Tectonic Processes and Hazards Flashcards
Trend, evidence and anomaly of location of volcanoes and earthquakes
Trend - lots of volcanoes and earthquakes along plate boundaries.
Evidence - Along north and South American
plates there are many active volcanoes and earthquakes
Anomaly - volcanoes and earthquakes where there is not plate boundaries - Pacific ocean
Oceanic plate
Newer, denser
Continental plate
Older, less dense
Example of a major crustal plate, minor and micro
•Major - African
•Minor - Cocos
•Micro - Sunda
What creates different types of plate boundaries
Plates moving in different directions and speeds
State and define the 3 plate movements
•convergent = coming together
•divergent = moving apart
•conservative = moving alongside each other
Define intra
Within
Define intra plate quakes
Occur away from a plate boundary, within the plate
Define active margins
A continental edge that is a plate boundary
Define passive margins
A continental edge that is not a plate boundary
A cluster of red dots is known as?
Episentric plate quakes
Why do scientists believe earthquakes happen at episentric plate quakes
Old faults within the rock
About earth’s crust
•Structure part: oceanic 7km thick, continental 70km thick
•Temp: about 400°C
•Density: Less dense (oceanic = 2.7g/cm3, continental = 3.3g/cm3)
•Composition: Granite (continental) and basalt (oceanic)
•Physical state: solid
•Earthquake (seismic) waves: Surface and body waves able to pass through
About mantle
•700km to 2890km deep
•Temp: 870°C
•Density: Less dense to medium density (3.3 to 5.4g/cm^3)
•Composition: Peridotite -> Upper = olivine, Lower = magnesium and solid in silicate
•Physical state: phases of liquid and solid in layers
•Earthquake (seismic) waves: Body wave pass through at variable rates due to density changes.
About outer core
•structure part: 2890km to 5150km deep
•temp: 4400°C to 6100°C
•density: Dense (9.9 to 12.3g/cm3
•composition: 12% sulphur 88% iron
•physical state: Liquid (+ generates a magnetic field)
•earthquake (seismic) waves: Only P waves able to pass through, an S wave ‘shadow zone’ created from about 105° from the focal point
About inner core
•structure part: 5150km deep to centre
•temp: 7000°C (Radioactive decay)
•density: Very dense (13.5g/cm3)
•composition: 20% nickel 80% iron
•physical state: Solid + radiates heat), maybe two parts with huge crystals aligned in opposite directions
•earthquake (seismic) waves: Only P waves read to the inner core and pass through, but their refraction at the core mantle creates a ring shadow zone between 105° and 140° from the focal point
Explain the 3 reasons plates move
•convection currents - mantle is heated closest to the core, the heated mantle rises, the mantle reaches the crust + moves under it, pulling it along, the mantle near the surface cools + sinks back to the core, completing the convection current
•slab pull - At subduction zones, the oceanic plates move into the mantle, this pulls the rest of the plate down with it, making it move faster. If a piece of the plate breaks off as it moves into the mantle, it melts and moves to the core, cooling down
•ridge push - At divergent plate margins, mantle that rises to the surface, pushes the plates apart, speeding up their movement
Explain the 4 plate margins
•divergent (constructive) - caused when two plates move apart, magma wells to the surface to fill the gaps left by the plates,
forming new crust
•convergent (destructive) - caused when the oceanic plate is subducted underneath the less dense continental plate. The oceanic plate melts as it reaches the subduction zone + can force its way to the surface as magma
•convergent (collision) - caused when two continental plates move towards each other. Fold mountains are created.
•conservative - caused when 2 plates move past each other in opposite directions or in same direction at different speeds
Explain the 3 different types of lava
•Andesitic Lava: 800-1000°C. Intermediate Silica (60%), gas content magnesium + iron. High water + hydrochloric acid. Low SO_2. gas content - 3 to 4%. Subducted oceanic plate melts + mixes with seawater, lithospheric mantle + continental rocks. Slow flow - intermediate viscosity traps gases. middle explosivity
•Rhyolitic lava: 650-800°C. high silica (70%) gas content 4-6%. potassium, sodium, aluminium + gas content. Low iron + magnesium. thick + stiff flow. very explosive
•Basaltic Lava: 1000-1200°C. Low Silica (50%), water, gases + aluminium. High CO_2, iron + magnesum. gas content low -
0.5 - 2% Thin+ runny flow. non explosive
Define lithosphere
Crust (rock part)
Define hypocentre
the focus point within the ground where the strain energy of the earthquake stored in the rock is first released. The distance between this + the epicentre on the surface is called focal length
Define epicentre
the location on the earth’s surface that is directly above the earthquake focus point where an earthquake originates
Define the 3 types of waves
•Primary wave: Arrives first, fast, moves through solid rock and fluids, pushes and pulls (compresses) in the direction that is travels.
•Secondary wave: Slower than P wave, only moves through solid rock, up and down movement.
•Love wave: Only travels through the surface of the crust, fastest of the surface waves and moves from side to side (horizontal) as it moves forward.
Definition and example of a hot spot
A small area of the Earth’s crust where an unusually high heat flow is associated with volcanic activity e.g. Yellowstone National Park
Define volcano
A volcano is a surface landform resulting from the extrusion of magma from underground
State and define Materials ejected by a volcano
•Jokulhlaup - catastrophic glacial outburst flood, rapid discharge of water, ice + debris
•Pyroclastic flows - Molten magma froths in the vent of the volcano - bubbles burst explosively + eject hot gases, pyroclastic material (glass shards, pumice, crystals + ash). The clouds can be 1000’C
•Lava - lava can be fast moving up to 15m/sec, can be viscous
•Tephra - when a volcano erupts + ejects material (rock fragments) into atmosphere
•Volcanic Gas - Water vapour, sulphur dioxide, hydrogen + carbon monoxide
•Lahars - volcanic mudflows - fine sand
+ silt material
Explain VEI
Volcanic Explosivity Index - measures the explosiveness of an eruption - open ended + ranges from 0-8
Define perception of the hazard
People’s judgements, beliefs and attitudes on the likelihood of the event
How can scientists predict/forecast volcanic eruptions
using Satelites (look for infrared radiation that indicates rising magma), ground instruments (measure gas emissions, ground deformation + resulting earthquake activity), evidence from past eruptions and hazard maps (indicate areas at greatest risk)
When do earthquakes become a hazard and what are the factors that influence this
An earthquake becomes a hazard when it impacts on people or on people’s activities. The factors that influence this are: tectonics + the global distribution of earthquakes, earthquake magnitude + depth, population density, building + structural vulnerability, extent of earthquake preparedness, levels of development and, nature of bedrock.
Where do earthquakes generally occur
At plate margins
How do we measure earthquakes
Using the Richter scale
State and explain the secondary hazards of an earthquake
•Soil liquefaction - water-saluated material - lose normal strength - behave like liquid under the presure of strong shaking. An earthquake can cause the water pressure to increase to the point where the soil particles can move easily.
•Landslides - slopes weaken + fail
•A tsunami - a series of larger waves usually caused by volcanic eruptions or underwater earthquakes
Define wavelength
distance between corresponding points of two consecutive waves
What causes a tsunami + definition + explanation
a single or series of waves generated by a sudden displacement of water in the ocean, can have massive wavelengths up to 100km, waves can be an hour apart + travel up to 800km/h - an earthquake happens under the sea - lifts up water - wave radiates outwards - starts low + large wavelength - shallow water - slow increase height - gravity collapses it - 5th wave could be largest
Wave shoaling
When tsunami waves increase in height when they reach shore
Factors affecting the impacts of a tsunami
•large events will cause more damage
•more distance = less effects
•shallow water = larger waves
•less impacts if coral reefs / mangroves
present
•night = more impacts - unaware
•tourism = more impacts - busier
undeveloped - poor quality homes.
Define hazard
a perceived natural event that has the potential to threaten both life and property
Define disaster
the reality of a hazard happening; when it causes a significant impact on a vulnerable population
What does Deggs Model say
shows the interaction between hazards, disasters + human vulnerability. Disaster may only occur when a vulnerable population is exposed to a hazard
What causes a disaster
Disaster vulnerability + hazard event = disaster
Disaster vulnerability:
-Underlying causes of vulnerability
• Poverty (limited access to power, infrastructure and resources)
• Failing political, social and economic systems
-Pressures
-Local scale
• Lack of education and training, food security, ethical standards
-Macro scale
• Rapid population change
•Rapid urbanisation
• Debt repayment issues
• Over-exploitation of resources/ deforestation
-Unsafe conditions of population
-Physical environment
• Dangerous locations
•Unprotected buildings
-Socioeconomic environment
•Weak local economy - poverty
• Lack of disaster preparedness
•Hunger and disease
Hazard event:
•High winds
•Floods
•Droughts
•Landslides
•Tsunamis
•Volcanic eryptions
•Earthquakes and secondary landslides
•Biohazards and pests
Define vulnerability
The ability to anticipate, cope with, resist and recover from a hazard
Define risk
The exposure of people to a hazardous event
Define resilience
The ability to protect lives, livelihoods, infrastructure from destruction and recover after
Define mega-disaster
2000+ deaths / 200,000+ homeless / GDP of country reduced by 5% / dependence on aid from abroad for a year or more after the event
Risk equation
risk = frequency or magniude of hazard (H) x level of vulnerability (V)
————————————————————
capacity of population to cope (C)
Define physical vulnerability
When the area people are living in has increased in hazard risk because of population pressure, forcing people into riskier areas.
Define economic vulnerability
When people risk losing their jobs, assets e.g. a house, and money
Define social vulnerability
When a household or community is unable to support the disadvantaged people within it, for example political isolation may exist for the poor, females, elderly.
Define knowledge vulnerability
When people lack education or training (and therefore understanding) and there are no warning or evacuation systems in place
Define environmental vulnerability
When people live in hazard prone areas in buildings that offer little protection
Factors that increase/decrease vulnerability
Increase:
•Ageing population
•Over reliance on technology to fix things
•Loss of community memory about hazards
•Environmental degradation
•Ageing infrastructure
•Population growth
•urbanisation and urban sprawl
•greater reliance on water, power and communication systems
Decrease:
•Warning and emergency response systems
•Insurance
•Hard engineering
•Economic wealth
•community initiatives
•government disaster assistance programmes
•scientific understanding
Vulnerability quadrant (Philip Allan)
represent how at risk + vulnerable a place is
High risk, high security (e.g. California)
Low risk, high security (e.g. UK)
High risk, low security (e.g. Haiti, Bangladesh, Somalia, Mali)
Low risk, low security (e.g. Bolivia, Angola)
Factors that increase/decrease resilience of a community
Increase:
•disaster preparedness plans
•good communication systems
•Efficient emergency services
•Positive attitude of people
•Pre-planning
•Medical services & supplies available
•good education and practised hazard responses
•’open’ political regime
•Accessibility of areas
•Wealth of a nation
•Emergency procedures
•An Integrated Infrastructure
Decrease:
•Low Doctor Patient Ratio
•Large scale rural to urban migration
•Unequal Trade Arrangements
•Lack of revenue
•An unrealistic perception of the disaster
•Foreign Debt repayments
•rapid population growth
•a lack of skills
•environmental degradation
Resilience framework
vulnerability adaptability
————> —————>
Exposure -> Damage -> Recovery
<—————-
Adaptation
<—————————————
Mitigation
-> Current Resilience Cycle
<- Next Resilience Cycle
What makes people change their reaction to a hazard
The level of risk
What makes you more at risk to a hazard
Old or very young
The pressure and release model
(V1 x V2 x V3 = V)
The progression of vulnerability:
•Root causes (V1)
-economic systems
-political systems
-limited access to: power, structure, resources
•Dynamic pressures (V2)
-lack of: local institutions, training, skills, local investments, local markets, press freedom, ethical standards
-macro-forces: rapid population change, rapid urbanisation, arms expenditure, debt repayment schedules, deforestation, decline in soil productivity
•Unsafe conditions (V3)
-Dangerous location, unprotected buildings
-livelihoods at risk, low income levels -special groups at risk, lack of local institution
-lack of disaster preparedness, prevalence of endemic diseases
Hazards:
earthquake, high winds, flooding, volcanic eruptions, landslides, drought, virus + pests, fire
Disaster:
Risk = hazard x vulnerability
Define duration
the length of time that a hazard lasts for - the longer the hazard the more severe it is likely to be
Define magnitude
the strength of a hazard - the stronger the more severe - measured on a scale
Define frequency
the return interval of hazards of certain sizes - if the hazard is a less frequent strong event = bigger impact
Define speed of onset
if the peak of the hazard arrives first or arrives quickly - affects are worse
Define regularity
if hazard happen often + in quick succession - greater damage
Define predictability
some hazards are easier to predict than others - hazards that hit with no warning are going to be more serious
Define spatial concentration
Where hazards are located or centred - in known areas = better prepared for + managed better
Define areal extent
if a hazard covers a large area = more severe
Define number of hazards
if a location is hit by multiple hazards that the affects can be more severe
Mercalli scale
I - Not felt - Changes in level and clarity of well water are occasionally associated with great earthquakes at distances beyond which the earthquakes felt by people.
II - Felt by a few - Delicately suspended objects may swing
III - Felt by several; vibration like passing of truck - hanging objects may swing appreciably
IV - Felt by many; sensation like heavy body striking building - dishes rattle - Walls creak; window rattle
V - Felt by nearly all; frightens a few - pictures swing out of place; small objects move; a few objects fall from shelves within the community - A few instances of cracked plaster and cracked windows with the community - Trees and bushes shaken noticeably
VI - Frightens many; people move unsteadily - Many objects fall from shelves - A few instances of fallen plaster, broken windows, and damaged chimneys within the community - Some fall of tree limbs and tops, isolated rockfalls and landslides, and isolated liquefaction
VII - Frightens most; some lose balance - heavy furniture overturned - Damage negligible in buildings of good design and construction, but considerable in some poorly built or badly designed structures; weak chimneys broken at roof line, fall of unbraced parapets - Tree damage, rockfalls, landslides, and liquefaction are more severe and widespread wiht increasing intensity.
VIII - Many find it difficult to stand - Very heavy furniture moves conspicuously - Damage slight in buildings designed to be earthquake resistant, but severe in some poorly built structures. Widespread fall of chimneys and monuments.
IX - Some forcibly thrown to the ground - Damage considerable in some buildings designed to be earthquake resistant; buildings shift.off foundations if not bolted to them.
X - Most ordinary masonry structures collapse; damage moderate to severe in many buildings designed to be earthquake resistant.
Richter scale
Higher = worse
Higher is less likely
What does Volcanic Explosivity Index (VEI) measure
•Volume of tephra (in m^3)
•How often
•VEI - 0-8
•Eruption type ( VEI range)
•plume height
Larger VEI = more explosive, more tephra, higher plume
What does Moment Magnitude Scale (MMS) measure
Magnitude
Number of Earthquakes per year (worldwide)
Energy release (equivalent kilograms of explosive)
Why are there more reported disasters but the number of disasters remain steady
- Improved monitoring + recording
- Improved communication technology - more reported
- Increased population
- increased occupied living space - more impermeable surfaces = increased risk of flood
Scales the measure hazards
Richter Scale - Earthquake - 0-9 - A measurement of the height (amplitude of the waves produced by an earthquake. The Richter Scale is an absolute scale; wherever an earthquake is recorded, it will measure the same on the Richter Scale.
Mercalli Scale (modified) - Earthquake - I-XII - Measures the experienced impacts of an earthquake. It is a relative scale, because people experience different amounts of shaking in different places. It is based on a series of key responses, such as people awakening, the movement of furniture and damage to structures.
Moment Magnitude Scale (MMS) - Earthquake - 0-9 - A modern measure used by seismologists to describe earthquakes in terms of energy released. The magnitude is based on the ‘seismic moment’ of the earthquake, which is calculated from: the amount of slip on the fault, the area affected and an Earth-rigidity factor. The USGS uses MMS to estimate magnitudes for all large earthquakes.
Volcanic Explosivity index (VEI) - Volcanic Eruption - 0-8 - A relative measure of the explosiveness of a volcanic eruption, which is calculated from the volume of products (ejecta), height of the eruption cloud and qualitative observations. Like the Richter Scale and MMS, the VEl is logarithmic: an increase of one index indicates an eruption that is ten times as powerful.
Examples of disasters
Earthquakes:
Haiti (LIC)
Turkey Syria (LIC)
New Zealand/Christchurch (HIC)
Volcanic Eruption:
Eyjafjallajökull (HIC)
Hunga Tonga (LIC)
Mt Pinatubo, Philippines (NIC)
Indonesia (HIC)
Tsunami:
Asian (LIC)
Japan (HIC)
Managing tectonic hazards
-evacuation zones
-warning system - sound or to phones
-education on how to respond
-Safety equipment
-emergency shelters
-Specifically structured buildings - tsunami, houses on stilts
- earthquake proot furniture
-bunkers
-land use zoning
-forecasting
-Tsunami wall
What are hazard profiles
compares the physical processes all hazards share - which Should be given most attention and resources. Compare the same hazard in different locations.
Disasters and development
-Disasters limit or destroy development - damage infrastructure, destruction of workers
-Development causes disaster risk - inequity
-Development reduces disaster risk - Safe drinking water
-Disasters create development opportunities - rebuild, aid
Governance
Governance - how well run a place is - fair, Safe, healthy, educated
- continuing process
- The sum of the ways individuals + institutions, public & private, manage their common affairs.
National Disaster Management Agencies - FEMA is USA, PHIVOLCS in Philippines
Factors of Governance:
1) meeting basic needs - food, water, health
2) Planning- reducing risk from hazards
3)environmental management - too much deforestation? Monitor hazards?
4) Preparedness - education of hazards
5) corruption - spend hazard money or are they bribed?
6) Open-ness - can be held to account + communicate with the news + media organisations
Define corruption
illegal practices (accepting bribes designed to influence decision making or paying people to stay silent about known problems)
Define land-use zoning
A planning tool used to decide what type of buildings (residential, commercial, industrial or none) are allowed in particular locations
Sendai framework
•What is it? For disaster risk reduction - call to action over the next 15 years
•Targets? Substantially reduce people affected globally, reduce mortality, less injured or homeless, economic loses, reduce damage to infrastructure, increase communication, increase early warning systems
•Priorities:
1) understanding disaster risk
2) strengthening disaster risk governance
3) investing in disaster risk reducion for resilience
4) importance of disaster preparedness
Patterns between the 4 hazards
In 2004 - 2014 tectonic hazards had a low occurrence compared to hydrological and meteorological hazards + a much lower number of victims compared to the other three hazards (climatological, hydrological + meteorological)
The overall longer-term natural hazard trends since 1960
•The total (aggregate) number of recorded hazards has increased over the last 50 years
•decrease in reported disasters, had an abnomal peak in early 2000s
•deaths lower than in recent past, but there are spikes with mega-events
•increase in people affected for some hazard + disaster types, especially meteorological + hydrological
•increase of economic costs of hazards + disasters
Reporting disaster impacts
-whether direct or indirect deaths are counted
-local or regional events in remote places are often under-recorded
-declaration of disaster deaths + casualties may be subject to political bias
-Statistics on major disasters are difficult to collect, particulary in remote rural areas of low human development countries
-time-trend analysis is difficult, much depends on the intervals selected + if the means of data collection have remained constant, trends can be upset by a cluster of mega-disasters
Tectonic mega-disasters
-large-scale on either an aerial/spatial Scale or in terms of their economic or human impact
-they pose serious problems for effective management to minimise impact
-communities often require international support
Tectonic mega-events + disasters
often classified as high-impact, low-probability (HILP) events. A high-profile crises require rapid responses at a global level.
The globalisation of production + supply chains
Has increased manufacturing efficiencies, but decreased resilience in some events. High-value manufacturing is often most at risk because of its just-in-time (JIT) business model
Where do metrological hazards occur
Between the tropics, near North America, Australia and the south of Asia
Where do tectonic hazards occur
Near the plate boundaries, on the west coast of north and South America
How to assess risk of damage + death
Estimate by combining exposure of 6 major natural hazards
Define disaster hotspot
A country or area that is extremely disaster prone for a number of reasons e.g. tectonic + metrological
Define megacity
A city with a population of over 10 million
Why are mega cities so vulnerable
-large population
-tall buildings
-density
-increased building density
-lack of healthcare
-informal housing
-deforestation, reduce interception, more impermeable surfaces, greater flood risk
-concentrated political, economic and other resources - implications for global financial markets
Multi-hazard zone examples
•California coast
•Philippines
Influences to how people cope with a multi-hazard zone
Experience, material well-being, personality
3 responses to multi-hazard zones
Do nothing and accept the hazard, adjust to the situation of living in a hazardous environment or leave the area
Level of adjustment will depend on the risk caused by the hazard:
Identification of the hazard, estimation of the risk (probability), evaluation of the cost (loss)
3 options of adjustment to the hazard
Modify the loss burden (insurance, disaster relief), modify the hazard event (food relief schemes, seawalls, avalanche shelters, etc), modify human vulnerability to hazard (emergency procedures, forecasting, warning)
Prediction and forecasting of tectonic hazards
Volcanoes: easiest to predict/forecast
•seismic activity
•gas emissions
•ground deformation
•thermal imagery
Earthquakes: hard
•historical patterns
•foreshocks
•seismic gap theory
•monitoring of plate movements
Tsunamis: hard
•seismic detection
•tsunami warning systems
•numerical models
Define and explain the hazard management cycle
continuous process used by governments, emergency services, and local communities to reduce the impact of natural hazards
•mitigation - land use zoning, building structures
•preparation - early warning systems, evacuation routes, supplies, public awareness, plans
•response - search + rescue, evacuation, rebuild
•recovery - food + shelter, rebuild
Define prediction
Knowing when, and where, a natural hazard will strike on a spatial and temporal scale that can be acted on effectively
Define forecasting
Provides a ‘percentage chance’ of a hazard occurring, e.g. a 25% chance of a magnitude 7 earthquake in the next 20 years
Define seismic gaps
Areas that haven’t experienced an earthquake for some time and are ‘overdue’
Park hazard response model
•stage 1 - modifying the cause and event
•stage 2 - hazardous event
•stage 3 - search, rescue and care
•stage 4 - Relief and rehabilitation period - may include outside help (national or international)
•stage 5 - Nature of recovery related to:
-the need to reduce vulnerability
-the need to restore normality as soon as possible
Define hazard mitigation
Strategies meant to avoid, delay or prevent hazard events
Define hazard adaptation
Strategies designed to reduce the impacts of hazard events
Hazard management strategies
•Hi-tech monitoring
•crisis mapping
•modelling hazard impact
•public education
•land use zoning
•diverting lava flows
•GIS mapping
•hazard resistant design and engineering defences
A framework for response analysis
•Modify the loss
-aid vital for poor people
-Insurance more useful for people in richer communities + countries
•Modify vulnerability
-prediction + warning
-community preparedness
-education to change behaviour + prevent hazards realising into disasters
•Modify the event
-further environmental control
-hazard avoidance by land use zoning
-hazard resistant design (e.g. - building design to resist earthquakes)
-engineering defences useful for coastal tsunami risk
-retro fitting of homes is possible for protection
•Modify the cause
-environmental control
-hazard prevention
-Only really possible for Small-scale hazards, e.g. landslides
Hyogo framework
The World conference on disaster reduction held in 2005 in Hyogo (Kobe), Japan + established a ‘framework of action’ - aims to reduce vulnerability + risks to hazards through building the resilience of nations + communities to disasters.
Sendai framework
Replaced the Hyogo framework in 2015 - 4 priories - understanding disaster risk, strengthening governance to manage disaster risk, investing in disaster-risk reduction for resilience + enhancing disaster preparednes for effective response, ‘build back better’ in recovery, rehabilitation + reconstruction
