Earth & Space Tells
Patterns for recognizing what an Earth & Space question is really asking — the clue that identifies the answer, the trap it's built to catch, and the shortcut that answers it fast.
Questions split almost evenly between Earth (geology, weather, oceans) and space (planets, stars, the sky), and no area falls below 8%, so cover the high-yield topics in every row.
| Subtopic | Share · highest-yield topics |
|---|---|
| Atmospheric Science & Weather | 15% · atmospheric layers, clouds and fronts, wind belts, greenhouse gases |
| Surface Processes, Sedimentology & Paleontology | 15% · glaciers, streams and groundwater, sedimentary rocks, geologic time |
| Observational Astronomy, Exoplanets & Cosmology | 15% · moon phases and seasons, magnitude, telescopes, galaxies and the Big Bang |
| Solar System & Planetary Science | 13% · planet superlatives, moons, comets and asteroids |
| Geophysics & Tectonics | 12% · plate boundaries, seismic waves, Earth's layers, volcanoes |
| Stellar Evolution & Stellar Physics | 12% · spectral types, a star's fate by mass, the Sun's layers, fusion |
| Mineralogy, Petrology & Metamorphism | 10% · igneous rock pairs, mineral identification, metamorphic grade |
| Oceanography | 8% · currents, tides, salinity, the seafloor |
These tells come from how a question is built, before you even reach its content.
"Which is NOT true / EXCEPT / LEAST accurate"
About one multiple-choice question in eight flips the logic: three choices are true and the false one is the answer. Rephrase it as "find the one that isn't true." The false choice is usually a real fact turned backward — a direction, a hemisphere, or the partner from a pair (eastern for western, aphelion for perihelion).
"Identify all of the following…"
Almost always a bonus. Judge each item on its own. Out of time on a three-item list? Two items is the most common answer (about half), one item next; "all" is about one in six, and "none" is very rare.
"Rank / order the following"
Almost always a bonus, usually layers by depth or height, events in time, stars by temperature or brightness, or rocks by grade or hardness. Place the two ends first, then check which direction is asked for.
Name exactly the thing asked for
Earth & Space answers are graded on precision, and the rejected answers are near misses:
- The specific part, not the whole — "outer core," not "core"; "plagioclase feldspar," not "feldspar"; "potassium-40," not "potassium."
- The object, not its family — "pulsar," not "neutron star"; "chondrules" (the spheres), not "chondrites" (the meteorites).
- Constellation vs. asterism — "Ursa Major" is the constellation; the Big Dipper is only a star pattern inside it.
- Plate boundary vs. fault — "transform" names the boundary; "strike-slip" names the fault.
When a fact has a second version, the question adds a word that pins down which one it means. When you hear one, ask "what would the answer be without this word?" That answer is the trap.
Which layer, which kind of layer?
- Compositional vs. mechanical — crust, mantle, and core are layers by material; lithosphere and asthenosphere are layers by stiffness. "What compositional layer has the steepest geothermal gradient" → crust; lithosphere is the trap.
- By volume vs. by mass — "the largest layer by volume" → mantle (about 84%). The dense core holds a larger share of mass than of volume, so don't be pulled toward it.
- "Primordial" atmosphere — Earth's first air was hydrogen and helium (with methane) from the solar nebula; CO2, water vapor, and nitrogen from volcanoes is the second atmosphere and the trap.
Which measure of a star or planet?
- Apparent vs. absolute — apparent magnitude is how bright it looks from here; absolute is how bright it would look from 10 parsecs. "A star 10 parsecs away has absolute magnitude 3.5; its apparent magnitude?" → 3.5.
- Bluest means hottest, not brightest — "the bluest: Arcturus, Sirius, Rigel, Barnard's Star" → Rigel; Sirius, the brightest in our sky, is the trap.
- Peak wavelength vs. the color you see — "a 2,500 K star's peak emission" → infrared; red, the color it looks, is the trap.
- Largest vs. most massive — Pluto is the largest dwarf planet; Eris, slightly smaller but denser, is the most massive.
Which version of the cycle?
- Short- vs. long-period comets — "short-period comets originate beyond Neptune in" → the Kuiper Belt; the Oort Cloud, source of long-period comets, is the trap.
- "In the North Atlantic" — the same storm is a hurricane in the Atlantic, a typhoon in the western Pacific, a cyclone in the Indian Ocean; a typhoon is never a weaker stage.
- Hemisphere words — Coriolis deflection, Ekman transport, gyre rotation, and seasons all reverse south of the equator. "Wind blowing south along the U.S. west coast; net water movement?" → west (90° to the right); south, the wind's own direction, is the trap.
Many terms come in easily confused pairs. When the answer is one term in a pair, the other is often a wrong choice. Learn each pair with the one difference that tells them apart.
| Pair | What tells them apart |
|---|---|
| P-wave vs. S-wave | Push-pull, fastest, crosses liquids vs. side-to-side, slower, solids only — so no S-waves in the outer core |
| Intrusive vs. extrusive | Cooled slowly underground, large crystals vs. cooled fast as lava, tiny crystals or glass |
| Mafic vs. felsic | Mg + Fe, dark, dense, runny, hotter melt vs. feldspar + silica, light, sticky, explosive |
| Weathering vs. erosion | Breaking rock down in place vs. carrying it away |
| Cold front vs. warm front | Steep, fast, brief thunderstorms (cumulonimbus) vs. gentle, slow, long steady rain (stratus) |
| Western vs. eastern boundary current | Warm, fast, narrow, poleward (Gulf Stream) vs. cold, slow, wide, toward the equator (California Current) |
| Spring vs. neap tide | Sun and Moon in line, at new and full moon, biggest range vs. at right angles, at the quarter moons, smallest range |
| Transgression vs. regression | Sea advancing, deeper-water rock on top (limestone over shale) vs. sea retreating, shallower rock on top |
| Perihelion vs. aphelion | Closest to the Sun, fastest (early January for Earth) vs. farthest, slowest (early July) |
| Dust tail vs. ion tail | Pushed by sunlight, curved, yellowish vs. pushed by solar wind, straight, bluish, points directly away from the Sun |
| Type Ia vs. Type II supernova | Exploding white dwarf, no hydrogen lines, no remnant vs. collapsing massive star, leaves a neutron star or black hole |
| Globular vs. open cluster | Old, round, in the halo vs. young, loose, in the disk |
Earth & Space terms are built from Greek and Latin parts, and the parts usually say what the thing is. An unfamiliar name can often be worked out from them.
| Word part | Meaning and examples |
|---|---|
| peri- (near) / ap-, apo- (away) + -helion (Sun), -gee (Earth) | Perihelion, aphelion; perigee, apogee |
| paleo- / meso- / ceno- (old / middle / new) + -zoic (life) | Era names: Paleozoic, Mesozoic, Cenozoic; Paleogene is the old part of the newest era |
| litho- (rock), xeno- (foreign), pyro- (fire) + -clast (broken) | Lithosphere; xenolith (a foreign rock caught in magma); pyroclastic |
| cirro- / cumulo- / strato- (curl / heap / layer), alto- (middle), nimbo-, -nimbus (rain) | Name any cloud from its parts: nimbostratus is a rainy layer |
| iso- (equal) | Isobar (equal pressure), isotherm (equal temperature), isostasy (equal standing — crust floating at balance) |
| anti- / syn- + -cline (lean) | Anticline arches up, oldest rock in the middle; syncline sags down, youngest in the middle; monocline is a single bend |
| epi- (above) / hypo- (below) | Epicenter is the point on the surface above the hypocenter (focus) |
| oro- (mountain), kata- (down), diurnal (daily) | Orographic rain, katabatic winds flowing downhill, diurnal tides (one high a day; semidiurnal = two) |
Many questions describe something instead of naming it. 1) Find the most specific detail — a location, a temperature, a texture, a direction. 2) If no single detail is unique, let each one eliminate candidates. 3) Before answering, name the look-alike the question is built to catch and confirm your answer beats it.
Igneous rocks and magma
Read crystal size (cooling speed) and color or silica (composition); together they pick the rock from a two-by-three grid.
| Clue in the question | Answer |
|---|---|
| Same magma, coarse / fine | Granite / rhyolite (felsic), diorite / andesite (intermediate), gabbro / basalt (mafic) |
| First mineral to crystallize; magma left behind | Olivine (then pyroxene, amphibole, biotite … quartz last), or calcium-rich plagioclase on Bowen's other branch; the leftover melt grows richer in silica |
| Gentle lava flows / explosive eruption | Low-silica basalt (shield volcanoes, ridges, Hawaii, Iceland) / high-silica magma at subduction zones (stratovolcanoes) |
Minerals
Identification questions name one property that settles it. Decide which property is being described, then recall the one mineral famous for it.
| Clue in the question | Answer |
|---|---|
| Hardness 1 … 10 | Talc, gypsum, calcite, fluorite, apatite, orthoclase, quartz (7), topaz, corundum, diamond (10) ("Tall Giraffes Can Find Alligators Of Quite Tiny Cuteness Daily") |
| Fizzes in dilute acid / only when powdered | Calcite (limestone, marble) / dolomite |
| Cleavage: one plane / two at about 90° / two at 56° and 124° / three, cubic | Mica / pyroxene, feldspar / amphibole / halite, galena; quartz has none |
| Brassy but black streak / heavy, soft, cubic, metallic gray | Pyrite ("fool's gold"; real gold streaks yellow) / galena (lead ore) |
Metamorphic rocks
Ask what caused the change and how far it went. The cause names the type; the degree of change places the rock in a sequence.
| Clue in the question | Answer |
|---|---|
| Shale at rising grade | Slate → phyllite → schist → gneiss (all foliated); index minerals chlorite → biotite → garnet → staurolite → kyanite → sillimanite |
| Limestone / sandstone / coal | Marble / quartzite / anthracite — all non-foliated |
| Heat from nearby magma / mountain-building / deep burial / impact | Contact (hornfels) / regional / burial (zeolites) / shock (tektites, shocked quartz) |
| Foliation requires | Directed (differential) pressure — heat alone doesn't do it |
Plates, earthquakes, and Earth's interior
Turn the described motion into a boundary type first; the boundary type then predicts the landforms, volcanoes, and earthquake depths.
| Clue in the question | Answer |
|---|---|
| Deep earthquakes (to 700 km) / largest earthquakes | Subduction zone only — the sinking slab (Wadati–Benioff zone); ridges and transform faults stay shallow |
| Chain of volcanoes getting older in one direction | Hotspot under a moving plate (Hawaii); the sinking, cooling islands end as atolls |
| Seafloor age and depth | Youngest at the ridge, older and deeper away from it (it cools and sinks); nowhere older than about 200 million years |
| Strength at one place vs. energy released | Intensity (Modified Mercalli, I–XII) vs. magnitude (moment magnitude; each step about 32× the energy) |
Weathering, glaciers, and water on land
Name the agent at work — ice, running water, groundwater, wind, or gravity — and the landform follows.
| Clue in the question | Answer |
|---|---|
| Curved sheets peeling off granite domes / most common chemical agent | Exfoliation (pressure release) / carbonic acid (CO2 in water) |
| Glacial landforms that show flow direction | Drumlins (blunt end faces up-ice), cirques (open downhill), striations; end moraines lie across the flow, lateral and medial along it |
| Stream above the water table / below it | Losing (influent: water flows into the ground) / gaining (effluent) |
| Limestone landscape with caves and sinkholes | Karst; cave deposits (stalactites, stalagmites) are calcite |
| Mass movement, slowest to fastest | Creep < slump and earthflow < mudflow and lahar < rockfall and pyroclastic flow |
Geologic time and the rock record
Place every name in its era before comparing; the era usually settles a chronology question by itself.
| Clue in the question | Answer |
|---|---|
| Paleozoic periods in order | Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian ("Camels Often Sit Down Carefully, Perhaps"); then Triassic, Jurassic, Cretaceous |
| Largest mass extinction / the dinosaurs' end | End-Permian (252 million years ago) / end-Cretaceous (66 million years ago) |
| Relative dating: lower layer / cutting feature / enclosed fragment | Older (superposition) / younger (cross-cutting) / older (inclusions) |
| Rock made by organisms: shells / plankton silica / plant matter | Limestone / chert / coal |
The atmosphere and weather
Locate the question in height first — which layer, which cloud level — then apply the one rule for that level.
| Clue in the question | Answer |
|---|---|
| Layers going up; where temperature rises | Troposphere (weather), stratosphere (ozone layer, warms with height), mesosphere (coldest; meteors burn), thermosphere (aurora) — jet streams sit at the tropopause |
| Wind belts, 0–30° / 30–60° / 60–90° | Trade winds (easterly) / westerlies / polar easterlies; rising air (low pressure, rain) at the equator and 60°, sinking air (deserts) at 30° |
| Lake-effect snow / hot, dry U.S. Southwest | Continental polar air / continental tropical air (continental = dry, maritime = moist) |
| Hurricane needs; spins | Ocean above about 26°C, away from the equator; counterclockwise in the Northern Hemisphere |
Oceans
Most ocean questions reduce to one driver — wind and Coriolis, density, or the Moon. Name it and the pattern follows.
| Clue in the question | Answer |
|---|---|
| Saltiest / freshest surface water | Subtropics (evaporation wins) / high latitudes and the rainy equator |
| Deep water forms where | Cold, salty water sinks in the North Atlantic and around Antarctica (thermohaline circulation) |
| Calcareous ooze vs. red clay on the deep seafloor | Shells dissolve below the carbonate compensation depth, shallower in the more acidic Pacific |
| Tsunami in the open ocean | Barely noticeable, but about 500–600 mph; slows and grows tall in shallow water |
Planets
"What planet…" questions are mostly superlatives. Learn each planet's records; the trap is usually its neighbor in size or distance.
| Clue in the question | Answer |
|---|---|
| Smallest; biggest day–night temperature swing; never far from the Sun in our sky; largest core for its size | Mercury |
| Hottest surface; highest albedo; spins backward, day longer than its year; Earth's twin in size | Venus |
| Densest; most nitrogen in its air / Olympus Mons, Valles Marineris; Kepler's elliptical orbits | Earth / Mars |
| Largest, fastest spin (about 10 h), Trojan asteroids, Kirkwood gaps / less dense than water | Jupiter / Saturn |
| Rotates on its side / found by mathematical prediction; Pluto and the Kuiper Belt in 3:2 resonance | Uranus / Neptune; both are blue from methane |
Moons and small bodies
A moon's name gives away its planet: each giant names moons from one source. Then a single trait picks the moon.
| Clue in the question | Answer |
|---|---|
| Names from Shakespeare and Pope / sea gods / Titans / Zeus's lovers | Uranus / Neptune / Saturn / Jupiter |
| Volcanoes / icy crust over an ocean / largest moon / most cratered | Io / Europa (also Saturn's Enceladus, with water plumes) / Ganymede / Callisto — tidal heating falls with distance from Jupiter |
| Thick nitrogen atmosphere, methane lakes and rain | Titan (Saturn) |
| Largest object in the asteroid belt | Ceres, a dwarf planet |
Stars
Convert every clue to temperature or mass. Temperature fixes the color and spectral type; mass fixes the lifetime and the ending.
| Clue in the question | Answer |
|---|---|
| Hottest → coolest; the Sun | O B A F G K M ("Oh Be A Fine Girl/Guy, Kiss Me"); lower number = hotter within a type; the Sun is G2; molecular bands = M |
| H–R diagram: top right / bottom left / diagonal band | Red supergiants / white dwarfs / main sequence (hot on the left, bright at the top) |
| End by mass: Sun-like / about 8–20 Suns / heavier | White dwarf (after a planetary nebula; limit 1.4 Suns) / neutron star / black hole |
| Energy source: newborn (T Tauri) / main sequence / red giant core | Gravitational contraction (Kelvin–Helmholtz) / hydrogen → helium (p–p chain in the Sun, CNO in heavier stars) / helium → carbon (triple alpha) |
| Standard candles: young stars / globular clusters | Cepheids (longer period = brighter) / RR Lyrae |
The Sun
Picture the layers in order from the center; most questions ask which layer does what.
| Clue in the question | Answer |
|---|---|
| Interior, center outward | Core, radiation zone (thickest), convection zone, then the photosphere (visible surface, sunspots) |
| Seen only in a total eclipse: pink rim / pearly halo | Chromosphere / corona |
| Hottest atmosphere; source of the solar wind | Corona (millions of K) — temperature rises outward from a minimum near the top of the photosphere |
| Sunspots | Cooler, strongly magnetic regions on an 11-year cycle |
The sky from Earth
Sketch the Sun, Earth, and Moon; phase, rising-time, and eclipse questions all come out of the geometry.
| Clue in the question | Answer |
|---|---|
| Moonrise at sunrise / noon / sunset / midnight | New / first quarter / full / third quarter |
| Solar eclipse / lunar eclipse / Moon too far to cover the Sun | New moon / full moon / annular (near apogee) |
| Galactic center / Andromeda Galaxy finder / pole star | Sagittarius / Great Square of Pegasus / Polaris, in Ursa Minor |
| Higher magnitude number | Dimmer — Sirius is about −1.5, the faintest naked-eye stars about +6 |
Telescopes, galaxies, and the universe
Match each telescope property to the one quantity that sets it; for cosmology, place the event on the universe's timeline first.
| Clue in the question | Answer |
|---|---|
| Resolving power / magnification / colored fringes in a lens | Aperture / objective ÷ eyepiece focal length / chromatic aberration (cured by mirrors) |
| Ground-based wavelengths / must go to space | Visible and radio (atmospheric windows) / X-ray, gamma, most UV and infrared |
| Universe became transparent; light left over | At about 3,000 K, 380,000 years after the Big Bang; now the cosmic microwave background at 2.7 K |
| Galaxy forming many stars / old, red, little gas | Spiral or irregular / elliptical (often made by mergers, which trigger starbursts) |
About a quarter of Earth & Space short-answer questions have a numerical answer, and the numbers are chosen to come out clean. These relationships answer them without the algebra.
| Question type | Shortcut |
|---|---|
| Orbital period around the Sun | T2 = a3 in years and AU: a = 4 → 8 years, a = 9 → 27 |
| Sunlight at another planet; light-gathering power | Flux ∝ 1/d2 (5 AU → 1/25); light gathered ∝ D2 (5× wider → 25×) |
| Magnitude differences | 5 magnitudes = 100× in brightness; 1 magnitude ≈ 2.5× |
| Distance from parallax | d (parsecs) = 1 / p (arcseconds); 1 pc ≈ 3.26 light-years |
| Star's luminosity | L ∝ R2T4: doubling T → 16×; on the main sequence, L ∝ M3.5 |
| Height of Polaris; noon Sun at an equinox | Polaris's altitude = your latitude; noon Sun altitude = 90° − latitude |
| Rising times day to day | Stars rise about 4 minutes earlier (sidereal day 23 h 56 min); the Moon about 50 minutes later |
| Rising air cools per kilometer | About 10°C unsaturated, about 6°C saturated |
Out of time on a multiple-choice question? A wrong answer after the question is read costs nothing, so guess. W is the most common answer in Earth & Space (27%) and Z the least (22%).