Internal Structure of Earth

MICRO-REALM 01

Chemical vs Mechanical

• Chemical: Crust, Mantle, Core
• Mechanical: Litho, Astheno, Meso
• Composition vs Rheology

MICRO-REALM 02

The Outermost Crust

<1% VOL

• Brittle outermost solid skin
• Under 1% Earth volume
• 0.5% of planetary mass

MICRO-REALM 03

Continental Crust (SIAL)

SIAL · 30 KM2.7 g/cm³

• Mean thickness $\sim 30\text{ km}$
• Felsic granitic rocks
• Lighter density ($2.7\text{ g/cm}^3$)

MICRO-REALM 04

Mountain Root Thickening

• Thickest under fold mountains
• 70 to 100 km in Himalayas
• Buoyant isostatic keel

MICRO-REALM 05

Oceanic Crust (SIMA)

SIMA · 5 KM

• Thinner ($5\text{ to }10\text{ km}$)
• Mafic basaltic rock
• Denser ($3.0\text{ g/cm}^3$)

MICRO-REALM 06

Oceanic Ophiolite Layers

• Top pelagic sediment ooze
• Pillow basalts & sheet dykes
• Young ($<200\text{ Ma}$) recycled

MICRO-REALM 07

Crustal Elements (OSiAlFe)

O

Si

• Oxygen: 46.6% by weight
• Silicon: 27.7% · Al: 8.1%
• Iron: 5.0% · Ca: 3.6%

MICRO-REALM 08

The Lithosphere

CRUST

TOP MANTLE

• Crust + uppermost solid mantle
• Thickness $10\text{ to }200\text{ km}$
• Brittle tectonic plates

MICRO-REALM 09

LAB Isotherm Boundary

1300°C LAB

• Lithosphere-Asthenosphere base
• Controlled by $1,300^\circ\text{C}$ heat
• Rigid rock turns ductile

MICRO-REALM 10

The Asthenosphere

• "Astheno" means weak
• Extends up to $400\text{ km}$
• Main source of magma

MICRO-REALM 11

Partial Melt & LVZ

• 1–2% intergranular melt
• Seismic Low-Velocity Zone
• Lubricates plate movement

MICRO-REALM 12

The Mantle (84% Volume)

84%

• Moho to $2,900\text{ km}$ depth
• 84% of Earth's volume
• 67% of Earth's mass

MICRO-REALM 13

Ultramafic Peridotite

• Olivine & pyroxene rich
• Upper density $3.4\text{ g/cm}^3$
• High Mg & Fe silicates

MICRO-REALM 14

Transition Zone (410–660)

RINGWOODITE H₂O

• $410\text{ to }660\text{ km}$ depth
• Wadsleyite & Ringwoodite
• Traps hydroxide water

MICRO-REALM 15

Lower Mantle (Mesosphere)

660–2,900 KM

• Beyond Asthenosphere to CMB
• Solid rigid state
• Density reaches $5.7\text{ g/cm}^3$

MICRO-REALM 16

Bridgmanite Perovskite

• Earth's most abundant mineral
• $(\text{Mg,Fe})\text{SiO}_3$ perovskite
• Stable under extreme pressure

MICRO-REALM 17

Solid-State Convection

• Creeps cm per year
• Hot mantle rises upward
• Drives surface tectonics

MICRO-REALM 18

Subducted Slab Graveyard

• Cold oceanic plates sink
• Pierce 660 km boundary
• Pile at base of mantle

MICRO-REALM 19

D'' (D-Double-Prime) Layer

• Bottom $200\text{ km}$ of mantle
• Post-perovskite phase
• Ultra-Low Velocity Zones

MICRO-REALM 20

Deep Mantle Plumes

• Buoyant thermal diapirs
• Rise from D'' boundary
• Feed Réunion & Hawaii

MICRO-REALM 21

Core-Mantle Boundary

SILICATE 5.7

IRON 9.9

• Located at $2,900\text{ km}$
• Density jumps $5.7 \to 9.9$
• Sharper than surface air-rock

MICRO-REALM 22

The Core (15% Volume)

• $2,900\text{ to }6,370\text{ km}$ center
• 15% of Earth's volume
• 32.5% of Earth's mass

MICRO-REALM 23

NIFE Alloy Composition

NiFe

• Nickel (Ni) + Iron (Fe)
• 85% Iron · 5–10% Nickel
• Light elements (S, Si, O)

MICRO-REALM 24

Liquid Outer Core

• $2,900\text{ to }5,150\text{ km}$ depth
• Molten fluid state
• Density $9.9\text{ to }12.2\text{ g/cm}^3$

MICRO-REALM 25

Geodynamo Engine

• Convecting liquid iron
• Coriolis spiral currents
• Sustains geomagnetic shield

MICRO-REALM 26

Solid Inner Core

• $5,150\text{ to }6,370\text{ km}$ center
• Solid metallic sphere
• Density $13.0\text{ g/cm}^3$ at center

MICRO-REALM 27

Pressure Freezing

360 GPa

• Temp $\sim 5,500^\circ\text{C}$ (Sun surface)
• 3.6 million atm pressure
• Raises Fe melting point

MICRO-REALM 28

Inner Core Anisotropy

• Aligned iron crystals
• P-waves faster N–S axis
• Grows as outer core cools