Module 3 - Earth's Formation and Differentiation Flashcards

1
Q

Solar System Formation

A
  • 4.6 billion years ago
  • Formed from a pre-solar nebula, giant molecular cloud, mostly H2 and He
  • Cloud undergoes gravitational collapse
  • Cloud spins faster and makes proto-planetary disk and proto-sun, fusion starts, solar wind is high
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2
Q

Planetary Formation: Condensation

A
  • Gases forming solids
  • Hot nebular gases cool and solidify into solid grains of dust
  • Liquids not stable because pressure is too low
  • Solar wind drives many volatiles to outer solar system
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3
Q

Planetary Formation: Accretion

A
  • Dust grains join to eventually become planets
  • Planetesimals attract each other gravitationally
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4
Q

Earth’s Bulk Composition

A
  • Dominated by Fe, O, Mg, Si
  • Earth depleted in volatile elements
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5
Q

Differentiation of Rocky Planets

A
  • Process of forming layers
  • Rocky planets and large asteroids tend to have layered structure with a metallic core and silicate-rich crust
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6
Q

Earth’s Formation: Homogenous Accretion Model

A
  • All matter condensed in early stages
  • Accreted homogenous bodies
  • Then differentiate
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7
Q

Earth’s Formation: Heterogenous Accretion

A
  • More likely than homogenous accretion
  • Simultaneous condensation and accretion
  • Multiple melting episodes occurred
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8
Q

Stony Meteorites: Ordinary Chondrites

A
  • Contain a mix of metal, silicate and sulfide grains
  • Low volatiles
  • Low silica
  • Everything mixed together, no separation of components
  • Formed in inner asteroid belts from small undifferentiated bodies
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9
Q

Stony Meteorites: Carbonaceous Chondrites

A
  • most primitive chondrites represent pre-planetary nebula solar nebula composition
  • Volatile rich
  • calcium-aluminium inclusions represent the first solids formed in the protoplanetary disk
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10
Q

Stony Meteorites: Achrondrites

A
  • Larger crystal sizes and fewer volatiles than chondrites
  • Similar to igneous rocks
  • Represent silicate mantle composition
  • Fragments of differentiated asteroids/planets
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11
Q

Stony-Iron Meteorites

A
  • About equal amount of Fe-Ni alloy and silicate minerals
  • Likely formed from edge of core/mantle of differentiated asteroids
  • Fe-Ni = core
  • Silicates = mantle
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12
Q

Iron Meteorites

A
  • Mainly Fe-Ni alloy
  • Likely from core of differentiated asteroids
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13
Q

Siderophile

A
  • Fe loving
  • Mostly high-density transition metals
  • Dissolve in liquid Fe, sink to core
  • Don’t form oxides
  • Mostly metallic bonds
  • Eg. Fe, Ni, Au, Pt, Ir
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14
Q

Chalcophiles

A
  • love Cu
  • Readily bond with S
  • Intermediate density minerals
  • Some everywhere in earth
  • Eg, S, Cu, Ag, Cd, Hg, Ti, Zn, As
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15
Q

Lithophiles

A
  • Love rocks
  • Readily bond with Si and/or O
  • Low density minerals, do not sink to core
    0 Vast bulk of mantle and crust as silicate minerals
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16
Q

Atmophiles

A
  • love gas
  • Gaseous or liquid at earth surface T and P
  • Concentrate in the atmosphere (and hydrosphere)
  • Eg, N, noble gases, O, H
17
Q

Earth’s Atmospheric Composition

A
  • Started off high in H and He from sun
  • Has changed over time through many biogeochemical cycles such as photosynthesis and weathering
  • Gained N2 and O2
  • Lost CO2 and CH4
18
Q

Dissolved ions in seawater - Conservative

A
  • Constant concentration in water column relative to salinity
  • Eg. Br-, Cl-, Mg2+, Na+
19
Q

Dissolved ions in seawater - Recycled

A
  • Non-conservative, concentration increases with deeper water depth
  • Organic matter recycled through organisms
  • Eg. C, NO3-, HCO3-
20
Q

Dissolved ions in seawater -Scavenged

A
  • Non-conservative, concentration decreases with water depth
  • Adsorb to surfaces of solid particles and sink into sediments