Earth Science Lesson Test for ASVAB General Science

Answer: C

Correct answer: Geosphere. Earth science often divides the planet into four interacting systems. The geosphere is the solid Earth: rock, soil, sediment and the interior. The hydrosphere is all water, the atmosphere is the gas envelope, and the biosphere is all living things. The prefixes help: geo- means earth, hydro- means water, atmo- refers to vapor or air, and bio- means life. Soil is mostly weathered rock, so it belongs to the geosphere.

• A: Hydrosphere includes water in its various reservoirs.
• B: Atmosphere refers to gases around Earth.
• C (correct): The geosphere is the solid Earth, including rocks, soil and landforms.
• D: Biosphere is the realm of living organisms.

Answer: B

Correct answer: Mantle. By composition, Earth has three main layers: a thin outer crust, a thick rocky mantle, and an iron-rich core. The core is split into a liquid outer core and a solid inner core, both far below the mantle. The mantle makes up most of Earth's volume, and slow flow in its solid rock helps drive plate motion. The troposphere belongs to the atmosphere, not the solid Earth.

• A: The troposphere is atmospheric, not solid Earth.
• B (correct): The mantle is the thick rocky layer below the crust and above the core.
• C: The inner core lies at Earth’s center.
• D: The outer core is deep below the mantle.

Answer: D

Correct answer: apart. At divergent boundaries, plates pull away from each other, and hot mantle rock rises and melts to fill the gap, forming new crust. Mid-ocean ridges such as the Mid-Atlantic Ridge and continental rifts such as the East African Rift are examples. To keep boundary types straight: divergent means diverge or separate, convergent means converge or come together, and transform means sliding past each other sideways.

• A: Collision defines a convergent boundary.
• B: Divergence involves increasing distance across the boundary.
• C: Horizontal sliding is transform movement.
• D (correct): Divergent boundaries separate and often form new crust at spreading centers.

Answer: C

Correct answer: igneous. The name comes from the Latin word for fire. Magma that cools slowly underground forms coarse-grained rocks like granite, while lava that cools quickly at the surface forms fine-grained rocks like basalt. Sedimentary rocks form from compacted and cemented sediment, and metamorphic rocks form when existing rock is changed by heat and pressure without melting. Remember the cue: if it started as melted rock, it is igneous.

• A: Metamorphic forms by solid-state change under conditions such as heat and pressure.
• B: Sedimentary often forms by deposition and lithification of sediments.
• C (correct): Igneous rocks form when magma or lava cools and crystallizes or solidifies.
• D: Biological is not one of the three main rock groups.

Answer: B

Correct answer: condensation. When water vapor cools, its molecules slow down and cling together into liquid droplets. This is how clouds, fog and dew form, and it releases the energy absorbed during evaporation. Evaporation is the reverse process, liquid becoming vapor. A cold glass on a humid day shows condensation: droplets appear on the outside because vapor in the air cools against the glass, not because water leaks through.

• A: Evaporation converts liquid water into vapor.
• B (correct): Condensation converts vapor to liquid droplets, an important cloud-forming process.
• C: Infiltration moves water into soil or rock.
• D: Runoff moves water over land.

Answer: B

Correct answer: weathering. Weathering breaks down or chemically changes rock where it sits, through processes like frost wedging, plant roots, or acid rain dissolving minerals. Erosion is the separate step of moving the loosened material by water, wind or ice, and deposition is when that material is dropped. A useful memory hook: weathering stays put, erosion goes, deposition stops. Subduction is a plate process, unrelated to surface wearing.

• A: Subduction is descent of one tectonic plate beneath another.
• B (correct): Weathering physically or chemically alters rock at its location without required transport.
• C: Deposition is settling of transported material.
• D: Revolution is orbital motion, not rock alteration.

Answer: C

Correct answer: epicenter. The focus, or hypocenter, is the point underground where the fault rupture begins. The epicenter is the spot on the surface straight above it; the prefix epi- means upon or over. News reports usually give the epicenter because it is easy to map, and shaking is often strongest near it. Depth is measured from the epicenter down to the focus, which can be a few kilometers or hundreds of kilometers.

• A: A rift forms where Earth’s crust extends.
• B: A trench is a deep seafloor feature often associated with subduction.
• C (correct): The epicenter lies directly above the earthquake’s underground focus or hypocenter.
• D: A magma chamber stores molten material and is not the earthquake’s surface reference point.

Answer: B

Correct answer: The region’s 30-year average rainfall is 900 mm per year. Weather is the condition of the atmosphere at a particular time and place, such as today's rain or tomorrow's wind. Climate is the long-term pattern of weather, usually summarized as averages over about 30 years. A quick test: if the statement describes a specific moment or forecast, it is weather; if it describes what is typical over decades, it is climate.

• A: A front arriving this evening is a short-term weather event, not a long-term average.
• B (correct): A 30-year average describes long-term conditions, which is climate rather than weather.
• C: Today’s rain is a current weather observation.
• D: Tomorrow’s wind is a weather forecast.

Answer: D

Correct answer: Troposphere. The troposphere is the lowest layer, extending roughly 8 to 15 km up, and it holds most of the atmosphere's mass and nearly all its water vapor. Because it is heated mainly from the ground, warm air rises and cools there, forming clouds and storms. Above it, the stratosphere contains the ozone layer and is much drier and more stable, which is why jets often cruise near its base.

• A: The thermosphere is high above the troposphere.
• B: The stratosphere contains much of the ozone layer.
• C: The mesosphere is much higher than weather-cloud levels.
• D (correct): The troposphere is the lowest main atmospheric layer and contains most everyday weather.

Answer: C

Correct answer: The tilt of Earth’s rotational axis as it orbits the Sun. Earth's axis is tilted about 23.5°, and it points the same direction in space all year. When a hemisphere leans toward the Sun, it gets more direct sunlight and longer days, which means summer. The common misconception is distance from the Sun, but Earth is actually closest to the Sun in early January, and the two hemispheres have opposite seasons at the same time.

• A: Moon phases do not cause seasons.
• B: Volcanoes can affect climate briefly but do not generate annual seasons.
• C (correct): Axial tilt changes sunlight angle and day length for each hemisphere throughout the year.
• D: Earth is closest to the Sun in early January, during Northern Hemisphere winter, so distance does not cause seasons.

Answer: D

Correct answer: Transform. At a transform boundary, plates grind past each other horizontally, so crust is neither created nor destroyed. Stress builds as the plates stick, then releases in earthquakes, but volcanoes are rare. California's San Andreas Fault is a well-known example. Contrast this with divergent boundaries, where plates separate, and convergent boundaries, where they collide and one may subduct beneath the other.

• A: Subduction generally involves a descending plate at convergence.
• B: Divergent plates separate.
• C: Continental collision involves compression rather than mainly sideways sliding.
• D (correct): Sideways sliding is the defining relative motion at a transform boundary.

Answer: A

Correct answer: An ocean trench and adjacent volcanic arc. When dense oceanic crust sinks beneath another plate, the bend creates a deep trench at the seafloor. As the sinking plate descends, water released from it lowers the melting point of the mantle above, producing magma that feeds a chain of volcanoes parallel to the trench. Japan and the Aleutian Islands are examples. A mid-ocean ridge is the opposite setting, where plates separate and new crust forms.

• A (correct): A trench and volcanic arc commonly characterize an oceanic plate descending beneath another plate.
• B: Deltas form mainly from river sediment deposition.
• C: Sand dunes are built by wind deposition at the surface and say nothing about plate subduction.
• D: A mid-ocean ridge with a rift valley marks a divergent boundary where plates separate, not where one sinks.

Answer: A

Correct answer: The rupture focus is mapped 15 km below the surface. The focus is where rock first breaks, and its depth is measured straight down from the epicenter. Seismologists find it by comparing arrival times of seismic waves at several stations. Surface details such as damage distance, epicenter size or nearby landforms say nothing direct about depth. The tempting error is mixing up horizontal distance on the surface with vertical depth below it.

• A (correct): An earthquake’s focal depth measures the rupture origin below the surface.
• B: Epicenter is a point, not inherently a fixed-width feature.
• C: How far away damage occurred is a surface distance and does not reveal how deep the rupture began.
• D: Volcano height is unrelated to the earthquake’s focal depth.

Answer: D

Correct answer: Metamorphism. Meta- means change and morph means form: metamorphic rock is existing rock transformed while staying solid. Heat and pressure let atoms rearrange into new minerals or line up into bands, as when shale becomes slate or limestone becomes marble. The key distinction is melting: if the rock had melted and then cooled, the result would be igneous. Erosion and deposition move material at the surface rather than changing it internally.

• A: Erosion transports material.
• B: Evaporation changes liquid water into vapor.
• C: Deposition drops transported sediment.
• D (correct): Metamorphism alters minerals and textures while the rock remains solid.

Answer: B

Correct answer: Deposition. Moving water can carry sediment only while it has enough energy; the faster it flows, the larger the particles it can hold. When a river enters a still lake, it slows sharply and drops its load, coarse sand first and fine clay farther out. This builds features like deltas. Weathering breaks rock down and erosion carries it away, but deposition is the step where sediment is laid down.

• A: Subduction moves plates, not sediment in a river.
• B (correct): Sand settling as carrying water loses transport ability is deposition.
• C: Chemical weathering alters minerals rather than directly describing sand settling.
• D: Condensation is a gas-to-liquid phase change.

Answer: A

Correct answer: It is harder on the scratch-hardness scale. Hardness is a mineral's resistance to being scratched, and a harder material can scratch a softer one but not the reverse. The Mohs scale ranks minerals from talc at 1 to diamond at 10 using exactly this test. Hardness reflects the strength of bonds at the surface, which is a different property from density, melting point or age, so the test reveals nothing about those.

• A (correct): Scratching generally indicates the scratching mineral is harder than the scratched material.
• B: Hardness does not establish density.
• C: Geological age is not measured by a scratch test.
• D: Scratch hardness does not directly determine melting point.

Answer: C

Correct answer: Sand deposition → compaction → cementation. Clastic means made of broken fragments of older rock. Sand grains are first deposited in layers by water or wind. As more sediment piles on top, the weight squeezes the grains together, which is compaction. Then minerals such as quartz or calcite precipitate from groundwater and glue the grains, which is cementation. Together these steps are called lithification. Melting or crystallizing from magma would instead produce igneous rock.

• A: That sequence is characteristic of igneous processes.
• B: Melting is not required to form sandstone.
• C (correct): Clastic sandstone forms when sand-sized sediment is deposited and lithified.
• D: Cloud and ice processes do not directly lithify sand.

Answer: A

Correct answer: The fault is younger than the three layers it cuts but older than the fourth. Two principles combine here. Cross-cutting relationships say a feature that cuts through rock must be younger than that rock, since the rock had to exist first. Superposition says undisturbed layers on top are younger than those beneath. So the layers formed, the fault broke them, and the fourth layer was deposited later, sealing the fault. This gives relative order without exact dates.

• A (correct): Cross-cutting makes the fault younger than the cut layers, and the overlying uncut layer postdates the rupture.
• B: A fault cutting a layer cannot predate its formation.
• C: By superposition, an undisturbed layer on top was deposited after the layers below it, so it is the youngest.
• D: Different relationships can order events even without numeric dates.

Answer: C

Correct answer: One quarter. A half-life is the time for half of the remaining radioactive parent atoms to decay. Each half-life cuts what is left in half again, so the remaining fraction is (1/2) raised to the number of half-lives: 1/2, then 1/4, then 1/8. The tempting mistake is thinking two halves make a whole, so nothing remains. Decay never reaches exactly zero this way, which is the basis of radiometric dating.

• A: Radioactive parent material does not automatically reach zero after two half-lives.
• B: One eighth remains after three half-lives.
• C (correct): One half remains after one half-life and half of that, one quarter, after two.
• D: One half is the amount after only one half-life.

Answer: A

Correct answer: Transpiration. Plants pull water up from the roots through xylem, and most of it escapes as vapor through tiny leaf pores called stomata. Think of it as evaporation that happens through a plant, which is why the word shares a root with "perspiration." Infiltration is tempting because it is also part of the water cycle, but it moves water down into soil, the opposite direction.

• A (correct): Transpiration transfers water through plants and releases water vapor from leaves.
• B: Deposition concerns material settling or some gas-to-solid changes, not plant water release.
• C: Infiltration moves water downward into the ground.
• D: Subduction is a plate-tectonics process.

Answer: D

Correct answer: infiltration and recharge. Infiltration is the first step, when water soaks through the surface into soil pores. Water that keeps percolating downward past plant roots eventually reaches the saturated zone and adds to the aquifer, which is called recharge. Evaporation can seem relevant because it also follows rainfall, but it sends water upward into the air rather than down into the ground, so it cannot refill groundwater.

• A: Mantle convection is unrelated to this groundwater movement.
• B: Evaporation moves liquid water into the air rather than into groundwater.
• C: Tides are sea-level oscillations.
• D (correct): Infiltration begins entry to the ground, and subsequent movement can recharge an aquifer.

Answer: A

Correct answer: Groundwater commonly moves through pores and fractures in rock or sediment. Most aquifers are like a sponge: water fills the small connected spaces between grains or along cracks, and permeability controls how fast it flows. The common misconception is the underground lake, but large open caverns are rare and mostly limited to limestone regions. Groundwater also feeds springs and streams, and heavy pumping can lower water tables faster than rain replaces them.

• A (correct): Groundwater usually occupies and moves through connected pore spaces and fractures.
• B: Springs and groundwater discharge often support streams.
• C: Recharge is often far slower than pumping, so heavy withdrawal can lower water tables for decades.
• D: Most aquifers store water in the pores and cracks of rock or sediment; large open caverns are uncommon.

Answer: D

Correct answer: More rapid runoff and less infiltration. Soil has pore spaces that absorb rainfall, while asphalt and concrete are nearly impermeable, so water that once soaked in must flow across the surface instead. That runoff moves quickly into gutters and streams, raising flood risk and carrying pollutants. Reasoning from cause to effect helps here: removing the absorbing layer can only shift water from infiltration toward runoff, never the reverse.

• A: The expected direction is the opposite for impermeable land cover.
• B: Land cover can substantially change runoff and recharge patterns.
• C: Surface paving does not cause mantle melting.
• D (correct): Impermeable pavement commonly reduces infiltration and increases fast surface runoff.

Answer: A

Correct answer: They consist of tiny liquid droplets, ice crystals, or both. A cloud is visible because these particles scatter sunlight. Water vapor is a transparent gas, so a cloud forms only when vapor condenses onto tiny particles such as dust or salt, called condensation nuclei. Low, warm clouds are mostly droplets, while high, wispy cirrus clouds are made of ice crystals. The tempting error is treating clouds as vapor, which you could never actually see.

• A (correct): Visible cloud particles are small liquid droplets, ice crystals, or a mixture.
• B: Volcanic gases can influence clouds but are not the defining constituent.
• C: Water vapor is an invisible gas; clouds become visible only after vapor condenses into droplets or ice.
• D: Clouds are collections of tiny particles, not single solid blocks.

Answer: A

Correct answer: It can cool during expansion until saturation is reached. Air pressure drops with altitude, so a rising parcel expands, and expanding gas does work on its surroundings and cools without losing heat to them. Cooler air holds less water vapor at saturation, so the vapor begins condensing onto tiny particles at the dew point. Assuming rising air warms is the common mistake; warm air rises, but it cools as it climbs.

• A (correct): Rising air often expands in lower pressure and cools, potentially reaching saturation and condensation.
• B: Friction is not what drives cloud formation, and warming air would move it away from saturation rather than toward it.
• C: Rising air commonly cools rather than always heating.
• D: The whole air parcel does not turn into solid matter.

Answer: D

Correct answer: Land heats faster than nearby water, producing an onshore breeze. Water has a high specific heat and mixes its warmth through a deep layer, so its surface warms slowly. Sunlit land warms quickly, heating the air above it, which rises and leaves lower pressure over land. Cooler, denser air over the sea flows in to replace it. At night the pattern often reverses, producing an offshore land breeze.

• A: Tectonic divergence is unrelated to this wind pattern.
• B: Lunar tidal forces do not alone drive daily sea breezes.
• C: Water warms more slowly than land on a sunny day, so the afternoon surface breeze typically blows onshore.
• D (correct): Daytime land warms faster than water, creating lower pressure over land that draws cooler sea air onshore.

Answer: A

Correct answer: There is less overlying air exerting weight. Air pressure at any point comes from the weight of the column of air above it, pulled down by gravity. Climb higher and part of that column is now below you, so less weight presses down. Air is also compressible, so it is densest near the ground. The misconception that high altitude has no air fails because air thins gradually; it does not suddenly stop.

• A (correct): Less air above a higher-elevation location generally means less atmospheric weight and pressure.
• B: High elevations still contain air molecules.
• C: Core state does not explain local air pressure.
• D: Gravity does not disappear because the Moon blocks it.

Answer: C

Correct answer: Cold front. Cold air is denser than warm air, so as it advances it wedges underneath the warm air and pushes it up steeply. That rapid lifting cools the warm air and often builds tall cumulonimbus clouds, bringing brief heavy rain or thunderstorms, followed by cooler, drier conditions. A warm front is the opposite case, with warm air gliding gently up over retreating cold air and producing broader, steadier precipitation.

• A: Transform boundaries are rock-plate features, not weather fronts.
• B: Stationary fronts do not have the same advancing cold-air pattern.
• C (correct): A cold front advances as cooler air displaces and often lifts warmer air.
• D: This label does not describe a standard frontal type.

Answer: A

Correct answer: It tends to have greater tidal range near new or full Moon. At those phases the Sun, Earth, and Moon line up, so the solar and lunar tidal bulges add together, giving higher highs and lower lows. The name comes from the idea of water springing up, not from the season, so spring tides happen about twice every month. Neap tides, with the smallest range, occur near quarter Moons when the pulls are at right angles.

• A (correct): The Sun and Moon have stronger combined tidal effects near alignment, increasing the spring tidal range.
• B: Rainfall is not the defining cause of astronomical spring tides.
• C: The smallest tidal ranges near quarter Moons describe neap tides, not spring tides.
• D: Spring tide names do not depend on the season.

Answer: B

Correct answer: Rotation gives the day–night cycle; revolution with axial tilt produces annual seasons. Earth spins once about every 24 hours, carrying each location into and out of sunlight. Its axis stays tilted about 23.5° as it orbits, so each hemisphere alternately leans toward the Sun, getting more direct rays and longer days. A tempting error is blaming seasons on distance, but Earth is actually closest to the Sun in early January, during Northern Hemisphere winter.

• A: The day-night cycle is primarily from rotation.
• B (correct): Rotation produces the daily light-dark rhythm; tilt during Earth’s annual orbit drives seasons.
• C: Day and night do come from rotation, but seasons come from axial tilt, not changes in Earth–Sun distance; Earth is nearest the Sun in early January.
• D: Earth rotates about an axis tilted relative to its orbital plane.

Answer: B

Correct answer: A trench, intermediate-depth earthquakes, and a volcanic arc on the overriding side. Oceanic crust is denser than continental crust, so it sinks, bending down to form a deep trench. Earthquakes occur along the descending slab at increasing depths inland. As the slab descends, water released from it lowers the melting point of the mantle above, producing magma that feeds volcanoes, as in the Andes and Cascades. A mid-ocean ridge reflects plates pulling apart instead.

• A: Horizontal slip describes transform movement, not a subducting slab.
• B (correct): Subduction makes a trench, can generate earthquakes at varied depths, and can create volcanism above the descending slab.
• C: A ridge with new seafloor and only shallow quakes describes a divergent boundary, not subduction.
• D: Wind-blown sand deposits do not explain a plate-scale volcanic mountain chain.

Answer: D

Correct answer: 45 seconds. Count up from the earlier time rather than subtracting digits directly: from 10:03:20 to 10:04:00 is 40 seconds, then 5 more seconds reaches 10:04:05. Because P waves travel faster than S waves, the gap between their arrivals grows with distance, so seismologists use this S–P interval to estimate how far away an earthquake occurred. A common slip is treating a minute as 100 seconds when borrowing.

• A: 25 seconds undercounts the gap; 10:03:20 to 10:04:00 alone is already 40 seconds.
• B: 85 seconds comes from subtracting 320 from 405 as plain numbers, treating a minute as 100 seconds.
• C: 35 seconds miscounts the 40 seconds from 10:03:20 to 10:04:00 before adding the final 5 seconds.
• D (correct): Subtract 10:03:20 from 10:04:05: 40 seconds to 10:04:00 plus 5 seconds = 45 seconds.

Answer: B

Correct answer: Metamorphic. Classify a rock by the last process that formed it, not by its history. Lava cooling into basalt is igneous; weathering, deposition, compaction, and cementation make sandstone sedimentary; heat and pressure that change a rock without melting it make it metamorphic, turning sandstone into quartzite. If the rock had melted, cooling would have made it igneous again. This sequence traces one path around the rock cycle.

• A: The material was cemented before the final heat-driven change.
• B (correct): The final solid-state alteration of sandstone under heat changes it into metamorphic rock.
• C: Sandstone was sedimentary before metamorphism, not afterward in the stated sequence.
• D: Igneous describes the original basalt formed from lava, not the final alteration.

Answer: C

Correct answer: 20. A half-life is the time for half of the remaining parent atoms to decay, so each half-life multiplies the current amount by 1/2. After three half-lives, the fraction left is (1/2)³ = 1/8, and

A tempting mistake is subtracting a fixed amount each time and reaching zero, but radioactive decay never removes the same number of atoms each step; it removes the same fraction.

• A: Decay does not reach exactly zero after three half-lives under the ideal fraction model.
• B: 40 is the result after two half-lives.
• C (correct): Three successive halvings give 160 → 80 → 40 → 20 parent atoms.
• D: 80 is the result after one half-life.

Answer: D

Correct answer: 1 m. Multiply rate by time: 2.5 cm per year × 40 years = 100 cm. Then convert units, since 100 centimeters equal 1 meter. Watch the units throughout, because most wrong answers here come from misplacing a factor of ten or a hundred. Real plates move at a few centimeters per year, roughly as fast as fingernails grow, which is why meaningful plate motion takes millions of years.

• A: 100 m is 100 times the computed 1-meter displacement.
• B: 1 km is far larger than the computed short-timescale motion.
• C: 10 cm is ten times too small.
• D (correct): Multiply 2.5 cm/year by 40 years to obtain 100 cm, which is 1 meter.

Answer: C

Correct answer: 33 1/3%. Percent difference uses the reference value in the denominator: (new − reference) ÷ reference × 100. Here the difference is

which is 33 1/3%. The usual trap is dividing by the wrong number; dividing 300 by 1,200 gives 25%, which answers a different question about how much smaller the station value is than the town's.

• A: 30% is an imprecise percentage for the stated values.
• B: 25% divides by the town’s 1,200 mm instead of the reference.
• C (correct): Difference 300 mm divided by reference 900 mm is $\frac{1}{3}$, or 33 $\frac{1}{3}$ percent.
• D: 75% is the station amount as a fraction of the town, not the requested difference.

Answer: B

Correct answer: Relative humidity rises toward 100%. Relative humidity compares the water vapor actually present with the maximum the air could hold at its temperature. Cooling lowers that maximum while the actual vapor stays the same, so the ratio climbs. When it reaches 100%, the air is at its dew point and condensation begins as dew, fog, or cloud. This is why humidity is often highest on cool early mornings even without added moisture.

• A: Absolute moisture need not drop before condensation begins.
• B (correct): Cooling lowers saturation vapor pressure, so unchanged water vapor makes relative humidity increase toward saturation.
• C: Relative humidity depends on temperature even if water-vapor amount stays fixed.
• D: Relative humidity generally increases, rather than decreases, as saturation capacity falls.

Answer: C

Correct answer: 4.5 m. Tidal range is the vertical distance between high water and the following low water, so you subtract:

Because both heights are measured from the same chart datum, the datum cancels out and only the difference matters. Adding the levels is a common error, but a range always means the gap between two values, never their total. Range varies with spring and neap tides.

• A: 5.0 m is an arithmetic error given the two reference levels.
• B: 3.1 m halves the high-tide value and ignores low tide.
• C (correct): Tidal range is high-water level minus low-water level: 6.2 − 1.7 = 4.5 meters.
• D: 7.9 m adds the two levels incorrectly.

Answer: B

Correct answer: Similar sediment alone does not prove identical ages; further dating or correlation is needed. The same kind of sediment, such as beach sand, can be deposited in many places at many different times, so appearance alone shows similar environments, not equal ages. Geologists match ages using index fossils, distinctive ash layers, magnetic reversals, or radiometric dating of volcanic beds. Claiming identical timing from composition is a classic error of mistaking similarity for correlation.

• A: No evidence suggests a different planetary source.
• B (correct): Similar material can form at different times; correlation or numerical dating requires further evidence.
• C: Matching composition is not sufficient to guarantee age identity.
• D: Relative and radiometric methods can help date geologic sequences under suitable conditions.

Answer: D

Correct answer: A single cold day is weather and does not by itself overturn the long-term climate trend. Weather is the day-to-day state of the atmosphere, while climate is the average pattern over decades, usually about 30 years. Trends are judged statistically across many data points, and individual cold or hot days are expected noise around the trend. A useful hook: climate is what you expect, weather is what you get.

• A: One day is insufficient to assess a statistical multi-decade trend.
• B: Weather is a short-term condition, while climate describes long-term patterns that one day cannot reverse.
• C: Temperature remains a key climate variable, alongside precipitation and other measures.
• D (correct): One observation of short-term weather does not invalidate a trend evaluated over many years.

Answer: C

Correct answer: Lava. Magma and lava are the same kind of molten material in different places: magma is underground, and lava is molten rock after it erupts onto the surface.

• A: Magma is molten rock still beneath the surface; once it erupts, it gets a different name.
• B: Basalt is a solid extrusive igneous rock that forms after lava cools, not the molten material itself.
• C (correct): Molten rock that has reached the surface is lava; the term describes its location above ground.
• D: Sediment is loose weathered particles carried by water, wind or ice, not molten rock.

Answer: A

Correct answer: Part of Earth's core is liquid. P waves are compressional and can pass through solids and fluids, but S waves are shear waves that cannot travel through liquids.

When direct S waves fail to reach stations across the planet, the best explanation is a liquid layer deep inside Earth, the outer core.

• A (correct): S waves are shear waves that cannot travel through liquids, so their failure to cross the deep interior points to a liquid outer core.
• B: The mantle is mostly solid rock that deforms slowly; S waves do travel through it.
• C: The inner core is solid under immense pressure; the liquid layer is the outer core.
• D: P waves normally arrive first because they are faster; their speed does not explain missing S waves.

Answer: C

Correct answer: Toward the northwest. A hotspot stays roughly in place while the plate slides over it. Each island forms above the hotspot and is then carried away, so older islands end up farther along the plate's direction of travel. Since ages increase toward the northwest, the plate is moving northwest.

• A: Moving southeast would place the older islands to the southeast of the active one, the opposite of the pattern.
• B: An age progression across an island chain is evidence that the plate moves over the melt source.
• C (correct): Older islands are carried farther along the plate's direction of motion, so the plate moves northwest.
• D: The ages change along a southeast–northwest line, so the motion is not toward the northeast.

Answer: D

Correct answer: Sample X, because its dew point is higher. Relative humidity depends on temperature, so it cannot be used alone to compare moisture in air samples at different temperatures. Dew point reflects the actual water-vapor content: the higher the dew point, the more vapor.

Sample X has the higher dew point (18 °C versus 11 °C), so it holds more water vapor despite its lower relative humidity.

• A: Relative humidity compares vapor to the saturation amount at that temperature, so a cool sample can have high relative humidity with little vapor.
• B: Their dew points differ by 7 °C, which shows they hold different amounts of water vapor.
• C: Cooler air reaches saturation at a lower vapor content, so it does not hold more vapor.
• D (correct): Dew point tracks actual moisture content, and X's dew point of 18 °C is higher than Y's 11 °C.

Answer: B

Correct answer: Chemical weathering. Weathering acts in place, while erosion and deposition involve moving material. Because the iron-bearing minerals are reacting with oxygen and water to form rust, the minerals' chemistry is changing, which makes it chemical weathering.

• A: Mechanical weathering breaks rock into smaller pieces without changing its minerals; the rusting shows a chemical change.
• B (correct): Oxidation of iron minerals changes their chemical makeup in place, which is chemical weathering.
• C: Erosion moves weathered material elsewhere, but the stem says the material stayed in place.
• D: Deposition is the settling of transported material, and nothing here was transported.

Answer: D

Correct answer: 5,200 years. Count the halvings: 1 → 1/2 → 1/4 → 1/8 → 1/16 is 4 half-lives.

Age = 4 × 1,300 years = 5,200 years.

• A: This multiplies the half-life by 16; 1/16 remaining means 4 half-lives, not 16.
• B: This is 2 half-lives, which would leave 1/4 of the parent isotope, not 1/16.
• C: This counts 8 half-lives by halving 16; the number of halvings to reach 1/16 is 4.
• D (correct): Halving four times gives 1/16 (1 → 1/2 → 1/4 → 1/8 → 1/16), and 4 × 1,300 = 5,200 years.

Answer: A

Correct answer: Neap tides, with a smaller difference between high and low tide. Near new and full Moon the Sun and Moon line up and produce spring tides with the largest range. Around the first- and third-quarter phases their effects are at right angles, giving neap tides with a smaller range.

• A (correct): At quarter phases the Sun's and Moon's tidal pulls work at right angles, so the tidal range is smaller.
• B: Spring tides occur near new and full Moon, when the Sun and Moon line up.
• C: The Sun only partly offsets the Moon's effect; tides still rise and fall.
• D: The word spring in spring tide has nothing to do with the season; it refers to a larger tidal range.

Answer: A

Correct answer: 20,000 years. Convert to the same unit first: 1 km = 1,000 m = 100,000 cm.

Time = distance ÷ rate = 100,000 cm ÷ 5 cm per year = 20,000 years.

• A (correct): 1 km = 100,000 cm, and 100,000 cm ÷ 5 cm per year = 20,000 years.
• B: This uses 10,000 cm for 1 km; a kilometer is 1,000 m, or 100,000 cm.
• C: This uses 1,000,000 cm for 1 km, ten times too large.
• D: This treats 1 km as 1,000 cm, confusing kilometers with centimeters and meters.

Answer: C

Correct answer: The color of the mineral's powder. A streak test identifies a mineral by the color of its powder left on a porcelain plate. It is different from a scratch test for hardness, from luster, and from cleavage.

• A: Resistance to scratching is hardness, which is tested on the Mohs scale, not by streak.
• B: Light reflected from the surface is luster, a different property.
• C (correct): A streak test shows the color the mineral leaves as a fine powder on the plate.
• D: Breaking along flat surfaces is cleavage, not streak.

Answer: D

Correct answer: It loses its supply of warm ocean water and moisture. Hurricanes draw their energy from warm ocean water: evaporated moisture rises, condenses and releases latent heat that sustains the storm. Over land that supply of warmth and moisture is cut off, so the storm weakens, although its rain can still cause inland flooding.

• A: Earth's rotation affects motion over land and sea alike; the Coriolis effect does not switch off.
• B: Land is heated by the Sun, often strongly; this does not explain the loss of the storm's fuel.
• C: Pressure over land varies; this is not why hurricanes weaken.
• D (correct): Hurricanes are fueled by warm water and moisture whose latent heat drives the circulation, so cutting off that supply weakens them.

Answer: B

Correct answer: Stratosphere. The troposphere is the lowest atmospheric layer and holds most weather. The stratosphere lies just above it and contains the ozone layer, which absorbs much of the incoming ultraviolet radiation.

• A: The troposphere is the lowest layer, where most weather happens; the ozone layer lies above it.
• B (correct): The stratosphere, directly above the troposphere, contains the ozone layer that absorbs much ultraviolet radiation.
• C: The lithosphere is the rigid outer shell of solid Earth, not part of the atmosphere.
• D: The hydrosphere is Earth's water, not a layer of the atmosphere.