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
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
3
Q
Planetary Formation: Accretion
A
- Dust grains join to eventually become planets
- Planetesimals attract each other gravitationally
4
Q
Earth’s Bulk Composition
A
- Dominated by Fe, O, Mg, Si
- Earth depleted in volatile elements
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
6
Q
Earth’s Formation: Homogenous Accretion Model
A
- All matter condensed in early stages
- Accreted homogenous bodies
- Then differentiate
7
Q
Earth’s Formation: Heterogenous Accretion
A
- More likely than homogenous accretion
- Simultaneous condensation and accretion
- Multiple melting episodes occurred
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
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
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
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
12
Q
Iron Meteorites
A
- Mainly Fe-Ni alloy
- Likely from core of differentiated asteroids
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
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
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
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
