Paper 1 - Section A Mixed

Question 1

1b) Describe the process of throughflow in the drainage basin system.

Answer 1

Throughflow is the horizontal movement of water within the soil layer towards a river or other water bodies. The key aspects of this process include:

Infiltration into the soil – When precipitation falls, some water infiltrates into the soil rather than running off the surface.
Movement through soil layers – Water moves through the soil’s pore spaces and natural channels, traveling parallel to the slope under the influence of gravity.
Emergence as springs or surface runoff – Some of the water may resurface at lower elevations as a spring, contributing to river flow.
Speed variation – Throughflow is slower than overland flow but faster than groundwater flow because it moves through soil pores rather than large rock fractures.

Question 2

Explain how land use can affect the movement of water in a drainage basin

Answer 2

Vegetation and Interception
Forested areas increase interception by leaves, delaying water reaching the ground.
Trees increase evapotranspiration, reducing overall water available for runoff and infiltration.
When trees are removed (deforestation), less water is intercepted, leading to more overland flow and increased risk of flooding.

Urbanization and Impermeable Surfaces
Roads, buildings, and pavements reduce infiltration, leading to higher surface runoff.
Storm drains increase the speed of water transfer, raising flood risks.
Concrete and asphalt have low albedo, causing higher evaporation rates in urban areas.

Agricultural Practices
Plowing and soil cultivation can improve infiltration in some cases.
Overgrazing and compaction from heavy machinery reduce infiltration, increasing surface runoff.
Irrigation can artificially increase soil moisture, affecting throughflow rates.

Land Use Comparisons
Forests: High infiltration, low runoff, high evapotranspiration.
Grasslands/Pasture: Moderate infiltration, higher runoff than forests.
Urban areas: Low infiltration, high runoff, low evapotranspiration.

Question 3

Explain why temperatures in urban areas are often higher than in surrounding areas. (6 marks)

Answer 3

Absorption of Heat by Urban Materials
Dark surfaces like asphalt, concrete, and buildings have low albedo, meaning they absorb and store heat during the day and release it slowly at night.
In contrast, natural landscapes such as forests and grasslands reflect more sunlight, keeping them cooler.

Reduced Vegetation and Evapotranspiration
Trees and plants cool the air through evapotranspiration, which is limited in urban areas.
Parks and green spaces help mitigate heat, but built-up areas lack sufficient vegetation.

Anthropogenic Heat Sources
Heat from vehicles, industries, air conditioning, and heating systems adds extra warmth to urban environments.
In winter, heating systems contribute significantly to warming.

Pollution and Greenhouse Effects
Air pollution from cars and factories creates a heat-trapping layer that prevents heat from escaping at night, increasing temperatures.
Smog and dust reduce outgoing longwave radiation, further warming the city.

Reduced Wind and Ventilation
Tall buildings create canyon effects, trapping heat and reducing wind speeds, which prevents heat dissipation.
In rural areas, more open landscapes allow for better air circulation, promoting cooling.

Question 4

Suggest how a landslide might have occurred.

Answer 4

Steep Slopes and Gravity
The slope is naturally steep, increasing shear stress and making it more prone to failure.

Deforestation and Vegetation Loss
Trees and vegetation roots bind soil together, preventing landslides.
Deforestation or land clearing weakens slope stability, increasing the chance of movement.

Heavy Rainfall and Water Infiltration
Rainwater infiltrates the soil, increasing pore water pressure and reducing cohesion.
Saturated soil loses strength, leading to a sudden slope failure.

Human Activities (Construction, Roads, and Mining)
Roads or construction projects cut into slopes, destabilizing them.
Quarrying or excavation can remove supportive rock layers, triggering landslides.

Seismic Activity (Earthquakes)
If the region is earthquake-prone, seismic shaking could trigger mass movement by suddenly increasing shear stress.

Question 5

3c) Explain how slopes may be modified to reduce mass movement. (4 marks)

Answer 5

Pinning (Rock Bolts and Anchors)
Metal rods are drilled into unstable rock layers to hold them in place.

Netting and Gabions
Wire mesh or gabions (rock-filled cages) prevent falling debris from reaching roads and settlements.

Drainage Systems
Excess water is a major trigger for landslides. Drainage pipes and trenches help remove groundwater, reducing pore water pressure.

Afforestation (Planting Trees and Vegetation)
Planting trees increases root strength, stabilizing the soil and preventing erosion.
Roots bind soil particles together, making the slope more resistant to failure.

Terracing and Grading
Slopes can be artificially terraced to reduce steepness and limit runoff speed.
Grading involves cutting back unstable slopes to reduce their angle, lowering the risk of landslides.

Question 6

2c) Explain why there might be a relationship between global temperature and carbon dioxide concentration in the atmosphere. (5 marks)

Answer 6

The relationship between carbon dioxide (CO₂) levels and global temperature is explained by the enhanced greenhouse effect:

CO₂ as a Greenhouse Gas
CO₂ is a greenhouse gas that traps heat in the Earth’s atmosphere, preventing it from escaping into space.

Absorption and Re-emission of Longwave Radiation
Incoming shortwave radiation from the Sun passes through the atmosphere.
The Earth’s surface absorbs and re-emits heat as longwave radiation.
CO₂ absorbs and re-emits this heat, causing global temperatures to rise.

Increasing CO₂ Leads to Higher Temperatures
Human activities such as burning fossil fuels, deforestation, and industrial processes increase CO₂ levels.
More CO₂ = More trapped heat, leading to global warming.

Feedback Mechanisms Enhance Warming
Higher temperatures cause more water vapor to form, intensifying the greenhouse effect.
Melting ice caps reduce Earth’s reflectivity (albedo), increasing heat absorption.

Other Factors Also Contribute
Other greenhouse gases, such as methane (CH₄) and nitrous oxide (N₂O), also contribute to warming.
Natural factors, such as volcanic eruptions and solar cycles, can cause short-term fluctuations.

Question 7

3c) Explain how rainfall influences the type of weathering. (6 marks)

Answer 7

1. Chemical Weathering Increases with More Rainfall
   Water is a key agent in chemical weathering, facilitating hydrolysis, oxidation, and carbonation.
   Carbonation: Rainwater absorbs CO₂, forming carbonic acid, which dissolves limestone.
2. Physical Weathering in Cold or Arid Climates
   Freeze-thaw weathering:
   Water enters cracks, freezes and expands, breaking rocks apart.
   Salt crystallization in dry climates:
   Evaporation leaves behind salt crystals, which expand and fracture rocks.
3. More Rainfall Supports Biological Weathering
   Higher rainfall = more plant growth, leading to root expansion and organic acid production, which break down rock.
4. Rainfall Variation Controls Weathering Dominance
   Low rainfall: Physical weathering dominates (e.g., freeze-thaw in cold regions).
   Moderate rainfall: Combination of physical and chemical weathering.
   High rainfall: Chemical weathering dominates, leading to deep soil formation.
5. Rainfall and Soil Formation
   More weathering creates more soil, leading to deeper, fertile soils in tropical regions.

Question 8

Describe two types of above ground flow. (4 marks)

Answer 8

1. Overland Flow (Surface Runoff)
   Definition: Overland flow occurs when precipitation exceeds the infiltration capacity of the soil, causing water to flow over the land surface. (1 mark)
   Description: This usually happens in urban areas with impermeable surfaces or on saturated or compacted soils where infiltration is reduced. (1 mark)
   Example: After heavy rainfall, roads and pavements in cities experience high overland flow, leading to flash flooding.
2. Throughfall
   Definition: Throughfall is the process by which raindrops pass through the gaps in a vegetation canopy and reach the ground. (1 mark)
   Description: When interception storage is exceeded, water drips off leaves, branches, and stems to the soil surface. (1 mark)
   Example: In tropical rainforests, intense rainfall causes a high rate of throughfall, increasing water availability for soil infiltration.

Question 9

1c) Explain why channel storage may change over time. (4 marks)

Answer 9

1. Variability in Inputs
   Precipitation: Higher rainfall increases direct water input into the channel, raising storage levels.
   Surface Runoff: More overland flow after storms leads to increased river discharge.
   Groundwater Flow Contribution: Baseflow from groundwater adds to channel storage during dry periods.
2. Variability in Outputs
   Evaporation: In hot climates, water evaporates from the channel, reducing storage.
   River Discharge: Water flows downstream, decreasing storage.
   Human Water Abstraction: Water may be removed for irrigation or domestic use, reducing the amount in the channel.
3. Seasonal and Climatic Effects
   During wet seasons, rainfall and snowmelt increase channel storage.
   During dry seasons, reduced rainfall and high evaporation lower channel storage.

Question 10

Describe the path of incoming (shortwave) solar radiation. (4 marks)

Answer 10

1. Absorption by the Atmosphere
   Some solar radiation is absorbed by gases such as ozone, oxygen, and carbon dioxide in the atmosphere.
   This absorption prevents some radiation from reaching the surface, reducing heat energy available.
2. Reflection by Clouds
   Clouds reflect a portion of incoming solar radiation back into space, reducing the energy reaching the Earth’s surface.
3. Absorption by the Earth’s Surface
   The remaining radiation reaches the Earth’s surface, where it is absorbed by land, water bodies, and vegetation, increasing surface temperature.
4. Scattering by Particles in the Atmosphere
   Dust, smoke, and water droplets scatter solar radiation, altering its direction and intensity.

Question 11

2c) Explain why reflected solar radiation may vary over time. (4 marks)

Answer 11

1. Cloud Cover
   More clouds → More reflection

Thick clouds have high albedo, meaning they reflect more solar radiation.
Example: During monsoon seasons, increased cloud cover reduces surface heating.
Fewer clouds → Less reflection

With clear skies, more radiation reaches the Earth’s surface, increasing temperature.

2. Changes in Surface Albedo
   Snow and Ice → High reflection

Snow and ice-covered surfaces reflect most of the incoming solar radiation (high albedo).
Example: The Arctic reflects more radiation in winter than in summer.
Dark Surfaces (Forests, Oceans) → Low reflection

Vegetation and water absorb more heat, decreasing the amount of radiation reflected.

3. Atmospheric Composition
   Pollution and Aerosols
   Dust, volcanic ash, and pollution increase reflection by scattering sunlight.
   Example: The 1991 Mount Pinatubo eruption released aerosols that blocked sunlight, cooling global temperatures.
4. Seasonal Variations
   Winter: More reflection due to higher snow and ice cover.
   Summer: Less reflection due to more vegetation and ice melt.

Question 12

3b) Describe how one method of slope modification that increases the stability of a slope. (3 marks)

Answer 12

Example: Netting (3 Marks)
Definition: Netting is placed over a slope to contain loose debris and prevent rockfalls. (1 mark)
Function: It prevents individual rocks from dislodging, reducing erosion and mass movement. (1 mark)
Application: Some netting is tensioned to restrain slope movement, maintaining long-term stability. (1 mark)

Alternative Example: Pinning (3 Marks)
Definition: Pinning involves inserting metal rods into the slope to anchor loose rock layers. (1 mark)
Function: The rods hold unstable rock masses in place, preventing landslides. (1 mark)
Application: Pinning is often used on steep slopes prone to failure, such as roadside cliffs. (1 mark)

Question 13

3c) Explain the role of water in the movement of sediment on a hillslope. (5 marks)

Answer 13

1. Rainsplash Erosion
   Raindrops dislodge soil particles, moving them downslope in random directions.
   On steep slopes, more particles move downhill, increasing erosion.
2. Sheetwash (Surface Flow)
   When rainfall exceeds soil infiltration capacity, thin sheets of water transport sediment downslope.
   This occurs in areas with bare soil or low vegetation cover.
3. Pore Water Pressure and Slope Failure
   Water infiltrates the soil, increasing pore water pressure and reducing soil cohesion.
   Saturated soil is prone to landslides and mudflows after heavy rain.
4. Subsurface Flow and Soil Creep
   Water seeps through soil, slowly moving particles downslope.
   Freeze-thaw cycles cause slow downslope movement of soil (soil creep).
5. River Undercutting at Slope Base
   Rivers erode the base of slopes, making them unstable.

Example: Coastal cliffs in England’s Holderness Coast collapse due to undercutting by waves.

Question 14

1b) Describe two types of below-ground flow. (4 marks)

Answer 14

1. Throughflow (2 marks)
   Definition: Throughflow is the horizontal movement of water within the soil layer towards the river channel. (1 mark)
   Process: Water infiltrates the soil and moves downslope due to gravity, traveling through the pore spaces in the soil. (1 mark)
   Example: Throughflow is faster in sandy soils (due to larger pore spaces) and slower in clay soils (due to smaller pores and high water retention).
2. Groundwater Flow (Baseflow) (2 marks)
   Definition: Groundwater flow refers to the slow movement of water through permeable rock layers (aquifers) before it reaches rivers, lakes, or the ocean. (1 mark)
   Process: Water percolates deep into the ground, reaching the water table and moving through porous rock layers such as limestone and sandstone. (1 mark)
   Example: Groundwater flow sustains river discharge during dry periods, such as in karst landscapes like the Yorkshire Dales, UK.

Question 15

1c) Explain why channel flow may change over time. (4 marks)

Answer 15

1. Changes in Inputs to the Channel
   Precipitation: Heavy rainfall directly increases channel flow by adding more water to the river.
   Surface Runoff: When the ground is saturated or impermeable, more water flows directly into the river, increasing discharge.
   Groundwater Contribution: During dry periods, groundwater flow (baseflow) contributes to maintaining river flow, but this declines if water tables drop.
2. Changes in Outputs from the Channel
   Evaporation: In hot and dry climates, high temperatures cause water loss from the river surface, reducing flow.
   Discharge to the Ocean or Other Water Bodies: Rivers naturally lose water as they flow downstream.
   Water Abstraction: Human activities such as irrigation, industry, or domestic water use reduce the amount of water in the channel.
3. Seasonal and Climatic Effects
   Wet season: Increased rainfall and snowmelt cause higher river discharge.
   Dry season: Reduced rainfall and increased evaporation lead to lower water levels.

Question 16

2b) Describe how solar radiation is absorbed. (4 marks)

Answer 16

1. Absorption by the Atmosphere (1 mark)
   Some solar radiation is absorbed by gases such as ozone, carbon dioxide, and water vapor in the atmosphere.
   This helps trap heat and regulate global temperatures.
2. Absorption by Clouds (1 mark)
   Water droplets in clouds absorb some incoming solar radiation, warming the atmosphere.
3. Absorption by the Earth’s Surface (1 mark)
   The majority of solar radiation reaches the Earth’s surface, where it is absorbed by land, water, and vegetation, increasing temperatures.
   Darker surfaces (forests and oceans) absorb more heat, while lighter surfaces (snow and ice) reflect more radiation.

Question 17

2c) Explain why reflected solar radiation from clouds may vary over time. (4 marks)

Answer 17

1. Cloud Thickness and Density
   Thicker clouds reflect more solar radiation due to their high albedo (reflectivity).
   Thin or scattered clouds allow more radiation to pass through, reducing reflection.
2. Cloud Type and Altitude
   High-altitude clouds (cirrus) are thin and let more radiation through, reflecting less sunlight.
   Low-altitude clouds (cumulonimbus, stratus) are thicker and denser, reflecting more radiation.
3. Presence or Absence of Clouds
   Clear skies = Less reflection (more solar energy reaches the surface).
   Cloudy conditions = More reflection, especially during storms or monsoon seasons.
4. Atmospheric Composition and Aerosols
   Pollution and volcanic eruptions can increase cloud reflectivity, blocking more solar radiation.
   Example: The 1991 Mount Pinatubo eruption injected aerosols into the atmosphere, increasing global reflection and temporarily cooling temperatures.

Question 18

3b) Describe one strategy that can increase the stability of a slope. (3 marks)

Answer 18

Example: Afforestation (3 marks)
Definition: Afforestation involves planting trees and vegetation on a slope to stabilize soil. (1 mark)
Process:
Tree roots bind soil particles together, reducing erosion and landslides. (1 mark)
Vegetation absorbs excess water, reducing surface runoff and preventing slope failure. (1 mark)

Alternative Example: Grading (Terracing) (3 marks)
Definition: Grading involves reshaping the slope to reduce steepness and create terraces. (1 mark)
Process:
Terraces slow down water movement, allowing more infiltration and reducing erosion. (1 mark)
The reduced gradient makes the slope more stable against mass movements. (1 mark)

Question 19

3c) Explain how human activities may decrease the stability of a slope. (5 marks)

Answer 19

1. Undercutting and Road Construction
   Excavation of slopes for roads and buildings removes supporting material, making the slope prone to collapse.
   Example: The Darjeeling Himalayas experience frequent landslides due to road construction.
2. Building on Steep Slopes
   Urbanization on slopes adds weight to the surface, increasing the risk of landslides and soil movement.
   Poorly planned settlements in Rio de Janeiro, Brazil, suffer from frequent slope collapses after heavy rains.
3. Deforestation and Agriculture
   Removing vegetation reduces root stability, leading to increased soil erosion and landslides.
   Example: Deforestation in Nepal has led to major slope failures during monsoon seasons.
4. Mining and Quarrying
   Extraction of rocks and minerals loosens slope material, triggering mass movement.
   Example: Open-pit mining in Indonesia has caused large-scale soil instability.
5. Disturbing Drainage Patterns
   Irrigation and water diversion increase soil saturation, reducing cohesion and triggering mudflows.
   Example: Over-irrigation in California’s farmlands has caused slope failures.

Question 20

1c) Suggest reasons for the formation of a braided river channel

Answer 20

1. High Sediment Load (1 mark)
   Excessive sediment supply (e.g., from glaciers, erosion, or landslides) clogs the river.
   The river cannot carry all the sediment, leading to deposition and channel splitting.
2. Variable Discharge (1 mark)
   Seasonal flow variations (e.g., glacial meltwater, monsoons) cause rivers to shift between high and low energy states.
   In dry seasons, deposition increases, creating bars and islands.
3. Easily Erodible Banks (1 mark)
   Braiding occurs where riverbanks are composed of loose sediment (e.g., sand, gravel).
   Weak banks cannot hold a single channel, causing frequent shifting.
4. Sudden Change in Gradient (1 mark)
   If the river loses velocity quickly, sediment deposition is more pronounced, leading to braiding.
5. Human and Climatic Factors (1 mark)
   Deforestation or mining can increase sediment supply, accelerating braiding.
   Climate change can cause flash floods or droughts, affecting river dynamics.

Example: The Brahmaputra River in India is a classic example of a braided river due to seasonal monsoon variations.

Question 21

2c) Suggest reasons for the upward trend in average global surface temperature

Answer 21

1. The Enhanced Greenhouse Effect (1 mark)
   Burning fossil fuels (coal, oil, gas) releases carbon dioxide (CO₂) and methane (CH₄).
   These gases trap outgoing longwave radiation, increasing global temperatures.
2. Industrialization and Population Growth (1 mark)
   Since 1950, rapid industrial expansion has led to increased CO₂ emissions.
   More factories, transport, and deforestation contribute to warming.
3. Urbanization and the Heat Island Effect (1 mark)
   Cities absorb and retain more heat than rural areas, contributing to temperature rise.
4. Deforestation and Land Use Change (1 mark)
   Fewer trees = Less CO₂ absorption, intensifying the greenhouse effect.
   Agriculture (e.g., rice farming) releases methane, a powerful greenhouse gas.
5. Aerosols and Feedback Mechanisms (1 mark)
   Aerosols (pollutants, volcanic ash) can temporarily reduce solar heating.
   However, melting ice caps decrease albedo, increasing heat absorption.
   Example: The Arctic ice decline since the 1970s has led to a positive feedback loop, accelerating warming.

Question 22

3b) Compare the tectonic landforms and processes between two different convergent plate boundaries: oceanic-continental and continental-continental.

Answer 22

1. Subduction vs. Collision (1 mark)
   Fig. 3.1 (oceanic-continental): The denser oceanic plate subducts beneath the continental plate, forming a deep ocean trench.
   Fig. 3.2 (continental-continental): Both plates collide and crumple, forming high mountain ranges (e.g., Himalayas).
2. Volcanic Activity (1 mark)
   Oceanic-continental subduction (Fig. 3.1) creates volcanoes, as melting occurs in the subduction zone.
   Continental-continental collision (Fig. 3.2) does not produce volcanoes, as there is no subducting plate.
3. Landforms Created (1 mark)
   Fig. 3.1: Ocean trenches, volcanic arcs, and fold mountains.
   Fig. 3.2: Only fold mountains, no volcanic arcs or trenches.
4. Earthquake Occurrence (1 mark)
   Both boundaries experience earthquakes, but subduction zones have deeper, more powerful quakes.
5. Example Comparison (1 mark)
   Fig. 3.1 Example: The Andes Mountains (South America).
   Fig. 3.2 Example: The Himalayas (India-Tibet boundary).

Question 23

3c) Explain the formation of tectonic landforms at divergent (constructive) plate boundaries. (4 marks)

Answer 23

1. Plate Separation and Magma Upwelling (1 mark)
   Convection currents in the mantle pull oceanic plates apart.
   Magma rises through the gap, solidifying into new crust.
2. Formation of a Mid-Ocean Ridge (1 mark)
   Repeated magma intrusion creates a ridge of volcanic mountains.
   Example: The Mid-Atlantic Ridge forms as the Eurasian and North American plates separate.
3. Rift Valleys and Volcanic Islands (1 mark)
   In continental divergence, the land stretches, forming rift valleys.
   Example: The East African Rift Valley is forming as Africa splits into two plates.
4. Transform Faults (1 mark)
   As plates move apart, fractures create faults, causing earthquakes.
   Example: The Icelandic volcanic zone, where rift valleys and volcanoes coexist.

Question 24

1c) Suggest the factors that can lead to flooding

Answer 24

1. High Rainfall and Increased River Discharge (1 mark)
   Heavy or prolonged rainfall increases river discharge, exceeding the channel’s capacity, leading to overbank flow.
   Example: Monsoon rainfall in Bangladesh frequently causes severe flooding.
2. High Antecedent Moisture (1 mark)
   If the soil is already saturated from previous rainfall, infiltration capacity is reduced, leading to increased surface runoff.
   This increases flood magnitude and duration.
3. Impermeable Surfaces and Urbanization (1 mark)
   Urban areas with concrete and tarmac reduce infiltration, increasing surface runoff into the river.
   Example: Flooding in London (UK) has been exacerbated by urban expansion.
4. Low-Lying Land and Natural Drainage Conditions (1 mark)
   Floodplains are naturally prone to flooding due to their low elevation and flat terrain, allowing water to spread easily.
   The settlement in the background is built on slightly higher ground, reducing its exposure.
5. Insufficient Flood Defenses (1 mark)
   Levees, embankments, or flood walls may not have been high enough to contain floodwaters.
   Example: The Hurricane Katrina (2005) flood in New Orleans was worsened by the failure of flood barriers.

Question 25

3b) Compare the features of mudflows and slumps

Answer 25

1. Shape and Extent (1 mark) B (mudflow) is long and narrow, extending far down the slope. C (slump) is shorter and wider, with a rotational movement. 2. Initiation and Material Composition (1 mark) B is a fluid, fast-moving mass of saturated debris. C consists of a semi-coherent mass of soil and rock, moving in a rotational slip. 3. Surface Features (1 mark) B has a smooth, channelized flow, exiting from a steep slope or gully. C has a steep headscarp, with visible cracks at the top. 4. Stability and Slope Gradient (1 mark) B is more fluid and occurs on steeper slopes. C is less fluid and moves more slowly, often stopping mid-slope.

Question 26

3c) Suggest how a mudflow is formed.

Answer 26

1. Heavy Precipitation and Soil Saturation (1 mark) Mudflows occur after intense rainfall, which saturates loose soil and debris. High pore water pressure reduces cohesion, triggering movement. 2. Steep Slopes and Gravity (1 mark) The force of gravity pulls the saturated material downslope. Example: Steep slopes in Andean valleys experience frequent mudflows during heavy rains. 3. Increased Pore Water Pressure (1 mark) Water infiltration reduces friction between soil particles, increasing instability. Example: In deforested areas, water is not absorbed by vegetation, worsening the flow. 4. Earthquakes or Human Activity as Triggers (1 mark) Seismic activity or excavation weakens slopes, increasing the likelihood of failure. Example: Earthquakes in Japan and Nepal have triggered deadly mudflows. 5. Channelized Flow Development (1 mark) Once initiated, the mudflow follows natural channels, accumulating more material as it moves.

Question 27

Describe the changes to catchment flows after urbanisation. (3 marks)

Answer 27

1. Decrease in Evapotranspiration (1 mark) Evapotranspiration reduces from 40% to 30%, meaning less water is returned to the atmosphere. This occurs due to the loss of vegetation, which reduces transpiration and interception. 2. Decrease in Infiltration (1 mark) Infiltration decreases from 50% to 15%, meaning less water seeps into the ground. This is because impermeable surfaces (roads, pavements, buildings) prevent infiltration, increasing runoff. 3. Increase in Surface Runoff (1 mark) Runoff increases from 10% to 55%, meaning more water moves quickly over the surface into drainage systems. More runoff = Higher flood risk, as water reaches rivers faster, overwhelming drainage capacity. Conclusion: Urbanisation reduces natural infiltration and increases rapid runoff, leading to higher flood risks and lower groundwater recharge.

Question 28

1c) Explain why catchment flows change after urbanisation. (5 marks)

Answer 28

1. Decrease in Vegetation Cover (1 mark) Less vegetation = Less evapotranspiration, meaning more water remains on the surface. Less interception by tree canopies allows more direct rainfall onto the ground, increasing runoff. 2. Impermeable Surfaces Reduce Infiltration (1 mark) Concrete, asphalt, and rooftops prevent water absorption, reducing groundwater recharge. More water flows overland instead of percolating into the soil. 3. Increased Surface Runoff and Flood Risk (1 mark) Water moves faster through artificial drainage systems, reaching rivers more quickly, increasing flood risk. Example: Urban floods in London have become more frequent due to rapid runoff. 4. Lower Groundwater and Baseflow (1 mark) Less infiltration reduces groundwater storage, meaning lower river flow during dry periods. Example: Los Angeles has reduced baseflow due to urban sprawl and excessive groundwater use. 5. Human Alterations to Drainage (1 mark) Storm drains and culverts divert water directly into rivers, preventing natural absorption into soils. Dams, reservoirs, and artificial channels modify the natural flow of water. Conclusion: Urbanisation decreases infiltration and evapotranspiration while increasing surface runoff, leading to higher flood risks and altered river flows.

Question 29

2b) Briefly explain the formation of hail

Answer 29

1. Strong Updrafts and Cooling (1 mark) Warm, moist air rises rapidly in thunderstorms, cooling as it ascends. This causes water droplets to freeze into ice pellets. 2. Repeated Layering Process (1 mark) The ice pellet is carried up and down within the storm cloud, accumulating layers of ice. Each cycle adds more ice, making the hailstone larger. 3. Final Fall as Hailstones (1 mark) Once too heavy to remain suspended, hailstones fall to the ground as frozen pellets.

Question 30

2c) Explain why the type of precipitation may vary in one location. (5 marks)

Answer 30

1. Air Stability and Uplift Mechanisms (1 mark) Stable air = Light, continuous rain (e.g., stratus clouds). Unstable air = Intense thunderstorms (e.g., cumulonimbus clouds). 2. Seasonal and Diurnal Changes (1 mark) In summer, convection causes thunderstorms and hail. In winter, cold air leads to snow or sleet instead of rain. 3. Passage of Weather Fronts (1 mark) Warm fronts bring prolonged rain, while cold fronts cause short, intense showers. Example: The UK experiences frontal rainfall from Atlantic depressions. 4. Altitude and Temperature (1 mark) Higher elevations receive snow instead of rain, as air cools with height. Example: The Rocky Mountains receive heavy snowfall in winter. 5. Local Microclimates (1 mark) Coastal areas may experience more rain due to moisture-laden air. Urban areas experience more intense storms due to the heat island effect.

Question 31

3b) Draw a sketch of an oceanic-continental convergent boundary. Label the main features. (4 marks)

Answer 31

1. Key Features to Include in the Sketch (2 marks) Subducting oceanic plate moving beneath the continental plate. Ocean trench at the subduction zone. Fold mountains on the continental plate due to compression. Volcanic arc inland due to magma rising from the subducted plate. 2. Correct Labeling (2 marks) Label the oceanic and continental plates. Identify the trench, volcanic arc, and fold mountains. Example: The Andes Mountains formed at the boundary between the Nazca Plate (oceanic) and the South American Plate (continental).

Question 32

3c) Explain the formation of an ocean trench (4 marks)

Answer 32

1. Subduction of the Oceanic Plate (1 mark) The denser oceanic plate is forced beneath the lighter continental plate, creating a deep trench. 2. Compression and Bending of the Plate (1 mark) As the oceanic plate subducts, it bends downward into the mantle, forming a deep depression in the ocean floor. 3. Melting and Magma Generation (1 mark) The subducting plate melts due to heat and pressure, producing magma that rises to form volcanoes. 4. Example: The Mariana Trench (1 mark) The Pacific Plate subducting under the Mariana Plate has formed the deepest trench in the world (over 11,000m deep).

Question 33

1b) Describe how a storm hydrograph might change following deforestation in an area. (4 marks)

Answer 33

1. Shorter Lag Time (1 mark) With fewer trees intercepting rainfall, more water reaches the ground quickly. This results in a shorter lag time (time between peak rainfall and peak discharge). 2. Steeper Rising Limb (1 mark) More water enters the river as surface runoff due to reduced infiltration. This leads to a rapid increase in river discharge, creating a steeper rising limb. 3. Higher Peak Discharge (1 mark) Without trees to absorb water, more rainwater enters the river, causing higher flood peaks. This increases the likelihood of flooding downstream. 4. Steeper Falling Limb (1 mark) Water drains more quickly from the basin, reducing the duration of high flows. The river level falls rapidly, leading to a steeper falling limb. Example: The Amazon Basin has experienced shorter lag times and increased flooding due to large-scale deforestation.

Question 34

1c) Explain reasons for the changes in a storm hydrograph following deforestation in an area.

Answer 34

1. Reduction in Vegetation Interception (1 mark) Trees and plants normally capture rainfall, delaying runoff. Without them, more water reaches the surface instantly, shortening lag time. 2. Increased Surface Runoff (1 mark) Impermeable soil surfaces develop, reducing infiltration. This causes rapid overland flow, increasing peak discharge. 3. Reduced Water Uptake by Plants (1 mark) Fewer trees mean less water is absorbed and transpired, increasing the volume of water reaching rivers. Example: In Borneo, deforestation has led to more frequent flash floods. 4. Soil Erosion and Sediment Load (1 mark) Loss of tree roots weakens soil stability, leading to higher erosion rates. More sediment enters the river, affecting channel capacity and increasing flood risk.

Question 35

2b) Briefly explain the formation of radiation fog

Answer 35

1. Air Cooling and Saturation (1 mark) Fog forms when warm, moist air cools, reaching dew point temperature. This causes condensation of water droplets, forming a dense mist. 2. Formation by Contact or Air Movement (1 mark) Radiation fog: Forms at night when the ground cools rapidly, cooling air above it. Advection fog: Forms when warm air passes over a cooler surface (e.g., over the ocean). 3. Condensation on Particles (1 mark) Tiny water droplets form around condensation nuclei (dust, pollution, salt particles). This makes fog visible and reduces visibility. Example: London experiences frequent radiation fog in winter due to high humidity and calm air conditions.

Question 36

2c) Explain how orographic uplift of air can lead to precipitation. (5 marks)

Answer 36

Orographic precipitation occurs when air is forced to rise over a mountain range, cooling and condensing to form precipitation. 1. Air is Forced to Rise Over Mountains (1 mark) When moist air encounters a mountain range, it rises along the windward slope. 2. Expansion and Cooling of Air (1 mark) As air ascends, it expands due to lower atmospheric pressure, cooling as it rises. 3. Condensation and Cloud Formation (1 mark) Cooling air reaches its dew point, leading to condensation and the formation of clouds. 4. Precipitation on the Windward Side (1 mark) Once the air is fully saturated, water droplets combine and fall as rain or snow. Heavy rainfall occurs on the windward side, while the leeward side remains dry. 5. Formation of Rain Shadows (1 mark) On the leeward side, the air descends and warms, leading to dry conditions.

Question 37

3b) What are the key features of an Oceanic and Continental plate boundary

Answer 37

Subducting oceanic plate moving beneath the continental plate. Fold mountains and volcanoes forming on the continental plate. Accretionary wedge and trench, formed by sediments scraped off the subducting plate.

Question 38

3c) Explain the formation of an ocean trench

Answer 38

1. Feature: Ocean Trench (1 mark) Ocean trenches form at convergent plate boundaries, where one oceanic plate subducts beneath another plate. 2. Subduction Process (1 mark) The denser oceanic plate sinks into the mantle, creating a deep depression in the ocean floor. 3. Compression and Sediment Accumulation (1 mark) As the oceanic plate bends downward, sediments accumulate along the trench edge. Example: The Mariana Trench (Pacific Plate subducting under the Mariana Plate) is the deepest ocean trench in the world.

Question 39

1c) Explain why the sediment size in a river channel might vary at different locations. (5 marks)

Answer 39

1. Energy and Velocity of the River (1 mark) Faster-flowing water (high energy) transports larger sediments further. Slower-moving water (low energy) deposits heavier particles first. Example: In a meandering river, pools contain finer sediment, while riffles contain coarser material. 2. Attrition and Abrasion (1 mark) Sediment breaks into smaller pieces as it collides with other particles. More attrition downstream = Smaller sediment sizes. 3. Role of Tributaries (1 mark) Tributaries introduce new sediment into the river, changing size distribution. Example: Mountain rivers supply large angular rocks, which gradually break down downstream. 4. Deposition Due to Obstacles (1 mark) Larger sediments are trapped by obstacles, such as boulders, dams, or natural river constrictions. Fine sediment continues to be transported. 5. Human Activities (1 mark) Dams trap coarser sediments, reducing their presence downstream. Example: The Aswan High Dam (Egypt) reduced sediment deposition in the Nile Delta.

Question 40

2c) Explain the role of greenhouse gases in global warming. (4 marks)

Answer 40

1. Types of Greenhouse Gases (1 mark) Main greenhouse gases: Carbon dioxide (CO₂), methane (CH₄), water vapour, nitrous oxides (N₂O), ozone (O₃), and CFCs. These gases vary in warming potential, with methane being 28 times more powerful than CO₂. 2. Trapping of Longwave Radiation (1 mark) Shortwave solar radiation enters the atmosphere. The Earth's surface absorbs energy and re-emits it as longwave infrared radiation. Greenhouse gases absorb and re-radiate this heat, preventing it from escaping into space. 3. Increased Atmospheric Warming (1 mark) As greenhouse gas concentrations rise, more heat is trapped, leading to higher global temperatures. Example: The burning of fossil fuels has increased CO₂ levels by 50% since pre-industrial times. 4. Positive Feedback Mechanisms (1 mark) Melting ice caps reduce Earth's albedo, causing more heat absorption. Thawing permafrost releases methane, accelerating warming.

Question 41

3b) Contrast the range of speeds of the mass movements

Answer 41

1. Fastest Mass Movement – Rockfall (1 mark) Rockfall is the fastest mass movement (up to 3 m/sec). Occurs suddenly on steep slopes due to gravity and lack of friction. 2. Slowest Mass Movement – Slump (1 mark) Slump has the slowest speed (30 cm/5 years). It is a rotational movement, occurring on weaker, saturated slopes. 3. Large Range in Speed – Rock/Debris Slide (1 mark) Can be slow (30 cm/5 years) or very fast (3 m/sec). Movement depends on slope angle, water content, and rock structure. 4. Variable Speed in Earth/Mud Flow (1 mark) Speeds range from 1.5 m/year to 3 m/sec. Water lubricates the material, making it faster than slides but slower than rockfalls.

Question 42

3c) Explain why mass movements have different rates of movement. (5 marks)

Answer 42

1. Influence of Water Content (1 mark) Water lubricates soil and reduces friction, making flows faster. Mudflows are rapid, whereas dry rockfalls happen instantly. 2. Slope Gradient and Gravity (1 mark) Steeper slopes = Faster movement due to higher gravitational force. Example: The Vaiont Dam disaster (Italy, 1963) involved a rapid landslide due to a steep valley. 3. Material Composition (1 mark) Loose sediment moves faster than solid rock. Clay-rich soils absorb water, leading to slow, creeping movements. 4. Triggering Events (1 mark) Earthquakes, storms, and human activity (e.g., mining) accelerate mass movement. Example: The 2008 Sichuan earthquake triggered thousands of landslides. 5. Vegetation and Human Influence (1 mark) Deforestation reduces slope stability, increasing movement. Example: Logging in Nepal has increased landslide frequency.

Question 43

1c) Explain how islands in a river may have formed.

Answer 43

Braided rivers carry high sediment loads and deposit coarse material when energy decreases. During low flow periods, exposed sediment forms islands (eyots/bars).

Question 44

2b) Compare the albedo values for different surface conditions

Answer 44

1. High Albedo Surfaces – Snow and Clouds (1 mark) Snow has the highest albedo (83-84.5%), meaning it reflects most sunlight. Clouds also have a high albedo, with values similar to snow. 2. Moderate Albedo Surfaces – Soil and Vegetation (1 mark) Dry soil has intermediate albedo values, lower than snow but higher than forests. Forests and crops have lower reflectivity, meaning more absorption of solar radiation. 3. Lowest Albedo – Water (1 mark) Water has the lowest albedo, meaning it absorbs most solar energy. The exact albedo varies with angle and wave conditions. 4. General Comparison of Trends (1 mark) Lighter surfaces (snow, clouds) have high albedo. Darker surfaces (water, forests) have low albedo. Bare soil and vegetation have intermediate values.

Question 45

2c) Explain how albedo affects the diurnal energy budget. (5 marks)

Answer 45

1. Absorption of Solar Radiation During the Day (1 mark) Surfaces with low albedo (e.g., water, forests) absorb more heat, increasing daytime temperatures. High albedo surfaces (e.g., snow) reflect more energy, keeping temperatures lower. 2. Reflection and Heat Balance (1 mark) A high albedo reduces energy available for warming the surface, affecting latent heat and sensible heat transfer. Example: Ice caps and deserts stay relatively cool during the day due to high reflection. 3. Longwave Radiation and Night Cooling (1 mark) At night, previously absorbed energy is released as longwave radiation. Surfaces with low albedo retain heat longer, while high albedo areas cool rapidly. 4. Cloud Cover and Energy Retention (1 mark) Clouds (high albedo) reflect incoming radiation during the day, keeping temperatures lower. At night, clouds trap outgoing radiation, preventing rapid cooling. 5. Example of Urban Heat Island Effect (1 mark) Urban areas have lower albedo due to concrete and asphalt, leading to higher daytime and nighttime temperatures.

Question 46

What are the similarities and differences between different convergent plate boundaries?

Answer 46

1. Similarity – Convergence of Plates (1 mark) Both figures depict plate convergence, where two lithospheric plates collide. Example: The Andes and Himalayas are both formed by plate convergence. 2. Difference in Plate Types – Oceanic vs. Continental Collision (1 mark) Fig. 3.1 shows oceanic-continental convergence, where an oceanic plate subducts beneath a continental plate. Fig. 3.2 shows continental-continental collision, where two continental plates push against each other. 3. Subduction and Volcanism vs. No Subduction (1 mark) Fig. 3.1: The subducting oceanic plate melts, forming magma and volcanic arcs. Fig. 3.2: No subduction occurs, so no volcanic activity is present. 4. Landform Differences – Trenches vs. Fold Mountains (1 mark) Fig. 3.1: Ocean trenches (e.g., Peru-Chile Trench) form due to subduction. Fig. 3.2: High fold mountains (e.g., Himalayas) form due to compression.

Question 47

3c) Explain the tectonic processes associated with divergent plate boundaries. (5 marks)

Answer 47

1. Plate Separation and Upwelling of Magma (1 mark) Mantle convection pulls plates apart, creating a gap in the lithosphere. Magma from the asthenosphere rises to fill the gap. 2. Formation of Mid-Ocean Ridges (1 mark) Magma cools and solidifies, forming oceanic ridges. Example: The Mid-Atlantic Ridge is created by the divergence of the Eurasian and North American plates. 3. Formation of Rift Valleys on Continents (1 mark) If divergence occurs on land, a rift valley forms. Example: The East African Rift Valley is splitting apart due to plate divergence. 4. Earthquakes and Volcanic Activity (1 mark) Divergent boundaries cause frequent shallow earthquakes. Magma eruptions create volcanic islands, such as Iceland. 5. Continuous Sea-Floor Spreading (1 mark) As new crust forms, older crust moves outward, leading to ocean expansion. Magnetic striping in ocean floor rocks confirms sea-floor spreading.

Question 48

1c) Suggest two reasons for differences between two rivers' annual hydrographs

Answer 48

1. Difference in Drainage Basin Size (2 marks) River à la Baleine has a larger drainage basin, meaning more tributaries contribute to higher discharge. River Chiriquí Viejo is smaller, resulting in lower total discharge levels. 2. Differences in Climate and Precipitation Patterns (2 marks) River à la Baleine peaks in June, likely due to snowmelt or seasonal rainfall. River Chiriquí Viejo peaks in October, suggesting monsoon rains or wet-season influence.

Question 49

2b) Describe the pattern of incoming (shortwave) solar radiation

Answer 49

1. Maximum Solar Radiation at the Equator (1 mark) The highest incoming solar radiation occurs around the equator (5°S), receiving 310 W/m². 2. Decreasing Solar Radiation Towards the Poles (1 mark) As latitude increases (both north and south), solar radiation decreases. The lowest radiation is at 85°S, with only 25 W/m². 3. Comparison Between Hemispheres (1 mark) The Northern and Southern Hemispheres show similar trends, but slight variations occur due to seasonal differences.

Question 50

Explain why there is an energy deficit at higher latitudes. (5 marks)

Answer 50

1. Reduced Incoming Solar Radiation (1 mark) Higher latitudes receive less solar radiation due to the Earth's curvature. The sun’s rays strike at a lower angle, spreading energy over a larger area. 2. Increased Atmospheric Absorption and Reflection (1 mark) At higher latitudes, solar radiation passes through more atmosphere, increasing absorption and scattering. Example: Clouds and dust absorb more radiation in polar regions. 3. High Albedo Effect (1 mark) Ice and snow reflect most incoming solar radiation (high albedo). Less energy is absorbed, leading to cooling and energy deficits. 4. Greater Longwave Radiation Loss (1 mark) Higher latitudes experience greater heat loss through outgoing longwave radiation. This is not balanced by sufficient incoming solar radiation. 5. Net Energy Transfer to Higher Latitudes (1 mark) Tropical regions have an energy surplus, transferring heat via winds and ocean currents to the poles. Example: The Gulf Stream transports heat from the tropics to Europe.

Question 51

3b) Suggest how a rock is weathered by freeze-thaw weathering. (2 marks)

Answer 51

1. Freeze-Thaw Process (1 mark) Water enters cracks in the rock and freezes overnight, expanding by 9%. This exerts pressure on the rock, widening the cracks. 2. Repeated Cycles Lead to Rock Breakup (1 mark) Repeated freezing and thawing weakens the rock, causing pieces to break off. Example: This process is common in cold mountain regions, such as the Alps.

Question 52

3c) Explain two factors which influence the rate of weathering. (4 marks)

Answer 52

1. Temperature and Climate (2 marks) Warmer temperatures increase chemical weathering (e.g., hydrolysis). Colder temperatures promote physical weathering (e.g., freeze-thaw cycles). Example: Tropical regions experience rapid chemical weathering, while polar areas have slow weathering rates. 2. Rock Type and Mineral Composition (2 marks) Some rocks weather faster than others due to their mineral composition. Limestone is highly susceptible to carbonation, while granite is more resistant. Example: The White Cliffs of Dover weather faster due to weak chalk composition.

Question 53

1(c) Suggest two reasons for a flashy storm hydrograph

Answer 53

Urban Land Use: Urban areas have impermeable surfaces like concrete and tarmac. This leads to less infiltration and more surface runoff, creating shorter lag time and higher peak discharge. Steep Slopes and Impermeable Rocks: Steep gradient increases runoff speed. Impermeable rocks (e.g., granite) prevent water infiltration, enhancing runoff. Both result in a sharp rising limb and quick recession.

Question 54

2(c) Explain how frontal precipitation occurs.

Answer 54

Occurs where warm and cold air masses meet, typically along a front. At the warm front, warm air is forced to rise gradually over cold air, leading to steady, light rainfall. At the cold front, cold air undercuts warm air, forcing it to rise rapidly, causing heavy showers and thunderstorms. Condensation occurs when air cools to its dew point, forming clouds. Cloud droplets grow and coalesce, falling as precipitation once heavy enough. Condensation nuclei help water vapor to condense and form raindrops.

Question 55

3(b) Describe the features of a slide

Answer 55

Steep, concave scar at the top, exposing bare earth. Detached blocks of soil and vegetation at the top and mid-slope. Bare, smooth slide surface with some signs of erosion (e.g., rills). The toe of the slide is gently sloped, with material deposited at the base.

Question 56

3(c) Explain how a slide is formed

Answer 56

Heavy rainfall increases water content, raising weight (shear stress) of the slope material. Pore water pressure increases, reducing cohesion and shear strength, leading to failure. Water acts as a lubricant, allowing the soil to slide or slump. Steep slope gradient contributes to instability. Removal of vegetation (e.g., deforestation) reduces root binding, increasing risk. Weathering weakens rock, making it more prone to failure. Human activity (e.g., construction, undercutting) can trigger mass movement. In some cases, earthquakes or undercutting by rivers or the sea can act as triggers.

Question 57

1(b) Describe the main features of a meander. [4 marks]

Answer 57

Asymmetrical channel shape Deeper on the outside bend (river cliff). Shallower on the inside bend (slip-off slope). Labels River cliff (undercut slope) on the outside bend. Slip-off slope (point bar) on the inside bend. Direction of flow (optional).

Question 58

1(c) Explain how an oxbox lake may have formed. [5 marks]

Answer 58

A meander develops due to lateral erosion and helicoidal flow. Erosion occurs on the outer bends, while deposition happens on the inner bends. The meander becomes more pronounced, and the neck narrows. During flooding or high discharge, the river cuts through the neck, forming a new, straighter channel. Deposition seals off the old bend, forming an oxbow lake. Over time, it may dry out or become a marsh.

Question 59

2(b) Compare the causes of frontal/cyclonic rainfall and convectional rainfall

Answer 59

Comparisons: Frontal uplift (2.1) vs. convective uplift (2.2). Evaporation/evapotranspiration occurs in 2.2, not in 2.1. Both involve rising warm moist air, leading to cooling and condensation. Cloud formation and precipitation occur in both cases.

Question 60

2(c) Explain how precipitation is caused by orographic uplift of air. [5 marks]

Answer 60

Moist air is forced to rise as it encounters a mountain or hill. As air rises, it cools adiabatically. When air cools to its dew point, condensation occurs. Clouds form, and if droplets coalesce and grow large enough, precipitation falls. Precipitation typically occurs on the windward side, while the leeward side may be drier (rain shadow effect).

Question 61

3(c) Explain the distribution of young fold mountains [5 marks]

Answer 61

Young fold mountains form at convergent plate boundaries. At oceanic-continental boundaries, the oceanic plate is subducted, causing uplift of sediments (e.g. Andes). At continental-continental collisions, plates crumple and uplift (no subduction), forming high mountains (e.g. Himalayas). Sediments from ancient seas are compressed and folded. Driven by convection currents in the mantle and plate movement.

Question 62

Explain why the minimum velocity needed for sediment erosion varies. [4 marks]

Answer 62

For small particles like clay, higher velocities are needed due to cohesion between particles — clay particles stick together, making them harder to erode. For medium particles like sand, lower velocities can erode them easily as they are non-cohesive and lightweight. For large particles like gravel or boulders, higher velocities are again needed because of their greater weight and mass. The Hjulström curve (Fig. 1.1) shows a U-shaped relationship, indicating these varying thresholds for erosion based on sediment size.

Question 63

1(c) Explain two reasons for the variation of deposition along a river channel. [4 marks]

Answer 63

Change in velocity When river velocity drops (e.g. when entering a lake or at inside bends of meanders), it loses energy and deposits sediment. Example: Deposition often occurs on the inside of a meander (point bars) where flow is slower. Obstacles and features in the channel Deposition can occur behind obstacles (e.g. rocks, vegetation) that disrupt flow. Also happens in riffle zones or where gradient decreases, reducing energy for transport.

Question 64

2(b) Suggest reasons for the difference in the state of water on two different surfaces

Answer 64

Albedo (reflectivity) Vegetation reflects more and absorbs less heat, so it remains colder, allowing water to freeze. Pavement absorbs more heat due to its dark colour, remaining warmer. Thermal properties and conduction Concrete or asphalt conducts heat better, keeping the surface slightly above freezing. Grass is a poor conductor, so it cools faster and allows freezing. Antecedent conditions Grass may have retained moisture from previous nights, encouraging ice formation. Pavement dries more quickly, preventing freezing. Human activity Foot traffic or vehicles can keep pavement warmer, while vegetation remains untouched.

Question 65

2(c) Explain why there can be a difference between the state of water during the daytime and night-time. [4 marks]

Answer 65

Insolation only occurs during the day Solar radiation heats the surface, melting ice or evaporating water. Evaporation increases during the day Leads to more water vapor and less surface water. Night-time radiative cooling The ground loses heat through longwave radiation, potentially cooling below dew point, causing dew or frost to form. Latent heat exchange At night, latent heat is released during condensation (dew formation), while during the day, latent heat is absorbed during evaporation.

Question 66

Suggest reasons for slope instability in an area. [4 marks]

Answer 66

Steep slopes shown by close contour lines Example: steep terrain where gravity increases the risk of mass movement. High elevation Suggests physical weathering, especially freeze-thaw processes, weakening rock structure. Presence of many springs and streams Indicates high water input, which increases pore water pressure, reducing slope stability. Lack of vegetation cover Reduces root binding, making slopes more vulnerable to erosion and movement.

Question 67

3(c) Explain how a mass movement can affect the slope of an area. [4 marks]

Answer 67

Creates a scar or oversteepened slope Material removal at the top steepens the upper slope, increasing potential for further collapse. Deposition at the slope base Fallen material accumulates at the toe, decreasing slope angle and forming a toe or debris lobe. Destabilizes remaining slope Exposed rock may experience increased weathering, and the slope may become prone to further movement. Change in slope shape and length The slope may become longer and more irregular, with potential for new flow paths and erosion zones.

Question 68

1(b) Describe the variations in velocity of flow for transport and deposition

Answer 68

The velocity required to transport sediment is generally higher than the velocity needed to deposit it. For small particles like clay, very low velocities can transport them once they're suspended, but they require high velocities to be eroded. As sediment size increases, the required velocity for transportation increases. Larger sediments like gravel or cobbles are deposited at higher velocities, indicating they need more energy to be moved. Use of data example: Clay can be transported at <0.1 cm/s; gravel is deposited at around 35–45 cm/s.

Question 69

Explain the relationship between velocity of flow and the erosion of different types of sediment. [4 marks]

Answer 69

Larger particles require higher velocities to be eroded due to their greater mass (e.g. cobbles need ~300–400 cm/s). Clay particles require high velocities for erosion due to their cohesive nature (they stick together), despite being small. Sand and silt show a more predictable pattern where larger grains need more velocity to be eroded. Use of data: Gravel (~2 mm) requires at least 50 cm/s to be eroded.

Question 70

1(c) Explain how changes in land use might cause a river to flood. [5 marks]

Answer 70

Urbanisation increases impermeable surfaces (e.g., concrete and tarmac), reducing infiltration and increasing surface runoff, causing higher and faster discharge in rivers. Deforestation reduces interception and the ability of soil to absorb water through roots, leading to more direct surface runoff. Agricultural changes, such as replacing woodland with arable crops or ploughing fields, reduce vegetation cover, allowing more runoff and sediment to enter rivers. Draining wetlands reduces natural storage of excess rainwater, contributing to flood peaks. Upstream changes (e.g., construction, development) can increase downstream flood risk by delivering more water quickly into channels.

Question 71

2(c) Explain the formation of snow. [5 marks]

Answer 71

Water vapour forms from evaporation and rises into the atmosphere. If temperatures are below freezing, water vapour deposits directly into ice crystals (sublimation). Supercooled water droplets can coexist with ice crystals and transfer moisture to them. As the ice crystals grow larger, they become heavy enough to fall through the cloud. If temperatures remain below freezing during their descent, they fall as snowflakes. Snowflakes may melt slightly at the edges, stick together, and fall as larger flakes if air remains humid but cold.

Question 72

1(c) Explain why annual hydrographs might vary from year to year. [5 marks]

Answer 72

Precipitation variation – Wet years with more rainfall or intense storms lead to greater runoff and higher peaks; dry years reduce flow. Temperature changes – Hotter years increase evaporation, reducing water availability; snowmelt in colder climates can alter flow patterns. Land use changes – Deforestation, urbanisation, or agricultural changes affect infiltration and runoff, altering discharge patterns. Water management – Dams, reservoirs, or water abstraction can regulate or reduce flow, causing differences in hydrographs. Soil saturation – Previous wet or dry conditions affect how much new rainfall is absorbed or runs off.

Question 73

2(c) Explain the enhanced greenhouse effect. [5 marks]

Answer 73

The greenhouse effect occurs when gases like CO₂, CH₄, and water vapour trap outgoing longwave radiation, warming the Earth. The enhanced greenhouse effect is caused by increased levels of these gases due to human activities. Fossil fuel combustion, deforestation, and agriculture increase CO₂ and methane emissions. As more longwave radiation is trapped, global temperatures rise, leading to climate change. This enhanced effect leads to melting ice caps, rising sea levels, and extreme weather patterns.

Question 74

3(b) Describe the features of a rotational slide [4 marks]

Answer 74

Steep upper scarp or cliff where material detached. Presence of rotational slip planes with curved failure surfaces. Several terraced slumped masses indicating multiple failure stages. A toe or lobe of debris accumulated at the bottom of the slope. Transverse cracks across the surface of the slumped material. The whole structure has a concave, bowl-shaped profile.

Question 75

3(c) Explain how the mass movement process of heave may occur. [5 marks]

Answer 75

Heave is a slow mass movement process caused by expansion and contraction of soil. It occurs due to freezing and thawing (freeze-thaw) or wetting and drying. Freezing causes water in soil pores to expand, lifting particles upwards. When thawing or drying occurs, particles settle downward, often slightly downslope. Repeated cycles of heave lead to downslope soil movement, contributing to soil creep.

Question 76

Suggest how recurrence intervals can be used in flood prediction and prevention. [6 marks]

Answer 76

Predict flood frequency – recurrence intervals allow calculation of the probability of a flood occurring in any given year (e.g. a 10-year flood = 10% chance annually). Estimate flood magnitude – planners can use the discharge values from the recurrence graph (e.g. 1250 cumecs = 10-year flood) to plan infrastructure. Inform flood defences – flood barriers and levees can be built to withstand specific discharges expected once every 10, 25, or 50 years. Zoning and land-use planning – flood-prone areas identified through recurrence intervals can be protected or avoided for development. Economic cost–benefit analysis – helps governments assess the economic justification for prevention investments based on the likelihood of floods. Limitations – recurrence intervals are based on past data and probabilistic, not exact forecasts.

Question 77

2(c) Give reasons for the urban heat island effect [4 marks]

Answer 77

Urban surfaces (e.g. asphalt, concrete) have low albedo, absorbing more heat and raising surface temperatures. Buildings, vehicles, and industry produce anthropogenic heat, especially in city centres. Lack of vegetation reduces evapotranspiration, which would otherwise cool the air. Air pollution and smog trap radiation, acting like an insulating layer, intensifying the urban heat island effect.

Question 78

3(b) Draw a labelled diagram of soil creep [3 marks]

Answer 78

A gentle slope with evidence of slow movement. Terracettes (ridges or step-like features) perpendicular to the slope. Arrows or labels indicating soil creep/heave – movement down slope over time.

Question 79

3(c) Explain two ways a slope may be modified to reduce mass movement. [6 marks]

Answer 79

Method 1: Afforestation Tree roots bind the soil, increasing shear strength. Vegetation intercepts rainfall, reducing soil saturation and pore water pressure. It also extracts moisture, lowering weight of the slope material. Method 2: Slope drainage systems Drains are installed to remove excess water from the slope. This reduces lubrication of soil and rock particles, preventing slippage. Helps prevent failures due to over-saturation.

Question 80

1(b) Draw a sketch map of a meander. Label the main features. [4 marks]

Answer 80

Main river channel – curving through the landscape. Meander bend – large, looping curve in the river. Slip-off slope / point bar – on the inside bend, where deposition occurs. River cliff – on the outside bend, where erosion is strongest. Vegetation or floodplain – surrounding the meander. Optionally label eyot/island and any secondary channels visible.

Question 81

1(c) Explain the formation of an oxbow lake. [5 marks]

Answer 81

Meanders form on a flat floodplain as the river erodes laterally. Erosion occurs on the outside bend (river cliff) due to faster flow. Deposition occurs on the inside bend (slip-off slope) due to slower flow. Over time, the neck of the meander narrows. During flooding or high discharge, the river cuts through the neck, creating a new straighter channel. The old meander is cut off and becomes an oxbow lake through deposition at both ends. Eventually, the lake may dry up due to evaporation and sedimentation.

Question 82

3(b) Compare the water content and rate of movement for landslide and rockfall. [2 marks]

Answer 82

Water content: Landslides have more water than rockfalls. Rockfalls are typically dry movements. Rate of movement: Rockfalls are faster than landslides. Landslides move more slowly and steadily.

Question 83

3(c) Explain the differences between the mass movement processes of slide and flow. [6 marks]

Answer 83

Nature of Movement: Slide: material moves as a coherent block along a defined slip plane. Flow: material moves chaotically, often as a slurry. Water Content: Slides have less water, so movement is more structured. Flows have high water content, making material behave like a liquid. Surface/Slip Plane: Slides occur along a distinct failure plane (planar or curved) Flows usually have no clear slip surface. Speed and Materials: Slides can be rapid or slow, involving rock or soil. Flows are typically faster, often involving mud or debris. Examples: Slide: landslide, rockslide. Flow: mudflow, earthflow.