I85PREP
⌘ K
QCAA Earth & Environmental Science study materials
QCAA Earth & Environmental Science study resources

QCAA Earth & Environmental Science practice questions

One question at a time. Build your QCAA Earth & Environmental Science understanding.

First 50 of 198 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Unit 3

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

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

Explanation

The inner core is solid because pressure is so great that iron and nickel remain solid despite temperatures above 5000 degrees Celsius. The outer core is liquid, and the mantle is dominated by silicate minerals rather than metal.

Question 2Unit 3

New oceanic crust is generated at which type of plate boundary?

  1. A transform boundary such as a major fault
  2. A convergent boundary at a deep ocean trench
  3. A divergent boundary at a mid-ocean ridge Correct answer.
  4. A passive continental margin

Explanation

At mid-ocean ridges, mantle material rises, decompresses and partially melts, producing magma that solidifies as new basaltic crust. Sea-floor spreading then moves this crust away from the ridge axis.

Question 3Unit 3

A rock sample contains a mineral that crystallised with equal parent and daughter isotopes of a radioactive decay series. If the half-life is 200 million years, approximately how old is the mineral?

  1. 400 million years
  2. 200 million years Correct answer.
  3. 800 million years
  4. 100 million years

Explanation

Equal parent and daughter amounts mean that exactly one half-life has elapsed, because half the original parent has decayed. With a half-life of 200 million years, the mineral is therefore about 200 million years old.

Question 4Unit 3

Which process most directly drives the movement of tectonic plates over geological time?

  1. Erosion and deposition of sediment at coastlines
  2. Tidal forces exerted by the Moon
  3. Rapid rotation of the solid inner core
  4. Convection of the mantle combined with slab pull Correct answer.

Explanation

Mantle convection transfers heat from depth to the surface, and the negative buoyancy of subducting slabs adds a strong driving force known as slab pull. Together these forces move lithospheric plates.

Question 5Unit 3

A mineral breaks along smooth parallel planes related to weak bonds in its crystal lattice. This property is called:

  1. Fracture
  2. Lustre
  3. Streak
  4. Cleavage Correct answer.

Explanation

Cleavage is the tendency of a mineral to break along planes determined by weaker bonding directions in its atomic structure. It differs from fracture, which is irregular breakage with no preferred plane.

Question 6Unit 3

Which igneous rock texture indicates that magma cooled slowly at depth, allowing large crystals to grow?

  1. Coarse-grained phaneritic texture Correct answer.
  2. Fine-grained aphanitic texture
  3. Glassy texture
  4. Vesicular texture

Explanation

Slow cooling at depth gives atoms time to arrange into large crystals, producing a coarse-grained phaneritic texture such as granite. Rapid surface cooling instead produces fine-grained or glassy rocks.

Question 7Unit 3

Which sedimentary structure is most useful for determining the original way-up of tilted strata?

  1. Horizontal lamination in a flat-lying shale
  2. Ripple marks preserved on a bedding plane
  3. A vertical joint set cutting across layers
  4. Graded bedding showing coarse grains below fine grains Correct answer.

Explanation

Graded bedding normally fines upward because a waning current deposits coarse material first, so the coarse base marks the original bottom of the bed. This asymmetry allows geologists to identify whether strata have been overturned.

Question 8Unit 3

During regional metamorphism, increasing temperature and pressure typically cause which change in a clay-rich sedimentary rock?

  1. It melts completely to form a coarse granite
  2. It recrystallises into a foliated metamorphic rock such as slate or schist Correct answer.
  3. It dissolves and is removed by groundwater
  4. It remains chemically and texturally unchanged

Explanation

Metamorphism recrystallises minerals in the solid state, and directed pressure aligns platy minerals to produce foliation. Increasing grade transforms shale through slate and phyllite to schist and gneiss.

Question 9Unit 3

Which soil horizon is typically richest in accumulated organic matter and supports most root growth?

  1. The A horizon Correct answer.
  2. The B horizon
  3. The C horizon
  4. The R horizon

Explanation

The A horizon is the surface mineral layer where organic matter accumulates and biological activity is greatest, making it the main zone of root growth. The B horizon is a subsoil accumulation zone and the C horizon is weathered parent material.

Question 10Unit 3

A soil has a high proportion of clay particles. Which property is most likely to result?

  1. Low cohesion and high susceptibility to wind erosion
  2. Very rapid drainage and low nutrient retention
  3. Neutral pH regardless of parent material
  4. High water-holding capacity and slow drainage Correct answer.

Explanation

Clay particles are extremely small with large surface area and negative surface charge, so they retain water and nutrient cations strongly. This produces high water-holding capacity but slow permeability.

Question 11Unit 3

Which process removes soluble salts from the upper soil profile in a humid climate?

  1. Calcification
  2. Erosion by wind
  3. Leaching Correct answer.
  4. Salinisation

Explanation

In humid climates, excess rainfall moves downward through the profile and dissolves and carries away soluble salts and bases, a process called leaching. Salinisation is the opposite accumulation of salts, typical of arid regions.

Question 12Unit 3

The greenhouse effect warms Earth's surface primarily because certain atmospheric gases:

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

Explanation

Greenhouse gases such as carbon dioxide and water vapour absorb long-wavelength infrared radiation emitted by the surface and re-radiate it, some of which returns to the surface. This reduces the rate at which Earth loses energy to space.

Question 13Unit 3

Which statement best describes the role of the ocean in the global carbon cycle?

  1. It releases more carbon dioxide than it absorbs each year
  2. It stores carbon only as dissolved carbonate with no biological involvement
  3. It has no significant exchange of carbon with the atmosphere
  4. It absorbs atmospheric carbon dioxide and stores it in deep water and sediments Correct answer.

Explanation

The ocean is a major carbon sink, taking up carbon dioxide through physical dissolution and biological pumps that carry organic matter and shells to depth. Over long timescales this carbon is stored in deep water and seafloor sediment.

Question 14Unit 3

A scientist measures carbon dioxide concentration in an air sample and reports 420 parts per million. This means that in every million molecules of air there are:

  1. 420 thousand molecules of carbon dioxide
  2. 420 billion molecules of carbon dioxide
  3. 420 molecules of carbon dioxide Correct answer.
  4. 420 molecules of oxygen

Explanation

Parts per million expresses the number of molecules of a gas per million molecules of the air mixture. A value of 420 ppm therefore corresponds to 420 carbon dioxide molecules in every million air molecules.

Question 15Unit 3

Which human activity is the largest single source of anthropogenic carbon dioxide emissions globally?

  1. Decomposition of soil organic matter in forests
  2. Volcanic degassing at subduction zones
  3. Combustion of fossil fuels for energy Correct answer.
  4. Evaporation of water from the ocean surface

Explanation

Burning coal, oil and gas for electricity, transport and industry releases the great majority of human carbon dioxide emissions. Volcanic degassing is natural and small compared with fossil fuel combustion.

Question 16Unit 3

An El Nino event is best described as:

  1. A sudden change in the salinity of the North Atlantic
  2. Weakening of the trade winds and warming of surface water in the eastern equatorial Pacific Correct answer.
  3. Strengthening of the trade winds and cooling of the eastern equatorial Pacific
  4. A seasonal shift of the monsoon over South Asia

Explanation

During El Nino, the Walker circulation weakens, trade winds slacken and warm water spreads eastward across the equatorial Pacific. This shifts rainfall patterns and disrupts upwelling off South America.

Question 17Unit 3

Upwelling along a coast brings cold, nutrient-rich water to the surface. This most directly supports:

  1. High primary productivity and large fish populations Correct answer.
  2. Coral reef growth in warm shallow water
  3. Formation of sea ice at low latitudes
  4. Rapid evaporation and salt deposition

Explanation

Upwelled water carries nutrients such as nitrate and phosphate from depth into the sunlit zone, fuelling phytoplankton growth. This high primary productivity supports productive fisheries.

Question 18Unit 3

Which factor most strongly increases the risk of mass movement on a steep hillslope?

  1. A gentle slope angle
  2. Deep root systems from mature forest
  3. Saturation of the soil by heavy rainfall Correct answer.
  4. A well-drained sandy surface layer

Explanation

Water infiltrating the soil increases pore pressure and reduces effective friction between particles, while adding weight to the slope. Both effects lower stability and can trigger landslides.

Question 19Unit 3

A river carries a heavy load of fine suspended sediment into a slow-moving reservoir. Which depositional feature is most likely to form where the river enters the standing water?

  1. A glacial moraine
  2. A sand dune field
  3. A deep canyon cut into bedrock
  4. A delta of sorted sediment Correct answer.

Explanation

When a river enters standing water, its velocity drops abruptly and its sediment-carrying capacity falls, so sediment is deposited. Repeated deposition builds a delta, with coarser material settling nearer the channel mouth.

Question 20Unit 3

In a catchment, the lag time between peak rainfall and peak river discharge is likely to be shortest when the catchment has:

  1. Gentle slopes with deep permeable soils and dense forest
  2. Extensive snow cover at high altitude
  3. Large areas of wetland and lakes
  4. Steep slopes with impermeable surfaces and little vegetation Correct answer.

Explanation

Steep, impermeable, sparsely vegetated catchments shed rainfall rapidly as overland flow, so little water is stored and the hydrograph peak arrives quickly. Storage features such as soils, wetlands and lakes delay and spread the peak.

Question 21Unit 3

A geologist finds a sedimentary sequence containing a trilobite fossil below a layer containing a dinosaur bone. Which conclusion is best supported?

  1. The dinosaur layer is older than the trilobite layer
  2. Both layers formed at exactly the same time
  3. The trilobite was transported into the upper layer
  4. The trilobite layer is older than the dinosaur layer Correct answer.

Explanation

The principle of superposition states that in an undisturbed sequence, lower layers are older than those above them. Since trilobites became extinct long before dinosaurs appeared, the fossil evidence is consistent with this ordering.

Question 22Unit 3

A rock unit is cut by an igneous dyke that does not continue into the overlying sedimentary layer. Which principle allows a geologist to conclude that the dyke is older than the overlying layer?

  1. Faunal succession
  2. Original horizontality
  3. Uniformitarianism
  4. Cross-cutting relationships Correct answer.

Explanation

The principle of cross-cutting relationships states that a feature cutting across another must be younger than the rock it cuts. Because the dyke is truncated by the overlying layer, the dyke formed first and the sediment was deposited over it later.

Question 23Unit 3

A sample of granite contains 12.5 percent of its original radioactive parent isotope. How many half-lives have elapsed?

  1. Four
  2. One
  3. Two
  4. Three Correct answer.

Explanation

After each half-life the remaining parent fraction halves, giving 50, 25, 12.5 percent after one, two and three half-lives respectively. A remaining fraction of 12.5 percent therefore indicates three half-lives.

Question 24Unit 3

Which evidence best supports the theory of continental drift proposed from matching coastlines and fossils?

  1. Matching rock sequences and fossil assemblages on now-separated continents Correct answer.
  2. The presence of deserts on every continent
  3. Uniform thickness of sediment on all ocean floors
  4. Identical weather patterns on all continents

Explanation

Similar rock types, structures and fossils found on continents now separated by oceans indicate that those landmasses were once joined. This correlation supports the reconstruction of past supercontinents.

Question 25Unit 3

A city replaces vegetated ground with dark asphalt and concrete. Which change to its local energy balance is most likely?

  1. Higher daytime surface temperatures because of greater heat absorption and reduced evapotranspiration Correct answer.
  2. Lower daytime temperatures because of increased albedo and shading
  3. Cooler nights because buildings radiate heat away more efficiently
  4. No change, because urban surfaces have the same thermal properties as vegetation

Explanation

Dark, dry urban surfaces absorb more solar radiation and lack the cooling effect of plant transpiration, producing an urban heat island. Buildings and pavement also store heat and release it slowly at night.

Question 26Unit 3

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

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

Explanation

Earth's outer core is molten iron-nickel alloy, and its convective motion of charged material generates the geomagnetic field through the geodynamo effect. The inner core is solid because of immense pressure despite high temperature.

Question 27Unit 3

Which type of plate boundary is associated with the formation of a deep ocean trench and a volcanic island arc?

  1. A passive margin within a continental interior
  2. A divergent boundary between two oceanic plates
  3. A transform boundary between two continental plates
  4. A convergent boundary where an oceanic plate subducts Correct answer.

Explanation

Where an oceanic plate meets another plate and subducts, the descending slab bends downward to create a deep trench, and melting above the slab feeds arc volcanism. Divergent and transform boundaries lack subduction, so trenches and arcs do not form there.

Question 28Unit 3

Which mineral property is defined as the colour of a powdered mineral sample on an unglazed porcelain plate?

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

Explanation

Streak is the colour of a mineral in powdered form and is often more diagnostic than the bulk colour because it is less affected by surface weathering or impurities. Lustre, cleavage and hardness describe surface appearance, breaking behaviour and scratch resistance respectively.

Question 29Unit 3

Which process in the rock cycle converts loose sediment into solid sedimentary rock?

  1. Compaction and cementation Correct answer.
  2. Melting followed by rapid cooling
  3. Foliation under directed stress
  4. Weathering and erosion

Explanation

Lithification occurs when accumulating sediment is buried, compacted by overburden and cemented by minerals precipitated from pore fluids. Melting produces igneous rock, foliation produces metamorphic rock, and weathering and erosion break rock down rather than build it up.

Question 30Unit 3

Which atmospheric layer contains most of the ozone that absorbs harmful ultraviolet radiation from the Sun?

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

Explanation

The stratosphere hosts the ozone layer, where ozone molecules absorb ultraviolet radiation and convert it into heat, which also produces the temperature inversion in that layer. The troposphere holds most atmospheric mass and weather but relatively little ozone.

Question 31Unit 3

Which term describes the proportion of incident solar radiation that a surface reflects back to space?

  1. Conductivity
  2. Emissivity
  3. Albedo Correct answer.
  4. Insolation

Explanation

Albedo is the reflectivity of a surface, expressed as a ratio of reflected to incoming radiation. Fresh snow has a high albedo while dark ocean water has a low one, so albedo strongly affects local and global energy budgets.

Question 32Unit 3

Which gas is the most abundant by volume in Earth's modern atmosphere?

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

Explanation

Nitrogen makes up roughly 78 percent of the dry atmosphere by volume, far exceeding oxygen at about 21 percent. Carbon dioxide and argon are present only in trace amounts.

Question 33Unit 3

Which feature forms where a river enters a standing body of water and loses velocity rapidly?

  1. A waterfall
  2. An alluvial fan
  3. A meander cut bank
  4. A delta Correct answer.

Explanation

When a river enters a lake or sea its velocity drops abruptly, so its sediment load is deposited in a fan-shaped body called a delta. Alluvial fans form where streams leave steep mountain fronts onto dry plains rather than entering standing water.

Question 34Unit 3

A geologist observes a sequence of horizontal sedimentary layers and then finds an intrusion of magma cutting across them. Which principle indicates that the intrusion is younger than the layers?

  1. The principle of faunal succession
  2. The principle of original horizontality
  3. The principle of cross-cutting relationships Correct answer.
  4. The principle of superposition

Explanation

Cross-cutting relationships state that a feature which cuts across another must be younger than the material it cuts. Because the intrusion disrupts the layers, it must have formed after they were deposited.

Question 35Unit 3

A rock contains a radioactive isotope with a half-life of 50 million years. If 25 percent of the original parent isotope remains, approximately how old is the rock?

  1. 200 million years
  2. 100 million years Correct answer.
  3. 25 million years
  4. 50 million years

Explanation

Each half-life halves the remaining parent, so 100 percent becomes 50 percent after one half-life and 25 percent after two. Two half-lives of 50 million years each give an age of about 100 million years.

Question 36Unit 3

A coastline experiences two high tides and two low tides of roughly equal height each day. Which condition best explains this tidal pattern?

  1. The Sun's gravitational pull dominates the Moon's
  2. Earth rotates once relative to the Moon each month
  3. The tidal influence of the Moon slightly exceeds that of the Sun Correct answer.
  4. The Moon and Sun are aligned at new and full Moon

Explanation

Semidiurnal tides with two similar highs and lows each day reflect the dominance of the Moon's tide-generating force, with the Sun adding a smaller effect. Alignment or opposition of Sun and Moon produces spring and neap variations in range rather than a change in the number of tides.

Question 37Unit 3

A coastal community builds a sea wall to protect property from erosion. Which consequence is most likely along the adjacent shoreline?

  1. Increased sediment supply to neighbouring beaches
  2. Rapid seaward growth of the neighbouring beach
  3. Permanent lowering of the local wave energy
  4. Accelerated erosion of the neighbouring beach because sediment supply is cut off Correct answer.

Explanation

A hard sea wall prevents waves from eroding the backshore and cuts off sediment that would otherwise feed the longshore drift, so down-drift beaches receive less sediment and can erode faster. The structure also reflects wave energy rather than absorbing it.

Question 38Unit 3

Which statement best explains why the leeward side of a mountain range is typically drier than the windward side?

  1. Mountain ranges block cold ocean currents from reaching the leeward side
  2. Air cools and loses moisture as it rises on the windward side, then warms and holds more moisture as it descends on the leeward side Correct answer.
  3. The leeward side receives more direct solar radiation throughout the year
  4. Air descending on the leeward side cools and condenses its moisture

Explanation

As moist air is forced up the windward slope it expands and cools, so water vapour condenses and falls as rain. On descending the leeward side the air is compressed and warms, lowering its relative humidity and creating a rain shadow.

Question 39Unit 3

A weather map shows a cold front approaching a town. Which sequence of weather changes is most likely as the front passes?

  1. Clear skies with rising temperature and falling pressure
  2. Persistent fog followed by strong steady easterly winds
  3. Gradual cloud thickening, steady rain, then warm humid conditions
  4. Sudden heavy showers and thunderstorms followed by cooler, drier air Correct answer.

Explanation

A cold front lifts warm air abruptly, producing a narrow band of intense showers or thunderstorms, after which cooler and drier air follows behind the front. The gradual thickening cloud and steady rain described in the other option are typical of a warm front.

Question 40Unit 3

A catchment is covered by dense urban development with connected stormwater drains. How does this most likely affect the flood hydrograph compared with the original forested catchment?

  1. Shorter lag time and higher peak discharge Correct answer.
  2. Longer lag time and lower peak discharge
  3. Longer lag time and higher peak discharge
  4. Shorter lag time and lower peak discharge

Explanation

Impervious surfaces and drains allow rainfall to reach the stream rapidly with little infiltration, so the lag time shortens and a larger volume of water arrives together, raising peak discharge. Forested catchments delay and spread runoff through infiltration and storage.

Question 41Unit 3

Which process transfers carbon from the atmosphere into living plant tissue?

  1. Photosynthesis Correct answer.
  2. Respiration
  3. Combustion
  4. Decomposition

Explanation

Photosynthesis uses atmospheric carbon dioxide and sunlight to build organic molecules in plants, moving carbon from the atmosphere into the biosphere. Respiration, combustion and decomposition all release carbon back toward the atmosphere.

Question 42Unit 3

A rock sample is composed of interlocking crystals of quartz, feldspar and mica and shows a foliated fabric. Which rock type is it most likely to be?

  1. A chemical sedimentary rock
  2. An intrusive igneous rock
  3. A clastic sedimentary rock
  4. A metamorphic rock Correct answer.

Explanation

Interlocking crystals with a foliated fabric indicate recrystallisation under directed pressure, which is characteristic of metamorphic rocks such as schist or gneiss. Sedimentary rocks are typically granular or crystalline in layers without foliation, and igneous rocks lack foliation.

Question 43Unit 3

Which factor most directly determines the viscosity of a magma and hence the style of volcanic eruption?

  1. The silica content and temperature of the magma Correct answer.
  2. The distance of the volcano from the coast
  3. The depth of the underlying mantle
  4. The age of the surrounding country rock

Explanation

High silica content and lower temperature increase magma viscosity by promoting polymerisation of silicate chains, trapping gas and producing explosive eruptions. Low-silica, hot magma is fluid and typically erupts effusively.

Question 44Unit 3

A fossil assemblage in a rock layer contains species that are known to have existed only during a narrow interval of geological time. Which term describes such a fossil?

  1. A body fossil
  2. An index fossil Correct answer.
  3. A trace fossil
  4. A microfossil

Explanation

An index fossil is a species with a short geological range and wide geographic distribution, making it useful for correlating and dating rock layers. Trace fossils record activity rather than the organism itself, and body or micro fossils may lack the narrow time range needed.

Question 45Unit 3

A sample of soil has a pH of 4.5 and low base saturation. Which management action would most directly raise its pH?

  1. Adding fresh organic mulch
  2. Increasing irrigation with saline water
  3. Adding gypsum
  4. Applying agricultural lime Correct answer.

Explanation

Agricultural lime, mainly calcium carbonate, neutralises soil acidity and raises pH by increasing base saturation. Gypsum adds calcium and sulfate without raising pH, and saline irrigation can worsen soil chemistry.

Question 46Unit 3

Which statement best explains why sea level is expected to rise as global average temperature increases?

  1. Thermal expansion of ocean water and melting of land-based ice Correct answer.
  2. Expansion of the ocean floor due to tectonic spreading
  3. Increased rainfall over the continents
  4. Increased evaporation from the ocean surface

Explanation

Warming causes ocean water to expand thermally and melts glaciers and ice sheets on land, both of which add to ocean volume and raise sea level. Evaporation and rainfall redistribute water but do not by themselves raise global mean sea level.

Question 47Unit 3

A scientist needs to determine the absolute age of a volcanic ash layer between two fossil-bearing sedimentary beds. Which method is most appropriate?

  1. Measuring the magnetic polarity of the sedimentary beds
  2. Counting annual tree rings in the sedimentary beds
  3. Comparing the thickness of the sedimentary beds
  4. Radiometric dating of minerals in the ash layer Correct answer.

Explanation

Volcanic ash contains minerals such as zircon that crystallise at eruption and can be radiometrically dated, giving an absolute age for the layer. Because the ash lies between the fossil beds, it brackets their ages.

Question 48Unit 3

Two rock outcrops on opposite sides of an ocean contain identical fossil species of the same age, but the species could not have dispersed across a wide ocean. Which interpretation is best supported?

  1. The two landmasses were once joined and have since separated Correct answer.
  2. The fossil ages were incorrectly measured
  3. The species evolved independently in both locations at the same time
  4. The fossils were transported by ocean currents between the outcrops

Explanation

Identical, non-dispersing species of the same age on now-separated continents imply that the landmasses were once connected and later split, supporting continental drift. Independent evolution is unlikely to produce identical species, and long-distance dispersal is ruled out by the species' biology.

Question 49Unit 3

A groundwater aquifer is bounded above and below by impermeable clay layers and is under pressure. Which consequence follows when a well is drilled into it?

  1. Water will rise above the level of the aquifer top without pumping Correct answer.
  2. Water will only flow when the water table is lowered by pumping
  3. Water will not enter the well because the aquifer is confined
  4. The aquifer will rapidly drain into the overlying clay

Explanation

A confined aquifer is sealed by impermeable layers and its water is under pressure, so a well penetrating it is an artesian well and water rises to the potentiometric surface, sometimes above ground. Pumping is not required to initiate flow in such a well.

Question 50Unit 3

A lake receives runoff containing high concentrations of nitrogen and phosphorus from fertiliser. Which sequence of events is most likely to follow?

  1. Decreased algal growth followed by increased oxygen levels
  2. Decreased nutrient cycling followed by lower turbidity
  3. Increased water clarity followed by increased fish populations
  4. Increased algal growth followed by oxygen depletion as algae decompose Correct answer.

Explanation

Nutrient enrichment triggers rapid algal blooms, and when the algae die and decompose, microbial respiration consumes dissolved oxygen, potentially causing hypoxia and fish kills. This process is eutrophication.