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NY Regents Earth Science study materials
NY Regents Earth Science study resources

NY Regents Earth Science practice questions

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Question 1Matter, Energy, and Change in Earth Systems

A student observes that a sample of the mineral halite breaks into small cubes with flat, smooth surfaces. Which physical property of minerals does this observation best describe?

  1. Streak
  2. Hardness
  3. Luster
  4. Cleavage Correct answer.

Explanation

Cleavage is the tendency of a mineral to break along flat planes determined by its internal atomic arrangement. Halite breaks into cubes because it has three directions of cleavage at right angles. Hardness, streak, and luster describe resistance to scratching, powder color, and surface reflection, none of which produce flat breakage surfaces.

Question 2Matter, Energy, and Change in Earth Systems

A sample of an igneous rock contains large crystals of quartz and feldspar visible to the naked eye. What does the crystal size most directly indicate about the rock's formation?

  1. It cooled rapidly at Earth's surface after an eruption.
  2. It was deposited in layers of sediment.
  3. It cooled slowly at depth, allowing crystals time to grow. Correct answer.
  4. It was metamorphosed under high pressure.

Explanation

Crystal size in igneous rocks reflects cooling rate. Slow cooling deep underground gives atoms time to arrange into large, visible crystals, producing a coarse-grained texture. Rapid surface cooling produces fine-grained or glassy rock, and metamorphism or sedimentation do not produce interlocking igneous crystals.

Question 3Matter, Energy, and Change in Earth Systems

Which statement correctly describes the relationship between density and the state of matter for most substances?

  1. Density is identical in all three states.
  2. The solid state is generally denser than the liquid state. Correct answer.
  3. The gas state is generally denser than the liquid state.
  4. The liquid state is always denser than the solid state.

Explanation

For most substances, particles in a solid are packed more closely than in a liquid, so the solid is denser. Gases are far less dense because their particles are widely separated. Water is a notable exception because ice is less dense than liquid water, which is why ice floats.

Question 4Matter, Energy, and Change in Earth Systems

During an exothermic chemical change, what happens to energy in the system?

  1. Energy is absorbed from the surroundings as bonds break.
  2. Energy is converted entirely into mass.
  3. Energy is released to the surroundings as bonds form. Correct answer.
  4. Energy is destroyed as the reaction proceeds.

Explanation

In an exothermic change, the products have less chemical energy than the reactants, and the difference is released, usually as heat. Energy is conserved, so it is transferred to the surroundings rather than destroyed. Absorbing energy describes an endothermic change.

Question 5Matter, Energy, and Change in Earth Systems

A pot of water is heated on a stove. Which heat-transfer mechanism carries energy through the water itself, producing circulation?

  1. Conduction
  2. Radiation
  3. Convection Correct answer.
  4. Reflection

Explanation

Convection transfers heat through fluids as warmer, less dense material rises and cooler, denser material sinks, creating circulation. Conduction moves heat through direct contact without bulk motion, and radiation transfers energy by electromagnetic waves. Reflection is not a heat-transfer mechanism.

Question 6Matter, Energy, and Change in Earth Systems

Which observation provides the best evidence that a change is a chemical change rather than a physical change?

  1. The material is broken into smaller pieces.
  2. The material dissolves in water.
  3. The material changes from solid to liquid.
  4. A new substance with different properties is produced. Correct answer.

Explanation

A chemical change produces one or more new substances with different compositions and properties, often signaled by color change, gas production, or precipitate formation. Melting, crushing, and dissolving are physical changes that alter form or state without creating new substances.

Question 7Matter, Energy, and Change in Earth Systems

A sample of gas in a sealed rigid container is cooled. According to the kinetic molecular theory, which change occurs in the particles of the gas?

  1. Their average kinetic energy decreases. Correct answer.
  2. The number of particles increases.
  3. Their average kinetic energy increases.
  4. The mass of each particle increases.

Explanation

Temperature is a measure of average kinetic energy of particles. Cooling lowers that average kinetic energy, so the particles move more slowly. Particle number and particle mass are unchanged by cooling in a sealed container.

Question 8Matter, Energy, and Change in Earth Systems

An object with a mass of 200 grams has a volume of 40 cubic centimeters. What is the density of the object?

  1. 5.0 g/cm³ Correct answer.
  2. 0.2 g/cm³
  3. 8,000 g/cm³
  4. 0.5 g/cm³

Explanation

Density is mass divided by volume. Dividing 200 g by 40 cm³ gives 5.0 g/cm³. This value is greater than the density of water, so the object would sink in water.

Question 9Matter, Energy, and Change in Earth Systems

A liquid at 20°C is placed in a freezer and becomes a solid at -10°C. Which statement best describes the energy change during freezing?

  1. The liquid releases energy to its surroundings as it becomes solid. Correct answer.
  2. The total energy of the material increases during freezing.
  3. The liquid absorbs energy from its surroundings as it becomes solid.
  4. The particles stop moving completely when the solid forms.

Explanation

Freezing is a phase change in which liquid particles lose energy and settle into fixed positions, releasing energy to the surroundings. The temperature stays constant during the change of state until freezing completes. Particles in a solid still vibrate, so they do not stop moving entirely.

Question 10Matter, Energy, and Change in Earth Systems

A rock sample is heated and its temperature rises steadily, but at a certain temperature the temperature stops rising while heating continues. What is the best explanation?

  1. Energy is being used to change the state of the material. Correct answer.
  2. The heat source has stopped supplying energy.
  3. The material has reached absolute zero.
  4. The material's density has become zero.

Explanation

During a phase change, added energy goes into breaking attractions between particles rather than increasing average kinetic energy, so temperature remains constant. This produces a plateau on a heating curve. Energy is still being added, so the source has not stopped.

Question 11Matter, Energy, and Change in Earth Systems

Which process transfers energy through the vacuum of space from the Sun to Earth?

  1. Evaporation
  2. Convection
  3. Radiation Correct answer.
  4. Conduction

Explanation

Radiation carries energy as electromagnetic waves and requires no medium, so it can cross empty space. Conduction and convection require matter to transfer heat. Evaporation is a phase change that moves energy within a fluid, not across a vacuum.

Question 12Matter, Energy, and Change in Earth Systems

A beaker of water at 25°C is placed in a room at 25°C. Which statement describes the net heat flow?

  1. There is no net heat flow because the temperatures are equal. Correct answer.
  2. Heat flows from the water into the room.
  3. Heat flows from the room into the water.
  4. Heat flows in both directions equally and continues to change temperature.

Explanation

Heat flows from warmer objects to cooler objects until thermal equilibrium is reached. When both are at the same temperature, forward and reverse transfers balance, so there is no net heat flow and no further temperature change.

Question 13Matter, Energy, and Change in Earth Systems

A student compares two samples of the same substance: a 100 g sample and a 200 g sample at the same temperature. Which statement is correct?

  1. Both samples contain identical total thermal energy.
  2. The 200 g sample contains more total thermal energy but has the same average particle kinetic energy. Correct answer.
  3. The 200 g sample has a higher temperature because it has more mass.
  4. The 200 g sample has a higher average particle kinetic energy.

Explanation

Temperature reflects average kinetic energy of particles, so equal temperatures mean equal average kinetic energy regardless of mass. Total thermal energy depends on both temperature and the amount of material, so the larger sample stores more total energy.

Question 14Matter, Energy, and Change in Earth Systems

A sealed container holds a fixed mass of gas. If the gas is compressed to half its volume while temperature is held constant, what happens to the pressure?

  1. The pressure drops to zero.
  2. The pressure stays the same.
  3. The pressure doubles. Correct answer.
  4. The pressure is halved.

Explanation

At constant temperature, pressure and volume are inversely related. Halving the volume doubles the number of collisions with the container walls per unit area, doubling the pressure. This is Boyle's law behavior.

Question 15Matter, Energy, and Change in Earth Systems

Which statement best explains why an increase in atmospheric carbon dioxide can raise average global temperatures?

  1. Carbon dioxide increases the albedo of Earth's surface.
  2. Carbon dioxide destroys the ozone layer, allowing more ultraviolet light to enter.
  3. Carbon dioxide absorbs outgoing infrared radiation and re-emits some back toward Earth. Correct answer.
  4. Carbon dioxide blocks incoming visible sunlight from reaching Earth's surface.

Explanation

Greenhouse gases such as carbon dioxide are transparent to incoming visible light but absorb outgoing infrared radiation, trapping energy in the atmosphere. This warms the lower atmosphere and surface. Blocking sunlight, ozone destruction, and higher albedo would all tend to cool the surface rather than warm it.

Question 16Matter, Energy, and Change in Earth Systems

A sample of ice at -20°C is heated until it becomes steam above 100°C. Which sequence correctly describes the changes of state that occur?

  1. Solid to liquid, then liquid to gas Correct answer.
  2. Gas to liquid, then liquid to solid
  3. Liquid to solid, then solid to gas
  4. Solid to gas directly, then gas to liquid

Explanation

Heating ice first melts it to liquid water at 0°C, then boils the liquid to steam at 100°C. Each change of state absorbs energy at a constant temperature. The reverse order describes cooling, and direct sublimation would require conditions not present here.

Question 17Matter, Energy, and Change in Earth Systems

Two rock samples have the same volume, but sample A has twice the mass of sample B. Which conclusion is best supported?

  1. Both samples have equal density because their volumes are equal.
  2. Sample A has lower density than sample B.
  3. Sample A has greater density than sample B. Correct answer.
  4. Sample B has greater density because it is lighter.

Explanation

Density equals mass divided by volume. With equal volumes, the sample with greater mass has greater density. Density is not determined by volume alone, and a lighter sample of the same volume is less dense, not more.

Question 18Matter, Energy, and Change in Earth Systems

A closed system contains a fixed amount of a substance that undergoes a chemical reaction. Which statement best reflects the conservation of mass and energy?

  1. The total mass decreases because energy is released.
  2. The total mass and total energy of the closed system remain constant. Correct answer.
  3. Mass is converted entirely into energy during the reaction.
  4. The total energy increases because new bonds form.

Explanation

In a closed system, matter and energy are conserved: atoms are rearranged but not created or destroyed, and energy is transferred between forms without net loss. Mass-energy conversion is negligible in ordinary chemical reactions. Released energy comes from stored chemical energy, not from disappearing mass.

Question 19Matter, Energy, and Change in Earth Systems

A metamorphic rock is found to contain large crystals of a mineral that typically forms only at high temperature and pressure. Which conclusion is most reasonable?

  1. The rock formed from a rapidly cooling lava flow.
  2. The rock cooled rapidly at Earth's surface.
  3. The rock experienced high-grade metamorphism at depth. Correct answer.
  4. The rock was deposited as loose sediment.

Explanation

Large crystals of minerals stable only at high temperature and pressure indicate that the rock recrystallized under intense metamorphic conditions, typically deep within Earth. Rapid surface cooling and sediment deposition cannot produce such crystals.

Question 20Matter, Energy, and Change in Earth Systems

A student claims that adding heat to a substance always raises its temperature. Which situation best refutes this claim?

  1. A metal bar is heated and expands slightly.
  2. A gas is heated in a rigid container and its pressure rises.
  3. Ice at 0°C is heated and melts while its temperature stays at 0°C. Correct answer.
  4. Water at 50°C is heated and its temperature rises.

Explanation

During a phase change, added energy breaks intermolecular attractions instead of increasing average kinetic energy, so temperature remains constant. Melting ice at 0°C is a clear example of heat input without a temperature rise. Heating a single phase, as in the other options, does raise temperature.

Question 21Earth's Interior, Plate Tectonics, and Geologic History

Which layer of Earth's interior is inferred to be liquid because S-waves cannot pass through it?

  1. the asthenosphere
  2. the lower mantle
  3. the outer core Correct answer.
  4. the inner core

Explanation

S-waves are shear waves and cannot travel through a liquid. Seismograph records show an S-wave shadow zone beyond about 103 degrees from an earthquake, which requires a liquid outer core. The inner core is solid, and both mantle layers transmit shear waves.

Question 22Earth's Interior, Plate Tectonics, and Geologic History

A seismic station records P-waves but no S-waves from a distant earthquake. What does this observation indicate about the path of the waves?

  1. The waves lost energy in the mantle.
  2. The waves were refracted back to the surface.
  3. The waves passed through a liquid zone. Correct answer.
  4. The waves traveled only through the crust.

Explanation

S-waves cannot propagate through fluids, while P-waves can. A record showing P-waves without S-waves therefore indicates that part of the wave path crossed a liquid region, interpreted as the outer core. Refraction alone would not eliminate the S arrival.

Question 23Earth's Interior, Plate Tectonics, and Geologic History

Compared with continental crust, oceanic crust is best described as

  1. thicker and less dense
  2. thinner and less dense
  3. thicker and more dense
  4. thinner and more dense Correct answer.

Explanation

Oceanic crust is basaltic, about 5 to 10 km thick, and denser than granitic continental crust. Continental crust is thicker, roughly 30 to 70 km, and less dense, which is why continents ride higher. Density and thickness must both be considered.

Question 24Earth's Interior, Plate Tectonics, and Geologic History

The Moho is best identified as the boundary between the

  1. outer core and the inner core
  2. crust and the mantle Correct answer.
  3. mantle and the outer core
  4. lithosphere and the asthenosphere

Explanation

The Mohorovicic discontinuity, or Moho, is the boundary where seismic wave velocities jump sharply between the crust and the mantle. It marks a change in rock composition and density. The other boundaries listed have their own names and seismic signatures.

Question 25Earth's Interior, Plate Tectonics, and Geologic History

A rock sample contains a mineral that is known to be about 4.0 billion years old. Which statement best describes what this age represents?

  1. the time since the rock last melted or crystallized Correct answer.
  2. the time when the rock was first weathered
  3. the time when the mineral was eroded
  4. the time since the sediment was deposited

Explanation

Radiometric ages date the event that closed the mineral's isotopic system, usually crystallization from melt or metamorphic recrystallization. Weathering and erosion do not reset most mineral clocks. Depositional age applies to sedimentary rocks, which are usually dated by cross-cutting relations instead.

Question 26Earth's Interior, Plate Tectonics, and Geologic History

Which principle states that in an undisturbed sequence of sedimentary rocks, the oldest layer is at the bottom?

  1. the principle of superposition Correct answer.
  2. the principle of lateral continuity
  3. the principle of cross-cutting relationships
  4. the principle of original horizontality

Explanation

Superposition holds that undisturbed sedimentary layers are deposited in order, so lower layers are older than those above them. Cross-cutting relationships deal with faults and intrusions, horizontality with depositional orientation, and lateral continuity with layer extent.

Question 27Earth's Interior, Plate Tectonics, and Geologic History

A basalt dike cuts across a horizontal sandstone layer. Which statement about relative ages is correct?

  1. The sandstone is younger than the dike.
  2. The age relation cannot be determined.
  3. The dike and the sandstone are the same age.
  4. The dike is younger than the sandstone. Correct answer.

Explanation

Under the principle of cross-cutting relationships, a feature that cuts another must be younger than the material it cuts. The dike therefore intruded after the sandstone was deposited. Contact metamorphism along the dike would support the same conclusion.

Question 28Earth's Interior, Plate Tectonics, and Geologic History

An index fossil is most useful for correlation because it

  1. is found only in one type of sedimentary rock
  2. is preserved only in metamorphic rock
  3. existed for a short time over a wide geographic area Correct answer.
  4. is the largest fossil in a rock layer

Explanation

A good index fossil comes from an organism that was widespread but short-lived, so its presence marks a narrow time interval across many locations. Abundance and wide distribution make correlation practical. Size and rock type are not the criteria.

Question 29Earth's Interior, Plate Tectonics, and Geologic History

A geologist finds the same distinctive trilobite species in shale beds on two continents now separated by an ocean. What is the best interpretation?

  1. The trilobites swam across the modern ocean.
  2. The shale formed at two unrelated times.
  3. The two shale beds were once part of one continuous environment. Correct answer.
  4. The fossils were carried by wind to one continent.

Explanation

Matching fossil assemblages in rocks of the same age indicate that the containing layers were once continuous and later separated. This evidence supported continental drift before seafloor spreading was understood. Independent evolution of identical species on separate continents is implausible.

Question 30Earth's Interior, Plate Tectonics, and Geologic History

The half-life of a radioactive isotope is 500 million years. If a mineral originally contained only the parent isotope, what fraction of the parent remains after 1.5 billion years?

  1. one-eighth Correct answer.
  2. one-half
  3. one-sixteenth
  4. one-quarter

Explanation

1.5 billion years equals three half-lives of 500 million years. Each half-life halves the parent, so the remaining fraction is 1/2 x 1/2 x 1/2 = 1/8. This corresponds to 87.5 percent of the parent having decayed.

Question 31Earth's Interior, Plate Tectonics, and Geologic History

The theory of plate tectonics explains that lithospheric plates move because

  1. tidal forces pull the plates apart
  2. convection in the mantle provides the driving energy Correct answer.
  3. the plates float freely on the outer core
  4. Earth's rotation drags the crust eastward

Explanation

Heat from Earth's interior drives mantle convection, and the resulting slab pull and ridge push move the rigid plates. Plates rest on the weak asthenosphere, not on the liquid outer core. Tides and rotation are far too weak to drive plate motion.

Question 32Earth's Interior, Plate Tectonics, and Geologic History

At which type of plate boundary does new oceanic lithosphere form?

  1. a subduction zone
  2. a divergent boundary Correct answer.
  3. a transform boundary
  4. a continental collision zone

Explanation

At divergent boundaries, such as mid-ocean ridges, plates pull apart and magma rises to form new oceanic crust. Subduction zones and collision zones consume or thicken crust, and transform boundaries slide plates past each other.

Question 33Earth's Interior, Plate Tectonics, and Geologic History

Deep-focus earthquakes and a volcanic island arc are most characteristic of which setting?

  1. a transform fault
  2. a mid-ocean ridge
  3. a subduction zone Correct answer.
  4. a continental hot spot

Explanation

At a subduction zone, a descending slab generates earthquakes to depths of hundreds of kilometers and releases water that promotes melting and arc volcanism. Ridges and transform faults have shallow seismicity only. Hot spots lack deep-focus earthquakes.

Question 34Earth's Interior, Plate Tectonics, and Geologic History

Magnetic striping on the seafloor on either side of a mid-ocean ridge is symmetrical because

  1. the ocean current aligns magnetic minerals
  2. the ridge periodically reverses Earth's magnetic field
  3. sediment settles evenly on both sides of the ridge
  4. new crust records field reversals as it spreads outward Correct answer.

Explanation

As magma cools at a ridge, magnetic minerals align with the field at that time, recording normal or reversed polarity. Seafloor spreading carries this record outward symmetrically. The field reverses on its own schedule, not because of the ridge.

Question 35Earth's Interior, Plate Tectonics, and Geologic History

A chain of volcanic islands shows progressively older ages with increasing distance from a hot spot. This pattern is best explained by

  1. the hot spot moving rapidly toward the islands
  2. sea level rising unevenly across the ocean
  3. the islands being eroded at different rates
  4. the lithospheric plate moving over a stationary hot spot Correct answer.

Explanation

A hot spot stays roughly fixed while the plate moves over it, so volcanoes form in sequence and grow older away from the active center. Erosion and sea-level change modify islands but do not create the age progression. The plate motion, not hot-spot motion, produces the trend.

Question 36Earth's Interior, Plate Tectonics, and Geologic History

Which evidence was used by Wegener to support the idea that continents have moved?

  1. measurements of mantle convection currents
  2. GPS measurements of plate motion
  3. matching mountain belts and glacial deposits on separate continents Correct answer.
  4. magnetic striping on the seafloor

Explanation

Wegener cited the fit of continental margins, matching fossils, and continuity of mountain belts and glacial deposits across the Atlantic. Seafloor magnetic striping and GPS came later and were not available to him. Mantle convection was not directly measured in his time.

Question 37Earth's Interior, Plate Tectonics, and Geologic History

A fault offsets a layer of volcanic ash that has been dated at 20 million years. Which statement is best supported?

  1. The fault moved after the ash was deposited. Correct answer.
  2. The fault and the ash formed at the same time.
  3. The ash is younger than the fault.
  4. The fault moved before the ash was deposited.

Explanation

A fault that displaces a dated layer must have moved after that layer formed, so the fault is younger than 20 million years. The dated ash provides a maximum age for the faulting event. This applies the principle of cross-cutting relationships.

Question 38Earth's Interior, Plate Tectonics, and Geologic History

An unconformity in which tilted sedimentary layers are overlain by horizontal layers represents

  1. an angular unconformity Correct answer.
  2. a fault with no displacement
  3. a period of continuous deposition
  4. a disconformity with no erosion

Explanation

An angular unconformity forms when layers are tilted, eroded, and then buried by new horizontal layers. The erosion surface records a gap in the rock record. Continuous deposition would leave parallel layers with no erosional break.

Question 39Earth's Interior, Plate Tectonics, and Geologic History

Which sequence of geologic events is most consistent with the principle of superposition and cross-cutting relationships?

  1. deposition of layers, intrusion of a dike, erosion, deposition of younger layers Correct answer.
  2. erosion, deposition of layers, intrusion of a dike, deposition of younger layers
  3. intrusion of a dike, deposition of layers, erosion, deposition of younger layers
  4. deposition of layers, erosion, intrusion of a dike, deposition of younger layers

Explanation

Layers are deposited first, then cut by the dike, then eroded to form a surface, and finally buried by younger layers. This ordering satisfies superposition and cross-cutting relationships. Any sequence placing the dike before the layers it cuts contradicts the principles.

Question 40Earth's Interior, Plate Tectonics, and Geologic History

The presence of pillow basalts in an ancient rock sequence indicates that the lava erupted

  1. beneath a glacier
  2. in a desert
  3. in a volcanic dome on land
  4. underwater Correct answer.

Explanation

Pillow structures form when basaltic lava is quenched rapidly under water, producing rounded, stacked shapes. Their presence in a rock sequence is evidence of subaqueous eruption. Subaerial lava typically forms flows and rubble, not pillows.

Question 41Earth's Interior, Plate Tectonics, and Geologic History

Which observation best supports the conclusion that Earth's core is much denser than its crust?

  1. The average density of Earth exceeds the density of crustal rock. Correct answer.
  2. Earthquake waves travel faster in the core than in the crust.
  3. The core is hotter than the crust.
  4. Volcanoes erupt dense lava at the surface.

Explanation

The bulk density of Earth is greater than the density of surface rocks, so denser material must exist at depth. Seismic velocities alone do not give density directly, though they help constrain composition. High temperature does not by itself imply high density.

Question 42Earth's Interior, Plate Tectonics, and Geologic History

A continent-continent collision zone such as the Himalaya is characterized by

  1. a mid-ocean ridge with new crust
  2. a deep ocean trench with island arc volcanism
  3. thickened crust and folded mountain belts Correct answer.
  4. a transform fault with lateral sliding

Explanation

When two continental plates collide, neither subducts easily, so the crust is compressed, folded, and thickened to build high mountains. Deep trenches and arc volcanism belong to oceanic subduction. Ridges and transform faults form at other boundary types.

Question 43Earth's Interior, Plate Tectonics, and Geologic History

The presence of marine fossils in sedimentary rock now exposed at high elevation in a mountain range is best explained by

  1. tectonic uplift of former seafloor Correct answer.
  2. fossils being blown uphill by wind
  3. volcanic eruption of fossils
  4. glaciers carrying fossils upslope

Explanation

Marine fossils in rock at high elevation indicate that the rock formed below sea level and was later uplifted by tectonic processes. Wind, glaciers, and volcanoes do not move intact marine fossils into bedrock at high altitude. Uplift is the standard interpretation.

Question 44Earth's Interior, Plate Tectonics, and Geologic History

Which statement best explains why the geologic time scale is divided into eons, eras, periods, and epochs?

  1. The divisions mark the locations of major cities.
  2. The divisions mark equal intervals of time.
  3. The divisions mark the depth of ocean basins.
  4. The divisions mark major changes in life and rock records. Correct answer.

Explanation

The geologic time scale is based on major events in Earth history, such as mass extinctions and changes in the fossil record, which define boundaries. The units are not equal in duration. They are not geographic or oceanographic divisions.

Question 45Earth's Interior, Plate Tectonics, and Geologic History

Which feature would most likely be found at a divergent plate boundary on the ocean floor?

  1. a deep trench
  2. a transform fault
  3. a folded mountain belt
  4. a mid-ocean ridge Correct answer.

Explanation

Divergent boundaries in the ocean form mid-ocean ridges where new basaltic crust is created. Deep trenches form at subduction zones, folded belts at collision zones, and transform faults at sliding boundaries. Ridge topography is the hallmark of seafloor spreading.

Question 46Earth's Interior, Plate Tectonics, and Geologic History

Seismic waves from a single earthquake are recorded at stations around the world. A shadow zone exists for S-waves at angular distances between about 103° and 142° from the epicenter. Which property of Earth's interior best explains this S-wave shadow zone?

  1. The outer core is liquid, so S-waves cannot pass through it Correct answer.
  2. The mantle reflects S-waves back toward the surface
  3. The inner core is solid iron and stops all seismic waves
  4. The crust bends S-waves so they cannot reach the far side

Explanation

S-waves are transverse shear waves and cannot travel through a liquid. A liquid outer core blocks S-wave transmission, producing a shadow zone on the far side of the earthquake. The inner core is solid, but the surrounding liquid outer core is what stops the S-waves.

Question 47Earth's Interior, Plate Tectonics, and Geologic History

A geologist maps a region where a sequence of folded sedimentary layers is overlain by a younger, undeformed conglomerate. The contact between the folded layers and the conglomerate is an erosional surface. Which term best describes this contact?

  1. Nonconformity
  2. Angular unconformity Correct answer.
  3. Disconformity
  4. Intrusion

Explanation

An angular unconformity forms when tilted or folded layers are eroded and then buried by younger, flat-lying sediments. The contrast in orientation between the folded beds and the overlying conglomerate is the key evidence. A disconformity would show parallel layers, and a nonconformity would involve eroded igneous or metamorphic rock below.

Question 48Earth's Interior, Plate Tectonics, and Geologic History

A rock sample from a lava flow contains 25% of its original radioactive parent isotope and 75% of its daughter product. If the parent isotope has a half-life of 200 million years, what is the most reasonable age of the lava flow?

  1. 100 million years
  2. 200 million years
  3. 400 million years Correct answer.
  4. 600 million years

Explanation

Each half-life reduces the parent fraction by half: after one half-life 50% remains, after two half-lives 25% remains. Reaching 25% parent therefore requires two half-lives. Two times 200 million years equals 400 million years.

Question 49Earth's Interior, Plate Tectonics, and Geologic History

Along a convergent boundary, a slab of oceanic lithosphere descends beneath a continental plate. Which set of features would most likely develop above the descending slab?

  1. A transform fault, offset rock layers, and shallow earthquakes
  2. A deep-ocean trench, a volcanic arc, and shallow-to-deep earthquakes Correct answer.
  3. A mid-ocean ridge, new seafloor, and shallow earthquakes
  4. A broad rift valley, normal faults, and a central magma body

Explanation

Where oceanic lithosphere subducts beneath a continent, a trench marks the down-going slab, a volcanic arc forms above it, and earthquakes occur along the slab from shallow to deep. The other options describe divergent or transform settings. Subduction zones are the only setting that produces deep-focus earthquakes.

Question 50Earth's Interior, Plate Tectonics, and Geologic History

A scientist compares the age of the seafloor on both sides of a mid-ocean ridge. The age of the basaltic crust increases steadily with distance from the ridge crest on both sides. Which conclusion is best supported by this pattern?

  1. Oceanic crust is not magnetic and cannot record reversals
  2. The ridge is a subduction zone where old crust is destroyed
  3. New oceanic lithosphere forms at the ridge and moves away from it over time Correct answer.
  4. The seafloor is older at the ridge than at the continents

Explanation

Symmetrical age patterns that increase away from a ridge indicate that new lithosphere is created at the ridge and spreads outward in both directions. This is a central prediction of seafloor spreading. The pattern also matches the symmetrical magnetic striping recorded in the basalt.