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HSC Earth and Environmental Science study materials
HSC Earth and Environmental Science study resources

HSC Earth and Environmental Science practice questions

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Question 1Earth's Systems and Processes

Which layer of Earth's interior is composed mainly of solid iron and nickel and lies at the centre of the planet?

  1. The crust
  2. The inner core Correct answer.
  3. The lower mantle
  4. The outer core

Explanation

Earth's inner core is a solid sphere of iron-nickel alloy at the very centre, kept solid despite extreme temperature because of immense pressure. The outer core is liquid, the mantle is silicate rock, and the crust is the thin rocky outer shell.

Question 2Earth's Systems and Processes

The theory of plate tectonics explains that lithospheric plates move because they are driven mainly by which process?

  1. Tidal forces from the Moon
  2. Conduction of heat through the crust
  3. Erosion of continental rock
  4. Convection currents in the mantle Correct answer.

Explanation

Heat escaping from Earth's interior drives slow convection in the mantle, and the movement of this hot rock, together with slab pull at subduction zones, drags the overlying lithospheric plates. Conduction, tides and erosion do not provide the sustained driving force for plate motion.

Question 3Earth's Systems and Processes

At a divergent plate boundary where two oceanic plates move apart, which feature typically forms?

  1. A mid-ocean ridge Correct answer.
  2. A transform fault valley
  3. A fold mountain belt
  4. A deep ocean trench

Explanation

Where oceanic plates separate, magma rises to fill the gap and solidifies, building a mid-ocean ridge with a central rift valley. Trenches form at convergent boundaries and fold mountains mainly at continental collisions.

Question 4Earth's Systems and Processes

Which type of seismic wave travels fastest and is the first to be recorded at a seismograph station?

  1. Love waves
  2. Surface waves
  3. Secondary (S) waves
  4. Primary (P) waves Correct answer.

Explanation

Primary waves are compressional body waves and travel fastest through rock, so they arrive first at a seismograph. Secondary waves are slower shear waves, and surface waves such as Love waves are slower again.

Question 5Earth's Systems and Processes

Which process in the rock cycle involves molten rock cooling and crystallising to form solid rock?

  1. Melting
  2. Weathering
  3. Compaction
  4. Crystallisation Correct answer.

Explanation

Crystallisation occurs when magma or lava cools and its minerals solidify into igneous rock. Melting does the reverse, weathering breaks rock down at the surface, and compaction helps form sedimentary rock from loose sediment.

Question 6Earth's Systems and Processes

Which gas makes up the largest proportion of Earth's modern atmosphere?

  1. Oxygen
  2. Carbon dioxide
  3. Nitrogen Correct answer.
  4. Argon

Explanation

Nitrogen accounts for roughly 78 percent of the modern atmosphere by volume, making it the dominant gas. Oxygen is about 21 percent, argon about 0.9 percent, and carbon dioxide a small fraction.

Question 7Earth's Systems and Processes

The greenhouse effect occurs because certain atmospheric gases do which of the following?

  1. Block ultraviolet radiation from reaching the surface
  2. Increase the speed of convection in the troposphere
  3. Absorb and re-emit outgoing infrared radiation Correct answer.
  4. Reflect incoming solar radiation back into space

Explanation

Greenhouse gases such as carbon dioxide, methane and water vapour absorb infrared radiation emitted by Earth's surface and re-emit it, some of which returns toward the surface and warms the lower atmosphere. They do not mainly act by reflecting incoming sunlight or blocking ultraviolet radiation.

Question 8Earth's Systems and Processes

Which of the following is a renewable energy source derived from Earth's internal heat?

  1. Natural gas
  2. Geothermal energy Correct answer.
  3. Coal
  4. Uranium

Explanation

Geothermal energy harnesses heat from Earth's interior, for example from hot rocks or magma, to generate electricity or heat buildings, and it is continually replenished by internal heat flow. Coal, natural gas and uranium are finite resources extracted from the crust.

Question 9Earth's Systems and Processes

A geologist finds a sedimentary rock layer containing the same index fossil species in two widely separated locations. What can be inferred?

  1. The fossil species lived only at one of the locations
  2. The two rock layers formed at exactly the same depth
  3. The two rock layers are likely of similar geological age Correct answer.
  4. The two locations experienced identical metamorphism

Explanation

Index fossils are species with a wide geographic distribution and a short geological lifespan, so their presence in separated layers indicates those layers formed during the same narrow time interval. Depth and metamorphic history are not established by the fossil alone.

Question 10Earth's Systems and Processes

A seismograph station records P waves arriving 40 seconds before S waves. If the S-P travel time increases, what does this indicate about the earthquake's distance from the station?

  1. The earthquake is closer to the station
  2. The earthquake is farther from the station Correct answer.
  3. The earthquake magnitude is larger
  4. The earthquake is shallower in depth

Explanation

Because P and S waves travel at different speeds, the gap between their arrival times grows with distance travelled, so a larger S-P interval indicates a more distant earthquake. The interval does not by itself give depth or magnitude.

Question 11Earth's Systems and Processes

At a convergent boundary where an oceanic plate meets a continental plate, which sequence of features is most likely to develop?

  1. Trench, volcanic mountain chain, subduction zone Correct answer.
  2. Hotspot volcano, island chain, no plate boundary
  3. Mid-ocean ridge, rift valley, new oceanic crust
  4. Transform fault, offset river channels, shallow quakes

Explanation

The denser oceanic plate subducts beneath the continental plate, forming a deep ocean trench and a subduction zone, while rising magma generates a volcanic mountain chain on the continent. Ridges and rift valleys form at divergent boundaries, and transform faults form where plates slide past each other.

Question 12Earth's Systems and Processes

Why are S waves not detected on the opposite side of Earth from an earthquake's epicentre?

  1. They cannot travel through the liquid outer core Correct answer.
  2. They travel too slowly to reach the far side
  3. They are converted into light energy in the mantle
  4. They are absorbed completely by the crust

Explanation

S waves are shear waves and cannot pass through liquids, so the liquid outer core blocks their passage and creates a shadow zone on the far side. P waves are slowed and refracted by the core but can still pass through it.

Question 13Earth's Systems and Processes

A student observes that a sample of granite contains visible crystals of quartz, feldspar and mica. What does the presence of these large interlocking crystals most likely indicate?

  1. The rock was metamorphosed under low pressure
  2. The magma cooled slowly at depth Correct answer.
  3. The lava cooled rapidly at the surface
  4. The rock was formed by compaction of sand

Explanation

Large interlocking crystals form when magma cools slowly underground, giving minerals time to grow, which is characteristic of intrusive igneous rocks such as granite. Rapid surface cooling produces fine-grained rock, and compaction or metamorphism would not produce this igneous texture.

Question 14Earth's Systems and Processes

During the formation of sedimentary rock, which combination of processes transforms loose sediment into solid rock?

  1. Melting followed by crystallisation
  2. Weathering followed by erosion
  3. Foliation followed by recrystallisation
  4. Compaction followed by cementation Correct answer.

Explanation

Loose sediment is buried, squeezed by compaction and then bound together by minerals precipitated from groundwater in a process called cementation, producing solid sedimentary rock. Melting and crystallisation produce igneous rock, and foliation is a metamorphic process.

Question 15Earth's Systems and Processes

Which statement best explains why the seasonal variation in atmospheric carbon dioxide concentration is greater in the Northern Hemisphere than in the Southern Hemisphere?

  1. The Northern Hemisphere contains more land and thus more deciduous vegetation Correct answer.
  2. The Southern Hemisphere receives more solar radiation
  3. The Southern Hemisphere has a thicker atmosphere
  4. The Northern Hemisphere has more industrial activity

Explanation

The Northern Hemisphere has a much larger area of land covered by seasonal vegetation, so photosynthesis and decay cause a larger annual swing in carbon dioxide. Industrial activity and atmospheric thickness do not explain the seasonal pattern.

Question 16Earth's Systems and Processes

A region experiences heavy rainfall on a steep slope with thin vegetation cover. Which combination of factors would most increase the risk of a rapid mass movement?

  1. Steep slope, dense vegetation, dry soil
  2. Gentle slope, dense forest, dry soil
  3. Steep slope, sparse vegetation, saturated soil Correct answer.
  4. Flat terrain, thick vegetation, dry soil

Explanation

Steep slopes increase the downslope component of gravity, sparse vegetation removes root reinforcement, and saturated soil reduces friction and adds weight, together promoting rapid mass movement such as a landslide. Dense vegetation and dry soil generally stabilise slopes.

Question 17Earth's Systems and Processes

Which process transfers water from the land surface directly into the atmosphere without passing through plants?

  1. Infiltration
  2. Percolation
  3. Transpiration
  4. Evaporation Correct answer.

Explanation

Evaporation changes liquid water at the surface into vapour that enters the atmosphere directly. Transpiration involves plants, infiltration moves water into soil, and percolation moves it downward through rock.

Question 18Earth's Systems and Processes

A geologist finds marine fossil shells in a sedimentary rock layer now located high in a mountain range. Which explanation is most consistent with plate tectonic theory?

  1. The rock formed on the seafloor and was later uplifted by tectonic forces Correct answer.
  2. The shells were carried uphill by wind
  3. The shells were deposited by a recent volcanic eruption
  4. The organisms lived in freshwater lakes at high altitude

Explanation

Marine fossils in high mountains indicate that the rock originally formed on the seafloor and was later raised by tectonic processes such as continental collision. Wind, freshwater lakes and volcanic eruptions do not explain uplifted marine deposits.

Question 19Earth's Systems and Processes

Which of the following best describes the role of ozone in the stratosphere?

  1. It absorbs ultraviolet radiation from the Sun Correct answer.
  2. It prevents convection in the troposphere
  3. It increases the concentration of carbon dioxide
  4. It absorbs infrared radiation from Earth's surface

Explanation

Stratospheric ozone absorbs most incoming ultraviolet radiation, shielding life at the surface and warming the stratosphere. It does not primarily absorb infrared radiation or affect carbon dioxide levels.

Question 20Earth's Systems and Processes

A mining company extracts a metal ore from a deposit. Which statement best distinguishes a renewable resource from a non-renewable one in this context?

  1. Non-renewable resources cannot be recycled
  2. Renewable resources are always cheaper to extract
  3. Renewable resources are found only at the surface
  4. Non-renewable resources are used faster than they can be replenished Correct answer.

Explanation

A non-renewable resource such as a metal ore forms over geological timescales far slower than human consumption, so its stock is effectively depleted by use. Cost, location and recyclability do not define whether a resource is renewable.

Question 21Earth's Systems and Processes

A rock sample is subjected to increasing heat and pressure during metamorphism. Which change is most likely to occur?

  1. The rock melts completely into magma
  2. New minerals grow and align, forming a foliated texture Correct answer.
  3. The rock develops large gas bubbles
  4. The rock becomes a loose sediment

Explanation

Metamorphism recrystallises minerals in the solid state without melting, and directed pressure commonly aligns platy minerals to produce foliation. Complete melting would form magma, and loose sediment or gas bubbles are not metamorphic features.

Question 22Earth's Systems and Processes

Which evidence was most important in supporting the theory of seafloor spreading?

  1. The presence of folded mountains in continental interiors
  2. Symmetrical magnetic stripe patterns on either side of mid-ocean ridges Correct answer.
  3. The distribution of deserts around the tropics
  4. Matching fossil species on separate continents

Explanation

Magnetic reversals recorded in new oceanic crust produce symmetrical stripes on either side of mid-ocean ridges, showing that new crust forms at the ridge and moves outward. Fossil matching supports continental drift but not the mechanism of seafloor spreading.

Question 23Earth's Systems and Processes

A coastal aquifer is pumped heavily so that seawater begins to enter the wells. Which explanation best accounts for this intrusion?

  1. Pumping cools the groundwater and causes it to contract
  2. The aquifer rock dissolves and creates new pathways for air
  3. Seawater rises because of increased rainfall inland
  4. Lowering of the freshwater table allows denser seawater to move inland Correct answer.

Explanation

Freshwater in a coastal aquifer sits above denser seawater, but heavy pumping lowers the freshwater pressure head, allowing seawater to migrate inland. The effect depends on the balance of pressures, not on rainfall inland, air pathways or temperature contraction.

Question 24Earth's Systems and Processes

A scientist notes that a large volcanic eruption injects sulphate aerosols into the stratosphere. What is the most likely short-term climate effect?

  1. Global surface temperatures fall slightly Correct answer.
  2. Carbon dioxide concentrations drop immediately
  3. The ozone layer disappears completely
  4. Global surface temperatures rise sharply

Explanation

Stratospheric sulphate aerosols reflect some incoming solar radiation, which can cool surface temperatures for a year or more after a major eruption. They do not cause sharp warming, destroy the ozone layer completely, or rapidly reduce carbon dioxide.

Question 25Earth's Systems and Processes

Two rock layers are separated by an unconformity. Which interpretation of the geological history is most reasonable?

  1. Deposition was continuous with no break in time
  2. A period of erosion or non-deposition occurred between the two layers Correct answer.
  3. The lower layer is younger than the upper layer
  4. The unconformity formed during the original deposition

Explanation

An unconformity represents a gap in the rock record, typically caused by erosion or a pause in deposition before younger layers were laid down. It therefore indicates missing time, and the lower layer is generally older under the principle of superposition.

Question 26Earth's Systems and Processes

Which type of plate boundary is characterised by two plates sliding horizontally past one another, producing shallow earthquakes but little volcanism?

  1. A transform boundary Correct answer.
  2. A subduction zone
  3. A convergent boundary
  4. A divergent boundary

Explanation

Transform boundaries involve lateral shear as plates move past each other, generating shallow-focus earthquakes along faults such as the San Andreas. Magma generation is limited because neither plate is being pulled apart nor pushed beneath another.

Question 27Earth's Systems and Processes

The Mohorovičić discontinuity, or Moho, marks the boundary between which two regions?

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

Explanation

The Moho is the seismic discontinuity where P and S wave velocities increase sharply, marking the base of the crust and the top of the mantle. It lies at roughly 5 to 10 kilometres depth beneath oceans and 30 to 70 kilometres beneath continents.

Question 28Earth's Systems and Processes

Which of the following best describes the process of chemical weathering by hydrolysis acting on feldspar?

  1. Feldspar is fractured by repeated freezing and thawing of water in cracks
  2. Feldspar is dissolved completely by acidic rainwater with no solid residue
  3. Feldspar is broken into smaller fragments without any change in composition
  4. Feldspar reacts with water to form clay minerals and dissolved ions Correct answer.

Explanation

Hydrolysis is a chemical reaction in which water, often with dissolved acids, attacks silicate minerals such as feldspar, converting them into clay minerals and releasing ions into solution. This differs from physical breakdown, which leaves the mineral's composition unchanged.

Question 29Earth's Systems and Processes

A river flows from a steep mountainous region onto a flat plain. Which change in the river's behaviour is most likely as it enters the plain?

  1. Its discharge falls to zero because the gradient has flattened
  2. Its velocity decreases and it deposits sediment as alluvium Correct answer.
  3. Its competence increases and it transports larger boulders
  4. Its velocity increases and it cuts a deeper V-shaped valley

Explanation

Entering a flat plain reduces the channel gradient, which lowers flow velocity and therefore reduces the river's capacity to carry sediment. Deposition of finer material forms alluvial plains and floodplains, while erosion dominates in the steep upper course.

Question 30Earth's Systems and Processes

Which factor most strongly increases the likelihood that a slope will fail by mass movement?

  1. A decrease in pore water pressure within the slope material
  2. The gradual cementation of loose grains by mineral precipitation
  3. An increase in the slope angle beyond the angle of repose Correct answer.
  4. The growth of deep-rooted vegetation across the slope

Explanation

Steepening a slope increases the downslope component of gravity relative to the resisting friction, pushing the slope toward or beyond its angle of repose. Mass movement occurs when driving stress exceeds the shear strength of the material.

Question 31Earth's Systems and Processes

A student compares two soil profiles: one developed on a steep slope and one on a gentle plain under the same climate. Which difference is most reasonably expected?

  1. The steep-slope soil will be thicker because erosion exposes fresh bedrock
  2. Both soils will have identical thickness because climate is the only soil-forming factor
  3. The steep-slope soil will be thinner because eroded material is removed faster than it forms Correct answer.
  4. The gentle-plain soil will be thinner because water drains away too quickly

Explanation

On steep slopes, gravity-driven erosion removes topsoil faster than weathering can produce it, so profiles tend to be thin and poorly developed. Gentle plains allow material to accumulate and remain in place, favouring thicker, more mature soil profiles.

Question 32Earth's Systems and Processes

Which process is the main mechanism by which water vapour enters the atmosphere from the oceans?

  1. Precipitation falling back into the sea
  2. Transpiration from marine algae
  3. Condensation at the ocean surface
  4. Evaporation driven by solar energy Correct answer.

Explanation

Solar radiation supplies the latent heat that converts liquid ocean water into vapour, making evaporation the dominant pathway for atmospheric moisture over the oceans. Transpiration contributes significantly over land but is minor over open ocean.

Question 33Earth's Systems and Processes

Ocean currents such as the Gulf Stream transfer heat from low to high latitudes. What is the main effect of this transfer on the climate of north-western Europe?

  1. It makes coastal winters colder than the latitude would otherwise allow
  2. It makes coastal winters milder than the latitude would otherwise allow Correct answer.
  3. It increases summer rainfall while leaving winter temperatures unchanged
  4. It has no measurable effect because air masses dominate regional climate

Explanation

Warm ocean currents release heat to the overlying atmosphere, moderating winter temperatures in downwind coastal regions at high latitudes. North-western Europe is therefore milder in winter than other landmasses at comparable latitudes.

Question 34Earth's Systems and Processes

Which statement best explains why the Coriolis effect deflects moving air and water to the right in the Southern Hemisphere?

  1. It deflects to the right only when winds blow from west to east
  2. It does not deflect moving fluids at all in the Southern Hemisphere
  3. It deflects to the left in the Southern Hemisphere because of the planet's rotation Correct answer.
  4. It deflects to the right in the Southern Hemisphere because of the planet's rotation

Explanation

The Coriolis effect arises from Earth's rotation and deflects moving fluids to the left of their path in the Southern Hemisphere and to the right in the Northern Hemisphere. The deflection depends on hemisphere and speed, not on wind direction.

Question 35Earth's Systems and Processes

A sequence of sedimentary layers contains a trilobite in the lowest layer and an ammonite in a layer above it. Assuming no overturning, which conclusion is best supported?

  1. The relative ages cannot be determined without radiometric dating
  2. Both fossils are the same age because they occur in one sequence
  3. The ammonite is older than the trilobite because it lies higher
  4. The trilobite is older than the ammonite because it lies lower Correct answer.

Explanation

The principle of superposition states that in an undisturbed sequence, lower layers were deposited before higher ones, so fossils in lower layers are older. Relative age can therefore be established from position alone, without absolute dating.

Question 36Earth's Systems and Processes

A geologist observes that a basalt sample shows a symmetric pattern of magnetic stripes on either side of a mid-ocean ridge. Which interpretation is most consistent with this observation?

  1. The ocean floor is a single continuous slab that never moved
  2. The stripes were produced by later metamorphism of the ocean floor
  3. The ridge has remained stationary while the magnetic field changed direction only once
  4. New crust formed during reversals of Earth's magnetic field and spread outward from the ridge Correct answer.

Explanation

As magma solidifies at a spreading ridge, it records the current magnetic polarity, producing parallel stripes of alternating polarity that mirror each other across the ridge. This symmetry is strong evidence that new crust forms at the ridge and moves away on both sides.

Question 37Earth's Systems and Processes

Which set of conditions would most favour the formation of a thick, well-sorted sandstone layer?

  1. Deposition of glacial till directly from melting ice
  2. Prolonged transport of sand by a river before deposition in a low-energy basin Correct answer.
  3. Chemical precipitation of dissolved salts in an evaporating lake
  4. Rapid deposition of unsorted debris from a landslide into a lake

Explanation

Long transport by moving water winnows away finer and coarser material, leaving well-sorted sand that accumulates in a low-energy basin. Sorting reflects the uniformity of grain sizes, which transport processes strongly influence.

Question 38Earth's Systems and Processes

An igneous intrusion cuts across several sedimentary layers, and a fault then displaces both the intrusion and the layers. Which relative age sequence is correct?

  1. The intrusion is oldest, then the sedimentary layers, then the fault
  2. The sedimentary layers and the fault are the same age, and the intrusion is youngest
  3. The sedimentary layers are oldest, then the intrusion, then the fault Correct answer.
  4. The fault is oldest, then the intrusion, then the sedimentary layers

Explanation

Cross-cutting relationships show that the sedimentary layers were deposited first, the intrusion cut across them later, and the fault displaced both, making it the youngest event. Each structure must post-date the features it cuts.

Question 39Earth's Systems and Processes

A region with a high water table and heavy irrigation develops rising salinity in its soils over several decades. Which explanation best accounts for the increased salinity?

  1. Salinity rises because plants remove salts from the soil and release them at the surface
  2. Salinity rises because rainfall dilutes the soil solution over time
  3. Irrigation water adds dissolved salts that remain as water evaporates from the surface Correct answer.
  4. Irrigation water flushes all salts downward into the groundwater permanently

Explanation

Irrigation water contains dissolved salts, and when evaporation removes water from the soil surface, those salts are left behind and accumulate. A high water table allows capillary rise to bring saline water to the surface, where evaporation concentrates it further.

Question 40Earth's Systems and Processes

A subduction zone forms where an oceanic plate meets a continental plate. Which feature is most characteristic of this type of plate boundary?

  1. A broad ridge of new oceanic crust where plates move apart
  2. A transform fault where plates slide horizontally past each other
  3. A deep ocean trench with a chain of volcanoes inland from the coast Correct answer.
  4. A shallow basin where sediments accumulate without deformation

Explanation

At an oceanic-continental convergent boundary the denser oceanic plate sinks beneath the continental plate, producing a deep trench at the point of subduction. Melting of the descending plate and overlying mantle generates magma that rises to form a volcanic arc inland from the boundary.

Question 41The Earth's Crust and Resources

Which layer of the Earth is composed mainly of solid iron and nickel and lies beneath the outer core?

  1. The inner core Correct answer.
  2. The lower mantle
  3. The asthenosphere
  4. The oceanic crust

Explanation

The inner core is the innermost zone of the Earth and is dominated by iron and nickel. Although temperatures are extremely high, pressure is so great that the metal remains solid. The outer core is liquid, while the mantle and crust are silicate-rich.

Question 42The Earth's Crust and Resources

The Mohorovicic discontinuity marks the boundary between which two regions?

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

Explanation

The Mohorovicic discontinuity, or Moho, is defined by a sharp increase in seismic wave velocity where crustal rocks give way to denser mantle rocks. It lies at roughly 5-10 km depth beneath oceans and 30-70 km beneath continents.

Question 43The Earth's Crust and Resources

A geologist identifies a mineral that scratches calcite but is scratched by quartz. Using Mohs hardness scale, which mineral could this be?

  1. Fluorite Correct answer.
  2. Talc
  3. Topaz
  4. Diamond

Explanation

Calcite has a hardness of 3 and quartz has a hardness of 7 on Mohs scale, so the unknown mineral must fall between them. Fluorite has a hardness of 4, satisfying both scratch tests. Hardness values allow minerals to be ranked by their resistance to scratching.

Question 44The Earth's Crust and Resources

Which property best distinguishes cleavage in a mineral from fracture?

  1. Cleavage occurs only in metals, whereas fracture occurs only in silicates
  2. Cleavage breaks along flat planes determined by atomic structure, whereas fracture produces irregular surfaces Correct answer.
  3. Cleavage depends on colour, whereas fracture depends on streak
  4. Cleavage produces curved glassy surfaces, whereas fracture produces flat shiny planes

Explanation

Cleavage reflects planes of weaker chemical bonding within the crystal lattice, so the mineral splits along flat, repeated surfaces. Fracture describes breaking that does not follow these planes, giving irregular or conchoidal surfaces. Both are diagnostic physical properties used in mineral identification.

Question 45The Earth's Crust and Resources

A magma chamber beneath a volcano cools slowly at depth. Which rock texture is most likely to form?

  1. Vesicular with abundant gas bubbles
  2. Coarse-grained with large interlocking crystals Correct answer.
  3. Glassy with no visible crystals
  4. Fine-grained with microscopic crystals

Explanation

Slow cooling at depth allows ions time to migrate and organise into large crystals, producing a coarse-grained intrusive texture such as granite or gabbro. Rapid cooling at the surface instead produces fine-grained or glassy rocks. Texture therefore records cooling history.

Question 46The Earth's Crust and Resources

Which sequence correctly orders the processes that transform loose sediment into sedimentary rock?

  1. Weathering, transport, deposition, compaction, cementation Correct answer.
  2. Deposition, melting, compaction, cementation, transport
  3. Cementation, transport, weathering, deposition, compaction
  4. Compaction, weathering, cementation, transport, deposition

Explanation

Sedimentary rocks form through a sequence beginning with weathering of source rock, followed by erosion and transport of grains. The grains are deposited, then buried and compacted as pore space closes, and finally cemented by minerals precipitated from groundwater.

Question 47The Earth's Crust and Resources

A rock sample contains aligned platy minerals that give it a finely layered, foliated appearance and it formed under moderate regional pressure. Which rock is it most likely to be?

  1. Obsidian
  2. Quartzite
  3. Slate Correct answer.
  4. Marble

Explanation

Slate is a low-grade foliated metamorphic rock formed from shale, in which clay minerals recrystallise into aligned mica. This alignment produces slaty cleavage at right angles to the maximum stress direction. Marble and quartzite are non-foliated, and obsidian is volcanic glass.

Question 48The Earth's Crust and Resources

Which statement correctly describes the relationship between plate boundaries and earthquake distribution?

  1. Earthquakes occur only along divergent boundaries
  2. Most earthquakes occur along plate boundaries where stress accumulates and is released Correct answer.
  3. Earthquakes occur only in the centre of continental plates
  4. Earthquakes are evenly distributed across all parts of the Earth's surface

Explanation

The global distribution of earthquakes closely follows plate margins, where friction and deformation cause stress to build up until rocks rupture. Shallow quakes dominate divergent boundaries, while deep quakes occur at subduction zones. Intraplate earthquakes are comparatively rare.

Question 49The Earth's Crust and Resources

At a convergent boundary where an oceanic plate meets a continental plate, which feature is most characteristic?

  1. A transform fault with lateral offset and no volcanism
  2. A mid-ocean ridge with new oceanic crust forming
  3. A broad rift valley with normal faulting
  4. A deep ocean trench with an adjacent volcanic mountain chain Correct answer.

Explanation

When dense oceanic lithosphere subducts beneath lighter continental lithosphere, a deep trench forms at the plate margin. Fluids released from the descending slab trigger melting in the mantle wedge, producing magma that feeds a volcanic arc on the continent.

Question 50The Earth's Crust and Resources

Which evidence most strongly supports the theory of seafloor spreading?

  1. The presence of folded rocks in continental mountain belts
  2. The occurrence of earthquakes at shallow depths worldwide
  3. Symmetrical magnetic striping recorded in oceanic crust on either side of mid-ocean ridges Correct answer.
  4. Uniform fossil assemblages found on all continents

Explanation

As new oceanic crust forms at a ridge, magnetic minerals record the prevailing field direction, producing stripes that are mirror images on each side of the ridge. This symmetry indicates that the seafloor has grown outward over time. The pattern is recorded in the crust rather than in sediments.