universe and the earth pt. 1 (mod #2)

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singularity

FORMATION OF THE UNIVERSE:

infinitely small region of space with zero volume and no dimensions;

this was the state of the universe before the Big Bang — it simply “was”

Big Bang Theory (Georges Lemaitre)

FORMATION OF THE UNIVERSE:

first proposed by _______ in the 1920s;

model that describes how the universe expanded from an initial state of extremely high density and temperature

93.5 billion light years

UNDER BIG BANG THEORY:

this is the diameter of the observable universe;

it’s increasing about 1.96 million km/s (6.5x faster than the speed of light)

Hubble’s Law

UNDER BIG BANG THEORY:

Galaxies move away from Earth at speeds proportional to their distance causing redshift

redshift

UNDER BIG BANG THEORY:

according to Hubble’s Law, _____ is the increase in wavelength of electromagnetic radiation from an object

Cosmic Microwave Background Radiation

EVIDENCE OF BIG BANG THEORY:

Relic electromagnetic radiation from the Epoch of Recombination where the

universe is 3000 K;

• Redshifted to present-day

• CMB radiation: 2.725 K

Abundance of Primordial Elements

EVIDENCE OF BIG BANG THEORY:

Hydrogen and Helium make up nearly all the nuclear matter

• Big Bang Nucleosynthesis: H, He and trace Be, Li

Nebular Hypothesis (Immanuel Kant & Pierre Simon de Laplace)

FORMATION OF THE UNIVERSE:
1. Sun, planets and objects in the Solar System formed from nebular material 4.6 (4.571) billions years ago;

2. Solar System began as a giant cloud of molecular gas and dust;

Nebular Hypothesis, Protoplanetary Disk

FORMATION OF THE UNIVERSE:

this hypothesis contains the following:
3. Rotating gas-dust cloud began to contract due to gravity;

4. Most material concentrated in the center to later form the Sun;

5. rest of the matter flattened out into the ________

hydrogen & helium

UNDER NEBULAR HYPOTHESIS:
the Sun is a main-sequence star composed mostly of ___ (~73%) and ____ (~25%) located at the center of the Solar System

• comprises 99.86% of the mass of the Solar System

stellar nucleosynthesis

UNDER NEBULAR HYPOTHESIS:

this refers to the ______ of chemical elements by nuclear fusion within stars

• H, He → … Fe, Ni

protoplanetary/accretionary disk

UNDER NEBULAR HYPOTHESIS:

refers to a rotating disc surrounding a young newly formed star;

electrostatic & gravitational interaction cause the dust and ice grains to condense and accrete into Planetesimals (kilometer-sized)

Planetisimals, Planetary embryos

UNDER NEBULAR HYPOTHESIS (PROTOPLANETARY DISK):

these are condensed from dust and ice grains due to electrostatic and gravitational interaction;

they then accrete to _____ _____ (moon-sized) that will collide and merge with each other to form the Terrestrial Planets

frost line

UNDER NEBULAR HYPOTHESIS (PROTOPLANETARY DISK):

this is the distance from a central protostar where it’s cold enough for volatiles to condense into solid ice grains

False; should be giant (jovian) planets

TRUE OR FALSE:

Planetary embryos made of ice that are more massive than those in the inner part, after attaining enough mass, begin to accumulate gas from the disk to form the terrestrial (inner) planet.

terrestrial (inner) planets

UNDER NEBULAR HYPOTHESIS (SOLAR SYSTEM):

rocky, composed mostly of silicates (Si, O) and metals (Fe, Ni) and lies within the frost line (less than 5 AU ~ 700 million km)

• Mercury, Venus, Earth and Mars

giant (jovian) planets

UNDER NEBULAR HYPOTHESIS (SOLAR SYSTEM):

composed of gases (H, He) and ice, and make up 99% of the mass of objects that orbit the Sun

• Jupiter, Saturn, Uranus and Neptune

asteroid belt; meteoroid

UNDER NEBULAR HYPOTHESIS (SOLAR SYSTEM):

belt of small bodies composed of refractory rock and metals located

between Mars and Jupiter

• ______: asteroid smaller than 1 m

Kuiper Belt

UNDER NEBULAR HYPOTHESIS (SOLAR SYSTEM):

disk composed of small bodies of rocks and ice (frozen volatiles like water, ammonia and methane) extending from the orbit of Neptune to ~50 AU from the Sun

Proto-earth

FORMATION OF THE EARTH:

this continued to accrete materials from the protoplanetary disk forming a body with relatively uniform composition

True

TRUE OR FALSE:

Heating caused the melting of materials in the protoplanet

• Collision of accreting materials

• Heat from the Sun absorbed by the Earth

• Contraction due to gravity

• Decay of radioactive materials.

siderophile, lithophile

FORMATION OF THE EARTH (DIFFERENTIATION):

*500 million years after earth formed (Hadean eon)

• Mobilization of denser Fe and Ni (_____) to migrate towards the center of the planet, forming the core – Iron Catastrophe

• Lighter and less dense silicates (_______; Si, O with Mg, Al, Ca, Na, K) rose to the surface forming the Mantle and the Crust

Giant-Impact hypothesis, Theia

FORMATION OF THE MOON:

Moon formed from the collision of the ancient planetesimal _____ with the proto-Earth around 4.5 billion years ago

origin of the atmosphere

FORMATION OF EARTH:

another stage of differentiation was the rise of the gasses towards the surface after

being trapped in the interior

Step 1: hydrogen & helium (atmophile elements)

ORIGIN OF ATMOSPHERE:

Step ___: 4.5 billion years ago, Primordial gases lost to space due to solar wind;

____ Atmosphere: _____ & _____ (______ elements)

Step 2: CO₂, NH₄, CH₄, H₂O (GHG)

ORIGIN OF ATMOSPHERE:

Step ___: 4.0 billion years, ago Volcanic venting (venting, outgassing, degassing) and gas capture of volatiles released from icy comets;

____ Atmosphere: _____ & _____ (______ elements)

Step 3: volcanic venting

ORIGIN OF ATMOSPHERE:

Step ___: Steady addition of gases from volcanoes (volcanic venting)

Step 4.0: cyanobacteria

ORIGIN OF ATMOSPHERE:

Step ___: 3.5 billion years ago, ______ (blue-green algae) developed photosynthesis and began converting CO₂ into O₂

Step 4.1: Great Oxidation event

ORIGIN OF ATMOSPHERE:

Step ___: refers to what happened ~2.4 billion years ago where there was a rise of O₂ in the atmosphere

comets, volcanic outgassing

ORIGIN OF OCEANS (HYDROSPHERE):

oceans may have began forming around 4.4 billion years ago;

hydrosphere was the result also of volcanic venting and gas capture;

Source of Water: ______, _____ ______

Young Earth Creationism → 6,000 years

AGE OF EARTH (EARLY ESTIMATES):

Based on biblical accounts (Genesis, Old Testament);

Estimated by Archbp. James Ussher (1650) based on successive generations

Cooling Rate → 75,000 years

AGE OF EARTH (EARLY ESTIMATES):

Proposed by Georges Louis Leclerc, Comte de Buffon (1788);

Based on the cooling rate of heated iron spheres

Earth’s Internal Heat → 20 to 30 million years

AGE OF EARTH (EARLY ESTIMATES):

Proposed by William Thomson (Lord Kelvin) (1897);

Based on estimated cooling rate of rocks by conduction

Saltiness of the Oceans → 100 million years

AGE OF EARTH (EARLY ESTIMATES):

proposed by John Joly (1899);

Based on accumulation of Na in the oceans

Sediment Deposition Rates → ~ 500 million years

AGE OF EARTH (EARLY ESTIMATES):

Proposed during the early 19th Century;

Based on total thickness of fossil

radiometric dating

AGE OF EARTH:

technique for dating materials by comparing the abundance of naturally occurring radioactive isotopes to the abundance of decay materials with respect to a known constant rate of decay

Narryer Gneiss Terrane Zircon, Acasta Gneiss

2 of oldest earth rocks

lunar rock, martian meteorites, canyon diablo meteorite, iron meteorite

4 examples of extraterrestrial materials

1. ____ ____ → 4.44 to 4.51 Ga

2. ____ ____ → 4.5 Ga

3. ____ ____ _____ → 4.53 to 4.58 Ga

4. ______ _______ → 4.54 ± 1% Ga

6,371 km, 5.98 × 10²⁴ kg, 23.44°

EARTH STATISTICS:

• Radius: _____ km

• Mass: ____ x 10___ kg

• Density: 5.51 g/cm3

• Axial Tilt: ___.__°

• Orbital Period: 365.256 days

• Distance (Sun): 149.6 million km (8.317 light-minutes)

• Chemical Composition (Bulk): Fe (32.1%), O (30.1%), Si, Mg, S, Ni, Ca, Al (1.4%)

1. Lithosphere

2. Asthenosphere

   1. Mantle Transition Zone

3. Lower Mantle

   1. D” Layer

4. Outer Core Inner Core

EARTH STRUCTURE:

Chemical Composition: Crust, Mantle, Core

Mechanical Properties/Rheology

1. Lithosphere

2. Asthenosphere (Mantle Transition Zone)

3. Lower Mantle (D” Layer)

4. Outer Core

5. Inner Core

Crust, Mohorovicic Discontinuity

EARTH LAYER (CHEMICAL COMPOSITION):

Thin and solid outermost layer

• Thickness: 5 to 70 km (varies)

• 0.7% of Earth’s mass

• <1% of Earth’s volume

• Bounded below by the _____ _____ (Crust-Mantle)

• Composed almost entirely of silicates

oceanic crust

2 TYPES OF CRUST:

Covers ~60% of the Earth’s surface

o Thickness: 5 to 10 km (average: 7 km)

o Dense and Homogenous

o Young (<200 Ma)

o Composition (SiMa):

o Silicates (Mg-rich)

o Basalt (Mg, Ca, Fe)

continental crust

2 TYPES OF CRUST:

Covers ~40% of the Earth’s surface

o Thickness: 30 to 70 km, up to 90 km (average: ~40 km)

o Less dense with diverse lithologies

o Old (>3.8 Ga)

o Composition (SiAl):

o Silicates (Alkali-rich)

o Volatiles / Radioactive

elements

o Granodiorite

mantle

EARTH LAYER (CHEMICAL COMPOSITION):

Thickness: ~2,800 km

o 67% of Earth’s mass

o 84% of Earth’s volume

o Bounded by the Mohorovičić

Discontinuity (Crust-Mantle) and

Gutenberg Discontinuity (Mantle-Core)

o Composition:

o Silicates (~45%) enriched in Fe-Mg

(relative to the Crust)

o Ultramafic (Peridotite-upper)

o Oxides (Fe, Mg, Al, Ca)

o Depleted in volatile and

radioactive elements

mantle

EARTH LAYER (CHEMICAL COMPOSITION):

Temperature: 200°C to 4,000°C

o Density: 4.5 g/cm3

o Pressure: 24 GPa to 139 GPa

o Subdivision:

o Upper Mantle

o Transition Zone

o Lower Mantle

core

EARTH LAYER (CHEMICAL COMPOSITION):

Thickness: 3,481 km

o 31 % of Earth’s mass

o 16% of Earth’s volume

o Composition:

o Fe (85.5%) – Ni (4.88%) alloy*

(siderophile elements)

o Minor O, H, C, S, Si (<10%)

o Trace K, U, Th (substantial source of heat)

o Bounded above by the Gutenberg

Discontinuity (Core-Mantle)

o Responsible for Earth’s Geodynamo /

Magnetic Field

melting, solidification

EARTH LAYER (RHEOLOGY):

Variability in Mechanical Properties

• Increase in both temperature and pressure

• Increase in temperature: melting

• Increase in pressure: solidification

• Response of each layer to dominant variable at

a certain depth

lithosphere

EARTH LAYER (RHEOLOGY):

Hard and rigid outermost shell

• Crust + Uppermost Mantle

• Subdivided into tectonic plates

• Thickness: 50 to 280 km

oceanic lithosphere

2 TYPES OF LITHOSPHERE:
Oceanic Crust + Uppermost Mantle

• Ocean basins, dense and young

• Thickness: 50 to 110 km

• Density: 2.9 g/cm3

• Composition:

• Mafic Crust (Basalt)

• Ultramafic Mantle

(Peridotite)

continental lithosphere

2 TYPES OF LITHOSPHERE:

Continental Crust + Uppermost Mantle

• Continents, light and old

• Thickness: 100 to 280 km

• Density: 2.7 g/cm3

• Composition:

• Felsic Crust (Granodiorite)

• Ultramafic Mantle

(Peridotite)

asthenosphere

EARTH LAYER (RHEOLOGY):

Asthenosphere

o Ductile layer below the lithosphere

o Mechanically weak and viscous

o Depth: 80 to 220 km

• Transition Zone

• Phase transition of olivine to wadsleyite

then ringwoodite

• Between 410 to 660 km depth

mesosphere

EARTH LAYER (RHEOLOGY):

Rigid, capable of flow

o Between 220 to 2900 km depth

o Bridgmanite (Mg-Perovskite) + Ferropericlase

• D” Layer

• 200 km thick layer at the Mantle-Core

boundary

• Hotspot plume source and slab graveyard

• Post-Perovskite

outer core

EARTH LAYER (RHEOLOGY):

Molten; low viscosity

o S-waves not transmitted

o Temperature: 2,730 to 4,230 °C

o Density: 9.9 to 12.2 g/cm3

• Lehmann Discontinuity (Outer-Inner Core Boundary)

inner core

EARTH LAYER (RHEOLOGY):

• Solid

o S-waves are transmitted

o Temperature: 5,100 to 5,400 °C

o Density: 12.6 to 13.0 g/cm