Tectonics

What is a tectonic hazard?
a perceived natural event formed by tectonic processes, with the potential to threaten both life and property.
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Name three features formed by tectonic processes.
Ocean trench, fold mountains, rift valley, plateau, hot spot volcano, mid-ocean ridge
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What is the benioff zone?
The zone where many deep earthquakes occur, at convergent destructive boundaries when an oceanic plate is subducted, caused by slab pull
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What is a batholith?
Where viscous lava cannot break through the crust.
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How and where are fold mountains formed?
At convergent collision boundaries, where sediments trapped between the two plates are pushed upwards into jagged, steep mountains.
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How do intra-plate earthquakes occur?
Collisions fracture crust away from boundaries too, earthquakes nearer the middle of plates are associated with ancient faults, e.g. Rhine Rift Valley
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What are the main differences between oceanic and continental plates?
Oceanic are denser, thinner, younger and composed of basaltic rock. Continental are less dense, thicker, older and made of granite rock.
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How do hot spot volcanoes form?
Volcanic activity near the centre of plates where a hot plume rises, breaks the crust, cools and forms a shield volcano, as the plate moves the volcano moves too but the hot plume does not so another hot spot volcano will form over the plume.
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What occurs at a mid-ocean ridge?
At divergent boundaries a gap forms where magma rises from the mantle, it cools into rock forming new land, can create fissure eruptions when lava erupts through gap.
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Describe the features of a convergent destructive plate boundary.
Where oceanic and oceanic or oceanic and continental plates collide, causes deep, high magnitude earthquakes, explosive eruptions, ocean trenches, fold mountains, volcanic islands and benioff zones.
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Describe the features of a convergent collision plate boundary.
Where two continental plates collide, creates shallow-medium depth, moderate magnitude earthquakes, little volcanic activity, creates fold mountains and plateaus.
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Describe the features of a divergent plate boundary.
Where two plates move away from each other, creates shallow, low magnitude earthquakes, effusive volcanic eruptions, ocean ridges and rift valleys
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Describe the features of a transform plate boundary.
When two plates move side by side/ parallel, creates shallow, moderate earthquakes, usually no volcanoes, creates ridges, scars.
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List the layers of the Earth.
Inner core, outer core, mesosphere, asthenosphere, lithosphere
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How are earthquakes caused?
Friction created by masses of rock trying to move past each other, sending seismic waves from the focus in all directions.
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What are p-waves and s-waves?
A p-wave arrives first, is longitudinal, can travel through solid and liquid and least damaging. A s-wave arrives second, is transverse, can only travel through solids and is more destructive.
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What are Rayleigh waves and love waves?
A Rayleigh wave has a rolling motion, travels on the Earth's surface and is very damaging. A love wave arrives last and moves side to side as it goes forwards, on the Earth's surface, most damaging.
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What secondary hazards can earthquakes cause?
Liquefaction, tsunamis, landslides
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What is liquefaction?
Water-saturated sediment loses strength and acts fluid, can cause building damage, destroy infrastructure and wash things away e.g. in Christchurch 2011
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What are landslides?
Earthquake loosens rock and material on steep slopes, which moves downwards due to gravity, may hit settlements, block roads and infrastructure e.g. Kashmir 2005 killed 87,300
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What are tsunamis?
Sequences of waves with deep troughs between them, more noticeable in shallow water due to shorter wave length, created by water column displacement due to a plate thrusting upwards/downwards, volcanic eruptions or landslides.
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What factors impact how destructive a tsunami may be?
Distance waves travel, shoreline gradient, coastal orientation, lowlands, land uses, ecosystem buffer, timing, warnings, population density...
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What are the three types of lava?
Basaltic: hottest, least viscous, low silica, from effusive eruptions. Andesitic: medium heat and viscosity, from pelean eruptions. Rhyolitic: coolest, most viscous, high silica, from plinian/vesuvian eruptions
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What are the three types of eruption?
Effusive: non-explosive, lava wells up and overflows, basaltic, e.g. Hawaii. Pelean: explosive, dome collapses, results in lots of tephra and a fast pyroclastic flow, andesitic. Plinian/Vesuvian: reach 2-45km high, long duration, rhyolitic lava.
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What secondary hazards can volcanoes cause?
Gas, tephra, pyroclastic flows, lahars, jokulhlaups
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What is a pyroclastic flow?
Dense mix of super-heated tephra and gas, moves fast (up to 700km/h), explosive eruptions, destroys all in path e.g. Montserrat 1997
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What is a Jokulhlaup?
Flood of melt-water from underneath an ice cap/glacier when a volcano erupts underneath, deposits material in lowlands, very fast and powerful e.g. EFJ eruption 2010
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What is lahar?
Water mixed with tephra, high speed, huge volume, can travel very far, bury towns, e.g. Amero 1985
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What is volcanic gas?
Water vapour which can cause heavy rainfall or sulphur dioxide which can cool Earth or cause acid rain.
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What is tephra?
Solid and molten rock, debris, ash can cause roof collapse, prevent flights, cause breathing problems and destroy machinery.
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Describe the convection current explanation for tectonic movement?
Created in the mantle as heat radiates outwards from inner core, hot material rises, spreads out below the crust, then sinks and cools.
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Describe the paleomagnetism explanation for tectonic movement?
Four times every million years Earth's magnetic field reverses, magma rises in mid-ocean ridges, magma cools into new crust which contains iron and so the magnetic direction can be identified, a alternate pattern of magnetism can be seen.
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Describe ridge push and slab pull.
Ridge push is where magma rises and convection current pull plates apart. Slab pull is the gravitational pull of the lithosphere as it is subducted at convergent destructive boundaries as the oceanic plate sinks under the continental plate.
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Describe any other explanations for tectonic movement?
Plates fit together, matching rock types, matching fossils, coal found in tropics, glaciation in Africa, hazards occur at boundaries.
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What is a tectonic disaster?
A hazard which causes a significant impact on a vulnerable population.
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What is a mega-disaster?
Large scale, serious problems, 2000+ dead/ 200,000 homeless/ 5% fall in GDP/ international aid for 1+ year.
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What are the three ways of measuring earthquakes?
Moment Magnitude: measures energy released. Richter Scale: uses arrival time of P and S waves, amplitude of S waves and distance from epicentre. Mercalli Scale: looks at effects on Earth's surface e.g. level of destruction (1-12)
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What scale is used to measure the intensity of volcanic eruptions?
Volcanic Explosivity Index: 0-8, each step is 10x greater.
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What is used to measure the intensity of tsunamis?
Time travel maps: shows the reach and time taken for tsunami to go from centre of event to a location.
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What is the risk equation?
Risk= hazard x exposure x vulnerability/ manageability
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Define risk in the pressure-release model
The probability of harm or loss taking place e.g. deaths, injuries, loss of livelihoods, damage to property and infrastructure.
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What is vulnerability?
Human geography factors, susceptibility to loss.
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List some examples of vulnerability.
Poverty, healthcare, education, resilience, protection and preparation, governance, inequality, infrastructure, building quality
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What is resilience?
Population's ability to resist, cope with, adapt to and recover from a hazard's impact in an efficient and reasonable time.
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What does the World Risk Index consider?
Exposure, susceptibility, coping capacity, adaptive capacity, development
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What is meant by exposure?
The hazard, its frequency and intensity, the population of the area affected
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What is meant by susceptibility?
Factors like infrastructure, food security, housing, income distribution, education and healthcare.
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What is meant by coping capacity?
Governance, warning systems, healthcare, preparedness, resilience, insurance.
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What is meant by adaptive capacity?
Preparing for the future, investment, speed of response, education, strategies.
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How does development effect the damage a hazard may cause?
Developed countries may have high damage costs but can afford this, but even a small cost to a developing country may not be met, explaining their higher vulnerability. Developing countries lack income, healthcare, infrastructure and education.
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State a country who has suffered long-term impacts of a disaster?
Japan, 2011 tsunami: Fukushima nuclear explosion, loss of jobs, crops, uninhabitable areas. Haiti, 2010 earthquake
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State some trends surrounding tectonic hazards.
Frequency fluctuates, more affected today due to higher population and urbanisation, deaths decrease due to development, hydrological and meterological increasing due to climate change.
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What factors affect the reliability of tectonic statistics?
Whether indirect or direct death rate is measured, remote locations, political bias, level of development.
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Discuss earthquake prediction.
It is challenging to predict earthquakes, but high risk areas can be identified, time gaps estimate stress build up, tiltmeters measure change in movements, gases are released when plates move, changes in water level, animal behaviour, coloured skies
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What methods are used in volcano prediction?
Gravity meters, gas measurements, tiltmeters.
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What are the stages of the disaster management cycle?
Mitigation, Preparedness, Response and Recovery
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What is mitigation?
Strategies to avoid, delay or prevent tectonic hazards before the disaster, management policies to minimise vulnerability and risk.
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What are some methods of mitigation?
Zoning and land-use planning, building codes, building design (86% deaths from building collapse), education, challenge behaviours, improve emergency services, get insurance, set up charities, improve technology
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What is preparedness?
A shorter-term solution to deal with hazard event by minimising loss of life and damage, facilitates responses and recovery
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What are some methods of preparedness?
Public awareness, warning systems, evacuation routes, stockpiling.
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What is the response phase?
Responding effectively to a hazard by coping with a disaster whilst and just after it occurs, aims to save lives, protect property and make areas safe.
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What are some methods of response?
Disaster aid: protect lives, rehabilitates and reconstructs. Bottom up management: local level reconstruction. Search and rescue, evacuations, restore critical infrastructure, ensure services, NGOs, government, international aid, expertise needed.
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What is recovery?
Getting back to normal, short-term and long-term
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What are some methods of recovery?
Short-term: immediate needs, essential services, safety, power and water, transport, food and shelter. Long-term: rebuild homes, infrastructure, business and schools.
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Who are some players involved in tectonics disasters?
Local people, emergency services, government, foreign countries, charities, military, builders
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Haiti Earthquake, 2010- Vulnerability
61% educated, poor sanitation, no strategies, poorest in West Hemisphere, poverty, storms in 2008, doctor:patient ratio of 1:4000, corrupt government, no building regulations
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Haiti Earthquake, 2010- Hazard and Impacts
Magnitude 7.0, shallow focus, 52 aftershocks, 230,000 deaths, 300,000 homeless, 90% building collapse, all hospitals destroyed, slow responses, cholera outbreak, looting and chaos.
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Bam Earthquake, 2003
Vulnerability: poor, lack of specialist medical training, weak building codes, cold winter, poor infrastructure, 6.6 magnitude, shallow, 26,000 deaths.
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Christchurch Earthquake, 2011- Vulnerability
High GDP, liquefaction risk identified so $20 million spent on soil compaction, insurance $4 billion, houses reinforced.
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Christchurch Earthquake, 2011- Hazard, Impacts, Responses
7.1 magnitude, shallow, one death, 2 injured, 20,000 tonnes silt uplifted by liquefaction, destroyed some infrastructure, 80% damage to sewage systems, army deployed, 90% energy restored in a day, 16 ambulances in 30 mins, boiled water.
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China, Sichuan Earthquake, 2008- Vulnerability
Population of 15 million, industrialised, frequent earthquakes, some earthquake-proof buildings (up to 6.1)
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China, Sichuan Earthquake, 2008- Hazard, Impacts and Responses
7.9 magnitude, shallow, 69,000 deaths (1/3 children due to school time), 4.8 million homeless, medical care quickly, 1 million temporary shelters housed all, did not rely on foreign aid, military control, damaged chemical plants.
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Monserrat Pyroclastic Flow, 1997
Destroyed capital, 350,000 rescued, 200m deposits.
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Amero Lahar, 1985
Nevado del Ruiz eruption, pryroclastic flow melted snow, lahars into 6 rivers, 60km/h, 50m deep, travelled 100km, burried Amero when sleeping, killed 23,000
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EFJ Eruption and Jokulhlaup, 2010
100,000 flights cancelled, Africa lost $65 million, economy suffered, main road closed and embankments prevent flood damage, economic cost of $3 billion but 0 deaths.
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Japanese Tsunami, 2011
9.0 earthquake, 18,500 deaths, $360 billion cost, 127,500 houses destroyed, affected many Pacific countries, decline in Japanese industry, Fukushima disaster, contaminated area and food.
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Heimaey Eruption, 1973
Largest in Iceland, 0 deaths, 5300 evacuated, given accommodation and $2 million compensation, seawater sprayed to cool lava, seisometers and tiltmeters detected magma rise.
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Other cards in this set

Card 2

Front

Name three features formed by tectonic processes.

Back

Ocean trench, fold mountains, rift valley, plateau, hot spot volcano, mid-ocean ridge

Card 3

Front

What is the benioff zone?

Back

Preview of the front of card 3

Card 4

Front

What is a batholith?

Back

Preview of the front of card 4

Card 5

Front

How and where are fold mountains formed?

Back

Preview of the front of card 5
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