0% of the question bank attempted

Four Earth spheres

Earth runs as interconnected systems exchanging matter and energy.
  • Geosphere: rocks, mantle, core — the solid Earth
  • Hydrosphere: all water (oceans 97%, glaciers 2%, fresh <1%)
  • Atmosphere: gas envelope — N₂ 78%, O₂ 21%, Ar ~1%
  • Biosphere: all life — overlaps every other sphere

Scientific method cycle

Science self-corrects through hypothesis testing.
  • Observation → question → hypothesis (testable!) → experiment → analysis → conclusion
  • Hypothesis must be falsifiable — 'untestable' claims aren't scientific
  • Theory = heavily-tested explanation bundle (not a 'guess'); law = what happens, theory = why
  • Controlled experiments change ONE variable (independent) and measure another (dependent)

Maps & rates

Topo maps and rate formulas are Earth science's daily tools.
  • Contour lines connect equal elevation; close spacing = steep slope
  • Gradient = (elevation difference) ÷ distance — usually ft/mi
  • Map scale converts map distance to real distance
  • Rate problems: distance ÷ time (stream flow, plate motion cm/yr)

Energy in Earth systems

Two engines power everything: solar (external) and planetary heat (internal).
  • Solar drives weather, ocean currents, water cycle, wind
  • Internal heat (radioactive decay + primordial) drives plate tectonics, volcanism
  • Energy transfers: conduction (contact), convection (fluid circulation), radiation (waves)
  • Density stratification explains layering: densest materials sink (iron core)
A theory is NOT a guess — it's a tested explanatory framework (theory of plate tectonics)
Ocean water is saltwater — don't count it as freshwater supply
Contour lines never cross — one point, one elevation

Layers & plates

The lithosphere rides on the asthenosphere in moving plates.
  • Crust (oceanic basalt denser / continental granite thicker) → mantle → outer core (liquid) → inner core (solid iron)
  • Lithosphere = crust + rigid upper mantle; floats on plastic asthenosphere
  • Plates move centimeters/year — about fingernail growth speed
  • Heat from radioactive decay powers convection currents driving plates

Divergent boundaries

Plates separate; new crust forms — mid-ocean ridges and rifts.
  • Seafloor spreading at mid-ocean ridges (Mid-Atlantic Ridge)
  • Magma rises, cools → new basaltic crust; magnetic striping records flips
  • Rift valleys on land (East African Rift) may become new oceans
  • Shallow earthquakes characterize divergent zones

Convergent boundaries

Collision courses produce subduction, mountains, and deep quakes.
  • Ocean-continent: denser oceanic plate SUBDUCTS → trench + volcanic arc (Andes)
  • Ocean-ocean: older/denser subducts → island arcs (Japan)
  • Continent-continent: no subduction, crumple into mountains (Himalayas)
  • Deep earthquakes only occur in subduction zones (Wadati-Benioff zone)

Transform boundaries & evidence

Slide-past boundaries and the proof that sealed the theory.
  • Transform faults: plates grind sideways — San Andreas Fault; shallow strong quakes
  • Fossil matches across oceans (Mesosaurus); mountain continuity
  • Glacial striations aligning when continents reassembled
  • Seafloor age increases with distance from ridge — smoking-gun proof
Inner core is SOLID despite being hottest — pressure forces solid state
Continents don't plow through ocean floor — plates carry both crust types
Not all boundaries make volcanoes: transform boundaries generally don't

Earthquake basics

Elastic rebound releases accumulated strain as seismic waves.
  • Focus (hypocenter) = rupture origin underground; epicenter = surface point above
  • P-waves: fastest, compressional, travel through solids AND liquids
  • S-waves: slower, shear, CANNOT pass liquids
  • Surface waves: slowest, most destructive (rolling/side-swipe)

Locating epicenters

Triangulation uses wave arrival-time differences.
  • P-S lag grows with distance from epicenter
  • One station gives a RADIUS circle; three stations' circles intersect at the epicenter
  • Travel-time graphs convert lag seconds into distance
  • Need minimum THREE stations for a unique location

Measuring & hazards

Magnitude scales measure energy; intensity varies locally.
  • Richter/modern moment magnitude: logarithmic — each unit = ~10× amplitude, ~32× energy
  • Mercalli intensity scale: I-XII based on observed damage (subjective)
  • Tsunamis from undersea quakes: warning = sudden sea withdrawal
  • Liquefaction: wet sediments behave like liquid during shaking

Volcano types & magma chemistry

Silica content controls explosiveness — the controlling variable.
  • Basaltic magma (low silica ~50%): runny → shield volcanoes, gentle Hawaiian eruptions
  • Andesitic (intermediate): composite/stratovolcanoes — alternating flows+ash (Fuji, St. Helens)
  • Rhyolitic (high silica ~70%): sticky → explosive caldera eruptions
  • Volatile (gas) content amplifies explosiveness with high silica
The epicenter is NOT underground — the focus is; epicenter is directly above on the surface
S-wave shadow zone proved the OUTER CORE is liquid — not inner
Bigger magnitude ≠ proportionally bigger shaking — logarithmic means counterintuitive jumps

Mineral properties

Minerals are naturally-occurring crystalline solids with defined chemistry.
  • Five criteria: natural, inorganic, solid, definite composition, ordered crystal structure
  • Hardness = Mohs scale 1-10 (talc→diamond); scratch tests order minerals
  • Luster: metallic vs non-metallic (glassy, pearly, dull)
  • Streak = powdered color on porcelain — more reliable than surface color
  • Cleavage vs fracture: clean planes vs irregular breaks

The rock cycle

Three rock families transform endlessly via melting, heat, pressure, weathering.
  • Igneous: cooled magma/lava (intrusive = inside, coarse crystals; extrusive = surface, fine/glassy)
  • Sedimentary: compacted/cemented sediments — often layered, sometimes fossils
  • Metamorphic: changed by heat+pressure WITHOUT melting (foliation banding)
  • Any rock type can become any other — cycle has no beginning

Rock identification logic

Texture + composition identify rocks stepwise.
  • Igneous texture: crystal size tells cooling speed (large=slow intrusive, small/fast=extrusive)
  • Sedimentary clues: layers, grains, fossils, cement
  • Metamorphic foliation: alignment from directed pressure (gneiss banding, slate splitting)
  • Common examples: granite, basalt, sandstone, limestone, shale, gneiss, marble, slate

Rock record & dating intro

Rocks archive Earth history; relative dating orders events.
  • Law of superposition: oldest layers on bottom (undisturbed)
  • Cross-cutting: intrusions/faults YOUNGER than the rocks they cut
  • Fossil succession: same fossil assemblage = similar age worldwide
  • Index fossils: widespread, abundant, short-lived species date layers
Streak beats color for ID — many minerals vary in surface color but constant in streak
Marble is METAMORPHosed limestone, not sedimentary anymore
Foliation needs PRESSURE direction, not just any metamorphism (marble doesn't foliate)

Weathering types

Breakdown happens chemically and physically in place.
  • Physical/mechanical: frost wedging, root pry, abrasion, exfoliation — size shrinks, composition unchanged
  • Chemical: oxidation (rust), hydrolysis (feldspar→clay), carbonation (limestone+dissolved CO₂)
  • Climate controls: chemical dominates warm-wet; physical dominates cold-dry/high altitude
  • Surface area feedback: broken pieces weather FASTER (more exposed faces)

Erosion & deposition agents

Gravity plus moving fluids transport and sort sediment.
  • Water #1 agent: streams carry, deposit by velocity (heavy first, fine last)
  • Sorted deposits: graded beds, deltas, point bars; unsorted: glaciers drop till
  • Wind: dunes and loess — only small particles
  • Wave action: beaches sort by wave energy; longshore drift migrates sand

Soil formation

Weathered rock + organics mature into soil horizons over centuries.
  • Horizons: O (organic litter), A (topsoil), B (subsoil accumulation), C (weathered parent)
  • Formation rates: ~1 inch per 100–400 years — effectively nonrenewable short-term
  • Climate + time + parent material + organisms + slope = five soil factors
  • Desert soils thin/salty; grassland soils deep/fertile (breadbaskets)

Geologic time & absolute dating

Deep time measured with radioactive decay clocks.
  • Half-life: time for HALF the parent isotope to decay — constant, measurable
  • Carbon-14 half-life 5,730 yrs → dates organic remains to ~50k yrs (not dinosaurs!)
  • U-238 (4.5 Byr) dates ancient igneous rocks → Earth ≈ 4.6 billion years
  • Geologic time scale: eons→eras→periods; K-Pg extinction 66 Mya
C-14 canNOT date rocks or dinosaurs (too old + not organic) — use U-Pb instead
Erosion ≠ weathering: breakdown in place vs TRANSPORT elsewhere
Glaciers deposit UNSORTED till; water sorts by size — mixing these up fails lab questions

Atmospheric layers

Temperature breaks define the layers — memorize the pattern.
  • Troposphere (0–12 km): weather lives here; temp falls with height
  • Stratosphere: rises (ozone absorbs UV); jets fly low-stratosphere
  • Mesosphere: falls again — meteors burn here
  • Thermosphere: rises sharply (absorbs X-rays); auroras & ISS altitude

Moisture, clouds & precipitation

Humidity, condensation nuclei, and lifting make rain.
  • Relative humidity = actual vapor ÷ capacity ×100%; capacity grows with temperature
  • Dew point = saturation temperature — closer dewpoint to air temp = muggier
  • Cloud formation needs: lift, cooling to dew point, condensation nuclei
  • Lifting mechanisms: convection, frontal (warm over cold), orographic (mountains → rain shadow)

Air masses, fronts & pressure systems

Air mass = vast body with uniform source-region traits (mT maritime tropical = humid warm),Cold front: dense air bulldozes under — steep, brief heavy storms, clear after,Warm front: gentle overrunning — long steady precipitation ahead of front,Low pressure = rising air, clouds/L-storms; High = sinking, fair skies,Coriolis deflects winds right (N hemisphere): cyclones spin counterclockwise

Severe weather & forecasting tools

Instability + moisture + lift = storms; instruments measure it all.
  • Thunderstorm ingredients: moisture, instability, lifting trigger
  • Tornado genesis in supercells via wind shear mesocyclones; EF-scale rates damage
  • Hurricanes feed on WARM OCEAN water (>26.5°C) — weaken over land (no fuel)
  • Station models, isobars (pressure lines), isotherms (temperature) map the forecast
Warm fronts produce LONG steady rain AHEAD of the front — not the brief burst of cold fronts
Orographic LEE side is dry (rain shadow) — windward gets the rain
Relative humidity can be high in COLD air with little vapor — it's a ratio, not amount

Weather vs climate & climate controls

Climate is the 30-year average personality; six factors set it.
  • Latitude: solar angle drives global temperature bands
  • Elevation: temp drops ~3.5°F/1000ft (6.5°C/km) — mountaintop tundra at equator
  • Proximity to water moderates: maritime = mild, continental = extreme seasons
  • Ocean currents redistribute heat (Gulf Stream warms Western Europe)
  • Mountain barriers create rain shadows; prevailing winds steer moisture

Greenhouse effect basics

Natural warming makes Earth livable; amplification is the problem.
  • Shortwave solar in → surface absorbs → longwave infrared out tries to escape
  • GHGs (CO₂, CH₄, H₂O vapor) absorb/re-radiate IR back downward
  • Natural greenhouse ≈ +33°C — without it Earth freezes (~0°F average)
  • Human additions (fossil fuels, deforestation) thicken the blanket

Evidence of modern climate change

Multiple independent lines agree — the case is cumulative.
  • Global temps up ~1.2°C since pre-industrial; fastest in Arctic amplification
  • Glaciers/ice sheets retreating worldwide; sea level ~20cm rise and accelerating
  • Ocean acidification as seas absorb CO₂ (pH dropping, shell-building suffers)
  • Earlier springs, species range shifts poleward/upward

Feedbacks & response options

Feedback loops amplify or dampen; responses split mitigation vs adaptation.
  • Ice-albedo feedback: melt exposes dark ocean → absorbs more heat → more melt (positive)
  • Permafrost methane release = another positive loop
  • Mitigation = cut emissions (renewables, efficiency); adaptation = adjust (seawalls, crops)
  • Carbon sinks: oceans/planting absorb CO₂ but have saturation limits
Weather ≠ climate: one cold day doesn't refute warming trends (trend vs event)
Ozone hole is a SEPARATE issue from global warming — different chemistry, recovering via Montreal Protocol
Sea level rise comes mostly from thermal expansion + land ice melt, not floating ice

Earth's motions & seasons

Tilt + revolution (not distance!) make seasons.
  • Axial tilt 23.5° fixed direction (points to Polaris) — hemisphere leaning toward Sun = summer
  • Solstices: max/min sun angle (Jun 21 / Dec 21); equinoxes equal day-night (Mar/Sep 21)
  • Revolution 365.25 d; rotation 24 h — leap years fix the quarter-day
  • Direct rays hit between tropics only; angle determines intensity

Moon phases & eclipses

Phases come from geometry, not shadow.
  • Lunar cycle 29.5 days; we always see the SAME lunar face (tidal lock)
  • Waxing = growing light (right side lit, N hemisphere); waning opposite
  • Solar eclipse = Moon's shadow on Earth (new moon phase ONLY); lunar = Earth's shadow on full moon
  • Eclipses don't occur monthly — 5° orbital tilt usually misses alignment

Tides

Moon's gravity pulls tidal bulges; Earth rotates through two bulges daily,Spring tides: Sun-Moon aligned (new/full) → extreme ranges,Neap tides: 90° apart (quarter moons) → minimal range,Tidal friction slows Earth's spin over eons

Solar system architecture

Formation disk explains layout patterns.
  • Terrestrial inner planets (rocky, dense): Mercury→Mars; Jovian outer (gas/ice giants): Jupiter→Neptune
  • Asteroid belt between Mars/Jupiter; Kuiper belt beyond Neptune (Pluto lives here)
  • Kepler/Newton laws: elliptical orbits, faster near perihelion (closer)
  • Retrograde rotation oddballs: Venus spins backwards; Uranus rolls on its side
Earth is CLOSEST to the Sun (perihelion) in JANUARY — Northern winter! Distance isn't the cause
Lunar eclipses need FULL moon, solar need NEW moon — swapping them fails tests
The Moon DOES rotate — once per orbit, which is why we see one face
Term
Press Enter or Space to flip the card. Left and right arrows move between cards. 1 marks it known, 2 marks it still learning.
Click or press Enter to flip · Rate yourself to track weak cards
Browse all 79 flashcards as a list

Unit 1: Earth Systems & Scientific Method

Four spheres
Geosphere, hydrosphere, atmosphere, biosphere — all interact.
Gradient formula
(change in elevation) ÷ horizontal distance — usually ft/mi.
Sphere interactions
Exchanges between geo/hydro/atmo/bio define Earth systems science.
Falsifiability
Hypotheses must be testable-in-principle to be scientific.
Contour interval
Elevation gap between adjacent contour lines — constant per map.
Density stratification
Densest sank to core; layered planet by density.
Insolation
Incoming solar radiation reaching Earth.
Asthenosphere
Plastic upper-mantle layer plates glide upon.
Gradient units
ft/mi or m/km — rise over run.

Unit 2: Plate Tectonics

Subduction
Denser oceanic plate dives beneath the other at convergent zones.
Transform boundary
Slide-past grinding — San Andreas; quakes but few volcanoes.
Lithosphere vs asthenosphere
Rigid plates ride the plastic flowing layer beneath.
Hotspot volcanoes
Intraplate volcanism (Hawaii) from mantle plumes, not boundaries.
Ridge push & slab pull
Forces driving plates: elevated ridges push; sinking slabs pull.
Paleomagnetism
Locked magnetic orientation recording field flips.
Slab pull
Dense sinking plate drives motion.
Convection cells
Hot rises, cool sinks in the mantle.
Pangaea
Wegener's all-continent supercontinent.

Unit 3: Earthquakes & Volcanoes

P vs S waves
P = push-pull through everything; S = shake sideways, liquids block.
Silica rule
Low silica → runny/gentle; high silica → sticky/explosive.
Moment magnitude
Modern energy-based earthquake scale replacing Richter usage.
Caldera
Collapsed magma chamber crater after catastrophic eruption.
Shadow zones
P-wave & S-wave shadows map Earth's interior layers.
Richter vs Mercalli
Energy scale vs damage scale.
Aa vs pahoehoe
Rough vs ropey basalt lava.
Focus vs epicenter
Underground origin vs surface point above.
Tsunami warning
Shaking + sudden sea withdrawal — run uphill.

Unit 4: Minerals & Rocks

Mohs hardness scale
1 talc → 10 diamond; scratch tests order minerals.
Intrusive vs extrusive
Slow cooling inside = big crystals; fast outside = small/glassy.
Cleavage vs fracture
Clean planar breaks vs irregular breaks — ID clue pair.
Index fossil trio
Widespread + abundant + short-lived = best layer daters.
Rock cycle driver
Internal heat + solar-powered surface processes recycle all rock.
Streak test
Powder color — steadier than surface color.
Foliation cause
Directed pressure aligning minerals.
Bowen's series
Mineral crystallization order.
Cleavage
Clean planar mineral breaks.
Luster
Metallic vs non-metallic reflection.

Unit 5: Weathering, Erosion & Geologic Time

Half-life
Time for half the parent isotope to decay — constant clock.
Rain shadow
Lee side of mountains stays dry after windward orographic rain.
O-horizon
Surface organic litter layer above topsoil A.
Law of cross-cutting
Intrusions/faults are younger than rocks they cut.
U-238 half-life
~4.5 billion years — dates Earth's oldest igneous rocks.
Graded bedding
Coarse below, fine above — tells 'this side was up' when tilted.
Inclusions rule
Fragments inside rock predate the rock itself.
Karst topography
Dissolved-limestone caves and sinkholes.
C-14 half-life
5,730 yr — dates recent organics only.
Oxidation
Iron + oxygen = rust, weakens rock.

Unit 6: Atmosphere & Weather

Dew point spread
Air temp minus dew point — small gap means near-saturation.
Coriolis deflection
Winds/curves deflect right in N hemisphere (left in S).
Atmosphere layers order
Troposphere, stratosphere, mesosphere, thermosphere (up).
Front types
Cold = fast/heavy storms · Warm = long steady rain ahead.
Isobar / isotherm
Equal-pressure lines / equal-temperature lines on weather maps.
SuperCell tornado genesis
Wind shear organizes rotating mesocyclone — EF damage scale rates it.
Dew point
Saturation temperature (100% RH).
Orographic lift
Windward rain; leeward rain shadow.
Station model
Compact weather-map symbols.
Coriolis effect
Deflects winds right (N hemisphere).
Isobar
Equal-pressure line on weather maps.

Unit 7: Climate & Climate Change

Greenhouse mechanism
GHGs absorb outgoing IR and re-radiate heat back down.
Mitigation vs adaptation
Cutting emissions vs adjusting to impacts.
Keeling curve
Mauna Loa CO₂ record showing steady rise + seasonal wiggle.
Carbon sink saturation
Oceans/forests absorb CO₂ but with limits as they acidify/fill.
Paris target frame
Hold warming well below 2°C, pursue 1.5°C vs pre-industrial.
Albedo
Reflectivity — ice high, ocean low.
Thermal expansion
Warmer water raises sea level.
Proxy record
Ice cores/tree rings encode past climate.
Milankovitch cycles
Orbit/tilt/wobble pacing ice ages.

Unit 8: Astronomy: Earth-Moon-Sun & Solar System

23.5° tilt cause
Tilt toward/away from Sun makes seasons — not distance.
Eclipse phases
Solar = NEW moon · Lunar = FULL moon (tilt skips most months).
Terrestrial vs Jovian
Inner rocky dense vs outer gas/ice giants — disk formation legacy.
Solstice dates
Jun 21 & Dec 21 — extreme day lengths by hemisphere.
Tidal lock
Moon's rotation period equals its orbital period around Earth.
Kuiper Belt
Icy bodies beyond Neptune — Pluto's home neighborhood.
Gas giant oddballs
Venus retrograde spin; Uranus sideways roll (~98°).
Tidal locking
Moon rotation = orbital period; one face shows.
Perihelion/aphelion
Closest Jan / farthest Jul points.
Light-year
Distance light travels in one year.
Season cause
23.5° tilt, NOT distance.
Asteroid belt
Rocky debris between Mars and Jupiter.
Press 1–4 to answer · Enter for next

Unit 1: Earth Systems & Scientific Method

Four Earth spheres
Earth runs as interconnected systems exchanging matter and energy.
Scientific method cycle
Science self-corrects through hypothesis testing.
Maps & rates
Topo maps and rate formulas are Earth science's daily tools.
Energy in Earth systems
Two engines power everything: solar (external) and planetary heat (internal).
Key fact
Atmosphere: 78% N₂ / 21% O₂ — the test's favorite numbers
Key fact
Gradient formula: Δelevation ÷ distance
Key fact
Convection requires fluidity — solids can't convect (mostly)

Unit 2: Plate Tectonics

Layers & plates
The lithosphere rides on the asthenosphere in moving plates.
Divergent boundaries
Plates separate; new crust forms — mid-ocean ridges and rifts.
Convergent boundaries
Collision courses produce subduction, mountains, and deep quakes.
Transform boundaries & evidence
Slide-past boundaries and the proof that sealed the theory.
Key fact
Oceanic crust DENSES under continental at convergent boundaries (subduction)
Key fact
Plate speed ≈ cm/yr — fingernail-growth pace
Key fact
Seafloor age increases away from ridges = spreading proof

Unit 3: Earthquakes & Volcanoes

Earthquake basics
Elastic rebound releases accumulated strain as seismic waves.
Locating epicenters
Triangulation uses wave arrival-time differences.
Measuring & hazards
Magnitude scales measure energy; intensity varies locally.
Volcano types & magma chemistry
Silica content controls explosiveness — the controlling variable.
Key fact
P-waves through everything · S-waves blocked by liquid outer core
Key fact
Logarithmic magnitude: +1 unit ≈ 10× amplitude / 32× energy
Key fact
Low silica = gentle; high silica = explosive

Unit 4: Minerals & Rocks

Mineral properties
Minerals are naturally-occurring crystalline solids with defined chemistry.
The rock cycle
Three rock families transform endlessly via melting, heat, pressure, weathering.
Rock identification logic
Texture + composition identify rocks stepwise.
Rock record & dating intro
Rocks archive Earth history; relative dating orders events.
Key fact
Mohs 1-10; fingernail ~2.5, penny ~3.5, glass ~5.5
Key fact
Intrusive = large crystals (slow cooling) · extrusive = small (fast)
Key fact
Superposition: undisturbed = bottom oldest

Unit 5: Weathering, Erosion & Geologic Time

Weathering types
Breakdown happens chemically and physically in place.
Erosion & deposition agents
Gravity plus moving fluids transport and sort sediment.
Soil formation
Weathered rock + organics mature into soil horizons over centuries.
Geologic time & absolute dating
Deep time measured with radioactive decay clocks.
Key fact
C-14 dates RECENT organic material only (~50k yr limit)
Key fact
Chemical weathering loves warm+wet; frost wedging loves cold cycles
Key fact
Half-life = half decays per interval — never fully zero

Unit 6: Atmosphere & Weather

Atmospheric layers
Temperature breaks define the layers — memorize the pattern.
Moisture, clouds & precipitation
Humidity, condensation nuclei, and lifting make rain.
Air masses, fronts & pressure systems
Air mass = vast body with uniform source-region traits (mT maritime tropical = humid warm),Cold front: dense air bulldozes under — steep, brief heavy storms, clear after,Warm front: gentle overrunning — long steady precipitation ahead of front,Low pressure = rising air, clouds/L-storms; High = sinking, fair skies,Coriolis deflects winds right (N hemisphere): cyclones spin counterclockwise
Severe weather & forecasting tools
Instability + moisture + lift = storms; instruments measure it all.
Key fact
Dew point spread small = saturated/near-saturated air
Key fact
Low pressure → rise → clouds; High → sink → clear
Key fact
Hurricanes need warm ocean ≥26.5°C — die over land/cool water

Unit 7: Climate & Climate Change

Weather vs climate & climate controls
Climate is the 30-year average personality; six factors set it.
Greenhouse effect basics
Natural warming makes Earth livable; amplification is the problem.
Evidence of modern climate change
Multiple independent lines agree — the case is cumulative.
Feedbacks & response options
Feedback loops amplify or dampen; responses split mitigation vs adaptation.
Key fact
Greenhouse effect natural +33°C keeps Earth habitable — excess is the issue
Key fact
Arctic warms fastest (ice-albedo positive feedback)
Key fact
Mitigation cuts causes; adaptation manages effects

Unit 8: Astronomy: Earth-Moon-Sun & Solar System

Earth's motions & seasons
Tilt + revolution (not distance!) make seasons.
Moon phases & eclipses
Phases come from geometry, not shadow.
Tides
Moon's gravity pulls tidal bulges; Earth rotates through two bulges daily,Spring tides: Sun-Moon aligned (new/full) → extreme ranges,Neap tides: 90° apart (quarter moons) → minimal range,Tidal friction slows Earth's spin over eons
Solar system architecture
Formation disk explains layout patterns.
Key fact
Seasons caused by 23.5° TILT, not Earth-Sun distance
Key fact
Same moon face always — tidally locked to Earth
Key fact
Spring tides at new+full moons; neap at quarter moons
Common mistakes for each unit — read the mistake, then make sure you know why it's wrong.

Unit 1: Earth Systems & Scientific Method

Watch out
A theory is NOT a guess — it's a tested explanatory framework (theory of plate tectonics)
Watch out
Ocean water is saltwater — don't count it as freshwater supply
Watch out
Contour lines never cross — one point, one elevation

Unit 2: Plate Tectonics

Watch out
Inner core is SOLID despite being hottest — pressure forces solid state
Watch out
Continents don't plow through ocean floor — plates carry both crust types
Watch out
Not all boundaries make volcanoes: transform boundaries generally don't

Unit 3: Earthquakes & Volcanoes

Watch out
The epicenter is NOT underground — the focus is; epicenter is directly above on the surface
Watch out
S-wave shadow zone proved the OUTER CORE is liquid — not inner
Watch out
Bigger magnitude ≠ proportionally bigger shaking — logarithmic means counterintuitive jumps

Unit 4: Minerals & Rocks

Watch out
Streak beats color for ID — many minerals vary in surface color but constant in streak
Watch out
Marble is METAMORPHosed limestone, not sedimentary anymore
Watch out
Foliation needs PRESSURE direction, not just any metamorphism (marble doesn't foliate)

Unit 5: Weathering, Erosion & Geologic Time

Watch out
C-14 canNOT date rocks or dinosaurs (too old + not organic) — use U-Pb instead
Watch out
Erosion ≠ weathering: breakdown in place vs TRANSPORT elsewhere
Watch out
Glaciers deposit UNSORTED till; water sorts by size — mixing these up fails lab questions

Unit 6: Atmosphere & Weather

Watch out
Warm fronts produce LONG steady rain AHEAD of the front — not the brief burst of cold fronts
Watch out
Orographic LEE side is dry (rain shadow) — windward gets the rain
Watch out
Relative humidity can be high in COLD air with little vapor — it's a ratio, not amount

Unit 7: Climate & Climate Change

Watch out
Weather ≠ climate: one cold day doesn't refute warming trends (trend vs event)
Watch out
Ozone hole is a SEPARATE issue from global warming — different chemistry, recovering via Montreal Protocol
Watch out
Sea level rise comes mostly from thermal expansion + land ice melt, not floating ice

Unit 8: Astronomy: Earth-Moon-Sun & Solar System

Watch out
Earth is CLOSEST to the Sun (perihelion) in JANUARY — Northern winter! Distance isn't the cause
Watch out
Lunar eclipses need FULL moon, solar need NEW moon — swapping them fails tests
Watch out
The Moon DOES rotate — once per orbit, which is why we see one face