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SACE Stage 2 Earth and Environmental Science study materials
SACE Stage 2 Earth and Environmental Science study resources

SACE Stage 2 Earth and Environmental Science practice questions

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Question 1Earth systems and their interactions

Which layer of Earth's interior is composed mainly of liquid iron and nickel and generates the planet's magnetic field through its motion?

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

Explanation

The outer core is molten iron-nickel alloy, and convective motion of this conductive fluid generates Earth's magnetic field by the geodynamo process. The inner core is solid despite its higher temperature because of immense pressure.

Question 2Earth systems and their interactions

The theory of plate tectonics explains that lithospheric plates move because they are carried by which underlying system?

  1. Convection currents in the asthenosphere and mantle Correct answer.
  2. Prevailing winds in the lower atmosphere
  3. Tidal forces exerted by the Moon
  4. Expansion of ocean water at mid-ocean ridges

Explanation

Heat from Earth's interior drives slow convection in the mantle and asthenosphere, and the rigid plates ride on these moving, ductile layers. Slab pull and ridge push are expressions of this same heat-driven motion.

Question 3Earth systems and their interactions

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

  1. A deep ocean trench with a volcanic arc
  2. A continental collision mountain belt
  3. A transform fault with no volcanism
  4. A mid-ocean ridge with new basaltic crust Correct answer.

Explanation

Where oceanic plates diverge, magma rises to fill the gap and solidifies as new basaltic crust, building an elevated mid-ocean ridge. This process is seafloor spreading, and the ridge axis is a zone of shallow earthquakes and volcanism.

Question 4Earth systems and their interactions

Which process transfers the greatest amount of water vapour from Earth's surface into the atmosphere?

  1. Combustion of fossil fuels
  2. Sublimation from glaciers
  3. Evaporation from the oceans Correct answer.
  4. Transpiration from forests

Explanation

The oceans cover most of Earth's surface and supply the large majority of atmospheric water vapour through evaporation. Transpiration adds a smaller but important contribution from vegetation.

Question 5Earth systems and their interactions

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

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

Explanation

Nitrogen accounts for roughly 78 percent of dry air by volume, making it the dominant atmospheric component. Oxygen is second at about 21 percent, while carbon dioxide and argon are trace gases.

Question 6Earth systems and their interactions

In the rock cycle, which process converts loose sediment into solid sedimentary rock?

  1. Melting and crystallisation
  2. Metamorphism under heat and pressure
  3. Weathering at the surface
  4. Compaction and cementation Correct answer.

Explanation

Sediments become sedimentary rock through lithification, which involves compaction by overlying weight and cementation by minerals precipitated from pore fluids. Melting and metamorphism produce igneous and metamorphic rocks instead.

Question 7Earth systems and their interactions

The greenhouse effect warms Earth's surface primarily because certain atmospheric gases do which of the following?

  1. Absorb outgoing infrared radiation and re-emit it in all directions Correct answer.
  2. Generate heat through chemical reactions in the atmosphere
  3. Reflect incoming visible sunlight back into space
  4. Prevent conduction of heat from the ground to the air

Explanation

Greenhouse gases absorb long-wavelength infrared radiation emitted by the surface and re-radiate it, some of which returns toward the surface and raises its temperature. They are largely transparent to incoming short-wave solar radiation.

Question 8Earth systems and their interactions

Which of the following best describes the role of decomposers in a nutrient cycle such as the carbon cycle?

  1. They precipitate dissolved minerals as sedimentary rock
  2. They fix atmospheric nitrogen directly into plant roots
  3. They break down organic matter and release carbon back to soil and air Correct answer.
  4. They convert sunlight into chemical energy stored in glucose

Explanation

Decomposers such as bacteria and fungi mineralise dead organic matter, releasing carbon as carbon dioxide and returning nutrients to the soil. This closes the loop of the carbon cycle by recycling matter from the biosphere back to the atmosphere and geosphere.

Question 9Earth systems and their interactions

A river carries a heavy load of dissolved calcium carbonate into a warm shallow sea. Which long-term Earth system interaction is most likely to result?

  1. Rapid evaporation of the sea producing atmospheric water vapour
  2. Immediate melting of nearby glaciers
  3. Increased volcanic activity along the coastline
  4. Precipitation of limestone, transferring carbon from water to the geosphere Correct answer.

Explanation

In warm shallow seas, dissolved carbonate can precipitate or be used by organisms to form calcium carbonate shells, which accumulate as limestone. This moves carbon from the hydrosphere into the geosphere and is a key part of the long-term carbon cycle.

Question 10Earth systems and their interactions

A coastal region experiences rapid erosion after native vegetation is cleared. Which interaction best explains this change?

  1. Vegetation removal increases the rate of plate movement
  2. Cleared land reflects more sunlight, cooling the local climate
  3. Loss of root binding reduces soil cohesion, increasing erosion by water Correct answer.
  4. Removal of plants increases rainfall intensity in the area

Explanation

Plant roots hold soil particles together and slow surface runoff, so clearing vegetation reduces cohesion and exposes soil to erosive water and wind. This is a clear biosphere-to-geosphere interaction affecting landform development.

Question 11Earth systems and their interactions

Ocean currents such as the Gulf Stream transfer heat from low latitudes toward high latitudes. What is the main effect of this transfer on regional climate?

  1. It warms adjacent coastal regions at higher latitudes Correct answer.
  2. It cools tropical regions to near freezing
  3. It eliminates seasonal temperature differences
  4. It prevents the formation of any precipitation

Explanation

Warm currents carry heat poleward and release it to the atmosphere over adjacent coasts, moderating winters in places like western Europe. This is a key hydrosphere-atmosphere interaction that redistributes global heat.

Question 12Earth systems and their interactions

A student observes that a subducting oceanic plate melts at depth, producing magma. Which explanation best accounts for this melting?

  1. Solar heating penetrates the crust to melt the slab
  2. Water released from the slab lowers the melting point of the overlying mantle Correct answer.
  3. The plate melts because pressure increases with depth
  4. Friction from plate sliding alone raises rock above its melting point

Explanation

As the subducting slab heats, hydrous minerals release water into the overlying mantle wedge, lowering the melting temperature of mantle rock. This flux melting generates the magma that feeds volcanic arcs above subduction zones.

Question 13Earth systems and their interactions

During the El Nino phase, trade winds weaken and warm surface water spreads across the central and eastern Pacific. Which consequence is most consistent with this pattern?

  1. Stronger trade winds across the equatorial Pacific
  2. Reduced upwelling of nutrient-rich water off the South American coast Correct answer.
  3. Colder sea surface temperatures near Peru
  4. Increased snowfall in eastern Australia

Explanation

Weakened trade winds reduce the offshore movement of surface water, suppressing upwelling of cold, nutrient-rich water along the eastern Pacific. This disrupts marine food webs and local fisheries.

Question 14Earth systems and their interactions

Which statement best explains why the atmosphere and hydrosphere are closely coupled in the water cycle?

  1. Evaporation and precipitation exchange water continuously between ocean and air Correct answer.
  2. Ice sheets absorb atmospheric nitrogen
  3. Groundwater never interacts with surface water
  4. Rivers flow uphill to return water to clouds

Explanation

Water evaporates from the ocean into the atmosphere and returns as precipitation, forming a continuous exchange between hydrosphere and atmosphere. This coupling drives weather, climate and the distribution of freshwater.

Question 15Earth systems and their interactions

A region's soils are rich in iron oxides and reddish in colour. Which combination of Earth system processes most likely produced this?

  1. Deposition of limestone in a deep marine basin
  2. Compaction of plant material into coal
  3. Weathering of iron-bearing rock under oxidising conditions Correct answer.
  4. Melting of granite followed by rapid cooling

Explanation

Iron-bearing minerals weather and oxidise when exposed to oxygen and water, producing iron oxides that give soils a red colour. This links the geosphere, atmosphere and hydrosphere in chemical weathering.

Question 16Earth systems and their interactions

Which of the following is the best example of a positive feedback in the climate system?

  1. Warming melts ice, lowering albedo and causing further warming Correct answer.
  2. Warmer oceans evaporate more water, forming reflective clouds
  3. Increased plant growth absorbs more carbon dioxide
  4. Higher temperatures increase rock weathering that consumes carbon dioxide

Explanation

Melting ice exposes darker land or ocean, which absorbs more solar energy and amplifies warming, a self-reinforcing positive feedback. The other examples dampen change and act as negative feedbacks.

Question 17Earth systems and their interactions

A volcanic eruption injects large quantities of sulphur dioxide into the stratosphere. What is the most likely short-term climatic effect?

  1. Immediate rise in sea level
  2. Permanent warming from increased carbon dioxide
  3. Temporary global cooling from reflective sulphate aerosols Correct answer.
  4. Loss of Earth's magnetic field

Explanation

Stratospheric sulphur dioxide forms sulphate aerosols that reflect incoming sunlight, reducing surface temperatures for a few years until the aerosols settle. This is a well-documented atmosphere-geosphere interaction.

Question 18Earth systems and their interactions

Which process in the long-term carbon cycle removes carbon dioxide from the atmosphere over geological timescales?

  1. Volcanic degassing
  2. Combustion of coal
  3. Chemical weathering of silicate rocks Correct answer.
  4. Respiration by animals

Explanation

Silicate weathering consumes atmospheric carbon dioxide as it reacts with rock, and the carbon is eventually stored in marine sediments. This is a slow but major sink over millions of years.

Question 19Earth systems and their interactions

Ocean acidification occurs as seawater absorbs excess atmospheric carbon dioxide. Which chemical change best explains this?

  1. Water temperature falls and lowers pH
  2. Dissolved oxygen increases and raises pH
  3. Salinity rises and acidifies the water
  4. Formation of carbonic acid lowers seawater pH Correct answer.

Explanation

Carbon dioxide dissolves to form carbonic acid, which releases hydrogen ions and lowers pH, reducing carbonate availability for shell-building organisms. This is a direct atmosphere-hydrosphere interaction.

Question 20Earth systems and their interactions

A geologist finds folded sedimentary layers cut by an igneous intrusion. Which principle allows the relative age of the intrusion to be determined?

  1. Uniformitarianism
  2. Cross-cutting relationships Correct answer.
  3. Superposition of strata
  4. Original horizontality

Explanation

An intrusion that cuts across existing layers must be younger than the layers it cuts, which is the principle of cross-cutting relationships. Superposition and original horizontality describe the order and attitude of sedimentary layers, not the age of intrusions.

Question 21Earth systems and their interactions

Two locations at the same latitude have very different annual temperature ranges. Which pair of factors best explains the difference?

  1. Atmospheric nitrogen content and altitude of the mesosphere
  2. Solar luminosity and distance from the Sun
  3. Distance from the ocean and prevailing wind direction Correct answer.
  4. Axial tilt and Earth's rotation rate

Explanation

Coastal sites experience maritime moderation because water has a high heat capacity, while continental interiors show larger seasonal ranges; prevailing winds determine whether maritime air reaches a site. Axial tilt affects all latitudes equally and does not explain local differences.

Question 22Earth systems and their interactions

A model shows that adding aerosols to the atmosphere increases cloud brightness but also reduces precipitation. Which interpretation is most defensible?

  1. Aerosol effects are identical to those of greenhouse gases
  2. Aerosols alter both the radiative balance and the hydrological cycle, creating competing effects Correct answer.
  3. Aerosols have no effect on either radiation or rainfall
  4. Precipitation changes prove that aerosols warm the planet

Explanation

Aerosols scatter sunlight and seed more numerous smaller droplets, brightening clouds while suppressing droplet coalescence and rainfall. The two effects must be evaluated together because they act on different parts of the climate system.

Question 23Earth systems and their interactions

A study finds that removing apex predators from a river system increases herbivore numbers, which then reduces streamside vegetation and destabilises banks. This is best described as which type of interaction?

  1. A trophic cascade linking biosphere and geosphere processes Correct answer.
  2. An example of convergent plate motion
  3. A negative feedback that restores the original state
  4. A purely atmospheric process

Explanation

Removing a top predator releases herbivores from control, and their increased grazing reduces vegetation, which in turn increases bank erosion. The chain links ecological (biosphere) change to geomorphic (geosphere) change, a trophic cascade with physical consequences.

Question 24Earth systems and their interactions

Ice-core records show that carbon dioxide and temperature varied together over glacial cycles. Why must this correlation be interpreted cautiously?

  1. Temperature never changed during glacial cycles
  2. Correlation does not establish causation, and feedbacks can operate in both directions Correct answer.
  3. Carbon dioxide has no radiative properties
  4. Ice cores cannot preserve gas bubbles from the past

Explanation

Carbon dioxide and temperature can reinforce each other through feedbacks such as ocean solubility and ice albedo, so correlation alone cannot fix the direction of cause and effect. Additional evidence from timing and modelling is needed to attribute causation.

Question 25Earth systems and their interactions

A catchment receives less snowfall but more winter rain. Which combination of downstream effects is most likely?

  1. Later spring melt and greater summer storage
  2. No change to river flow timing
  3. Earlier peak river flow and reduced summer water storage Correct answer.
  4. Increased glacier growth in the headwaters

Explanation

Rain runs off quickly compared with snowmelt stored until spring, so a shift from snow to rain advances peak flows and reduces the natural reservoir that supplies summer baseflow. This couples atmospheric change to hydrological and water-resource impacts.

Question 26Earth systems and their interactions

Which layer of Earth's interior is composed mainly of liquid iron and nickel and generates the planet's magnetic field?

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

Explanation

The outer core is molten iron-nickel alloy whose convective motion, coupled with rotation, drives the geodynamo that produces Earth's magnetic field. The inner core is solid despite its higher temperature because pressure is far greater.

Question 27Earth systems and their interactions

Which process transfers the greatest amount of water from the ocean surface to the atmosphere?

  1. Infiltration of water into seafloor sediment
  2. Evaporation driven by solar energy Correct answer.
  3. Condensation of water vapour into droplets
  4. Subduction of seawater at trenches

Explanation

Solar heating supplies latent energy that converts liquid seawater into vapour, and evaporation over the oceans dominates the global flux to the atmosphere. Condensation releases that energy again but converts vapour back to liquid, moving water in the opposite direction.

Question 28Earth systems and their interactions

Which of the following is a direct consequence of the biosphere influencing the atmosphere over geological time?

  1. Oxygen accumulated as photosynthetic organisms released it Correct answer.
  2. Earth's magnetic field reversed polarity
  3. The mantle began convecting faster
  4. Sea level fell because of increased evaporation

Explanation

Photosynthetic organisms, especially cyanobacteria, released oxygen that accumulated in the atmosphere and ocean, transforming surface chemistry. This is a clear example of the biosphere reshaping another Earth system.

Question 29Earth systems and their interactions

Which of the following best describes the lithosphere in plate tectonic theory?

  1. The plastic zone that flows to move the plates
  2. The entire mantle plus the crust
  3. The molten layer directly beneath the crust
  4. The rigid outer shell that is broken into moving plates Correct answer.

Explanation

The lithosphere is the cool, rigid outer shell comprising the crust and uppermost mantle, and it is fractured into plates that move over the weaker asthenosphere. Its rigidity is what allows plates to behave as coherent units.

Question 30Earth systems and their interactions

Which of the following is the main natural source of the carbon dioxide that enters the atmosphere over short timescales?

  1. Photosynthesis in forests
  2. Volcanic and metamorphic degassing Correct answer.
  3. Precipitation of limestone in shallow seas
  4. Chemical weathering of silicate rock

Explanation

Volcanic and metamorphic degassing releases carbon stored in Earth's interior into the atmosphere, balancing carbon removed by weathering and burial over long timescales. The other processes listed remove carbon from the atmosphere.

Question 31Earth systems and their interactions

A cyclone forms over warm tropical ocean water. Which energy transfer best explains how the ocean strengthens the storm?

  1. Reflection of sunlight from the ocean surface
  2. Friction between waves and the sea surface
  3. Sensible heat conducted directly from the seafloor
  4. Latent heat released as water vapour condenses in the storm Correct answer.

Explanation

Warm ocean water evaporates, and the vapour later condenses in the storm, releasing latent heat that warms the air column and lowers pressure, strengthening the circulation. This couples the hydrosphere and atmosphere through energy transfer.

Question 32Earth systems and their interactions

Which of the following best explains why the asthenosphere allows tectonic plates to move?

  1. It is completely liquid and plates float on it
  2. It is rigid and transmits stress without deforming
  3. It deforms slowly and flows, allowing plates to slide over it Correct answer.
  4. It is denser than the plates and pulls them downward

Explanation

The asthenosphere is hot enough to deform plastically over long timescales, so the rigid plates above can move across it. It is not a true liquid, but its slow flow provides the weak layer that enables plate motion.

Question 33Earth systems and their interactions

Which of the following is an example of the atmosphere influencing the hydrosphere?

  1. Volcanoes add ash to the air
  2. Prevailing winds drive surface ocean currents Correct answer.
  3. Rivers erode valleys in bedrock
  4. Glaciers carve U-shaped valleys

Explanation

Wind stress from atmospheric circulation pushes surface water, creating large-scale ocean currents that redistribute heat. This illustrates a direct transfer of influence from the atmosphere to the hydrosphere.

Question 34Earth systems and their interactions

A large igneous province erupts and releases enormous volumes of carbon dioxide over about a million years. Which chain of effects is most consistent with the geological record?

  1. Atmospheric oxygen rises, oceans cool, and reefs expand
  2. Atmospheric nitrogen rises, oceans become alkaline, and reefs expand
  3. Atmospheric carbon dioxide rises, oceans warm and acidify, and carbonate reef growth declines Correct answer.
  4. Atmospheric carbon dioxide falls, oceans cool, and sea ice spreads

Explanation

Sustained volcanic carbon release raises atmospheric carbon dioxide, which warms the surface and increases dissolved carbon in seawater, lowering pH and hampering carbonate-secreting organisms. Reef decline follows because calcification becomes harder under warmer, more acidic conditions.

Question 35Earth systems and their interactions

A mountain range grows and intercepts moist prevailing winds. Which combination of changes is most likely on the leeward side?

  1. Increased rainfall and denser forest
  2. Higher humidity and more river discharge
  3. Greater snowfall and larger glaciers
  4. Reduced rainfall and increased aridity Correct answer.

Explanation

Air loses moisture as it rises over the windward slope, so descending air on the leeward side is drier, producing a rain shadow. Aridity there reduces vegetation cover and river flow.

Question 36Earth systems and their interactions

A scientist compares two catchments with similar rainfall but different vegetation cover. Which observation would most strongly support the claim that vegetation increases infiltration?

  1. The bare catchment has lower peak streamflow after storms
  2. The vegetated catchment has higher infiltration and lower surface runoff Correct answer.
  3. Both catchments have identical groundwater recharge
  4. The vegetated catchment has higher surface runoff and more erosion

Explanation

Roots and organic matter create pore space and slow water at the surface, so vegetated ground absorbs more water and sheds less as overland flow. Higher infiltration and lower runoff are the expected signature of that effect.

Question 37Earth systems and their interactions

Which of the following best explains why melting ice sheets can raise global sea level even though floating sea ice does not?

  1. Floating ice is colder than land ice
  2. Sea ice melts more slowly than glacial ice
  3. Land ice contains more salt than sea ice
  4. Land-based ice adds new water to the ocean when it melts Correct answer.

Explanation

Ice resting on land holds water that is not yet part of the ocean, so melting transfers new water into the sea and raises level. Floating ice already displaces its own weight in water, so its melting leaves the level essentially unchanged.

Question 38Earth systems and their interactions

A region's groundwater is pumped faster than it is recharged. Which set of consequences is most likely?

  1. Water table decline, land subsidence, and reduced baseflow to streams Correct answer.
  2. Water table rise, land uplift, and increased spring flow
  3. Higher soil salinity only, with no change to streamflow
  4. Increased recharge and higher stream baseflow

Explanation

Over-extraction lowers the water table, and compaction of drained aquifer sediments can cause the ground surface to sink. With less groundwater storage, discharge to streams during dry periods falls, reducing baseflow.

Question 39Earth systems and their interactions

Which of the following best describes the role of the cryosphere in regulating global temperature?

  1. It supplies carbon dioxide to the atmosphere
  2. It absorbs most incoming solar radiation
  3. High albedo reflects solar radiation, cooling the surface Correct answer.
  4. It releases large amounts of latent heat to warm the air

Explanation

Snow and ice are highly reflective, so they return much of the incoming solar energy to space and keep surface temperatures lower. Loss of ice therefore reduces albedo and amplifies warming.

Question 40Earth systems and their interactions

A sedimentary basin subsides and accumulates thick organic-rich mud. Which long-term change in the carbon cycle is most likely?

  1. Carbon is rapidly returned to the atmosphere by respiration
  2. Carbon is buried as organic matter and later stored as fossil fuel Correct answer.
  3. Carbonate minerals dissolve and release carbon dioxide
  4. Photosynthesis stops because the mud is buried

Explanation

Rapid burial removes organic carbon from contact with oxygen, slowing decomposition and allowing carbon to be stored in sediments over geological time. Some of this buried carbon later forms fossil fuels.

Question 41Earth systems and their interactions

Which of the following best explains why the atmosphere has a much shorter residence time for water vapour than for carbon dioxide?

  1. Water vapour reacts with nitrogen and disappears instantly
  2. Carbon dioxide is removed only by volcanic eruptions
  3. Water vapour is heavier than carbon dioxide and settles out
  4. Water vapour condenses and precipitates within days, while carbon dioxide cycles over years Correct answer.

Explanation

Water vapour is removed quickly when air cools and condensation forms precipitation, giving a residence time of days. Carbon dioxide is removed by slower processes such as ocean uptake, photosynthesis, and weathering, so it persists far longer.

Question 42Earth systems and their interactions

A student claims that an increase in evaporation must always increase local rainfall. Which response best evaluates this claim?

  1. It is weak because rainfall also requires condensation and lifting of moist air Correct answer.
  2. It is strong because evaporation directly forms raindrops
  3. It is weak because evaporation never contributes to rainfall
  4. It is strong because rainfall equals evaporation everywhere

Explanation

Evaporation supplies water vapour, but rain requires that vapour to be lifted, cooled, and condensed into droplets large enough to fall. Without suitable atmospheric dynamics, extra evaporation may not produce local rainfall.

Question 43Earth systems and their interactions

Which of the following best describes a negative feedback that stabilises Earth's climate over long timescales?

  1. Warmer temperatures increase water vapour, which traps more heat
  2. Warmer temperatures increase silicate weathering, which removes carbon dioxide Correct answer.
  3. Warmer temperatures melt ice, which lowers albedo
  4. Warmer temperatures thaw permafrost, releasing methane

Explanation

Higher temperatures and rainfall speed silicate weathering, which consumes atmospheric carbon dioxide and draws temperatures back down. This counteracts the initial warming, so it is a stabilising negative feedback.

Question 44Earth systems and their interactions

A river's headwaters are deforested while its lower course is urbanised. Which combined effect on the hydrograph is most likely?

  1. No change in peak discharge but higher baseflow
  2. Lower peak discharge with a longer lag time
  3. Higher and earlier peak discharge with greater flood risk Correct answer.
  4. Lower runoff volume and reduced erosion

Explanation

Deforestation reduces infiltration and urban surfaces shed water quickly, so runoff reaches the channel faster and in greater volume. The hydrograph therefore shows a higher, earlier peak and increased flood risk.

Question 45Earth systems and their interactions

Which of the following best explains why the ocean is a major sink for atmospheric carbon dioxide?

  1. Carbon dioxide is denser than seawater
  2. Seawater is warmer than the atmosphere
  3. Carbon dioxide dissolves in seawater and reacts to form bicarbonate Correct answer.
  4. Marine organisms convert carbon dioxide into nitrogen

Explanation

Carbon dioxide dissolves in surface water and reacts with water to form carbonic acid, which dissociates into bicarbonate and hydrogen ions. This chemical conversion allows the ocean to hold far more carbon than the atmosphere.

Question 46Earth systems and their interactions

A scientist models a planet with no atmosphere and the same solar input as Earth. Which surface temperature pattern is most likely?

  1. Much colder average temperature with extreme day-night contrast Correct answer.
  2. The same average temperature with the same contrast
  3. Warmer nights but colder days than Earth
  4. Slightly warmer average temperature with mild day-night contrast

Explanation

Without an atmosphere, there is no greenhouse warming to raise the average temperature and no air to transport heat from day to night. The result is a much colder mean and far larger temperature swings between day and night.

Question 47Earth systems and their interactions

Two coastal cities at similar latitude differ in annual temperature range. One sits beside a warm ocean current, the other beside a cold current. Which explanation is most consistent?

  1. The cold-current city has a smaller range because cold water holds more heat
  2. Both cities should have identical ranges because latitude is the same
  3. The warm-current city has a smaller range because the ocean moderates temperature Correct answer.
  4. The warm-current city has a larger range because warm water evaporates faster

Explanation

A warm offshore current raises winter temperatures and maritime air keeps summers moderate, reducing the annual range. Cold currents cool the adjacent coast and, by stabilising the air, tend to produce drier, more continental conditions.

Question 48Earth systems and their interactions

A model predicts that warming permafrost will release methane, which causes further warming. Which statement best evaluates this prediction?

  1. It describes a positive feedback that could accelerate warming, but its magnitude is uncertain Correct answer.
  2. It describes a negative feedback that will stabilise climate
  3. It is impossible because methane is not a greenhouse gas
  4. It is certain to be the dominant control on future climate

Explanation

Methane release from thawing permafrost is a self-reinforcing, positive feedback because the gas adds to warming. However, the amount and timing of release depend on complex soil, hydrological, and microbial factors, so the magnitude remains uncertain.

Question 49Earth systems and their interactions

A lake receives excess nitrogen and phosphorus from farmland. Which sequence of changes is most likely?

  1. Algal blooms grow, then decompose, lowering dissolved oxygen and harming fish Correct answer.
  2. Nutrients are buried and the lake becomes clearer
  3. Phytoplankton decline and water clarity improves
  4. Dissolved oxygen rises, then fish populations increase

Explanation

Nutrient enrichment fuels rapid algal growth; when the algae die, decomposition consumes dissolved oxygen and can create hypoxic conditions that harm fish and other animals. This is the classic pathway of eutrophication.

Question 50Earth systems and their interactions

A geologist finds that a river has cut a deep gorge through uplifted limestone while nearby caves contain similar limestone. Which interpretation best links the lithosphere and hydrosphere?

  1. Uplift increased the hydraulic gradient, so groundwater and river incision together shaped the landscape Correct answer.
  2. The river deposited the limestone and then eroded it
  3. The gorge formed by wind erosion alone
  4. Cave formation requires volcanic heat, not water

Explanation

Tectonic uplift raises the land and steepens the water table gradient, driving faster groundwater flow and cave development while the river incises downward. The landscape reflects combined lithospheric uplift and hydrospheric erosion.