Paper 1 - Section A Mixed Flashcards
1b) Describe the process of throughflow in the drainage basin system.
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.
Explain how land use can affect the movement of water in a drainage basin
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.
Explain why temperatures in urban areas are often higher than in surrounding areas. (6 marks)
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.
Suggest how a landslide might have occurred.
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.
3c) Explain how slopes may be modified to reduce mass movement. (4 marks)
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.
2c) Explain why there might be a relationship between global temperature and carbon dioxide concentration in the atmosphere. (5 marks)
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.
3c) Explain how rainfall influences the type of weathering. (6 marks)
- 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. - 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. - More Rainfall Supports Biological Weathering
Higher rainfall = more plant growth, leading to root expansion and organic acid production, which break down rock. - 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. - Rainfall and Soil Formation
More weathering creates more soil, leading to deeper, fertile soils in tropical regions.
Describe two types of above ground flow. (4 marks)
- 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. - 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.
1c) Explain why channel storage may change over time. (4 marks)
- 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. - 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. - Seasonal and Climatic Effects
During wet seasons, rainfall and snowmelt increase channel storage.
During dry seasons, reduced rainfall and high evaporation lower channel storage.
Describe the path of incoming (shortwave) solar radiation. (4 marks)
- 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. - Reflection by Clouds
Clouds reflect a portion of incoming solar radiation back into space, reducing the energy reaching the Earth’s surface. - 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. - Scattering by Particles in the Atmosphere
Dust, smoke, and water droplets scatter solar radiation, altering its direction and intensity.
2c) Explain why reflected solar radiation may vary over time. (4 marks)
- 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.
- 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.
- 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. - Seasonal Variations
Winter: More reflection due to higher snow and ice cover.
Summer: Less reflection due to more vegetation and ice melt.
3b) Describe how one method of slope modification that increases the stability of a slope. (3 marks)
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)
3c) Explain the role of water in the movement of sediment on a hillslope. (5 marks)
- Rainsplash Erosion
Raindrops dislodge soil particles, moving them downslope in random directions.
On steep slopes, more particles move downhill, increasing erosion. - 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. - 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. - Subsurface Flow and Soil Creep
Water seeps through soil, slowly moving particles downslope.
Freeze-thaw cycles cause slow downslope movement of soil (soil creep). - 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.
1b) Describe two types of below-ground flow. (4 marks)
- 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). - 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.
1c) Explain why channel flow may change over time. (4 marks)
- 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. - 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. - 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.
2b) Describe how solar radiation is absorbed. (4 marks)
- 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. - Absorption by Clouds (1 mark)
Water droplets in clouds absorb some incoming solar radiation, warming the atmosphere. - 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.
2c) Explain why reflected solar radiation from clouds may vary over time. (4 marks)
- 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. - 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. - 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. - 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.
3b) Describe one strategy that can increase the stability of a slope. (3 marks)
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)
3c) Explain how human activities may decrease the stability of a slope. (5 marks)
- 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. - 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. - 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. - 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. - 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.
1c) Suggest reasons for the formation of a braided river channel
- 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. - 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. - 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. - Sudden Change in Gradient (1 mark)
If the river loses velocity quickly, sediment deposition is more pronounced, leading to braiding. - 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.
2c) Suggest reasons for the upward trend in average global surface temperature
- 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. - 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. - Urbanization and the Heat Island Effect (1 mark)
Cities absorb and retain more heat than rural areas, contributing to temperature rise. - 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. - 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.
3b) Compare the tectonic landforms and processes between two different convergent plate boundaries: oceanic-continental and continental-continental.
- 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). - 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. - 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. - Earthquake Occurrence (1 mark)
Both boundaries experience earthquakes, but subduction zones have deeper, more powerful quakes. - Example Comparison (1 mark)
Fig. 3.1 Example: The Andes Mountains (South America).
Fig. 3.2 Example: The Himalayas (India-Tibet boundary).
3c) Explain the formation of tectonic landforms at divergent (constructive) plate boundaries. (4 marks)
- 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. - 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. - 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. - Transform Faults (1 mark)
As plates move apart, fractures create faults, causing earthquakes.
Example: The Icelandic volcanic zone, where rift valleys and volcanoes coexist.
1c) Suggest the factors that can lead to flooding
- 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. - 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. - 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. - 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. - 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.
3b) Compare the features of mudflows and slumps
- 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. - 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. - 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. - 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.
3c) Suggest how a mudflow is formed.
- 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. - 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. - 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. - 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. - Channelized Flow Development (1 mark)
Once initiated, the mudflow follows natural channels, accumulating more material as it moves.
Describe the changes to catchment flows after urbanisation. (3 marks)
- 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. - 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. - 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.
1c) Explain why catchment flows change after urbanisation. (5 marks)
- 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. - 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. - 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. - 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. - 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.
2b) Briefly explain the formation of hail
- 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. - 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. - Final Fall as Hailstones (1 mark)
Once too heavy to remain suspended, hailstones fall to the ground as frozen pellets.
2c) Explain why the type of precipitation may vary in one location. (5 marks)
- Air Stability and Uplift Mechanisms (1 mark)
Stable air = Light, continuous rain (e.g., stratus clouds).
Unstable air = Intense thunderstorms (e.g., cumulonimbus clouds). - 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. - 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. - 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. - 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.
3b) Draw a sketch of an oceanic-continental convergent boundary. Label the main features. (4 marks)
- 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. - 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).
3c) Explain the formation of an ocean trench (4 marks)
- Subduction of the Oceanic Plate (1 mark)
The denser oceanic plate is forced beneath the lighter continental plate, creating a deep trench. - 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. - Melting and Magma Generation (1 mark)
The subducting plate melts due to heat and pressure, producing magma that rises to form volcanoes. - 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).
1b) Describe how a storm hydrograph might change following deforestation in an area. (4 marks)
- 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). - 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. - 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. - 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.
1c) Explain reasons for the changes in a storm hydrograph following deforestation in an area.
- 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. - Increased Surface Runoff (1 mark)
Impermeable soil surfaces develop, reducing infiltration.
This causes rapid overland flow, increasing peak discharge. - 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. - 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.
2b) Briefly explain the formation of radiation fog
- 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. - 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). - 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.
2c) Explain how orographic uplift of air can lead to precipitation. (5 marks)
Orographic precipitation occurs when air is forced to rise over a mountain range, cooling and condensing to form precipitation.
- Air is Forced to Rise Over Mountains (1 mark)
When moist air encounters a mountain range, it rises along the windward slope. - Expansion and Cooling of Air (1 mark)
As air ascends, it expands due to lower atmospheric pressure, cooling as it rises. - Condensation and Cloud Formation (1 mark)
Cooling air reaches its dew point, leading to condensation and the formation of clouds. - 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. - Formation of Rain Shadows (1 mark)
On the leeward side, the air descends and warms, leading to dry conditions.
3b) What are the key features of an Oceanic and Continental plate boundary
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.
3c) Explain the formation of an ocean trench
- Feature: Ocean Trench (1 mark)
Ocean trenches form at convergent plate boundaries, where one oceanic plate subducts beneath another plate. - Subduction Process (1 mark)
The denser oceanic plate sinks into the mantle, creating a deep depression in the ocean floor. - 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.
1c) Explain why the sediment size in a river channel might vary at different locations. (5 marks)
- 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. - Attrition and Abrasion (1 mark)
Sediment breaks into smaller pieces as it collides with other particles.
More attrition downstream = Smaller sediment sizes. - 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. - 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. - 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.
2c) Explain the role of greenhouse gases in global warming. (4 marks)
- 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. - 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. - 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. - Positive Feedback Mechanisms (1 mark)
Melting ice caps reduce Earth’s albedo, causing more heat absorption.
Thawing permafrost releases methane, accelerating warming.
3b) Contrast the range of speeds of the mass movements
- 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. - 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. - 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. - 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.
3c) Explain why mass movements have different rates of movement. (5 marks)
- Influence of Water Content (1 mark)
Water lubricates soil and reduces friction, making flows faster.
Mudflows are rapid, whereas dry rockfalls happen instantly. - 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. - Material Composition (1 mark)
Loose sediment moves faster than solid rock.
Clay-rich soils absorb water, leading to slow, creeping movements. - Triggering Events (1 mark)
Earthquakes, storms, and human activity (e.g., mining) accelerate mass movement.
Example: The 2008 Sichuan earthquake triggered thousands of landslides. - Vegetation and Human Influence (1 mark)
Deforestation reduces slope stability, increasing movement.
Example: Logging in Nepal has increased landslide frequency.
1c) Explain how islands in a river may have formed.
Braided rivers carry high sediment loads and deposit coarse material when energy decreases.
During low flow periods, exposed sediment forms islands (eyots/bars).
2b) Compare the albedo values for different surface conditions
- 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. - 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. - 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. - 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.
2c) Explain how albedo affects the diurnal energy budget. (5 marks)
- 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. - 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. - 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. - 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. - 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.
What are the similarities and differences between different convergent plate boundaries?
- 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. - 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. - 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. - 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.
3c) Explain the tectonic processes associated with divergent plate boundaries. (5 marks)
- 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. - 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. - 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. - Earthquakes and Volcanic Activity (1 mark)
Divergent boundaries cause frequent shallow earthquakes.
Magma eruptions create volcanic islands, such as Iceland. - 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.
1c) Suggest two reasons for differences between two rivers’ annual hydrographs
- 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. - 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.
2b) Describe the pattern of incoming (shortwave) solar radiation
- Maximum Solar Radiation at the Equator (1 mark)
The highest incoming solar radiation occurs around the equator (5°S), receiving 310 W/m². - 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. - Comparison Between Hemispheres (1 mark)
The Northern and Southern Hemispheres show similar trends, but slight variations occur due to seasonal differences.
Explain why there is an energy deficit at higher latitudes. (5 marks)
- 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. - 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. - 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. - 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. - 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.
3b) Suggest how a rock is weathered by freeze-thaw weathering. (2 marks)
- 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. - 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.
3c) Explain two factors which influence the rate of weathering. (4 marks)
- 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. - 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.
