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Form 6 Geography Practice Paper: Plate Tectonics, Volcanoes, Earthquakes and the Rock Cycle (12 questions, 100 marks, 75 minutes)
Form 6 Geography – 12 questions – 100 marks – 75 minutes
Form 6 Geography practice paper: 12 questions, 100 marks, 75 minutes on plate boundaries, spreading, seismic waves, magnitude, volcanoes, the rock cycle and hazard management.
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Paper details Form 6 Geography practice paper with 12 original data-response questions on plate tectonics, earthquakes, volcanoes, the rock cycle and hazard management, each with worked answers and marking points.
Section A: Plate boundaries, sea-floor spreading and seismic waves (Q1-Q4)
Calculations need the formula, the substitution from the data and the units.
| # | Question | Answer and marking notes |
|---|---|---|
| 1 | (a) An oceanic plate spreads symmetrically from a mid-ocean ridge at 65 mm per year. Calculate the total width of new ocean crust added in 4 million years, in km. (4 marks) (b) State the width measured on one side of the ridge only, and give two pieces of evidence for symmetrical spreading. (4 marks) | (a) 65 mm/yr x 4,000,000 yr = 260,000,000 mm = 260 km. One mark for converting mm to km. (4 marks) (b) One side = 260 / 2 = 130 km. (2 marks) Evidence: magnetic stripes are mirror images across the ridge; sediment and crust age increase away from the ridge; the same rock types and magnetic record appear on both sides. (1 mark each, max 2) |
| 2 | (a) P waves travel at 8 km/s and S waves at 4 km/s. A station records a 42 second gap between the first P arrival and the first S arrival. Calculate the distance from the epicentre, in km. (4 marks) (b) Explain why the gap differs between stations and how three stations locate an epicentre. (4 marks) | (a) d/4 – d/8 = 42, so d/16 = 42 and d = 336 km. (4 marks) (b) The gap grows with distance because the two waves travel at different speeds, so each station gives a different distance; three circles drawn from three stations meet at the epicentre, assuming a homogeneous crust with constant wave speeds. (4 marks) |
| 3 | (a) A normally magnetised stripe lies with its outer edge 90 km from a ridge and formed 1.5 million years ago. Calculate the average spreading rate in mm per year. (3 marks) (b) Explain why the magnetic stripes are mirror images on the two sides of the ridge. (3 marks) (c) State the factor-of-two error most often made in this calculation. (2 marks) | (a) 90 km / 1.5 Myr = 60 km per million years = 60 mm/yr. (3 marks) (b) New crust cools and records the field direction at the ridge, then moves away on both sides, so the same polarity sequence is preserved as mirror images. (3 marks) (c) Using the full width instead of the half width doubles the answer; divide the one-sided distance by the age. (2 marks) |
| 4 | (a) A volcano erupts 0.45 km3 of ash in 3 days. Calculate the average discharge in cubic metres per second, to the nearest whole number. (4 marks) (b) Give two reasons why the real discharge differs greatly from this average. (4 marks) | (a) 0.45 km3 = 450,000,000 m3; 3 days = 259,200 s; 450,000,000 / 259,200 is about 1,736 m3/s. (4 marks) (b) The eruption stage: explosive opening phases far exceed later quiet phases; magma gas content and viscosity control explosivity; wind, rain and ash compaction affect the volume estimate. (2 marks each, max 4) |
Section B: Volcanoes, the rock cycle and geological structures (Q5-Q8)
Description and explanation must cite the data or figure features given, not recite definitions.
| # | Question | Answer and marking notes |
|---|---|---|
| 5 | (a) Granite contains about 72% silica and basalt about 50%. Calculate the difference in percentage points. (2 marks) (b) Compare the viscosity, eruption style and resulting volcano shape of the two magmas. (4 marks) (c) Explain how the two rock types are converted into each other in the rock cycle. (2 marks) | (a) 72 – 50 = 22 percentage points, not per cent. (2 marks) (b) Granitic magma is viscous, traps gas and gives explosive eruptions, ignimbrite and lava domes; basaltic magma is fluid and gives shield volcanoes, lava plateaus and pillow lavas. (4 marks) (c) Both are weathered, eroded, transported and deposited as sedimentary rock, then metamorphosed or melted back to magma, completing the rock cycle. (2 marks) |
| 6 | (a) A bed dips at 30 degrees. A borehole 500 m down-dip from the outcrop meets the same bed. Calculate the vertical drop in metres, to the nearest whole number. (3 marks) (b) Explain why drilling and engineering risks are higher in folded terrain. (3 marks) (c) State two field measurements used to fix the position of a bed. (2 marks) | (a) Drop = 500 x tan 30 degrees, about 289 m. (3 marks) (b) Folding repeats the same bed and varies the dip, so a small error in the borehole position misses the target bed; fractured and jointed rock also lowers bearing capacity and complicates tunnel support. (3 marks) (c) Measure strike and dip with a geological compass; map outcrop positions along a section and draw a geological cross-section. (2 marks) |
| 7 | (a) Earthquake A has magnitude 5.2 and earthquake B has magnitude 6.6. Calculate the ratio of their wave amplitudes. (3 marks) (b) Given that energy rises about 31.6 times per magnitude unit, calculate the energy ratio, to the nearest whole number. (3 marks) (c) Explain why a small rise in magnitude causes a large rise in damage. (2 marks) | (a) Amplitude ratio = 10^1.4, about 25.1 times. (3 marks) (b) Energy ratio = 31.6^1.4, about 126 times. (3 marks) (c) Magnitude is logarithmic and energy scales with amplitude to the power 1.5, so a 25-fold amplitude also raises ground acceleration and pushes simple structures past their elastic limit. (2 marks) |
| 8 | (a) A tsunami crosses an ocean of average depth 4,000 m. Taking g as 9.8 m/s2, calculate its speed in m/s and in km/h, to the nearest whole number. (4 marks) (b) Explain why the wave height rises sharply near the coast. (4 marks) | (a) v = square root of (9.8 x 4,000), about 198 m/s or 713 km/h. (4 marks) (b) In shallow water the speed falls while the energy flux is conserved, so the height grows; the wavelength shortens, crests pile up and bays or estuaries focus the wave, producing rapid run-up and inundation. (4 marks) |
Section C: Hazard management, regional risk and resources (Q9-Q12)
Discussion questions need both sides of the argument supported by specific examples or data.
| # | Question | Answer and marking notes |
|---|---|---|
| 9 | (a) A coastal city of 2,400,000 people has 35% of its residents inside a volcanic hazard zone. Calculate the exposed population. (3 marks) (b) Propose three management measures that reduce volcanic risk and state the hazard each targets. (6 marks) | (a) 2,400,000 x 35% = 840,000 people. (3 marks) (b) Land-use zoning and building limits in the hazard zone target lava flows and pyroclastic flows; monitoring of earthquakes, gas and ground deformation with evacuation drills and warning levels targets pre-eruption warning; ash clearance, water protection, public education and insurance target secondary impacts and recovery. (2 marks each) |
| 10 | (a) Explain how earthquake energy from a plate boundary decays with distance. (3 marks) (b) Give two reasons why tremors are still felt in a city far from any plate boundary. (4 marks) (c) State one building design requirement linked to this setting. (2 marks) | (a) Energy spreads geometrically and is absorbed by the medium, so amplitude and acceleration fall sharply with distance, and deep events attenuate even more. (3 marks) (b) Old faults in the region still produce small to moderate earthquakes; tall buildings and soft soils amplify long-period shaking; moderate events in nearby regions are felt. (2 marks each, max 4) (c) Tall buildings must be designed for seismic and wind lateral loads and should avoid sensitive uses on soft soil or steep slopes. (2 marks) |
| 11 | (a) A project needs 120,000 tonnes of sand and gravel and each lorry carries 20 tonnes. Calculate the number of lorry trips. (2 marks) (b) Discuss the effects of large-scale river sand mining on rivers and coasts. (4 marks) (c) Propose three alternatives or mitigation measures. (3 marks) | (a) 120,000 / 20 = 6,000 trips. (2 marks) (b) River beds are incised and banks and bridge piers are undermined; the loss of sediment makes deltas retreat and coasts erode; turbidity destroys fish habitat and spawning grounds. (4 marks) (c) Use recycled aggregate and construction waste; replace river sand with quarry aggregate under a extraction cap; restrict haulage hours and routes to cut traffic and emissions. (1 mark each) |
| 12 | The data are: site A on a divergent boundary, earthquake depth 35 km, volcano present; site B on a convergent boundary, depth 120 km, volcano present; site C on a convergent boundary, depth 480 km, no volcano. (a) Calculate the mean earthquake depth, to the nearest whole number. (3 marks) (b) Write two conclusions supported by these data. (6 marks) | (a) (35 + 120 + 480) / 3 = 635 / 3, about 212 km. (3 marks) (b) Conclusion one: depths at convergent boundaries exceed those at divergent boundaries, consistent with a descending slab; conclusion two: no volcano occurs where earthquakes are deeper than 300 km, showing magma forms at shallow levels. (3 marks each) |
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A TutorZone practice paper; original questions and passages, not publisher material.