hydrogen) expand → Super Red Giant
33
Q

Problem of Iron (During Fusion)

A

Fusion stops at iron because it requires more energy than is produced = cost inefficient
- Iron will always weigh less than any combination of protons/neutrons

34
Q

Supernova (High-Mass Star Stage)

A
  1. Iron last to undergo fusion → gravity WINS and star contracts (creation of neutrons from electrons and protons)
  2. Star rebounds as a result of internal nuclear reactions; result is explosion

***Output of light is equal to the sun over it’s entire main sequence lifetime

35
Q

Evidence for the Formation of the Solar System

A
  1. Astronomical Observations = sequence of events
    - T Tauri Stars
    - Proplyds
  2. Meteorite Studies = snapshots of time, age
    Carbonaceous Chondrites
36
Q

T Tauri Stars

A

Stars similar in mass to our sun, but only 1 million years old
- Central mass ignites and warms the inner part of nebula, while the outer nebula cools
- Observed in other nebulae

37
Q

Proplyds

A

Disks of dust and gas around young stars (the contraction of “protoplanetary disks”)
- Observed in other nebulae

38
Q

Nebula
***Formation of Our Solar System

A

Dusty, dense gas cloud (1000 gas molecules/10cm3)
- Molecules become attracted to one another during gravitational collapse
- Cause = supernova nearby

39
Q

Nebular Contraction

A

A flat spinning disk of gas as a result of angular momentum conserving motion around one axis
- Gasses collapse and cool in other direction
- Rotation of gas (centrifugal force) exactly matches pull of gravity = contraction stops

40
Q

Nebular Condensation

A

Gas condenses into solid material (the building blocks of planets); 2 types:
1. Refractory = materials that form solids at high temperatures
2. Volatile = Materials that form solids (condense) at low temperatures

41
Q

Location of Nebular Condensation

A

Refractory = inner/terrestrial planets, Kuiper belt (ice rich comets)

Volatile = gas giants and their icy moons

***Snow Line = approximately at the asteroid belt, the outer rim where solids can exist

42
Q

Meteorites

A

An extraterrestrial rock that has fallen though our atmosphere

43
Q

Carbonaceous Chondrites

A

One type of meteorite, derived from the asteroid belt
- Preserve a record of processes happening in the solar nebula
1. Calcium Aluminum Inclusions = first solids to form (volatile)
2. Chondrules = silicate from cooling droplets
3. Matrix = dust
4. Pre-Solar Grains = diamonds, etc. (from previous supernovas)
5. Radioactive Elements

44
Q

Accretion of Planets

A

Collision and cohesion of matter (and planetesimals) under the influence of gravity
- Abide by Gravitational Focusing → “the rich get richer and the poor get poorer”

45
Q

Planetesimals

A

Small solid bodies formed from grain to grain accretion of dust (electrostatic forces)
- Will collide to form planets (via accretion)

46
Q

Type of Planet Accretion: Runaway Growth

A

Early growth stage, planetesimal developed it’s own gravity

47
Q

Type of Planet Accretion: Oligarchic Growth (Pac-Man)

A

Later growth stage, swoops in and attracts everything
- Earth’s Heavy Bombardment period

48
Q

***Differentiation in Planets (“layer cake”)

A

The separation of materials in a planetary body according to density and chemical affinity
- Most dense = core
- Heat required (for elements to flow)

49
Q

Sources of Planetary Heat

A
  1. Accretionary
  2. Core Formation
  3. Radiogenic
  4. Solar Energy
  5. Tidal
50
Q

Sources of Planetary Heat: Accretionary

A

Kinetic Energy converted into Heat → trapped in the planet
- During Planet Accretion/Differentiation period

51
Q

Sources of Planetary Heat: Core Formation

A

Gravitational Potential Energy converted into Heat → molten iron moves to core
- During Planet Differentiation period

52
Q

***Sources of Planetary Heat: Radiogenic

A

Decay of radioactive atoms in planet interior
- Current source

53
Q

Sources of Planetary Heat: Solar Energy

A

Electromagnetic waves (light) from the nuclear fission in the sun
- Current source

54
Q

Sources of Planetary Heat: Tidal

A

Friction-produced heat from the expansion/contraction of a nearby body (moon) due to changes in gravitational forces
- Current source

55
Q

Methods of Heat Transfer
***convection in planet interior → heat conducted to surface → radiated into space

A
  1. Conduction
  2. Convection
  3. Radiation
56
Q

Conduction

A

Vibrational energy of an atom is transferred to adjacent atoms
- Ex. For rigid solids, like Lithosphere

57
Q

Convection
***More efficient than conduction!

A

Warm material expands and moves upwards → displaces cold/dense material downwards
- Ex. Liquid core (Magnetosphere and Asthenosphere)

58
Q

Radiation

A

Electromagnetic waves from a hot body emit to its surroundings
- Ex. The Sun

59
Q

Geological History Reflects Thermal History

A

Amount of heat lost by planet depends on crustal thickness

60
Q

***Effect of Planetary Size on Heat Loss

A

Larger surface area (relative to mass) = larger heat loss
- Moon = most heat loss

61
Q

**Impact Cratering
**Formation of Earth’s moon, mass extinction events

A

Collision of a planetary bodies that results in shock metamorphism from the hypervelocity of the 2 bodies
- Lots of energy/heat upon collision

62
Q

Bolide

A

Meteorite or comet

63
Q

Stages of Impact Cratering

A
  1. Compression
  2. Excavation
  3. Modification
64
Q

Stage of Impact Cratering: Compression

A

Shock waves expand out from point of impact
- Rock compressed to ⅓ original size
- Rock flows like fluid (hot temp accompanying impact = melting)

65
Q

Stage of Impact Cratering: Excavation

A

Target rock/bolide (now vaporized) flows, sprayed out of the transient (growing) cavity
- Ejecta = rock traveling out of cavity as a conical sheet

66
Q

Stage of Impact Cratering: Modification
***For larger structures

A

Inability of gravity to sustain the cavity results in a rebound (slumping of crater walls, central uplift)

67
Q

Impact Melt Sheet

A

Sheet of molten rock around the crater (result of heat)

68
Q

Breccia

A

Pieces of rock that flow out of crater, fall back in

69
Q

Tektites

A

Molten rock cools in atmosphere, then fall back down

70
Q

Ejecta Rays

A

Result when a piece of ejecta creates its own nearby crater = Secondary Crater

EAS 206 (4 decks)

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