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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
Fusion
Combination of two or more nuclei; byproduct is radiation (heat, light) Responsible for the formation of elements
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***Example of Fusion: Hydrogen Burning
Occurs at ~10 million K
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Hydrostatic Equilibrium
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!
28
Star Collapse (ex. For Hydrogen Burning)
Run out of hydrogen at the core → fusion stops → pressure from hot gas lost → collapse (star transitions to ‘dying phase’)
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Evolution Rate in Stars: Low-Mass VS High-Mass
Low-Mass: - Evolution slow = dramatic change at each stage High-Mass: - Evolution fast = stages blur together
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Low-Mass Star Evolution
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
Red Giant (Low-Mass Stars)
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
High-Mass Star Evolution ***For stars at more than 8 solar masses
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
Problem of Iron (During Fusion)
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
Supernova (High-Mass Star Stage)
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
Evidence for the Formation of the Solar System
1. Astronomical Observations = sequence of events - T Tauri Stars - Proplyds 2. Meteorite Studies = snapshots of time, age Carbonaceous Chondrites
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T Tauri Stars
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
Proplyds
Disks of dust and gas around young stars (the contraction of “protoplanetary disks”) - Observed in other nebulae
38
Nebula ***Formation of Our Solar System
Dusty, dense gas cloud (1000 gas molecules/10cm3) - Molecules become attracted to one another during gravitational collapse - Cause = supernova nearby
39
Nebular Contraction
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
Nebular Condensation
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
Location of Nebular Condensation
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
Meteorites
An extraterrestrial rock that has fallen though our atmosphere
43
Carbonaceous Chondrites
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
Accretion of Planets
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
Planetesimals
Small solid bodies formed from grain to grain accretion of dust (electrostatic forces) - Will collide to form planets (via accretion)
46
Type of Planet Accretion: Runaway Growth
Early growth stage, planetesimal developed it’s own gravity
47
Type of Planet Accretion: Oligarchic Growth (Pac-Man)
Later growth stage, swoops in and attracts everything - Earth’s Heavy Bombardment period
48
***Differentiation in Planets (“layer cake”)
The separation of materials in a planetary body according to density and chemical affinity - Most dense = core - Heat required (for elements to flow)
49
Sources of Planetary Heat
1. Accretionary 2. Core Formation 3. Radiogenic 4. Solar Energy 5. Tidal
50
Sources of Planetary Heat: Accretionary
Kinetic Energy converted into Heat → trapped in the planet - During Planet Accretion/Differentiation period
51
Sources of Planetary Heat: Core Formation
Gravitational Potential Energy converted into Heat → molten iron moves to core - During Planet Differentiation period
52
***Sources of Planetary Heat: Radiogenic
Decay of radioactive atoms in planet interior - Current source
53
Sources of Planetary Heat: Solar Energy
Electromagnetic waves (light) from the nuclear fission in the sun - Current source
54
Sources of Planetary Heat: Tidal
Friction-produced heat from the expansion/contraction of a nearby body (moon) due to changes in gravitational forces - Current source
55
Methods of Heat Transfer ***convection in planet interior → heat conducted to surface → radiated into space
1. Conduction 2. Convection 3. Radiation
56
Conduction
Vibrational energy of an atom is transferred to adjacent atoms - Ex. For rigid solids, like Lithosphere
57
Convection ***More efficient than conduction!
Warm material expands and moves upwards → displaces cold/dense material downwards - Ex. Liquid core (Magnetosphere and Asthenosphere)
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Radiation
Electromagnetic waves from a hot body emit to its surroundings - Ex. The Sun
59
Geological History Reflects Thermal History
Amount of heat lost by planet depends on crustal thickness
60
***Effect of Planetary Size on Heat Loss
Larger surface area (relative to mass) = larger heat loss - Moon = most heat loss
61
***Impact Cratering ***Formation of Earth’s moon, mass extinction events
Collision of a planetary bodies that results in shock metamorphism from the hypervelocity of the 2 bodies - Lots of energy/heat upon collision
62
Bolide
Meteorite or comet
63
Stages of Impact Cratering
1. Compression 2. Excavation 3. Modification
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Stage of Impact Cratering: Compression
Shock waves expand out from point of impact - Rock compressed to ⅓ original size - Rock flows like fluid (hot temp accompanying impact = melting)
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Stage of Impact Cratering: Excavation
Target rock/bolide (now vaporized) flows, sprayed out of the transient (growing) cavity - Ejecta = rock traveling out of cavity as a conical sheet
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Stage of Impact Cratering: Modification ***For larger structures
Inability of gravity to sustain the cavity results in a rebound (slumping of crater walls, central uplift)
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Impact Melt Sheet
Sheet of molten rock around the crater (result of heat)
68
Breccia
Pieces of rock that flow out of crater, fall back in
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Tektites
Molten rock cools in atmosphere, then fall back down
70
Ejecta Rays
Result when a piece of ejecta creates its own nearby crater = Secondary Crater

EAS 206 (4 decks)

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