Unit 9 - Essays - Tectonic Hazards Flashcards
(4 cards)
Evaluate the relative importance of hazards resulting from earthquakes
Evaluate the relative importance of hazards resulting from earthquakes
Paragraph 1 – Shaking (Primary Hazard)
Japan 2011: Shaking caused infrastructure collapse but few deaths due to strict building codes.
Haiti 2010: Main killer – shallow quake and poor construction caused ~220,000 deaths.
Nepal 2015: Major destruction in Kathmandu; traditional masonry homes collapsed.
Paragraph 2 – Tsunami (Secondary Hazard)
Japan 2011: 40m waves caused 90% of deaths and huge infrastructure loss (e.g., Sendai).
Haiti: Only a small tsunami (3m); negligible impact.
Nepal: No tsunami due to being landlocked.
Paragraph 3 – Soil Liquefaction
Japan: Coastal areas like Urayasu affected; tilted buildings and road subsidence.
Haiti & Nepal: Localised in urban areas (e.g., Kathmandu); moderate damage but not widespread.
Paragraph 4 – Landslides
Nepal: Especially deadly in rural, mountainous zones (e.g., Langtang).
Haiti: Significant locally but not a national-scale hazard.
Japan: Present (e.g., Fukushima) but less damaging than tsunami.
Paragraph 5 – Long-Term Secondary Hazards
Japan: Fukushima meltdown caused radiation, mass evacuations.
Haiti: Cholera outbreak from contaminated aid efforts.
Nepal: Delayed aid due to landslides, rural isolation.
Conclusion
Judgement: The most important hazards vary by location and development level. In LICs like Haiti and Nepal, shaking is most deadly due to weak infrastructure. In HICs like Japan, secondary hazards like tsunamis or nuclear accidents dominate due to high exposure and infrastructure vulnerability.
‘The type of eruption is the most important factor influencing the hazards from volcanoes.’ How far do you agree?
‘The type of eruption is the most important factor influencing the hazards from volcanoes.’ How far do you agree?
Paragraph 1 – Explosive vs. Effusive Eruptions
Etna (effusive): Predictable lava flows; destructive but rarely fatal.
Montserrat (Peléan): Andesitic magma → pyroclastic flows and dome collapse → 19 deaths, city destroyed.
Paragraph 2 – Secondary Hazards Influenced by Volcano Type
Nevado del Ruiz (Plinian + glacier): Small eruption triggered massive lahars – ~23,000 dead.
Etna: Volcanic landslides but no mass fatalities.
Montserrat: Lahars from ash + rain buried valleys.
Paragraph 3 – Atypical Eruption Types
Lake Nyos: Limnic eruption – no magma, no ash, but deadly gas release killed 1,700.
Not linked to traditional eruption type – caused by gas buildup in lake water.
Paragraph 4 – Influence of External Conditions
Eyjafjallajökull: Moderate eruption, but phreatomagmatic style + glacial melt caused global airspace shutdown.
External factors (glacier + wind) amplified hazard over eruption type.
Paragraph 5 – Preparedness vs. Type
Montserrat: Poor initial response worsened impact of Peléan eruption.
Etna: Excellent monitoring and preparedness mitigated frequent eruptions.
Conclusion
Judgement: While eruption type strongly influences hazard type, the context (e.g. glacier, human settlement, monitoring) is equally or more important. Plinian and Peléan styles are deadly, but secondary hazards and response levels can outweigh eruption type in importance.
‘Perception of risk varies depending on the type of hazard.’ To what extent do you agree?
‘Perception of risk varies depending on the type of hazard.’ To what extent do you agree?
Paragraph 1 – High Perceived Risk (Well-Known Hazards)
Japan: High risk awareness of earthquakes and tsunamis; regular drills and EEW system.
Etna: Long-term co-existence with lava flows has created strong risk awareness and systems.
Paragraph 2 – Low Perceived Risk (Rare Hazards)
Lake Nyos: No perceived risk before the event; silent gas release = high fatality.
Haiti: Earthquake risk was underestimated – no memory or preparation.
Paragraph 3 – Changing Perceptions Post-Disaster
Montserrat: Risk perception low before 1997 pyroclastic flow; now high with clear exclusion zones.
Nevado del Ruiz: Warnings were ignored; disaster changed national understanding of lahars.
Paragraph 4 – Risk Awareness vs. Resource Level
Nepal: Moderate urban awareness; rural communities lacked knowledge.
Haiti: Even if warned, poverty and poor governance limited perception and response.
Paragraph 5 – Nature of Hazard Itself
Earthquakes: High-impact, low-warning – perception depends on frequency and memory.
Volcanoes: Variable – people more fearful of pyroclastic flows than lava flows.
Conclusion
Judgement: Strong agreement – perception of risk is closely tied to hazard type, past experience, and visibility. Rare, silent hazards (e.g. CO₂ gas, lahars) are underestimated; frequent visible hazards (e.g. lava, shaking) are better perceived, especially in HICs.
‘It is more difficult to produce a hazard map of earthquakes than for volcanic eruptions.’ How far do you agree?
‘It is more difficult to produce a hazard map of earthquakes than for volcanic eruptions.’ How far do you agree?
Paragraph 1 – Predictability and Monitoring
Volcanic eruptions (e.g. Etna, Iceland): Seismic swarms, gas emissions offer early warning.
Earthquakes (e.g. Haiti, Nepal): Cannot be precisely predicted in time; no foreshock systems fully reliable.
Paragraph 2 – Mapping Based on Past Data
Volcanoes: Lava flows, ash zones, pyroclastic paths can be modelled from past eruptions (e.g. Montserrat hazard zones).
Earthquakes: Seismic hazard maps (Japan) rely on fault mapping, but earthquake intensity and exact epicenter are uncertain.
Paragraph 3 – Variability of Secondary Hazards
Volcanoes: Lahars and ash can be modelled with topography (e.g. Nevado del Ruiz), but influenced by rainfall/glacial melt.
Earthquakes: Tsunamis and liquefaction vary drastically depending on terrain and soil type (e.g. Japan vs. Nepal).
Paragraph 4 – Resource and Data Availability
HICs (e.g. Japan) produce accurate seismic hazard maps using dense instrumentation.
LICs (e.g. Haiti): Limited mapping due to lack of investment and monitoring tech.
Paragraph 5 – Complexity of Each Hazard Type
Volcanoes: More site-specific; easier to model for specific volcanoes.
Earthquakes: Can occur over vast fault systems; rupture propagation is poorly understood.
Conclusion
Judgement: Earthquake hazard mapping is more difficult overall due to unpredictable timing and widespread impact zones. Volcanoes, though dangerous, are more spatially and temporally constrained, making them easier to model when monitoring systems are in place.
