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New Zealand Scholarship Earth and Space Science study materials
New Zealand Scholarship Earth and Space Science study resources

New Zealand Scholarship Earth and Space Science practice questions

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Question 1Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Which layer of Earth's interior is the primary source of the convection that drives plate tectonics?

  1. The asthenosphere within the upper mantle Correct answer.
  2. The rigid lithosphere
  3. The solid inner core
  4. The outer crust

Explanation

Mantle convection occurs in the asthenosphere and underlying mantle, where slow plastic flow transfers heat from depth toward the surface. This motion drags and pushes the overlying rigid plates. The lithosphere is the rigid outer shell that moves, not the convecting medium.

Question 2Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

A parcel of air is forced to rise over a mountain range. Which combination best explains why it cools and produces orographic rainfall on the windward slope?

  1. Descending air on the windward side cools and condenses
  2. Rising air expands and cools adiabatically, reducing its capacity to hold water vapour Correct answer.
  3. Air cools because it loses heat to the cold rock by conduction only
  4. Rising air is compressed and warms, causing condensation

Explanation

As air rises, pressure falls and the parcel expands, doing work and cooling adiabatically. Cooler air holds less water vapour, so relative humidity rises and condensation forms cloud and rain. Conduction to rock is minor compared with adiabatic cooling.

Question 3Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Which process transfers carbon from the atmosphere into the geosphere over geological timescales?

  1. Respiration by soil microbes
  2. Evaporation of ocean surface water
  3. Silicate rock weathering followed by carbonate deposition Correct answer.
  4. Photosynthesis in forest canopies

Explanation

Chemical weathering of silicate rocks consumes atmospheric carbon dioxide, and the resulting bicarbonate is carried to the ocean and precipitated as carbonate sediment. This sequesters carbon in the geosphere over long timescales. Photosynthesis and respiration cycle carbon rapidly within the biosphere and atmosphere.

Question 4Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

The biosphere influences the hydrosphere primarily through which mechanism in a forested catchment?

  1. Intercepting rainfall and promoting infiltration through root channels Correct answer.
  2. Preventing all evaporation from the soil surface
  3. Increasing surface runoff by compacting soil
  4. Raising groundwater salinity by transpiration

Explanation

Vegetation intercepts rainfall, slowing it and reducing erosive impact, while roots create channels that increase infiltration into soil. This shifts water from fast surface runoff toward slower subsurface flow. Transpiration returns water to the atmosphere but does not salinify groundwater.

Question 5Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Which statement correctly describes the role of the atmosphere in the rock cycle?

  1. The atmosphere removes dissolved ions from groundwater
  2. The atmosphere compacts sediment into sedimentary rock
  3. The atmosphere directly melts crustal rock to form magma
  4. The atmosphere supplies oxygen and water that drive chemical weathering of exposed rock Correct answer.

Explanation

Atmospheric oxygen and moisture react with minerals at the surface, driving oxidation and hydrolysis that break rock down chemically. This weathering produces ions and sediment that feed the rest of the rock cycle. Melting and lithification occur at depth, not through atmospheric action.

Question 6Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

What is the dominant driver of surface ocean currents in the open ocean?

  1. Differences in seawater density alone
  2. Prevailing winds transferring momentum to the surface layer Correct answer.
  3. Geothermal heating of the seafloor
  4. Tidal forces from the Moon

Explanation

Wind stress drags the ocean surface, and the Coriolis effect turns the resulting flow, producing large gyres. Density differences drive deep thermohaline circulation rather than the surface wind-driven currents. Tides produce oscillatory flows, not the persistent gyres.

Question 7Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Which of the following best describes a positive feedback within the climate system?

  1. More evaporation producing more clouds that reflect sunlight
  2. Increased cloud cover reflecting more sunlight and cooling the surface
  3. Warming that melts sea ice, lowering albedo and causing further warming Correct answer.
  4. Enhanced weathering removing carbon dioxide and reducing warming

Explanation

A positive feedback amplifies the initial change. Melting sea ice exposes darker ocean, which absorbs more solar energy and reinforces warming. The other options describe responses that counteract the initial change, which are negative feedbacks.

Question 8Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Which sphere is the primary long-term reservoir of phosphorus in the Earth system?

  1. The atmosphere
  2. The biosphere
  3. The hydrosphere
  4. The geosphere (rocks and sediments) Correct answer.

Explanation

Phosphorus has no significant gaseous phase, so it cycles mainly between rocks, soils, water and organisms. The largest store is phosphate-bearing rock and sediment in the geosphere, released slowly by weathering. This contrasts with carbon and nitrogen, which have large atmospheric reservoirs.

Question 9Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

A subducting oceanic plate carries water-rich sediment and hydrated minerals into the mantle. What is the main consequence for magmatism?

  1. The water freezes the mantle, stopping all melting
  2. The water escapes directly to the surface without affecting melting
  3. The water reacts to form limestone at depth
  4. The released water lowers the melting point of the overlying mantle wedge, generating magma Correct answer.

Explanation

As the slab descends and heats, dehydration releases water into the overlying mantle wedge. Water lowers the solidus of mantle rock, causing partial melting and producing the arc magmatism typical of subduction zones. This process is called flux melting.

Question 10Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Why does the Intertropical Convergence Zone (ITCZ) shift seasonally?

  1. Because ocean salinity changes with the seasons
  2. Because the zone of maximum solar heating migrates with the overhead Sun Correct answer.
  3. Because the Moon's gravity pulls the atmosphere equatorward
  4. Because the Coriolis effect reverses direction each season

Explanation

The ITCZ marks the zone of strongest convection and rising air, which follows the region of maximum solar heating. As the overhead Sun migrates between the tropics, this heating maximum shifts, dragging the ITCZ with it. The Coriolis effect does not reverse seasonally.

Question 11Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

A river's sediment load changes as it passes from a steep mountain reach to a broad floodplain. Which change is most expected?

  1. Decreased flow velocity, causing deposition of coarser material Correct answer.
  2. Complete loss of suspended sediment at the mountain front
  3. Increased channel gradient downstream
  4. Increased competence and increased bedload transport

Explanation

On entering a floodplain the gradient and velocity decrease, reducing the river's competence and capacity. Coarser bedload is deposited first, while finer sediment stays in suspension. Gradient typically decreases downstream, not increases.

Question 12Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Which process most directly links biological productivity in surface waters to carbon storage in the deep ocean?

  1. Coral reef calcification at the surface
  2. Upwelling of nutrient-rich deep water
  3. The biological pump, where sinking organic matter transports carbon downward Correct answer.
  4. Evaporation of surface water

Explanation

The biological pump is the set of processes by which surface photosynthesis fixes carbon into organic matter that sinks, carrying carbon to depth where it is remineralised or buried. Upwelling brings carbon back toward the surface, opposing deep storage. Calcification stores carbon in reefs but is not the main downward transport pathway.

Question 13Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Why do coastal upwelling zones support high biological productivity?

  1. They reduce surface salinity to levels favoured by phytoplankton
  2. They transport nutrient-rich deep water into the sunlit surface layer Correct answer.
  3. They bring warm, oxygen-poor water to the surface
  4. They eliminate grazing pressure on phytoplankton

Explanation

Upwelling lifts deep water that is rich in nitrate and phosphate into the photic zone, where light and nutrients together allow rapid phytoplankton growth. This fuels productive food webs and fisheries. Upwelled water is typically cold and nutrient-rich, not warm and depleted.

Question 14Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Which pairing correctly links an atmospheric process to its effect on the hydrosphere?

  1. Advection of dry air increasing river discharge
  2. Sublimation of ice directly increasing groundwater recharge
  3. Condensation in rising air forming clouds and precipitation that returns water to the surface Correct answer.
  4. Evapotranspiration directly raising sea level

Explanation

Condensation in cooling, rising air forms cloud droplets that grow into precipitation, completing the return of atmospheric moisture to the land and ocean surface. This is a central link in the water cycle between atmosphere and hydrosphere. The other pairings misdescribe the direction or mechanism of water transfer.

Question 15Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Which of the following best explains why the deep ocean is cold and dense despite receiving no direct solar heating at depth?

  1. Tides continuously chill the deep water
  2. Deep water is warmed by geothermal heat and then sinks
  3. Cold, salty water sinks at high latitudes and spreads along the seafloor Correct answer.
  4. The seafloor cools the water by conduction to the surface

Explanation

At high latitudes, surface water becomes cold and saline enough to be dense, so it sinks and forms deep water masses that spread through the ocean basins. This thermohaline circulation maintains the cold, dense deep layer. Geothermal heating is far too small to warm the deep ocean appreciably.

Question 16Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

How does the presence of vegetation most directly affect the local water balance of a catchment?

  1. It eliminates groundwater recharge entirely
  2. It increases total runoff by reducing infiltration
  3. It increases evapotranspiration and reduces the proportion of rainfall becoming runoff Correct answer.
  4. It prevents any water from returning to the atmosphere

Explanation

Vegetation takes up soil water and transpires it, adding to evaporation from surfaces, so a larger share of rainfall returns to the atmosphere. This reduces the fraction that becomes runoff. Roots generally enhance infiltration rather than eliminate recharge.

Question 17Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

A volcanic eruption injects sulphate aerosols into the stratosphere. What is the most likely short-term climate response?

  1. Increased surface humidity because aerosols add water vapour
  2. No effect because stratospheric aerosols settle within hours
  3. Surface warming because aerosols absorb infrared radiation
  4. Surface cooling because aerosols reflect incoming solar radiation Correct answer.

Explanation

Stratospheric sulphate aerosols scatter and reflect incoming solar radiation, reducing the solar energy reaching the surface and causing short-term cooling. Because they reside in the stratosphere for months to years, the effect can persist for a few years. They do not add water vapour or warm the surface.

Question 18Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

In the geological carbon cycle, which process acts as a long-term negative feedback on rising atmospheric carbon dioxide?

  1. Increased volcanic degassing as temperatures rise
  2. Melting permafrost releasing stored carbon
  3. Increased silicate weathering consuming carbon dioxide as temperatures rise Correct answer.
  4. Warmer oceans releasing dissolved carbon dioxide

Explanation

Warmer, wetter conditions accelerate silicate weathering, which consumes atmospheric carbon dioxide and draws it into carbonate rock. This counteracts the initial warming, so it is a negative feedback operating over long timescales. The other options release carbon and amplify warming.

Question 19Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Which statement best explains why the biosphere and geosphere are coupled in soil formation?

  1. Soil forms only from atmospheric deposition, independent of rock
  2. Organisms prevent chemical weathering of bedrock
  3. Soil minerals are derived entirely from decaying plants
  4. Organisms weather rock and add organic matter, while weathered minerals supply nutrients to organisms Correct answer.

Explanation

Soil is a zone where the geosphere and biosphere interact: roots and microbes accelerate chemical and physical weathering of bedrock, and organic matter accumulates, supplying nutrients that support further biological activity. This two-way exchange is what builds fertile soil. Soil is not formed independently of rock.

Question 20Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Which combination of factors most strongly controls the density of seawater?

  1. Temperature and salinity Correct answer.
  2. Light intensity and salinity
  3. Pressure and wind speed
  4. Dissolved oxygen and temperature

Explanation

Seawater density depends mainly on temperature and salinity: colder and saltier water is denser. These two properties drive thermohaline circulation. Pressure has a small effect, and wind, light and dissolved oxygen do not determine density in the same way.

Question 21Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

A region experiences a strong El Niño. Which change is most consistent with the typical pattern?

  1. Weakened trade winds and warmer eastern Pacific surface water Correct answer.
  2. Strengthened trade winds and colder eastern Pacific surface water
  3. Complete shutdown of the biological pump worldwide
  4. Permanent reversal of the Coriolis effect in the tropics

Explanation

During El Niño the trade winds weaken, allowing warm surface water to spread eastward across the equatorial Pacific. This warms the eastern Pacific and suppresses upwelling there. The Coriolis effect does not change, and the biological pump continues elsewhere.

Question 22Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Consider a mountain glacier in a warming climate. Which feedback most strongly accelerates its retreat once its surface lowers to a darker, debris-covered level?

  1. Reduced meltwater production
  2. Increased albedo reducing absorbed solar energy
  3. Increased snowfall burying the glacier
  4. Lowered albedo increasing absorbed solar energy and melt Correct answer.

Explanation

A darker, debris-covered or lower glacier surface has lower albedo, so it absorbs more solar radiation and melts faster, which further lowers and darkens the surface. This is a positive feedback accelerating retreat. Higher albedo would slow melt, and snowfall would add mass.

Question 23Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

In a subduction zone, which sequence best explains the link between plate convergence and the composition of arc lavas?

  1. Mantle wedge melting occurs without any contribution from the slab
  2. Slab melting directly produces mafic magma identical to mid-ocean ridge basalt
  3. Slab dehydration releases fluids that metasomatise the mantle wedge, producing silica-rich melts Correct answer.
  4. Seawater directly erupts as lava at the trench

Explanation

Fluids released from the dehydrating slab enrich the mantle wedge in water and mobile elements, lowering its solidus and causing partial melting. These melts evolve to produce the silica-rich, volatile-bearing arc magmas. Direct slab melting is limited, and mid-ocean ridge basalt forms at divergent boundaries.

Question 24Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Which reasoning best explains why atmospheric carbon dioxide concentrations show a seasonal sawtooth pattern in the Northern Hemisphere?

  1. Solar output varies strongly between summer and winter
  2. Ocean circulation reverses direction each season
  3. Northern Hemisphere vegetation absorbs carbon dioxide in summer and releases it in winter, while fossil fuel emissions add a steady background Correct answer.
  4. Volcanic eruptions occur mainly in summer

Explanation

Because the Northern Hemisphere holds most of the land and vegetation, summer photosynthesis draws down atmospheric carbon dioxide and winter respiration and decay release it, creating the seasonal sawtooth. Fossil fuel emissions add a rising background trend on top of this cycle. Solar output and ocean circulation do not vary enough to explain it.

Question 25Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

A large igneous province erupts rapidly, releasing carbon dioxide and sulphate aerosols. Which combination of effects on the Earth system is most plausible over the following centuries?

  1. No climate effect because the eruptions are short-lived
  2. Immediate and permanent cooling with no ocean chemistry change
  3. Immediate cooling from aerosols followed by longer-term warming and ocean acidification from carbon dioxide Correct answer.
  4. Immediate warming with no effect on ocean pH

Explanation

Sulphate aerosols reflect sunlight and cause short-term cooling, while the large carbon dioxide release persists far longer and drives warming and ocean acidification as the ocean absorbs the gas. The two effects operate on different timescales. A short eruption pulse can still have lasting consequences because carbon dioxide is long-lived.

Question 26Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Which layer of the atmosphere contains most of the water vapour that drives weather systems?

  1. The troposphere Correct answer.
  2. The thermosphere
  3. The stratosphere
  4. The mesosphere

Explanation

The troposphere holds the great majority of atmospheric water vapour because temperature decreases with height there, allowing convection and cloud formation. Nearly all weather, including precipitation, occurs within this layer.

Question 27Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

What is the main reason that soil moisture is depleted more rapidly on a bare slope than on a vegetated slope with the same rainfall?

  1. Vegetated slopes receive less rainfall because plants suppress convection
  2. Bare soil has lower albedo and therefore stays cooler
  3. Vegetation shades the surface and adds organic matter that increases infiltration and water retention Correct answer.
  4. Bare soil has a higher clay content that absorbs water more strongly

Explanation

Plant canopies reduce direct solar heating of the soil surface and lower evaporation, while litter and roots improve soil structure and infiltration. Together these effects keep more water in the soil profile for longer.

Question 28Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Which of the following is a reservoir in the Earth system that exchanges material directly with both the atmosphere and the geosphere?

  1. The thermosphere
  2. The mesosphere
  3. The magnetosphere
  4. The hydrosphere Correct answer.

Explanation

The hydrosphere exchanges water vapour and gases with the atmosphere and exchanges dissolved ions and sediment with the geosphere. The other options are either atmospheric layers or magnetic regions that do not act as material reservoirs in this way.

Question 29Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

A catchment is underlain by granite and experiences high rainfall. Which combination best explains why its river water is typically dilute and slightly acidic?

  1. Rapid runoff limits water-rock interaction and the dominant minerals are slow to weather Correct answer.
  2. Granite contains abundant halite that raises the chloride concentration
  3. High rainfall dissolves abundant carbonate minerals and neutralises the water
  4. The river receives large inputs of dissolved organic acids from deep groundwater

Explanation

Granite consists largely of silicate minerals that weather slowly, so rapid throughflow leaves little time for dissolution. The result is low total dissolved solids with a slightly acidic character from dissolved carbon dioxide and organic acids.

Question 30Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

During a strong La Niña, which change in the tropical Pacific is most consistent with the typical pattern?

  1. A collapse of the Walker circulation with warm water spreading eastward
  2. Stronger trade winds and enhanced upwelling in the eastern equatorial Pacific Correct answer.
  3. Reduced sea-surface temperatures in the western Pacific
  4. Weaker trade winds and reduced upwelling in the eastern equatorial Pacific

Explanation

La Niña strengthens the east-west sea-level pressure gradient, intensifying the trade winds and pushing warm surface water westward. This enhances equatorial upwelling in the east, where cooler water rises to the surface.

Question 31Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Why does the formation of sea ice increase the salinity of the underlying ocean water?

  1. Melting of glacial ice adds freshwater that raises salinity
  2. Salt is largely excluded from the ice lattice and rejected into the surrounding water Correct answer.
  3. Sea ice absorbs dissolved salts from the atmosphere and releases them downward
  4. Freezing removes water molecules and concentrates all ions equally in the ice

Explanation

As seawater freezes, the ice crystal lattice excludes most dissolved ions, so the rejected brine remains in the liquid and raises its salinity. This process, called brine rejection, also makes the underlying water denser.

Question 32Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Which process most directly returns carbon stored in marine sediments to the atmosphere over geological time?

  1. Burial of organic carbon in deltas
  2. Photosynthesis by marine phytoplankton
  3. Subduction, metamorphism and volcanic degassing Correct answer.
  4. Precipitation of calcium carbonate on reefs

Explanation

Carbon buried in sediments can be carried into subduction zones, where heating and metamorphism release it, and volcanoes then return it to the atmosphere as carbon dioxide. This completes the long-term geological carbon cycle.

Question 33Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

A large delta is supplied with sediment at a rate lower than the rate of subsidence and sea-level rise. Which outcome is most likely?

  1. Increase in the delta's elevation above sea level
  2. Rapid progradation of the delta seaward
  3. Formation of a deep incised canyon across the delta plain
  4. Coastal erosion and landward migration of the shoreline Correct answer.

Explanation

When sediment supply cannot keep pace with subsidence and rising sea level, the delta surface loses elevation relative to the sea. This leads to shoreline retreat, erosion and landward migration of the coastal system.

Question 34Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Which feature of the biosphere most strongly influences the albedo of a high-latitude land surface during winter?

  1. The extent to which vegetation protrudes above the snow cover Correct answer.
  2. The salinity of soil pore water
  3. The depth of the active layer in permafrost
  4. The rate of photosynthesis in evergreen needles

Explanation

Snow has a very high albedo, so a surface where vegetation remains buried by snow reflects more solar radiation than one where tall vegetation protrudes. The structural height of vegetation therefore controls how much dark canopy is exposed.

Question 35Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Why does deforestation in a tropical catchment typically increase the peak discharge of rivers after heavy rainfall?

  1. Higher soil organic matter increases the water-holding capacity of the soil
  2. Increased canopy interception delays water delivery to channels
  3. Reduced soil erosion lowers the sediment concentration of floodwaters
  4. Reduced infiltration and evapotranspiration cause more rainfall to reach channels rapidly Correct answer.

Explanation

Removing vegetation lowers evapotranspiration and degrades soil structure, so less water infiltrates and more runs off the surface quickly. This concentrates rainfall into channels over a shorter period and raises peak discharge.

Question 36Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Which combination best explains why the tropical stratosphere is colder than the tropical troposphere at the same altitude range would otherwise be?

  1. Rapid surface heating and strong sensible heat flux into the stratosphere
  2. Descending air in the troposphere and ozone-rich air in the lower stratosphere
  3. High water-vapour concentrations throughout the stratosphere
  4. Strong upwelling in the troposphere and ozone-poor air in the lower stratosphere Correct answer.

Explanation

Tropical tropospheric air rises and cools, and the tropopause is particularly high there, so air entering the lower stratosphere has already cooled. The lower tropical stratosphere also contains relatively little ozone, so it absorbs little ultraviolet radiation and remains cold.

Question 37Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

A mountain range receives moist air on its windward side. Which set of changes best describes the leeward side?

  1. Descending, warming air with low relative humidity and reduced precipitation Correct answer.
  2. Ascending, cooling air with high relative humidity and enhanced precipitation
  3. Descending, cooling air with high relative humidity and enhanced precipitation
  4. Ascending, warming air with low relative humidity and reduced precipitation

Explanation

Air that has lost moisture on the windward side descends the leeward slope and warms adiabatically, which lowers its relative humidity. This produces the dry rain-shadow effect with markedly reduced precipitation.

Question 38Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

Consider a coastal upwelling system where wind-driven divergence removes surface water. Which chain of effects best explains the resulting biological response?

  1. Warm surface water sinks, reducing nutrient availability and lowering productivity
  2. Nutrient-rich water rises, fuelling phytoplankton growth that supports higher trophic levels Correct answer.
  3. Surface water becomes fresher, increasing stratification and enhancing productivity
  4. Dissolved oxygen increases in surface water, directly stimulating fish reproduction

Explanation

Wind-driven divergence allows deeper water, which is rich in nitrate and phosphate, to rise into the sunlit layer. The combination of nutrients and light fuels phytoplankton blooms that support productive food webs.

Question 39Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

A large increase in atmospheric water vapour from warming is expected to affect the hydrological cycle. Which consequence is most consistent with physical reasoning?

  1. Intensified heavy rainfall and increased global precipitation minus evaporation contrasts between wet and dry regions Correct answer.
  2. A decline in atmospheric water-vapour content as temperature rises
  3. Uniform increases in precipitation everywhere with no change in extremes
  4. Reduced evaporation from the oceans as humidity rises

Explanation

Warmer air can hold more water vapour, roughly following the Clausius-Clapeyron relation, which increases the moisture available for intense rainfall. Because energy and moisture transport constrain the global mean, the increase concentrates in extremes and in contrasts between wet and dry regions.

Question 40Earth systems and interactions (geosphere, atmosphere, hydrosphere, biosphere)

A shallow, well-mixed lake in a temperate region receives a large pulse of dissolved nitrate from farmland after heavy rain. Within days, algal biomass rises sharply, and within weeks dissolved oxygen in the bottom waters falls to near zero. Which chain of Earth-system interactions best explains this sequence?

  1. Nitrate in the hydrosphere raises the density of surface water, which sinks and displaces oxygen-rich bottom water, lowering oxygen throughout the lake.
  2. Nitrate volatilises from the hydrosphere into the atmosphere, reducing atmospheric oxygen pressure, which is then transferred back into the lake.
  3. Runoff delivers nitrate to the hydrosphere, which fertilises the biosphere; excess organic matter sinks and is decomposed by microbes, consuming dissolved oxygen in the hydrosphere. Correct answer.
  4. Nitrate is taken up by the geosphere through sediment adsorption, releasing stored oxygen from lake sediments into the overlying water.

Explanation

The sequence is a cross-sphere cascade driven by nutrient supply: the hydrosphere carries limiting nutrient to the biosphere, where photosynthesis converts it to biomass. When that biomass dies and settles, microbial respiration in the hydrosphere consumes dissolved oxygen faster than it is replenished, producing hypoxia. Oxygen solubility and stratification set the timing, but the causal driver is the nutrient pulse.

Question 41Solid Earth: plate tectonics, rocks, minerals, and geological processes

At a mid-ocean ridge, new oceanic lithosphere is created as two plates move apart. Which process directly generates the basaltic magma that erupts there?

  1. Decompression melting of upwelling asthenospheric mantle Correct answer.
  2. Friction melting along the transform faults that offset the ridge
  3. Partial melting of continental crust stretched by rifting
  4. Flux melting caused by water released from a subducting slab

Explanation

Mantle rock rises beneath a spreading ridge and crosses its solidus as pressure falls, even though temperature stays nearly constant. This decompression melting produces basaltic magma that feeds the ridge axis. Water-flux melting is the signature of subduction zones, not spreading centres.

Question 42Solid Earth: plate tectonics, rocks, minerals, and geological processes

A rock sample contains aligned platy minerals that give it a planar fabric, and the fabric formed during regional metamorphism. Which rock name best fits this description?

  1. Quartzite
  2. Hornfels
  3. Schist Correct answer.
  4. Marble

Explanation

Schist is a medium-grade metamorphic rock defined by a well-developed foliation produced by aligned micas and other platy minerals. Marble and quartzite are generally non-foliated, and hornfels is a fine-grained contact-metamorphic rock lacking a strong planar fabric.

Question 43Solid Earth: plate tectonics, rocks, minerals, and geological processes

Which mineral property is most directly explained by the sheet-like silicate structure of the mica group?

  1. High density
  2. Conchoidal fracture
  3. Magnetic attraction
  4. Perfect basal cleavage Correct answer.

Explanation

In micas, silica tetrahedra are linked into continuous sheets held together by weaker cation bonds between layers. When the mineral breaks, it parts along these weak interlayer planes, giving perfect basal cleavage. Density, magnetism and conchoidal fracture are not controlled by the sheet structure in this way.

Question 44Solid Earth: plate tectonics, rocks, minerals, and geological processes

Along a convergent boundary where one oceanic plate subducts beneath another, what is the main reason magma is generated in the overlying mantle wedge?

  1. Radioactive heating raises the wedge above its melting point
  2. Friction along the megathrust melts the overriding plate
  3. The subducting slab melts completely at shallow depth
  4. Addition of water lowers the mantle solidus temperature Correct answer.

Explanation

As the subducting slab heats, hydrous minerals break down and release water into the overlying mantle wedge. Water lowers the solidus of mantle peridotite, triggering partial melting at temperatures below the dry melting point.

Question 45Solid Earth: plate tectonics, rocks, minerals, and geological processes

Which statement correctly describes the relationship between the Mohs hardness scale and actual hardness?

  1. Each step represents an equal increase in resistance to scratching
  2. The scale is ordinal, so the numerical intervals do not represent equal increases in resistance to scratching Correct answer.
  3. Diamond sits at value 10 because it is exactly twice as hard as talc at value 1
  4. The scale measures density, which correlates directly with scratching resistance

Explanation

Mohs hardness is a relative ranking in which each mineral can scratch those below it. The numerical gaps are not proportional to real hardness differences, so the scale is ordinal rather than a linear measurement.

Question 46Solid Earth: plate tectonics, rocks, minerals, and geological processes

What type of plate boundary is marked by a deep ocean trench and a parallel chain of volcanic arc islands?

  1. Divergent boundary
  2. Transform boundary
  3. Ocean-ocean convergent boundary Correct answer.
  4. Passive continental margin

Explanation

Where oceanic lithosphere subducts beneath oceanic lithosphere, a trench marks the down-going slab and a volcanic island arc forms above the mantle wedge. This combination is diagnostic of ocean-ocean convergence.

Question 47Solid Earth: plate tectonics, rocks, minerals, and geological processes

A sedimentary layer contains graded bedding, with coarse grains at the base fining upward. What does this most likely indicate about the depositional event?

  1. Long-term chemical precipitation from evaporating seawater
  2. Deposition from a single waning flow, such as a turbidity current Correct answer.
  3. Deposition beneath a slowly advancing glacier
  4. Formation of the layer by contact metamorphism

Explanation

Graded bedding forms when a single current carrying mixed grain sizes loses energy, so larger, heavier grains settle first and finer grains follow. Turbidity currents are a classic cause. The upward fining records declining flow strength.

Question 48Solid Earth: plate tectonics, rocks, minerals, and geological processes

Which feature is characteristic of a shield volcano built from low-viscosity basaltic lava?

  1. A large caldera produced by a single explosive eruption
  2. A dome of viscous lava piled over a vent
  3. Gentle slopes formed by long lava flows Correct answer.
  4. Steep sides formed by alternating ash and lava

Explanation

Low-viscosity basaltic lava travels far before solidifying, building broad, gently sloping shields. Explosive ash layers and steep profiles belong to stratovolcanoes, and viscous domes form from evolved, silica-rich magma.

Question 49Solid Earth: plate tectonics, rocks, minerals, and geological processes

A seismic station records P-waves but no S-waves from a distant earthquake. Which interpretation is most consistent with this observation?

  1. The station was inside the S-wave shadow zone caused by the mantle
  2. The waves travelled through a liquid outer core that does not transmit S-waves Correct answer.
  3. The P-waves were refracted away from the station
  4. The earthquake was too small to generate S-waves

Explanation

S-waves are shear waves and cannot pass through fluids, so the liquid outer core blocks them from reaching stations on the far side of the Earth. P-waves, which are compressional, can still travel through the core. This is key evidence for a liquid outer core.

Question 50Solid Earth: plate tectonics, rocks, minerals, and geological processes

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

  1. Compaction, weathering, transport, cementation
  2. Weathering, transport, deposition, compaction, cementation Correct answer.
  3. Melting, crystallisation, cooling, erosion
  4. Deposition, foliation, recrystallisation, metamorphism

Explanation

Clastic sedimentary rock forms when weathered material is transported and deposited, then buried and compacted as pore space shrinks, and finally cemented by precipitated minerals. Metamorphic and igneous steps do not belong in this sequence.