Earth Science – 1st Quarter Comprehensive Revision Notes

Introduction and Course Overview

• Course: C10 – Earth Science (STEM), Senior High School, Assumption College of Davao.
  • Core intent: Provide a planetary-scale background of Earth, its history, internal/external processes, resources, and related socio-ethical issues.
  • Pedagogical ethos: “MASAYA MAGING ASSUMPTIONISTA!” – learning should be fun, curiosity-driven, ethically rooted (cf. Laudato Si).
• Four major 1st-quarter modules covered in the transcript
  • Module 1 – The Universe & Solar System (Origin + Structure)
  • Module 2 – The Universe & Solar System (Characteristics of Earth)
  • Module 3 – Earth System (Subsystems & Interactions)
  • Module 5 – Earth Materials & Resources (Minerals & Rocks)

Structure, Composition, and Age of the Universe

• Working definition: “Universe” = all of space-time, matter, energy.
• Current composition (Planck/WMAP data)
  • $4.6\%$ baryonic matter (protons, neutrons, electrons ➔ atoms, planets, stars, etc.)
  • $24\%$ cold dark matter (gravitationally effective, non-luminous)
  • $71.4\%$ dark energy (drives accelerated expansion)
• Density: $\rho_{\text{universe}}\approx4.5\times10^{-31}\,\text{g\,cm}^{-3}$
• Size & age
  • Age: $13.8\,\text{Gyr}$ (twofold constraint: oldest stars + Hubble expansion rate)
  • Current observable diameter ≥ $91\,\text{Gly}$ (1 ly = $9.4607\times10^{12}\,\text{km}$)
• Homogeneity & isotropy
  • Large-scale (>100 Mpc) universe appears smooth (Cosmological Principle)
  • Clumpy on smaller scales: stars ⇒ galaxies ⇒ clusters ⇒ superclusters separated by vast voids.

Dark Matter and Dark Energy

• Dark Energy
  • Discovery pivot: 1998 HST observations of Type Ia supernovae ➔ accelerating expansion.
  • Candidate explanations
  • Cosmological constant $\Lambda$: energy intrinsic to space itself (Einstein’s “blunder”).
  • Quintessence: dynamic scalar field permeating space.
  • Modified gravity: breakdown of General Relativity (GR) at cosmic scales.
  • Quantitative dominance: $\sim68\%$ of total cosmic energy budget.
• Dark Matter
  • Evidenced by galaxy rotation curves, gravitational lensing, cosmic structure formation.
  • Exclusions: stellar/planetary baryons, baryonic gas clouds, antimatter, galactic-scale black holes.
  • Viable candidates
  • MACHOs (brown dwarfs, compact halo objects – baryonic but dark)
  • Non-baryonic WIMPs, axions, sterile neutrinos.

Stellar Evolution

• Primordial elements: H, He, Li ➔ form stars inside nebulae via gravitational collapse.
• Protostar stage ➔ onset of thermonuclear fusion (H → He) ➔ Main-Sequence.
  • Sun-like stars: main-sequence lifetime ≈ $10^{10}\,\text{yr}$.
• Post-main-sequence pathways
  • Low-/intermediate-mass (≤1.4 $M_\odot$ core): red giant ➔ planetary nebula ➔ white dwarf.
  • Possible novae in close binaries; Chandrasekhar limit $1.4\,M_\odot$ triggers Type Ia supernovae.
  • Massive stars (>8 $M<em>\odot$): core iron build-up ➔ core collapse supernova ➔ neutron star ($1.4{-}3\,M</em>\odot$) or black hole (≥$3\,M_\odot$).
• Stellar deaths recycle heavy elements (“metals”) into the ISM, seeding future generations of stars & planetary systems.

Galaxies and Large-Scale Structure

• Galaxy: gravitationally bound ensemble of $10^{8}{-}10^{12}$ stars + gas + dark matter.
• Galaxies cluster → superclusters; immense voids between.
• Despite clumpiness, averaged cosmic scales satisfy homogeneity/isotropy assumptions.

Theories on the Origin of the Universe

• Pre-scientific cosmogonies: Egyptian sun-emergence myth; Kuba (Mbombo) creation vomiting; countless cultural narratives.
• Steady-State Model (Bondi, Gold, Hoyle, 1948)
  • Eternal universe with continuous matter creation to keep density constant as it expands.
  • Falsified by discovery of cosmic microwave background (CMB) and observed element abundances.
• Big Bang Theory (current consensus)
  • Initial hot, dense singular state at $t=0$ followed by expansion & cooling.
  • Underpinned by
  • General Relativity (geometry-gravity link)
  • Cosmological Principle (homogeneous & isotropic baseline)
  • Timeline highlights
  • $10^{-43}\,\text{s}$ – Planck epoch (all forces unified).
  • $10^{-32}\,\text{s}$ – Inflation (exponential expansion).
  • $10^{-6}\,\text{s}$ – quark confinement; hadrons form.
  • $3\,\text{min}$ – Big Bang nucleosynthesis ➔ $\text{H},\,\text{He},\,\text{Li}$ nuclei.
  • $3.8\times10^{5}\,\text{yr}$ – recombination; photons decouple ➔ CMB.
  • $1\times10^{8}\,\text{yr}$ – first stars, galaxies; stellar nucleosynthesis makes C, heavier elements.
  • $9.8\,\text{Gyr}$ – Solar System forms.
  • $13.8\,\text{Gyr}$ – present; expansion accelerates (dark-energy dominance).

Evidence Supporting the Big Bang Theory

• Universal Expansion (Hubble 1929)
  • Galaxy redshifts obey $v=H<em>0d$ where $H</em>0\approx70\,\text{km\,s}^{-1}\text{Mpc}^{-1}$.
  • Redshift analogous to Doppler shift (longer wavelengths ⇒ recession).
• Cosmic Microwave Background (Penzias & Wilson 1964)
  • Black-body spectrum at $T\approx2.725\,\text{K}$, isotropic to $10^{-5}$ level.
  • Tiny anisotropies imaged by COBE, WMAP, Planck ➔ seeds of structure formation.
• Primordial element abundances
  • Big Bang nucleosynthesis predicts $\sim75\%$ H, $\sim25\%$ He, traces of $\text{Li},\,\text{D}$ – matches observations.

Earth and Planetary Habitability

• Terrestrial planet comparison (NASA planetary fact sheet)
  • Mass/size: Venus ~$0.815\,M<em>\oplus$, Earth $1\,M</em>\oplus$, Mars ~$0.107\,M_\oplus$.
  • Surface temp: Venus $\sim735\,\text{K}$, Earth $288\,\text{K}$, Mars $210\,\text{K}$.
  • Atmospheric composition: Venus $\text{CO}<em>2$-dom., Earth N$</em>2$–O$<em>2$, Mars thin $\text{CO}</em>2$.
  • Pressure: Venus $\sim92\,\text{bar}$, Earth $1\,\text{bar}$, Mars $0.006\,\text{bar}$.
• Key habitability factors
  • Liquid-water stability zone (circumstellar habitable zone)
  • Suitable atmosphere (pressure & composition) for greenhouse regulation and UV shielding
  • Magnetic field for solar wind protection
  • Plate tectonics for carbon-silicate feedback & nutrient recycling
  • Stable climate timescales $\geq10^{8}\,\text{yr}$ for biological evolution
  • Presence of life-essential chemicals (CHNOPS elements).

Earth as a System of Interacting Subsystems

• System concept: interdependent components exchanging matter & energy.
• Four subsystems
  • Atmosphere – gaseous envelope (~80 000 km; 97 % within first 29 km).
  • Hydrosphere – liquid & frozen water (~70 % of surface, includes cryosphere).
  • Geosphere/Lithosphere – rocks, minerals, interior layers.
  • Biosphere – all living organisms.
• Cross-boundary fluxes
  • Water cycle, carbon cycle, energy balance (radiation ↔ greenhouse gases), biogeochemical interactions.

Minerals: Definition, Properties, Classification, and Importance

• Mineral criteria: inorganic, naturally occurring, solid, definite chemical composition, orderly internal (crystal) structure.
• Physical properties (hand-specimen ID)
  • Luster (metallic vs non-metallic subtypes)
  • Color vs Streak (powder color)
  • Hardness (Mohs scale 1–10; talc 1, diamond 10)
  • Crystal habit/form (prismatic, tabular, etc.)
  • Cleavage (planes of weakness) vs Fracture (conchoidal, uneven…)
  • Specific gravity $\text{SG}=\frac{W<em>{\text{mineral}}}{W</em>{\text{water}}}$ (dimensionless)
  • Special tests: magnetism (magnetite), effervescence in $\text{HCl}$ (calcite), taste (halite), odor (sulfur).
• Chemical classes (anion basis)
  • Silicates $(\text{SiO}<em>4)^{4-}$ – e.g., olivine $(\text{Mg,Fe})</em>2\text{SiO}<em>4$, quartz $\text{SiO}</em>2$.
  • Sulfides $\text{S}^{2-}$– pyrite$\text{FeS}_2$, galena$\text{PbS}.
  • Carbonates (\text{CO}3)^{2-}$– calcite$\text{CaCO}3$, dolomite$\text{CaMg(CO}3)2.
  • Oxides $\text{O}^{2-} – hematite $\text{Fe}<em>2\text{O}</em>3$, magnetite $\text{Fe}<em>3\text{O}</em>4$.
  • Halides (F⁻, Cl⁻, Br⁻, I⁻) – halite $\text{NaCl}$.
  • Sulfates $(\text{SO}<em>4)^{2-}$ – gypsum $\text{CaSO}</em>4·2\text{H}_2\text{O}$.
  • Phosphates $(\text{PO}<em>4)^{3-}$ – apatite $\text{Ca}</em>5(\text{PO}<em>4)</em>3\text{F}$.
  • Native elements – Au, Ag, Cu, C (diamond, graphite).
• Societal value & issues
  • Minerals underpin technology, construction, energy, agriculture.
  • Unsustainable extraction ➔ habitat loss, pollution, social conflicts (e.g., Surigao nickel mining, Mindanao coal vs IP communities).
  • Mitigation: responsible mining, rehabilitation, strict EIA, community consultation.

Rocks: Igneous, Sedimentary, Metamorphic, and the Rock Cycle

• Rock definition: coherent aggregate of one or more minerals.
• Igneous Rocks
  • Origin: cooling & solidification of magma/lava.
  • Intrusive (plutonic) vs Extrusive (volcanic).
  • Textures: phaneritic, aphanitic, porphyritic, glassy, pegmatitic, pyroclastic.
  • Compositional spectrum: mafic ↔ felsic; intermediate as middle.
• Sedimentary Rocks
  • Steps: weathering → erosion → transport → deposition → burial → compaction + cementation (lithification).
  • Types
  • Clastic (breccia, conglomerate, sandstone, shale).
  • Chemical (rock salt, chert, flint, some dolomites).
  • Organic/Bioclastic (limestone, coal).
• Metamorphic Rocks
  • Metamorphism drivers: heat, pressure, chemically active fluids.
  • Regional (orogenic) vs Contact (thermal) settings.
  • Foliated (slate → phyllite → schist → gneiss) vs Non-foliated (marble, quartzite, hornfels).
• Rock Cycle
  • Continuous transformation among three rock families via internal (endogenic) & surface (exogenic) processes.
  • Conceptual pathways
  • Magma crystallization ➔ igneous.
  • Weathering/erosion ➔ sediments ➔ sedimentary.
  • Heat/pressure ➔ metamorphic.
  • Melting of any rock ➔ magma (cycle restarts).
  • Practical relevance: soil genesis, reservoir prediction (fossil fuels in sedimentary basins), building material sourcing.

Environmental and Societal Implications of Mineral Extraction

• Mining impacts
  • Land degradation, deforestation, biodiversity loss.
  • Water contamination (acid mine drainage, heavy-metal runoff ➔ rust-red rivers in Surigao example).
  • Airborne particulates, greenhouse emissions.
  • Socio-political conflicts: displacement of Indigenous Peoples (e.g., Mindanao IP protests vs coal & military presence).
• Mitigation & stewardship principles (aligned with Laudato Si)
  • Sustainable development, circular economy, stringent environmental regulations.
  • Community participation, equitable benefit sharing.
  • Post-mining land rehabilitation, monitoring, and transparent reporting.