Earth Science Review Bullets

Continental Drift & Plate Tectonics

• Alfred Wegener: proposed Continental Drift (continents once in $Pangaea$, later split)

• Key evidence: matching coastlines, fossil distribution (Glossopteris, Lystrosaurus), glacial striations, coal in polar regions, rock/mountain belts (Caledonian–Appalachian)

• Replaced by Plate Tectonics (lithosphere broken into $ext{≈15}$ major/minor plates)

• Abraham Ortelius: early atlas hinting at continental fit

Seafloor Spreading & Magnetic Reversals

• Harry Hess (SONAR mapping) → new oceanic crust forms at mid-ocean ridges, oldest near trenches

Plate Boundaries

• Divergent: plates move apart → mid-ocean ridges, rift valleys

• Convergent: plates collide → subduction zones, volcanic arcs, mountain ranges

• Transform: plates slide past → strike-slip faults (conservative)

Major & Minor Plates (examples)

• Pacific (largest), North American, Eurasian, African, Indo-Australian, Antarctic, South American

• Minor: Philippine Sea, Nazca, Arabian, Caribbean, Juan de Fuca, Somali

Earth’s Internal Structure

• Crust (continental, oceanic)

• Mantle: lithosphere (rigid) over asthenosphere (plastic; convection)

• Core: outer (liquid Fe-Ni) vs. inner (solid Fe-Ni)

• Discontinuities: $\text{Moho}$ (crust–mantle), Gutenberg (mantle–outer core), Lehmann (outer–inner core)

Earthquake Basics

• Sudden rock rupture along faults; studied by seismology (seismograph)

• Focus energy (magnitude: Richter) vs. surface effects (intensity: Mercalli)

• Pacific Ring of Fire: $\text{≈40 000 km}$ belt of quakes & volcanoes

Fault Types

• Normal (extension), Reverse/Thrust (compression), Strike-Slip (lateral), Oblique, Horst & Graben blocks

Volcano Classification

• Shield: broad, fluid lava (e.g.
  $Mauna\ Loa$)

• Composite/Stratovolcano: steep, explosive (e.g.
  $Mt.\ Mayon$)

• Cinder Cone: small, single-vent, short-lived

• Lava Dome: viscous plug

• Activity: Active (erupting/likely), Dormant ($\le10^4$ yr silence), Extinct (>$10^4$ yr, no signs)

Weathering, Erosion & Deposition

• Physical: temperature changes, frost-wedging, abrasion, biotic action, salt crystallization

• Chemical: dissolution, oxidation; forms sediments

• Erosion agents: water, wind, gravity, ice, organisms

• Deposition: settling of transported material

Endogenic vs. Exogenic Processes

• Endogenic (internal): diastrophism, orogeny, epeirogeny, volcanism, plutonism

• Exogenic (external): weathering, erosion, mass wasting, driven by solar energy & gravity

• Uniformitarianism: present processes = key to past; Catastrophism: sudden, rare events

Hydrosphere & Water Cycle

• 97.5% ocean (saline water); 2.5% freshwater (1.7 glaciers, 0.77% readily consumable)

• Processes: evaporation → condensation → precipitation → runoff/infiltration → storage

• Reverse osmosis: desalination method

Biogeochemical Cycles (core points)

• Oxygen: produced by photosynthesis (plants, phytoplankton)

• Carbon: exchange among atmosphere, biosphere, oceans; human emissions raise carbon dioxide

Geological Time & Supercontinents

• Supercontinent sequence: Valbara (3.6 billion years ago), Ur (3.1 billion years ago), Kenorland  (2.6  billion years ago), Columbia/Luna (1.8 Billion years ago), Rodinia (1.1 years ago),  Pannotia (600-540 million years ago), Pangaea (300 years ago)

• Geological Time Scale: eons → eras → periods → epochs; established via stratigraphy & fossil records

Atmosphere Layers (bottom ↑)

• Troposphere (weather): Extends from surface to ≈8−15 km≈8−15 km; temperature decreases with altitude from an average of 15∘C15∘C at the surface to −55∘C−55∘C at the tropopause.

  Stratosphere (ozone): Extends from ≈15−50 km≈15−50 km

  Mesosphere: Extends from ≈50−85 km≈50−85 km

  Thermosphere (ionosphere): Extends from ≈85−600 km≈85−600 km

  Exosphere: Extends from ≈>600 km≈>600 km outwards

Key Institutions & Tools

• PHIVOLCS: monitors Philippine volcanism & earthquakes (est. Sept 17 1984)

• SONAR & GPS(Global Positioning System: map seafloor, track plate motion