Hazardous Earth | OCR A-Level Geography (H481)

Hazardous Earth

361 questions
24 subtopics
Component 03: Geographical debates, two of five
Component 03

Hazardous Earth is examined in Component 03, Geographical debates.

It covers the Earth's internal structure and the global pattern of plates, continental drift and the evidence from fossils, rocks and ancient glaciations, sea-floor spreading, palaeomagnetism and the age of the ocean floor, divergent boundaries and the landforms of the mid-ocean ridges, subduction at oceanic-continental and oceanic-oceanic boundaries, continental collision and conservative boundaries, magma chemistry, viscosity and explosive volcanism at subduction zones, effusive eruptions, shield volcanoes and hot-spot volcanism, volcano size and shape, super-volcanoes and the Volcanic Explosivity Index, lava flows, pyroclastic flows and volcanic gases, tephra, ashfall, lahars and volcanic tsunamis, earthquake focus, depth and the seismic waves released, measuring earthquakes: Richter, moment magnitude and Mercalli intensity, fault scarps, rift valleys and the landscapes faulting creates, ground shaking, ground displacement and liquefaction, earthquake-triggered landslides, avalanches and flooding, tsunamis from sea-bed uplift and underwater landslides, why people choose to live in tectonically active places, the impacts of volcanic eruptions in countries at contrasting levels of development, the impacts of earthquakes in countries at contrasting levels of development, predicting, monitoring and managing volcanic hazards, land-use zoning, building design and managing earthquake risk, changing risk over time and the disaster risk equation and the Park model of disaster response.

Sample questions from Hazardous Earth

Answer each one closed book first, then open the answer.

The Earth's internal structure and the global pattern of plates

Why is the inner core solid when it is hotter than the liquid outer core?

Show the answer
The pressure at the centre of the Earth is so great that it raises the melting point of iron above the temperature there, so the inner core stays solid.
Divergent boundaries and the landforms of the mid-ocean ridges

Why does a mid-ocean ridge stand higher than the ocean floor on either side?

Show the answer
The crust at the ridge is newly formed and still hot, so it is less dense and more buoyant, and as it cools and contracts away from the ridge it becomes denser and sinks.
Magma chemistry, viscosity and explosive volcanism at subduction zones

Which magma type is typical of subduction-zone volcanoes?

Show the answer
Andesitic magma, with an intermediate silica content of roughly 57 to 63%.
Lava flows, pyroclastic flows and volcanic gases

Why is a pyroclastic flow so much more lethal than a lava flow?

Show the answer
It travels far faster than anyone can escape and kills instantly by heat and asphyxiation, so there is no time to evacuate once it has begun.
Measuring earthquakes: Richter, moment magnitude and Mercalli intensity

A magnitude 7 earthquake releases how much more energy than a magnitude 5?

Show the answer
About 1,000 times more, since each step is roughly 32 times and 32 × 32 is close to 1,000.
Earthquake-triggered landslides, avalanches and flooding

What is a landslide dam, and why is it dangerous?

Show the answer
A barrier of debris that blocks a river and impounds a lake behind it; the loose dam can fail suddenly and release a destructive flood downstream.
The impacts of volcanic eruptions in countries at contrasting levels of development

What political impacts can follow an eruption?

Show the answer
Governments may be blamed for slow warnings or relief, resettlement and exclusion zones become contested, emergency powers are used, and a state may become dependent on international aid.
Land-use zoning, building design and managing earthquake risk

How does an earthquake early warning system work?

Show the answer
Sensors near the fault detect the fast P wave and transmit an alert electronically, which outruns the slower and far more destructive S and surface waves and gives seconds of notice.

The 24 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
The Earth's internal structure and the global pattern of plates	Recall questions on the layers of the Earth, the lithosphere and asthenosphere, oceanic and continental crust, the solid inner core, the Moho, radioactive heat and mantle convection, ridge push and slab pull, plate speeds, the seven major plates, the distribution of earthquakes and volcanoes, the Pacific Ring of Fire, mantle plumes, and GPS measurement.	17
Continental drift and the evidence from fossils, rocks and ancient glaciations	Recall questions on Wegener and the theory of continental drift, Pangaea, Laurasia and Gondwanaland, and the fossil, rock and glacial evidence for the theory.	14
Sea-floor spreading, palaeomagnetism and the age of the ocean floor	Recall questions on sea-floor spreading and Harry Hess, palaeomagnetism and the Curie point, geomagnetic reversals and symmetrical magnetic stripes explained by Vine and Matthews, the age of oceanic crust and why it is young, sediment thickness and heat flow across ocean basins, and confirmation by ocean drilling.	14
Divergent boundaries and the landforms of the mid-ocean ridges	Recall questions on divergent boundaries and decompression melting, the Mid-Atlantic Ridge and the form of mid-ocean ridges, transform faults, shallow earthquakes, pillow lava and black smokers, Iceland, effusive eruptions, continental rifting and the Red Sea, and a worked spreading-rate calculation.	14
Subduction at oceanic-continental and oceanic-oceanic boundaries	Recall questions on subduction, ocean trenches and the Challenger Deep, Benioff zones, how magma forms above a subducting slab and why it is silica-rich, accretionary prisms, the Andes, island arcs such as the Marianas and Aleutians, back-arc basins, great and deep-focus earthquakes, and violent eruptions.	15
Continental collision and conservative boundaries	Recall questions on continental collision, the Himalayas and the Tethys Sea with a worked convergence calculation, why collision zones lack volcanoes but have destructive earthquakes, thick Himalayan crust, conservative boundaries such as the San Andreas and North Anatolian faults, stick-slip movement, shallow earthquakes, seismic gaps, and offset landscapes.	15
Magma chemistry, viscosity and explosive volcanism at subduction zones	Recall questions on viscosity and what controls it, the silica content of basaltic, andesitic and rhyolitic magma, temperature, why viscous magma erupts explosively, water from the subducting plate, composite volcanoes, Plinian, Peléean and Strombolian eruptions, Mount St Helens in 1980, and lava domes.	16
Effusive eruptions, shield volcanoes and hot-spot volcanism	Recall questions on effusive eruptions and fluid basaltic lava, shield volcanoes and Mauna Loa, fissure eruptions and Laki in 1783, lava plateaus and basalt columns, pahoehoe and aa lava, cinder cones, mantle plumes and the Hawaiian chain with a worked age calculation, Yellowstone, and the volcanoes of the East African Rift.	18
Volcano size and shape, super-volcanoes and the Volcanic Explosivity Index	Recall questions on the slopes and volumes of shield, composite and cinder cone volcanoes, calderas and how they form, super-volcanoes, the Toba and Yellowstone super-eruptions and their climatic effects, the Volcanic Explosivity Index, its range, tenfold steps and a worked comparison, Pinatubo's rating, and the limits of the index.	17
Lava flows, pyroclastic flows and volcanic gases	Recall questions on the damage and reach of lava flows, pyroclastic flows, their speed, temperature, lethality and origins, Mount Pelée and Saint-Pierre in 1902, volcanic gases, carbon dioxide, sulphur dioxide and acid rain, cooling after Pinatubo, fluorine poisoning, volcanic smog, and the deadly gases of long effusive eruptions.	15
Tephra, ashfall, lahars and volcanic tsunamis	Recall questions on tephra, ash, lapilli and volcanic bombs, ashfall damage to buildings, farming, water, aircraft and health, the 2010 Eyjafjallajökull ash cloud, lahars and their water sources, Armero and Nevado del Ruiz in 1985, lasting lahar risk, jökulhlaups, volcanic tsunamis, and Krakatoa in 1883.	16
Earthquake focus, depth and the seismic waves released	Recall questions on the focus and epicentre, elastic rebound, stress and strain, P, S, Love and Rayleigh waves and how they move rock, the S-wave shadow zone, locating an epicentre, shallow-focus and deep-focus earthquakes and why depth matters, the 700 km limit, Benioff zones, and aftershocks.	17
Measuring earthquakes: Richter, moment magnitude and Mercalli intensity	Recall questions on magnitude and intensity, the Richter scale, amplitude and energy steps with a worked comparison, its saturation, seismic moment and the moment magnitude scale, the 1960 Chile earthquake, the Modified Mercalli scale and its range, why intensity varies, the drawbacks of intensity scales, and isoseismal lines.	14
Fault scarps, rift valleys and the landscapes faulting creates	Recall questions on faults, normal, reverse and strike-slip movement, fault scarps and escarpments, grabens and horsts, how rift valleys form, the East African Rift system and the Ruwenzori block mountains, offset streams and ridges along strike-slip faults, and coastal uplift in earthquakes.	13
Ground shaking, ground displacement and liquefaction	Recall questions on ground shaking as the primary hazard, peak ground acceleration, duration and resonance, amplification on soft ground in Mexico City in 1985, ground displacement and infrastructure, the mechanism and conditions of liquefaction, its effects on buildings, sand boils, and Christchurch in 2011.	15
Earthquake-triggered landslides, avalanches and flooding	Recall questions on why shaking triggers landslides and which slopes fail, landslides in the 2008 Sichuan earthquake, landslide dams and how they are made safe, avalanches at Yungay in 1970 and after the 2015 Nepal earthquake, flooding from failed dams, levees and subsidence, and what makes a landslide a disaster.	13
Tsunamis from sea-bed uplift and underwater landslides	Recall questions on how subduction earthquakes and underwater landslides generate tsunamis, why strike-slip faults rarely do, open-ocean wavelength and speed with a worked calculation, shoaling, run-up and drawback, successive waves, the 2004 Indian Ocean and 2011 Japanese tsunamis, sea-bed pressure sensors, and warning times.	15
Why people choose to live in tectonically active places	Recall questions on fertile volcanic soils on Java, geothermal energy in Iceland, minerals and tourism in tectonic regions, inertia and poverty as reasons to stay, the probability of events, risk perception and past experience, why large cities lie in active areas, and confidence in technology and government.	13
The impacts of volcanic eruptions in countries at contrasting levels of development	Recall questions on primary and secondary impacts and the social, economic, environmental and political effects of eruptions, with Eyjafjallajökull in 2010, Pinatubo in 1991, Nyiragongo at Goma in 2002 and Soufrière Hills on Montserrat, and why deaths, costs and recovery differ between lower-income and higher-income countries.	16
The impacts of earthquakes in countries at contrasting levels of development	Recall questions on why buildings rather than earthquakes kill, the social, economic, environmental and political impacts of earthquakes, the 2010 Haiti earthquake and the cholera that followed, the 2011 Tōhoku earthquake, tsunami and Fukushima, and why death tolls, costs, recovery and development setbacks differ with national wealth.	16
Predicting, monitoring and managing volcanic hazards	Recall questions on why eruptions can be forecast, earthquake swarms, harmonic tremor, tiltmeters, satellite radar and gas monitoring, hazard maps and exclusion zones, mitigating the event by diverting lava at Heimaey and on Mount Etna, sabo dams, mitigating vulnerability and losses, community preparedness, and careful evacuation warnings.	16
Land-use zoning, building design and managing earthquake risk	Recall questions on why earthquakes cannot be predicted but can be forecast, land-use zoning along California's faults and in fast-growing cities, early warning systems, base isolation, cross-bracing, tuned mass dampers and deep foundations, retrofitting, simple house reinforcement, earthquake insurance and its uneven uptake, and public drills.	16
Changing risk over time and the disaster risk equation	Recall questions on the disaster risk equation, vulnerability, capacity to cope and exposure, why tectonic events are not becoming more frequent while people affected and economic costs rise, how urbanisation and development raise or reduce risk, probability and low-probability, high-magnitude events, and future risk reduction strategies.	14
The Park model of disaster response	Recall questions on what the Park model shows, its stages from steady state through relief, rehabilitation and reconstruction, what sets the steepness of its downward limb, its three possible outcomes, how curves differ between high-income and low-income countries, why a community can end up better off, and the model's criticisms and uses.	12

Hazardous Earth is 361 of the 3,740 questions in the guide.Get the guide, £7

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.