Eduqas A-level Geology · T1

Geohazards

50 exam-style questions with answers for T1 Geohazards in Eduqas A-level Geology (spec A480QS). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below. Not official Eduqas material.

All 50 questions and answers

Question 1 · Spec T1, Key Idea 1 · Hazard and risk
Distinguish between a geohazard and risk. [2 marks]
Answer:
A geohazard is the probability of a damaging geological event occurring in a given place and time (1); risk is the potential loss of life or damage to property that results (1).
Question 2 · Spec T1, Key Idea 1 · Earthquakes
Explain how movement on a fault causes an earthquake. [2 marks]
Answer:
Friction locks the fault, so elastic strain builds up in the rocks (1); when the stress exceeds friction, the fault slips suddenly and releases energy as seismic waves (1).
Question 3 · Spec T1, Key Idea 1 · Earthquake measurement
Distinguish between moment magnitude and Modified Mercalli intensity. [2 marks]
Answer:
Moment magnitude measures the energy released at the source (1); Mercalli intensity describes the observed effects and damage at a location (1).
Question 4 · Spec T1, Key Idea 1 · Earthquake measurement
Using energy ratio = 10^(1.5 × magnitude difference), compare two earthquakes 2 magnitude units apart. [2 marks]
Answer:
10^(1.5 × 2) = 10³ (1); the larger releases about 1000 times more energy (1).
Question 5 · Spec T1, Key Idea 1 · Earthquake damage
State three factors other than distance that affect earthquake damage. [3 marks]
Answer:
Any three from: ground conditions, e.g. soft sediment amplifies shaking (1); building design and standards (1); population density (1); time of day (1); preparedness (1).
Question 6 · Spec T1, Key Idea 1 · Earthquake damage
Explain why shallow-focus earthquakes cause more damage. [2 marks]
Answer:
Seismic waves travel a shorter distance to the surface (1); so less energy is lost and ground shaking is more intense (1).
Question 7 · Spec T1, Key Idea 1 · Liquefaction
Explain how liquefaction occurs. [3 marks]
Answer:
Shaking of loose, saturated sediment increases pore water pressure (1); reducing the friction (effective stress) between grains (1); so the sediment behaves like a liquid and buildings sink or tilt (1).
Question 8 · Spec T1, Key Idea 1 · Tsunamis
Explain how an undersea earthquake generates a tsunami. [2 marks]
Answer:
Sudden vertical movement of the sea floor on a fault, often at a subduction zone (1); displaces the whole column of water above it (1).
Question 9 · Spec T1, Key Idea 1 · Tsunamis
Explain why tsunami height varies along a coastline. [2 marks]
Answer:
The waves slow and grow taller in shallow water (1); and bays and inlets funnel the water, increasing wave height (1).
Question 10 · Spec T1, Key Idea 1 · Probability
A hazard has a return period of 200 years. Calculate its annual probability. [1 mark]
Answer:
1 ÷ 200 = 0.005 (0.5% per year).
Question 11 · Spec T1, Key Idea 1 · Probability
Annual probability is 0.01. Use 1 − (1 − p)^n to calculate the probability of at least one event in 10 years. [2 marks]
Answer:
1 − 0.99¹⁰ (1); = 0.096 (9.6%) (1).
Question 12 · Spec T1, Key Idea 2 · Prediction
Explain why precursors such as radon changes cannot reliably predict earthquakes. [2 marks]
Answer:
They do not occur before every earthquake and can have other causes (1); so they cannot give a reliable time, place and magnitude (1).
Question 13 · Spec T1, Key Idea 2 · Monitoring
Compare the information given by seismometers and GPS. [2 marks]
Answer:
Seismometers record ground vibrations from earthquakes (1); GPS measures ground deformation and the build-up of strain over time (1).
Question 14 · Spec T1, Key Idea 2 · Prediction
Explain why changes in groundwater level must be used with caution as an earthquake precursor. [1 mark]
Answer:
Rainfall, pumping and seasonal changes also cause water levels to change.
Question 15 · Spec T1, Key Idea 2 · Early warning
Distinguish between earthquake early warning and prediction. [2 marks]
Answer:
Early warning detects an earthquake that has already started and gives seconds of warning before shaking arrives elsewhere (1); prediction would forecast the earthquake before it starts (1).
Question 16 · Spec T1, Key Idea 2 · Building design
Explain how base isolation reduces earthquake damage. [2 marks]
Answer:
Flexible bearings separate the building from the ground (1); reducing the amount of shaking transferred to the building (1).
Question 17 · Spec T1, Key Idea 2 · Risk communication
Explain why risk communication should include uncertainty. [2 marks]
Answer:
People must understand that forecasts give probabilities, not exact predictions (1); so they still prepare and know what action to take (1).
Question 18 · Spec T1, Key Idea 1 · Slope stability
State two ways a slope can become unstable without extra load being added. [2 marks]
Answer:
Any two from: weathering weakens the rock (1); erosion undercuts the toe of the slope (1); rising groundwater (1); earthquake vibration (1).
Question 19 · Spec T1, Key Idea 1 · Landslides
Explain how heavy rainfall triggers landslides. [2 marks]
Answer:
Water infiltrates and raises the pore water pressure (1); which reduces friction along potential slip surfaces (1).
Question 20 · Spec T1, Key Idea 1 · Landslides
Explain why beds dipping out of a slope are a hazard. [2 marks]
Answer:
The bedding planes act as slip surfaces (1); along which blocks can slide if they daylight in the slope face (1).
Question 21 · Spec T1, Key Idea 1 · Mass movement
Distinguish between a rock avalanche, a landslide and a debris flow. [3 marks]
Answer:
Rock avalanche: rapid fall of fragmented rock (1); landslide: a mass sliding on a slip surface (1); debris flow: a fast-flowing mixture of water and sediment (1).
Question 22 · Spec T1, Key Idea 2 · Slope monitoring
Explain how an inclinometer is used to monitor a slope. [2 marks]
Answer:
It measures changes in tilt down a borehole (1); showing the depth of the slip surface and the rate of movement (1).
Question 23 · Spec T1, Key Idea 2 · Slope monitoring
Explain why GPS surveys are combined with pore pressure measurements on a slope. [2 marks]
Answer:
GPS records the amount of movement (1); pore pressure shows whether water is the trigger (1).
Question 24 · Spec T1, Key Idea 2 · Slope stabilisation
Explain how drainage improves slope stability. [2 marks]
Answer:
It lowers pore water pressure (1); increasing the friction along potential slip surfaces (1).
Question 25 · Spec T1, Key Idea 2 · Slope stabilisation
Explain why rock bolts must be designed using a geological investigation. [2 marks]
Answer:
The orientation of joints and potential failure surfaces must be known (1); so bolts can be placed to pin blocks across these planes (1).
Question 26 · Spec T1, Key Idea 1 · Case studies
Explain how the 2011 Tōhoku earthquake shows that hazards can be linked. [2 marks]
Answer:
The subduction zone earthquake caused severe ground shaking (1); and also generated a destructive tsunami that flooded the coast (1).
Question 27 · Spec T1, Key Idea 1 · Case studies
Explain why the 1963 Vajont landslide was a cascading hazard. [2 marks]
Answer:
A huge landslide fell into the reservoir behind the dam (1); creating a wave that overtopped the dam and destroyed towns downstream (1).
Question 28 · Spec T1, Key Idea 1 · Case studies
Explain why the Storegga slide is relevant to UK hazard assessment. [2 marks]
Answer:
This submarine landslide off Norway (about 8200 years ago) caused a tsunami (1); whose deposits are found on the coasts of Scotland, showing the UK could be affected (1).
Question 29 · Spec T1, Key Idea 1 · Ground hazards
Explain how expansive clays damage buildings. [2 marks]
Answer:
Clay swells when wet and shrinks when dry (1); causing uneven ground movement that cracks foundations (1).
Question 30 · Spec T1, Key Idea 1 · Ground hazards
Explain how limestone dissolution causes sinkholes. [2 marks]
Answer:
Acidic groundwater dissolves limestone, forming underground cavities (1); the overlying material collapses into them (1).
Question 31 · Spec T1, Key Idea 3 · Mining subsidence
Explain why land above old mine workings can subside long after mining has stopped. [2 marks]
Answer:
Roof supports decay and the roofs of voids collapse (1); and the collapse migrates upwards to the surface (1).
Question 32 · Spec T1, Key Idea 1 · Radon
Explain why some areas have a higher radon hazard. [2 marks]
Answer:
Rocks such as granite contain uranium, which decays to radon (1); radon gas escapes through fractures and permeable rock into buildings (1).
Question 33 · Spec T1, Key Idea 1 · Radon
Explain why radon risk cannot be predicted from bedrock alone. [2 marks]
Answer:
Superficial deposits, fractures and permeability also control radon movement (1); so measurements in buildings are needed (1).
Question 34 · Spec T1, Key Idea 3 · Quarries
State three geological factors to assess for rockfall hazard at a quarry face. [3 marks]
Answer:
Any three from: orientation and spacing of joints (1); bedding dip relative to the face (1); degree of weathering (1); groundwater (1).
Question 35 · Spec T1, Key Idea 3 · Quarries
Explain how dewatering a quarry affects groundwater. [2 marks]
Answer:
Pumping lowers the water table around the quarry (1); which can dry up nearby wells and springs (1).
Question 36 · Spec T1, Key Idea 3 · Mine waste
Explain how sulfide-rich mine waste causes water pollution. [2 marks]
Answer:
Sulfide minerals such as pyrite oxidise to form sulfuric acid (acid mine drainage) (1); which dissolves toxic metals that pollute rivers and groundwater (1).
Question 37 · Spec T1, Key Idea 3 · Mine waste
Explain why waste tips must be assessed for both stability and pollution. [2 marks]
Answer:
Loose waste can become saturated and slide, as at Aberfan (1); and reactive minerals can pollute drainage water (1).
Question 38 · Spec T1, Key Idea 3 · Landfill
Explain why low-permeability rock is useful beneath a landfill site. [2 marks]
Answer:
It stops leachate escaping into groundwater (1); but fractures must be checked and an engineered liner is still needed (1).
Question 39 · Spec T1, Key Idea 3 · Landfill
Explain how landfill produces a gas hazard. [2 marks]
Answer:
Organic waste decomposes anaerobically to produce methane (1); which can migrate through permeable rocks and explode in buildings (1).
Question 40 · Spec T1, Key Idea 3 · Hazardous waste
Explain why multiple barriers are used for storing radioactive waste. [2 marks]
Answer:
If one barrier fails, the others still contain the waste (1); combining engineered containers with impermeable, stable geology (1).
Question 41 · Spec T1, Key Idea 3 · Contaminated land
State three things that must be investigated before remediating a contaminated site. [3 marks]
Answer:
Any three from: the type and location of contaminants (1); ground conditions (1); groundwater flow (1); who or what could be affected (1).
Question 42 · Spec T1, Key Idea 3 · Pollution
Explain why fractured rock can transmit pollution even if the rock itself has low permeability. [2 marks]
Answer:
Connected fractures provide fast pathways for fluids (1); bypassing the impermeable rock between them (1).
Question 43 · Spec T1, Key Idea 3 · Dams
Explain why faults beneath a dam site are a problem. [2 marks]
Answer:
Fault zones contain weak, crushed rock (1); and can allow water to leak or the fault could move (1).
Question 44 · Spec T1, Key Idea 3 · Reservoirs
Explain why fractured limestone is a problem beneath a reservoir. [2 marks]
Answer:
Water may leak through fractures and solution cavities (1); and further dissolution could make the ground unstable (1).
Question 45 · Spec T1, Key Idea 3 · Tunnels
Explain why a fault zone causes problems in tunnelling. [2 marks]
Answer:
Crushed fault rock is weak and may collapse (1); and the fault may carry large flows of groundwater into the tunnel (1).
Question 46 · Spec T1, Key Idea 3 · Road cuttings
Explain why all joint sets must be considered when designing a road cutting. [2 marks]
Answer:
Intersecting joints can form wedges that slide out of the face (1); even if the bedding dips into the slope (1).
Question 47 · Spec T1, Key Idea 3 · Foundations
Explain why a building on both bedrock and soft fill may suffer differential settlement. [2 marks]
Answer:
The soft fill compresses more under the load than the bedrock (1); so the building settles unevenly and cracks (1).
Question 48 · Spec T1, Key Idea 3 · Construction
Explain how pumping groundwater during construction can affect ground stability. [2 marks]
Answer:
Lowering the water table reduces water pressure in the pores (1); causing clays and peat to compact and the ground to subside (1).
Question 49 · Spec T1, Key Idea 3 · Site selection
Explain why site suitability is usually a comparison rather than a simple 'safe' or 'unsafe'. [2 marks]
Answer:
Each site has different hazards and uncertainties (1); so the choice weighs evidence, consequences and the cost of engineering solutions (1).
Question 50 · Spec T1, Key Idea 2 · Evaluation
State three features of a good evaluation of a hazard management scheme. [3 marks]
Answer:
Any three from: links each measure to the hazard mechanism (1); uses monitoring or case study evidence (1); identifies limitations and remaining risk (1); judges whether the cost is proportionate (1).

← G4 Earth materials and natural resources T2 Geological map applications →

Geohazards

All 50 questions and answers

More Eduqas A-level Geology topics

Cookies on Knowledge Noodles

Cookie settings