2 What is this option about? The Tectonic Activity and Hazards option focuses on the range of natural hazards generated by plate tectonicsIn addition to understanding why these hazards happen, you will need to understand:The impact of tectonic processes on the landscapeThe impact of tectonic hazards on peopleThe ways in which people respond to, and try to manage, natural hazards.Primary hazardsSecondary hazardsEarthquakesTsunamiLandslidesLiquefactionVolcanoesLahars
3 Tectonic activity and causes Tectonic hazards physical impacts CONTENTSTectonic activity and causesTectonic hazards physical impactsTectonic hazards human impactsResponse to tectonic hazardsClick on the information icon to jump to that section.Click on the home button to return to this contents page
4 1. Tectonic activity and causes Tectonic activity can produce a very large range of hazard eventsNot all of these events are ‘disasters’A natural hazard event becomes a disaster when the event causes a significant impact on a vulnerable population.These impacts could be human (death, injury) and / or economic (property losses, loss of income).Definitions vary, but ‘significant’ losses usually means 10+ deaths / 100+ affected / $1 million losses.The Dregg disaster model
5 Event profilesNot all tectonic hazards are the sameEvent profiles are a common way of comparing different hazardsIn this example the 2004 Asian Tsunami and ongoing eruption of Kilauea on Hawaii are comparedHazard profiles can be drawn for any event.
6 Earth’s heat engineTectonic processes are driven by radioactive decay in the coreThis decay generates heat inside the earth, which drives vast convection currentsThis convection is largely responsible for plate movement
7 Tectonic settings and plates Most tectonic hazards are concentrated at plate margins (boundaries), although ‘hotspots’ are a notable exception.Different types of boundary generate very different tectonic hazards.
8 The range of volcanic hazards Dangerous volcanic hazards are found along subduction zones at destructive plate marginsThe most dangerous volcanoes are themselves multiple hazard areas.Volcanoes at constructive plate margins (Iceland) and oceanic hotspots(Hawaii) are much less hazardous and destructive.
9 Magma generationMagma, molten rock in the earth’s crust, has an important relationship with volcanic explosivity and hazard levelAndesitic magmas, formed by wet partial melting at subduction zones produce highly explosive and destructive composite volcanoesMagmatypeGenerationTectonic settingHazardsBasalticLow silica, low gas, low viscosity.Dry partial melting of upper mantleOceanic Hot spot (Hawaii)Constructive (Iceland)Lava flowAndesiticIntermediateWet partial melting of subducting platesDestructive plate margin (Andes)Island arc margin (Montserrat)Lava flow, ash and tephra, pyroclastic flow, lahar, gas emissionRhyoliticHigh silica, high gas, high viscosity.In situ melting of lower continental crust(very rare eruptions)Continental Hot spot (Yellowstone)Continent collision zone (Himalayas)Cataclysmic explosion, pyroclastic flow
10 Measuring volcanic explosivity: The Volcanic Explosivity Index (VEI) is used to measure volcanic power.VEI measures: Volume of ejecta Height of the eruption column Duration of the eruption.Modern humans have never experienced a VEI 7 or 8
11 EarthquakesEarthquakes are a very common, sudden release of energy that generate seismic wavesMost occur along faults (cracks in the earth’s crust) which become ‘locked’Opposing tectonic forces push against the locked fault, building up strain, which eventually gives way releasing stored energyThis energy spreads out rapidly from the earthquake origin (the focus) reaching the surface at the epicentre, and then spreading horizontally.
12 Tsunami Tsunami are relatively rare events. They are generated by submarine earthquakes, volcanic collapse, and coastal landslides, which suddenly displace huge volumes of waterThe 1993 Okushiri tsunami (Japan), 2004 Asian Tsunami and 2009 Samoa events are all useful as case studies.Tsunami waves are radically different from normal wind generated ocean waves.When a tsunami hits a coastline, the effect is more like a devastating coastal flood than a single breaking waves
13 2. Tectonic hazards physical impacts Tectonic processes play a key role in forming the landscape around usVolcanic activity and the movement of tectonic plates create mountains, plateaux and other landscape featuresThese landscapes are then modified by geomorphological processes (weathering, rivers, ice, wind and slope processes)
14 Magma type and volcano morphology Volcanoes are extrusive igneous landforms. The form of volcanoes is related to magma types, and therefore to different tectonic settings:Basaltic – huge, low relief shield volcanoes plus small scoria cones and fissure vents.Andesitic – steep sided strato-volcanoes; layers of lava, ash and tephra.Rhyolitic – central craters with lava plugs / domes, due to high viscosity of the lava. Calderas and collapse calderas.
15 Extrusive igneous activity Large scale outpourings of basaltic magma, called flood basalts, have occurred at various times in the past.These produce distinctive lava plateaux and stepped or ‘trap’ topography
16 Intrusive igneous activity The injection (intrusion) of magma below the surface can produce characteristic landformsIgneous rock normally resists weathering and erosion in comparison to surrounding rocks, which produces positive relief features.Large intrusions such as batholiths produce upland areas, whereas minor intrusions produce smaller landscape features
17 Earthquakes and faults Tectonic movements and movements along faults (which generate earthquakes) also produce distinctive landforms and relief:Note: diagram not to scale
18 3. Tectonic hazards human impacts Living in areas of tectonic risk?Ignorance of the risks and / or underestimation of riskInertia; always lived thereNowhere else to go / lack of alternativesChoice e.g. fertile farmland or tourismA surprising number of people live in areas of active tectonic processesMajor tectonic hazards can strike with devastating forceThe 2005 Kashmir Earthquakes killed around 85000, the 2008 Sichuan ‘quake over 65,000 and 200,000+ died in the 2004 Asian TsunamiIt is important to consider why people live, in such large numbers, in areas of great risk
19 ImpactsEvery hazard event is different, and therefore the specific impacts of disaster varyWhen researching case studies, it is important to be able to identify specific impacts and be able to explain theseSome impacts are tangible and can be given a financial value. Others are intangible, such as the destruction of a temple or artwork.Many losses are direct and immediate such as property damage, but others are indirect – these come later and are harder to quantify, such as stress and psychological damage.Impacts are often considered as human (death, injury, illness), economic (property loss, loss of income, cost of relief effort) and physical (changes to landscape and topography).
20 (South Asian) Earthquake (Wenchuan) Earthquake Examine the two earthquakes below and consider how factors such as economic development, building types, the geography of the area affected and the relief effort may have affected the impacts(South Asian) EarthquakeOctober 2005, Kashmir(Wenchuan) EarthquakeMay 2008, Sichuan, ChinaDetailsMagnitude 7.6. Huge number of landslides accounting for 30%+ of deathsMagnitude 8.0. Thrust fault at continentcontinent convergenceFault displacementLargely horizontaldisplacement of up to 10mUp to 5m vertically and 4m horizontally at the surfaceFocus depth10 km19 kmAftershocks900+ over magnitude 4.0250+ aftershocks over magnitude 4.0Deaths80,00070,000People affected8 million3-4 million homeless15-30 million5 million homelessInjuries200,000+380,000Damage estimateUS$5 billionUS$150 billionBuildingsAround 1 million damaged/ destroyed / severely damagedOver 2 million damaged200,000+ buildings destroyed
21 Developed versus developing world Death Toll Event Location Date5,115Mount Kelut eruptionIndonesia199123,000Nevado del Ruiz eruptionColombia198525,000Spitak EarthquakeArmenia198830,000Bam earthquakeIran200335,000Manjil Rudbar earthquake199036,000Krakatoa eruption tsunami188366,000Ancash earthquakePeru197069,197Sichuan earthquakeChina200886,000Kashmir earthquakePakistan2005100,000TsunamiMessina, Italy1908105,000Great Kanto earthquakeJapan1923230,000Indian Ocean tsunamiIndian Ocean2004245,000Tangshan earthquake1976It is often said that disaster impacts in the developed world are largely economic, whereas in the developing world they are human (death).You should carefully consider if this generalisation is true. (see the table, right)The 1995 Kobe earthquake in Japan and 1991 eruption of Mt Pinatubo in the Philippines are useful examples to consider
22 Impacts over timeA simplified version of Park’s hazard response model is shown belowDifferent hazard events have different impacts, shown by the speed of the drop in quality of life, the duration of the decline, and the speed and nature of recovery.The differences in the 3 lines might be related to type of hazard, degree of preparedness, speed of the relief effort and the nature of recovery and rebuilding.
23 4. Response to tectonic hazards Do nothing (ignore the risk)Move to a safer locationAttempt to prevent the hazardAdapt lifestyle to the hazardPeople cope with natural hazards in very different waysThe chosen ways are often related to wealth and access to technologyHumans do have a capacity to ignore or seriously underestimate risk, even when it seems obvious to othersOften it may seem obvious that people should move out of harms way, but in reality this may be impossible.
24 Hazard modificationSeveral different approaches can be taken to reduce the impacts of tectonic hazards:Modify the event (hazard mitigation)Modify human vulnerabilityModify the lossTsunamiCoastal defences and engineeringWarming and prediction systemsCoastal zone management and landuse planningProvision of emergency kitsLoss modification involves immediate rescue efforts, followed by relief efforts which focus on food, shelter, water and sanitation.Insurance can help recovery.Long term reconstruction is needed.EarthquakesNot possibleGround shaking and liquefaction risk mappingAseismic buildingsEarthquake education and drillsPrediction not possibleVolcanoesLava diversionMonitoring, prediction warning and evacuation systemsHazard mapping e.g. lahar riskEducationShelters
25 The hazard management cycle Successful hazard management involves a cycle (see diagram) which focuses on the 3 types of modification from the previous slide.A focus on modifying loss only, will not improve survival chances when the next hazard strikesLong before a natural hazard event, there needs to be a focus on mitigation and prevention (if possible) as well as human preparedness.