2023 HKDSE Geography Practice Paper with Answers

At an oceanic-continental convergent boundary, the denser oceanic plate subducts beneath the lighter continental plate. This subduction forms a deep ocean trench in the ocean basin and compresses continental crust to form fold mountains along the continental margin. A mid-ocean ridge is formed at divergent plate boundaries, not convergent boundaries. Therefore, only (1) and (2) are correct.

A (1 mark): Both (1) and (2) are correct, while (3) is incorrect.

A spit develops when longshore drift moves sediment along the coastline and deposits it across an indentation, such as an estuary or bay where the coastline abruptly changes direction. This requires prevailing winds arriving at an angle to the coast, an abundant supply of beach material, and sheltered, shallow water where energy drops.

A (1 mark): Oblique prevailing waves generate longshore drift, and bays provide depositional sites.

In tropical rainforests, dense evergreen vegetation locks up the majority of nutrients in the biomass store (statement 1 is correct). The litter store is small and decomposes rapidly because warm, humid conditions accelerate biological decomposition (statement 3 is correct). High precipitation causes intense leaching through the porous soil, meaning leaching loss is high, not low (statement 2 is incorrect). Therefore, (1) and (3) only are correct.

B (1 mark): (1) and (3) are correct; (2) is incorrect because leaching is severe in tropical rainforests.

Aligning transport corridors parallel to prevailing winds creates urban ventilation channels that disperse heat (1 is correct). High-albedo materials reflect incoming solar radiation rather than storing heat (2 is correct). Wall-like waterfront buildings block maritime breezes from penetrating inland, exacerbating urban heat trapping (3 is incorrect). Thus, (1) and (2) only are effective mitigation strategies.

B (1 mark): Strategies (1) and (2) alleviate urban heat, while (3) aggravates the heat island effect.

Constructing stone contour bunds (stone lines) along slope contours slows down surface runoff during sporadic, intense rainstorms, allowing water more time to infiltrate the soil and trapping fertile sediment behind the stones. Extensive monoculture, deep dry-season ploughing, and overstocking worsen desertification and soil erosion.

B (1 mark): Stone contour bunds act as physical barriers to impede runoff and promote infiltration.

An international division of labour allows companies to optimize costs by placing assembly plants in developing countries where labour is cheaper (1 is correct) while keeping higher-value R&D close to skilled engineers and top universities in more developed economies (2 is correct). However, separating component manufacturing and assembly across multiple countries increases, rather than eliminates, international freight transport costs (3 is incorrect).

A (1 mark): Statements (1) and (2) are correct; statement (3) is incorrect.

Step 1: Calculate actual horizontal distance.
Horizontal distance = \( 4.5\text{ cm} \times 20\,000 = 90\,000\text{ cm} = 900\text{ m} \).

Step 2: Calculate vertical height difference.
Vertical difference = \( 520\text{ m} - 160\text{ m} = 360\text{ m} \).

Step 3: Calculate gradient.
Gradient = \( \frac{\text{Vertical difference}}{\text{Horizontal distance}} = \frac{360\text{ m}}{900\text{ m}} = \frac{1}{2.5} \) or 1 : 2.5.

B (1 mark): Correct computation of gradient \( 360\text{ m} : 900\text{ m} = 1 : 2.5 \).

According to the Bradshaw model of fluvial systems:
(1) Bed roughness decreases downstream because sediment is broken down by attrition into smaller, rounder particles.
(2) River discharge increases downstream as more tributaries join the main river.
(3) Channel gradient decreases downstream as the landscape flattens towards base level.
Therefore, (1) and (3) decrease, while (2) increases.

B (1 mark): (1) and (3) decrease downstream; (2) increases downstream.

At an oceanic-continental convergent boundary, the denser oceanic plate subducts beneath the continental plate, creating a deep ocean trench along the boundary. Compressional forces crumple the continental edge into fold mountains accompanied by volcanic activity due to subduction melting. Mid-ocean ridges, however, are formed at divergent plate boundaries.

A (1 mark) - Statements (1) and (2) only are correct.

Downstream, river bed materials become smoother and rounder due to progressive attrition and hydraulic action, which decreases channel bed roughness (1). Reduced friction, increased river discharge, and higher hydraulic efficiency lead to an increase in mean flow velocity downstream (2). Average sediment particle size decreases (not increases) downstream (3).

B (1 mark) - Statements (1) and (2) only are correct.

In tropical rainforests, high temperatures and high precipitation cause rapid decomposition of leaf litter. However, the abundant vegetation takes up nutrients very rapidly, and excessive precipitation causes intense leaching in the porous soil, keeping the soil nutrient store very small.

B (1 mark) - Rapid uptake by roots and intense leaching prevent large nutrient storage in the soil.

Green roofs increase evapotranspiration and reduce sensible heat gain (1). Urban breezeways improve ventilation and heat dispersal through wind channels (2). Replacing permeable pavers with dark impermeable asphalt increases sensible heat storage and reduces evaporative cooling, worsening the urban heat island effect (3).

B (1 mark) - Measures (1) and (2) only are effective mitigation strategies.

High-technology industries produce light, high-value components with low transport cost sensitivity (footloose nature) and do not rely on heavy, bulky raw materials (1 is incorrect). They require heavy investment in R&D (2) and employ a high proportion of skilled engineers and scientists (3).

C (1 mark) - Statements (2) and (3) only are correct.

Secondary salinisation occurs when excessive irrigation water without adequate drainage raises the groundwater table close to the surface (1). In arid climates, high rates of evapotranspiration cause upward capillary movement of saline water, leaving crystalline salts on the topsoil upon evaporation (2). Organic matter accumulation does not cause salinisation (3).

A (1 mark) - Statements (1) and (2) only are correct.

A positive feedback loop amplifies the initial change: warming temperatures melt polar sea ice and glaciers, which replaces reflective ice with darker ocean or ground, reducing the planetary albedo. This causes greater absorption of solar radiation, which leads to further warming.

A (1 mark) - Ice-albedo feedback is a classic positive feedback mechanism.

When investigating continuous environmental or topographical gradients (such as changes down a slope profile), setting up a transect line from the crest to the valley floor and taking measurements at regular intervals (systematic sampling along a transect) is the most suitable method.

B (1 mark) - Systematic sampling along a slope transect is standard for continuous spatial gradient investigations.

Statement (1) is incorrect because composite volcanoes at subduction zones typically erupt andesitic or rhyolitic magma, which has high viscosity and high silica content, rather than low-viscosity basaltic lava. Statements (2) and (3) are correct: composite volcanoes are built up by alternating strata of pyroclastic materials (tephra/ash) and viscous lava flows, and the high viscosity traps expanding gases under high pressure, leading to explosive eruptions.

Award 1 mark for option D. No marks for options A, B, or C.

Alluvial fans develop where a confined mountain stream leaves a steep canyon and debouches onto an unconfined, gently sloping plain. Statement (1) is correct because the abrupt drop in channel gradient causes an immediate reduction in river energy. Statement (2) is correct because unconfined flow spreads outward, drastically increasing wetted perimeter and hydraulic resistance, reducing velocity and competence. Statement (3) is correct because an ample supply of coarse sediments from upstream weathering and mass wasting provides the depositional load.

Award 1 mark for option D. No marks for options A, B, or C.

Statements (1) and (3) are correct: assembly of electronic consumer goods is labour-intensive and cost-sensitive, so firms relocate routine production to less developed regions to reduce operational costs (cheap labour, low rent, lower environmental compliance costs). Statement (2) is incorrect because proximity to high-level research clusters and specialized knowledge pools is critical for high-end R&D and design (which remain in more developed countries), not for basic assembly line production.

Award 1 mark for option B. No marks for options A, C, or D.

Statement (1) is correct: dense, multi-layered vegetation stores the vast majority of nutrients in the tropical rainforest. Statement (2) is incorrect: the soil store in a rainforest is typically small because soluble nutrients are rapidly absorbed by dense roots or washed away. Statement (3) is correct: copious daily rainfall and high soil permeability cause intense leaching, washing dissolved nutrients downward beyond root reach.

Award 1 mark for option B. No marks for options A, C, or D.

(a)
Advantage (any ONE with elaboration, 2 marks):
- Stable weather conditions / dry season: River discharge is relatively low and stable, reducing the risk of sudden flash floods and ensuring safety for students wading into the water.
- Weekday / afternoon: Less disturbance from recreational visitors/hikers along the river course; daylight conditions provide sufficient visibility for measuring and reading instruments.

Limitation (any ONE with elaboration, 2 marks):
- Low flow in dry season: Surface velocity and wetted width may not represent annual average or bankfull conditions, underestimating typical river energy.
- Single-day snapshot: Weather in a single afternoon cannot reflect seasonal variations in discharge, velocity, and bedload movement.

(b)
- Systematic sampling ensures regular spatial coverage along the entire longitudinal profile from upper to lower course.
- It prevents spatial clustering of data points that could happen with random sampling.
- It provides an even and structured gradient of data points to identify continuous downstream trends.
- It makes field navigation and site planning straightforward along the 4 km stream.

(c)
(i)
There is a strong negative relationship / as distance from source increases, mean bedload particle size decreases progressively from 14.6 cm at Site 1 to 2.1 cm at Site 4.

(ii)
- Attrition: As river bedload is transported downstream, rock fragments constantly collide with one another and the riverbed, breaking edges and becoming smaller, smoother, and rounder.
- Hydraulic action and abrasion: Force of water and rubbing wear down rock particles over distance.
- Selective deposition (sorting): Heavier, larger boulders are deposited upstream when discharge/energy is insufficient to transport them, while smaller pebbles and sands continue to be transported downstream.

(d)
Evaluation and Improvements:
1. Velocity measurement:
- Limitation: Surface velocity measured at only 3 points; surface water is affected by wind and friction, not representing mean flow.
- Improvement: Measure velocity at 0.6 of depth from surface (or average of 0.2 and 0.8 depth) across more intervals across the cross-section to calculate a true average.
2. Bedload sampling:
- Limitation: Collecting 20 pebbles 'randomly' by hand involves subjective bias (operator touches larger, more obvious rocks on top of the riverbed).
- Improvement: Use a standardized grid frame / Wolman pebble count method at predetermined intersections to eliminate hand-selection bias; increase sample size (e.g., 50 or 100 pebbles per site).
3. Spatial and temporal coverage:
- Limitation: Only 4 sites along 4 km; data collected on only one day.
- Improvement: Increase number of sampling transects (e.g., every 500 m) and repeat measurements across wet and dry seasons.

(a) (4 marks)
Advantage (2 marks):
- 1 mark for stating valid advantage (e.g., safety/stable water level/good weather/less human disturbance).
- 1 mark for explanation.
Limitation (2 marks):
- 1 mark for stating valid limitation (e.g., under-representation of high-energy flows/unrepresentative dry-season discharge).
- 1 mark for explanation.

(b) (4 marks)
- Systematic sampling provides regular/even spatial coverage along the stream course (1 mark).
- Enables direct detection and continuous comparison of downstream trends/gradients (1 mark).
- Avoids spatial bias/clustering that could occur under random sampling (1 mark).
- Feasibility and ease of locating predetermined distance intervals along a linear feature (1 mark).

(c) (4 marks)
(i) 1 mark for correct description (inverse/negative relationship, quoting figures: from 14.6 cm at Site 1 to 2.1 cm at Site 4).
(ii) 3 marks:
- Attrition: particles collide with each other during transport, chipping and reducing size (1 mark).
- Abrasion/corrasion: mechanical wearing against river bed/banks (1 mark).
- Progressive sorting / selective deposition: decreasing river carrying capacity causes larger bedload to be deposited first in the upper course (1 mark).

(d) (6 marks)
Marking criteria:
- Sound evaluation of at least 2 distinct data collection methods (velocity, bedload sampling, width/sites) with detailed, logical improvements (5-6 marks).
- Adequate evaluation of data collection methods with relevant improvements (3-4 marks).
- Elementary/brief comments on data collection drawbacks or improvements (1-2 marks).

(a)
- Destructive plate boundary / subduction zone: Denser oceanic Indo-Australian Plate converges with and subducts beneath the less dense continental Eurasian Plate at the oceanic trench.
- Partial melting and magma generation: The descending oceanic slab carries water and sediments into the asthenosphere, lowering the melting point of mantle rocks to produce magma.
- Magma rise: Being less dense than the surrounding solid rock, viscous and gas-rich andesitic/dacitic magma rises through fractures in the overriding crust.
- Alternating eruptions: Explosive eruptions deposit alternating layers of viscous lava, tephra, and pyroclastic materials around the vent, creating a steep-sided, composite cone (stratovolcano).

(b)
- Abundant loose volcanic material: Explosive eruptions deposit thick layers of unconsolidated tephra, volcanic ash, and rock debris on the steep upper slopes.
- Triggering mechanism (heavy rainfall): Tropical monsoon rains quickly saturate the loose ash deposits, turning them into dense, fast-moving mudflows (lahars).
- Channelization along river valleys: River valleys originating from the volcano act as natural funnels that guide lahars over long distances (up to 25 km).
- High vulnerability: Dense farming settlements and roads are concentrated in river valleys and alluvial fans, leading to burying of homes, bridge destruction, and riverbed siltation causing severe flooding.

(c)
- Fertile volcanic soil (andosols): Weathered volcanic ash is rich in essential plant nutrients (e.g., potassium, phosphorus, calcium), allowing intensive multi-cropping and high yields of rice and vegetables.
- Favourable climate and water supply: High relief captures orographic rainfall, and porous volcanic aquifers provide constant freshwater springs for irrigation.
- Economic livelihoods and mineral resources: Abundant volcanic sand and gravel provide profitable aggregate mining for the construction industry; geothermal energy and agro-tourism also generate revenue.
- Cultural and generational ties: Long historical attachment to ancestral lands and reliance on traditional farming communities.

(d)
Effectiveness:
- Monitoring and early warning systems: Seismic monitoring, gas emission detection, and tiltmeters provide days to weeks of warning time (e.g., 3 weeks in 2006, 10 days in 2010), enabling mass evacuation of over 350,000 people and keeping casualty rates remarkably low relative to eruption magnitude.
- Sabo dams and diversion channels: Physical engineering works trap lahar debris and protect downstream bridges and settlements.

Limitations:
- Rapid hazard onset / unpredictable surges: Explosive pyroclastic surges can travel at high speeds (> 100 km/h), overwhelming evacuation routes if warnings are issued late.
- High economic and property losses: Evacuation prevents loss of life but cannot prevent the destruction of homes, farmlands, livestock, and infrastructure buried under ash and lahars.
- Resistance to evacuation: Reluctance of farmers to abandon livestock and livelihoods often delays evacuation until hazards are imminent.

(a) (5 marks)
- Subduction of denser oceanic plate beneath continental plate (1 mark).
- Deep mantle melting / generation of magma due to heat, pressure, and flux melting (1 mark).
- Magma rises through crustal fissures/cracks due to buoyancy (1 mark).
- Viscous / gas-rich magma leads to explosive eruptions (1 mark).
- Repeated eruptions build alternating layers of lava and ash/pyroclastic deposits forming a steep-sided cone (1 mark).

(b) (4 marks)
- Presence of large quantities of loose volcanic ash/tephra on steep slopes (1 mark).
- High intensity tropical rainfall mobilizes debris into rapid mudflows/lahars (1 mark).
- Valley topography channels lahars across extensive distances downriver (1 mark).
- High human concentration / settlements and farmland situated along valley floors (1 mark).

(c) (4 marks, max 4)
- Highly fertile volcanic soils (andosols) supporting high agricultural productivity / intensive rice cultivation (1 mark + 1 elaboration).
- Abundant water supply from volcanic springs / orographic precipitation for farming (1 mark).
- Economic opportunities (volcanic aggregate mining, tourism, fertile land) (1 mark).
- Cultural/ancestral attachment and lack of affordable alternative land (1 mark).

(d) (5 marks)
Marking criteria:
- Comprehensive discussion covering both effectiveness (e.g., warning systems, early detection, organized mass evacuation) and limitations (e.g., property damage, lahar management difficulties, economic loss, evacuation resistance), supported with data from Table 2b (4-5 marks).
- Adequate discussion covering either effectiveness or limitations with some data support (2-3 marks).
- Brief/general points without clear reference to data or concepts (1 mark).

### Part 1: Geological and Physical Factors Influencing Earthquake Severity (6 marks)

1. Magnitude and Energy Released:
- Higher magnitude (e.g. on the Moment Magnitude Scale) means exponential increase in seismic energy released, generating stronger seismic waves and more intense ground shaking.

2. Focal Depth:
- Earthquakes with shallow foci (0–70 km) lose less energy as seismic waves travel to the surface, resulting in far more violent ground shaking and surface displacement compared to deep-focus earthquakes.

3. Distance from the Epicentre:
- Wave amplitude attenuates with distance. Areas closest to the epicentre generally experience the most severe shaking and primary damages, though geological variations can modify this pattern.

4. Geology and Nature of Regolith/Subsoil:
- Solid Bedrock: Dampens seismic wave amplitude, reducing violent surface shaking.
- Loose, Unconsolidated Alluvium or Reclaimed Land: Amplifies seismic waves and is highly prone to soil liquefaction, leading to the collapse of building foundations.

5. Topography:
- Steep mountainous terrains are prone to triggering secondary hazards such as landslides, rockfalls, and mudflows, which block evacuation routes and bury settlements.

6. Coastal Configuration:
- Undersea earthquakes displacing water columns can trigger tsunamis. Funnel-shaped bays and shallow coastal bathymetry can amplify tsunami wave heights, devastating coastal areas.

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### Part 2: Effectiveness of Land-Use Zoning in MDCs vs LDCs (6 marks)

1. Concept and Mechanism of Land-Use Zoning:
- Restricts high-density residential, commercial, or critical infrastructure (e.g. hospitals, nuclear plants) from high-risk hazard zones (e.g. active fault lines, liquefaction-prone riverbanks, steep slopes, tsunami inundation zones).
- Allocates hazard-prone areas for low-density uses such as parks, open spaces, or agriculture to minimise potential casualties and economic loss.

2. Effectiveness in More Developed Countries (MDCs):
- High Effectiveness: Supported by comprehensive GIS mapping, detailed geological surveys, and strict legal enforcement.
- Institutional Capacity: MDCs have sufficient financial and administrative resources to relocate populations, enforce building codes, and compensate landowners.
- Limitations: High land values and strong demand for space in urban centres may lead to political or economic resistance against strict development bans.

3. Effectiveness and Challenges in Less Developed Countries (LDCs):
- Low to Moderate Effectiveness: Difficult to implement and enforce due to rapid urbanisation, severe land scarcity, and weak institutional governance.
- Socio-economic Constraints: Low-income residents often live in informal settlements/slums located on marginal, high-risk land (e.g. steep unstable slopes, floodplains) because they cannot afford safer locations.
- Need for Integrated Approaches: Zoning alone is insufficient without poverty alleviation, community education, early warning systems, and low-cost structural retrofitting.

4. Conclusion / Overall Judgement:
- Land-use zoning is a vital proactive non-structural measure. While highly effective in MDCs, its success in LDCs is heavily constrained by socio-economic vulnerabilities and requires complementary pre-disaster planning and international support.

### Marking Guidelines

#### Part 1: Physical and geological factors influencing earthquake severity (Max. 6 marks)
- Relevant concepts: Magnitude, focal depth, epicentral distance, bedrock/soil properties (liquefaction), topography (landslides), coastal morphology (tsunami risk).

| Performance of Candidates | Marks |
| :--- | :---: |
| - Comprehensive and accurate knowledge and understanding of geological and physical factors.
- Systematic and logical explanation with relevant geographical concepts and terminology.
- Good balance of primary seismic factors and site-specific geological/topographical factors. | 6 |
| - Adequate to good knowledge and understanding of factors influencing earthquake damage.
- Appropriate explanation of several physical/geological factors.
- May lack depth in explaining specific processes (e.g. wave amplification, liquefaction). | 3–5 |
| - Elementary to basic knowledge of physical factors.
- Brief/general descriptions with limited explanation. | 1–2 |

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#### Part 2: Discussion on the effectiveness of land-use zoning in MDCs and LDCs (Max. 6 marks)
- Relevant concepts/arguments: Non-structural mitigation, hazard mapping, risk avoidance, socio-economic differences (financial resources, governance, informal settlements, population pressure).

| Performance of Candidates | Marks |
| :--- | :---: |
| - Accurate and comprehensive knowledge and understanding of land-use zoning as a hazard mitigation measure.
- Coherent and logical discussion comparing the feasibility, effectiveness, and limitations in both MDCs and LDCs.
- Provides appropriate judgement supported by well-elaborated geographical arguments. | 6 |
| - Adequate to good knowledge of land-use zoning.
- Appropriate discussion of its effectiveness with some comparison between MDCs and LDCs.
- May focus heavily on one group of countries or provide unbalanced arguments. | 3–5 |
| - Elementary to basic knowledge of land-use zoning.
- Superficial description of zoning without meaningful discussion of developmental differences. | 1–2 |