Tectonics Flashcards
Jökulhlaup
A glacial outburst flood
pyroclastic flow
a mixture of rock fragments gas and lava that travels quickly
lahar
a volcanic mudflow comprised of fine sand and silt
tephra
materials such as rock fragments ejected into the air during a volcanic eruption
magnitude
the strength of an earthquake
intensity
the power of a hazard
benioff zone
the area where friction is created between colliding tectonic plates
fault line
a place where the fault can be seen or mapped on the surface
divergent/constructive boundary
plates move away from each other
convergent/destructive boundary
plates move towards each other
conservative plate boundary
plates slide past each other horizontally
what is the hazard-risk equation?
risk = (hazard x vulnerability) / capacity to cope with
name two pressures in the pressure and release model
technological accidents and conflicts
define a disaster
a hazard that has an adverse affect on people or property
What does the Richter scale measure?
The Richter scale measures the magnitude of an earthquake based on the amplitude of seismic waves.
What does the Mercalli scale measure?
Mercalli Intensity scale assesses the intensity of an earthquake based on observed effects and damage to structures, as perceived by people.
What is VEI and what does it measure?
VEI stands for Volcanic Explosivity Index. It is a scale used to measure the magnitude of volcanic eruptions based on the volume of volcanic material ejected, the height of the eruption column, and other factors.
what are the four stages of the hazard management cycle? (the first one is literally 2 things they’re so stupid for calling it the 4 stages girl yk it’s 5) (HINT: P(M)PRR)
prediction/mitigation, preparedness, response, recovery
what is a hydrometeorological hazard?
In simpler terms, a hydrometeorological hazard is a dangerous event caused by weather or water, like floods, storms, or hurricanes.
what are earthquake hazard profiles?
Earthquake hazard profiles provide information about the seismic risks in a specific region. These profiles include details such as the frequency and magnitude of earthquakes, the geological characteristics of the area, and the potential impact on structures and communities. Hazard maps may also be part of these profiles, illustrating areas at higher risk. Understanding earthquake hazard profiles is crucial for implementing effective building codes, emergency preparedness, and risk mitigation strategies in seismic-prone regions.
Identify one process that occurs only at destructive plate boundaries
One process that occurs only at destructive plate boundaries is subduction. In this process, one tectonic plate is forced beneath another due to their collision. As the descending plate sinks into the Earth’s mantle, it often leads to the formation of deep-sea trenches and volcanic arcs. Subduction zones are typically associated with intense geological activity, including powerful earthquakes and volcanic eruptions.
what is a secondary hazard?
an event that happens as a result of a primary natural disaster or event
Explain the tectonic hazards that may result from volcanic activity
volcanoes and earthquakes
Explain two characteristics of volcanic hotspots
a fixed magma source
the formation of volcanic island chains
Explain why volcanic eruptions vary in their magnitude
type of magma (basaltic eruptions are less explosive)
gas content (more gas = more explosivity)
volcano type
Explain the value of Park’s hazard-response curve in understanding the management of the impacts of tectonic hazards.
- Asses the damage to a country/region by displaying it on a disaster response curve
- Measures 3 factors: quality of life, level of economic activity and social stability
- Measures 4-5 stages
what is the value of hazard mitigation strategies?
They assist in predicting when tectonic hazards might happen, understanding the impact they could have, and figuring out how to manage and lessen their effects. These frameworks use organized ideas to make studying earthquakes and volcanoes easier and help us plan better for safety.
With reference to earthquake waves, explain two reasons why it is difficult for buildings to remain intact during an earthquake event.
- Shaking Ground:The ground shakes vigorously during an earthquake, and this shaking can cause buildings to sway or vibrate. If a structure is not well-designed or lacks proper reinforcement, it may not withstand this movement, leading to structural damage or collapse.
- Energy Transfer: Earthquake waves carry a lot of energy, and when they reach a building, that energy tries to move through and around it. If a building isn’t designed to absorb or distribute this energy effectively, it can experience stress and damage, making it challenging for the structure to remain intact during the seismic event.
Explain the link between plate boundary type and the strength of earthquake waves
Different types of plate boundaries affect how strong earthquakes can be:
- Pulling Apart (Divergent):
- Link: Earthquakes are not very strong.
- Why: Plates move slowly away from each other, causing mild shaking.
- Crashing Together (Convergent):
- Link: Strong earthquakes happen here.
- Why: Plates collide or one goes beneath the other, creating powerful shaking.
- Sliding Past Each Other (Transform):
- Link: Strong earthquakes can occur.
- Why: Plates rub against each other, building up stress and causing significant shaking when released.
Explain the geographical criteria that can be used to decide if a tectonic event is a hazard, disaster or mega-disaster.
- Tectonic Hazard:
- Criteria: Possible danger.
- Explanation: When there’s a chance of something harmful, like an earthquake.
- Tectonic Disaster:
- Criteria: Real impact.
- Explanation: When the harmful event actually happens and causes damage.
- Tectonic Mega-Disaster:
- Criteria: Extremely big and damaging.
- Explanation: When the harmful event is exceptionally powerful and causes widespread devastation.
Explain the correlation between the magnitude and intensity scales used for measuring earthquakes and their secondary hazards
The magnitude scale measures how powerful an earthquake is overall, while the intensity scale describes its effects in specific areas. Higher magnitudes indicate more power and a higher likelihood of secondary hazards like landslides and tsunamis. The intensity scale helps understand localized impacts, such as building damage, caused by these secondary hazards.
Assess the reasons why earthquakes create more disasters than volcanic eruptions
Earthquakes create more disasters than volcanic eruptions because they can happen in many places globally, affect densely populated areas, and trigger additional hazards like tsunamis and landslides, making their impact more widespread and severe. Volcanic eruptions, on the other hand, are often localized and may impact fewer people.
Assess the relative importance of the physical characteristics of volcanic eruptions in creating risk for people
The physical characteristics of volcanic eruptions, like eruption type, explosiveness, and lava flow, are crucial in determining the risk for people. The more explosive and widespread an eruption is, the higher the risk, as it can lead to lava flows, ash clouds, and other hazards that pose threats to communities. Understanding these physical traits is essential for effective risk assessment and planning for volcanic events.
where do intraplate earthquakes happen?
can happen anywhere the crust is cracked
small movements build up friction and strain overtime which suddenly releases causing low mag. earthquakes
what can isostatic readjustment cause
isostatic readjustment can cause earthquakes as the crust moves up and down
intraplate volcanoes
oceanic plates: magma rising though the mantle is able to melt its way through creating volcanoes that grow from the sea bed
continental plates: much thicker but get stretched enough in places for the magma from a hot spot to break through
mantle plumes
molten material rises from the outer core to about 700km beneath the crust or lithosphere
what do mantle plumes create
hot spots - where magma rises through the asthenosphere and may break through the crust
mantle convection
heat radiating from the inner core causes a plate to convect (travel). the convection cells make contact with the base of the crust causing friction and so drag the crust along in the general direction of the convection.
palaeomagnetism and sea floor spreading
the outer core is mainly liquid iron and it convects. This creates a magnetic field for the earth which flips every 100 000 years. When igneous rocks cool to form solid rocks they trap the magnetic field at a point in time. This can be used as a record.
subduction and slab pull
at destructive plate boundaries denser oceanic plates are subducted under less dense continental plates eg at deep ocean trenches
as a slab of oxeanic plate dcends it often pulls with some force the rest of the plate behind it
ridge push
where the new crust formed at divergent
plate margins is less dense than the surrounding crust and so it rises to form oceanic ridges
what is shown by magnetic field directions in rocks
continents have moved and rotated
plate boundary diagrams
at what boundary do the strongest earthquakes occur
destructive: this is where here is the greatest friction and build up of pressure betwen plates
destructive plate boundaries = most destructive
when are volcanoes more explosive
where the magma is viscous with a high silica and gas content. These are usually found at destructuve plate margins with subduction where the subducted plate is melted usually under a continental plate
what are the 3 types of earthquake waves
P (primary) waves, S (secondary) waves and L (Love) waves
primary waves
arrives first, moves fast and throigh solid rock and fluids, compresses in the direction of travel
secondary waves
slower than P waves and moves more up and down only through solid rock
love waves
only travels through the surface of the crust, fastest of the surface waves and moves from side to side horizontally as it moves forward
how do waves move the ground in different ways and what differing effects do they have?
Shockwaves move the ground in different ways, with S waves being the most damaging of the body waves due to high amplitude (up and down) and slow speed. Love waves are the most damaging of the surface waves, arriving after P and S waves have weakened buildings
what are some hazards caused by earthquake waves?
crustal fracturing
ground shaking
liquefaction
landslides
crustal fracturing
primary
shockwaves travel quickly through rock and can increase stress until the rock fractures
causes faults which can rupture causing damage to anything on them
ground shaking
primary
happen quickly in short bursts and multiple directions
buildings may be damaged or collapse whch presents a real threat to their inhabitants
liquefaction
secondary
occurs when shokwaves travel through loose unconsolidated material shaking it so that it acts like a fluid
causes buildings to tilt or collapse and threatens underground cables or pipes
landslides
secondary
shockwaves loosen rock on steep slopes causing it to move downslope en mass
may hit settlements or block roads
ash falls
– Forced to a high altitude so they can be carried around the planet in the atmosphere and disrupt flight paths
– can fall locally causing roofs to collapse.
– can get into machinery and electronics causing them to fail
pyroclastic flows
– Dense mixture of superheated solid particles (tephra) and poisonous gases which erupt from a crater moving down the side of a volcano.
– travel at great speed of up to 700 km an hour
– can cause flooding due to blocked River channels
gas eruptions
- gases such as sulphur can cause acid rain when combined with water vapour damaging water and plants.
– sulphur may also cool the Earth when it’s carried high into the atmosphere by blocking the sons energy. This can cause crop failures and famine.
lava flows
– Molten magma is erupted from volcanoes flows down the sides until it calls
– Basaltic lava flows fastest making it the most dangerous
lahars
– A mixture of water and erupted volcanic material various sizes
– flow very fast (60 km an hour) down River valleys.
– the water make come from rainfall, a crater lake, or the melting of snowcap on the top of a volcano
jokulhlaups
– Where a volcano erupts underneath an ice cap the heat will melt some of the eyes.
– the meltwater builds up around the top of the volcano trapped by the surrounding ice.
– eventually the warm water will melt and lift the ice away from the ground causing the water to burst out from under the ice and flow rapidly to lower ground
features of tsunamis
- the largest wave is not the first
- long wavelength in open ocean but short in shallow water
- very far in deep water but slow in shallow
- low in open ocean but high in shallow
causes of tsunamis
an undersea earthquake may cause a rapid movement of the seabed. if this is up or down then water is displaced creating a wave
tsunamis can also occur due to volcanic eruptions on islands, and major landslides into the sea or underwater on the edge of continental shelves
pressure and release model
natural hazard
A natural event that causes disruption to daily lives or death and destruction
disaster
A disaster occurs when the scale of an impact of a natural hazard are great. It is measured by the number of deaths (UN suggests 500+) all the cost of the damage (millions of dollars).
mega-disaster
a mega-disaster occurs when they are over 2000 deaths as a result of a natural hazard and a GDP reduction of 5% or more.
what is the hazard risk equation?
hazard risk involves potential loss of life and injury and destruction and damage to buildings infrastructure in an area.
The equation involves consideration of the hazard, degree and frequency of exposure to the hazard, vulnerability the people and systems, and the capacity to recover.
Risk = Hazard x Vulnerability
R = H x V
resilience
The ability of capacity of community or society to withstand the effects of a natural hazard through methods of adaption and recovery
vulnerability
The extent to which community could be damaged or disrupted by hazard. Is based on the human geography of a community or area.
Factors include:
– the location of settlements
– peoples knowledge and understanding
– peoples ability to prepare, react to and withstand the effects of a hazard
– the presence of advance warning systems
– the involvement of local people in planning and preparation.
how is development measured?
– Economic development (GDP per capita)
– social development
– social and economic development (HDI)
– political development
– environmental development
trends in deaths (social)
– There are higher losses of life and developing an emerging countries then in HICS
– people developed an emerging countries are more vulnerable due to low understanding link to levels education and lower levels of technology because there’s less money to spend on a size buildings, warning systems or emergency rescue and healthcare.
– emerging countries have rapidly growing cities which increase rested denser populations and uncertainties over building codes and land use zoning
– Corruption and government departments
how are the economic impacts of a hazard different in developed and developing countries?
– When the characteristics of a tectonic hazard are comparable, it is clear that developed countries have greater costs of damage than emerging or developing countries.
– Richard countries have more expensive buildings, infrastructure and technology to be damaged.
– developing countries may only have significant construction in urban areas, if rural areas are affected by hazard cost tend to be low.
– cost to emerging countries are increasing because they have increased construction and rapid urban growth.
However even low damage costs can be expensive to poor people who have to buy new construction materials, or find a new job because their place of work has been destroyed
moment magnitude scale
- for earthquakes
- logarithmic where each level has 10x the energy of the level below
mercalli intensity scale
- for earthquakes
volcanic explosively index
- magnitude
- logarithmic scale where each level has 100 times the energy of the level below it
tsunami intensity scale
- logarithmic where each level has twice the energy of the level below
what 6 characteristics to tectonic hazards profiles consider?
– spatial predictability
– aerial extent
– frequency
– magnitude
– speed of onset
– duration
spatial predictability
an area that has never had an event will experience greater impacts as people and places will be unprepared
areal extent
The larger the area affected by the event, the greater the impact will be as more people and places are affected
frequency
an event that occurs often is more likely to create cumulative impact (although rare events have more energy)
magnitude
The greater the amount of energy released by an event, the greater the impacts are like to be
speed of onset
The faster the event occurs, the shorter the warning time and the greater the impacts as places are unprepared.
duration
The longer an event lasts, the more likely that there will be greater impacts
how can you compare hazard profiles?
– Volcanoes have very specific locations and usually give signs they are about to erupt, but earthquakes are found in broad zones and are unpredictable.
– not all under seas earthquakes produce tsunamis.
– Hazard profile showed differences in social and economic impacts between countries at different stages of development
summary diagram of influences on vulnerability and resilience
what are the reasons for tectonic disaster trends?
- population increase – more people affected.
- urbanisation rates high – more people affected in a small area.
- Widespread poverty – people living in risky areas in insecure housing.
- More expensive construction and belongings in increasing the cost of damage.
- Inequality – the increased risk of those lacking access information and services.
- Climate change – increasing the severity of climate, weather, river and biological hazards.
- Environmental degradation – reducing protection from natural systems.
- More reporting – information through media
what can be the effects of mega-disasters?
– over 2000 deaths or
– over 200,000 people made homeless or
– losses of 5% of National GDP or higher or
– dependence on external aid for one year or longer
– Global energy policies (nuclear power stations damaged)
– global and regional economic activities (international air travel disrupted)
– global pollution
– multi-national losses of life
– global temperatures and regional food supplies affected
multiple hazard zones
hazards can be grouped into several categories:
- meteorological (such as strong winds in a storm)
- hydrological (such as river floods)
- geophysical (such as tectonic and mass movements)
- climatological (such as long term drought)
- biological (such as a diseas)
what are some deadly combinations of multiple hazard zones?
- volcanic eruptions colliding with heavy rains or tropical cyclones; produces a heavy rain and tephra mix creating lahars
- earthquakes in remote areas of developing countries where there are no health services may lead to outbreaks of disease, where there is no clean water and medicine
predicting and forecasting: earthquakes
- predicting the TIMING of earthquakes is impossible
- there is some evidence that animals and birds can sense danger but only just before
- modern seismic monitoring and communications allow for warning to be given minutes before shockwaves arrive
- foreshocks can be an indication of a larger event but the pattern is not certain until after
- The absence of earthquakes along and known fault as a concern as it shows that stress and strain a building up instead of being released by smaller earthquakes.
– earthquakes may travel along a fault line overtime until it’s possible to say which part of the fault will move next (but not when)
– some faults are unknown and earthquakes catch people by surprise
predicting and forecasting: volcanoes
– Volcanoes have a fixed location and this allows constant monitoring. However constant monitoring requires technology and is expensive. So many volcanoes and developing countries are not monitored.
– geological evidence of past eruptions provides clues about the type of extent of future eruptions.
– measurements can include gas emissions, harmonic tremors, bulging of the volcano, and the composition of magma. There are usually changes in these readings, before an eruption, which allows relatively accurate prediction of warnings to be given, although the exact magnitude is more difficult to forecast
predicting and forecasting: tsunamis
– Any submarine earthquake may create a tsunami, especially if it is large magnitude on subduction zones with mega thrust.
– warning systems exist in the Pacific and also in the Indian ocean (after 2004), based on size Moura readings percent buoys monitoring movement of the sea
– computer modelling has been used to predict arrival times and wave heights but does not always accurately count for ocean depth or the shape of the sea floor
why is prediction and forecasting important?
There are several groups of people (players) involved with predictable forecasting. At the forefront of these are the scientist who are working to understand the Temic processes and carry out monitoring using the latest tech technology. Prediction forecasting is hugely important to reducing future rest, although some believe it will never be possible to predict earthquakes precisely so uncertainty will always remain.
what are the three hazard management stages?
- pre-disaster:
risk assessment
mitigation/prevention
preparedness
💥warning/ evacuation
- response:
Saving people
Providing immediate assistance
Assessing damage
– post-disaster:
Ongoing assistance
Restoration of infrastructural services
Reconstruction (settlement/relocation)
Economic and social recovery
Ongoing development activities
Risk assessment/mitigation/prevention
parks model
strategies to modify events
- geographic information systems (GIS):
shows where movement was greatest and reveals where land-use zoning could be imposed including regulations requiring hazard resistant designs - hazard zones:
hazard zoning maps can forecast where the biggest dangers are. people can be prevented from living in these areas through land-use zoning. - modifying the tectonic event:
earthquakes: Modifying earthquakes as difficult because of their power and unpredictable.They can be avoided by not living near plate boundaries or faults or designing buildings to withstand powerful seismic waves.
volcanoes: modifying some volcanic hazards as possible, hazard learning maps forecast where the biggest danger are and land use zoning stops people living there; training crater lakes reduces the formation of lahars; lava flows can be diverted by barriers or diversion channels or sprayed with water to cool and slow movement.
Tsunamis: tsunamis can be modified at the coast to prevent development near the shore (building offshore barriers, higher and stronger, using natural defences like mangrove forests)
mitigation
involves actions and interventions by a community that will reduce the severity of a hazard, such as reducing vulnerability and increasing resilience
adaptations
changes or responses to a hazard situation designed to help a community cope with a hazard such as taking precautions
ways to modify vulnerability and resilience:
– Hazard risk mapping: modelling of hazard zones within an area for example liquid action areas or Lahar routes
– land use zoning: strict planning regulations to stop building in risky areas.
– food supplies: increasing food production with better storage methods
– monitoring and warning systems: to give people enough time to evacuate.
– hazard resistant designs: any construction to be built to a specification strong enough to withstand impacts.
– investment services: healthcare systems can be better prepared and education can raise the level of a community understanding of hazards and actions to take.
– improved evacuation routes: to enable people to escape in time
ways to modify loss:
– Rescue teams: fully equipped with the latest technology.
– emergency relief aid: involving food, water, sanitation and shelter as well as medical care
– community volunteers: local people specifically trained for emergency events to help guide and help other locals.
– Insurance: large or microscale insurance to reduce financial losses for individuals and families especially lively had been lost.
– evacuation: move away from the areas that may be hit again, including permanent settlement locations
– development aid: long-term assistance from other countries to help rebuild what has been lost
what is the asthenosphere?
zone of Earth’s mantle lying beneath the lithosphere and believed to be much hotter and more fluid than the lithosphere
what’s the difference between surface and body waves?
Body waves can travel through the Earth’s inner layers, but surface waves can only move along the surface of the planet like ripples on water
convection current diagram
structure it the earth with mantle plumes and hot spots
Where there is a spot of extra energy and heat a mantle plume may form which can cause a hot spot
what is paleomagnetism and sea floor spreading?
the sea floor spreads outwards because it is at a different plate margin which means it is pushing away and causing different bands of rock to face different directions depending on which direction they were pointing when the earths magnetic field were at north or south
What is a destructive plate boundary?
Where an oceanic and continental plate move towards each other
What’s a constructive plate boundary?
Where two plates (usually oceanic) pull apart
What’s a transform (conservative) boundary?
Where two plates move alongside each other (either in the same or opposite directions)
What’s a collision plate boundary?
When two continental plates move towards each other
What’s a complex plate boundary?
Where several types of plate boundary are found in a short distance
What is a volcano? What types of plate boundaries do they occur at?
An example of a tectonic hazard
They are often found at collision boundaries and can be explosive due to the mantle material and plate forcing their way to the surface
Gentle volcanic activity is found at constructive plate boundaries as mantle material moves upwards to fill the gaps left by diverging plates
What is an earthquake? What type of plate boundaries do they occur at?
Constructive plate boundaries may cause small earthquakes as there is not much friction as plates diverge
Conservative plate boundaries have a large amount of friction meaning they can cause strong earthquakes
Converging plates (destructive and collision) create the largest amount of friction and strain with earthquake focal points following the Benioff zone to considerable depths
What is an earthquake focal point?
The point where an earthquake starts is termed the focal or hypocentre and may be many kilometres deep within the earth. The point at the surface directly above the focal is called the earthquake epicentre.
The focal depth is the depth of the focal point.
What’s the Benioff zone?
The Benioff zone is a sloping region of seismic activity that occurs along a subduction zone, where one tectonic plate is forced beneath another into the Earth’s mantle. It is characterised by earthquakes that originate at varying depths, from shallow near the surface to deep within the mantle (up to 700 km). These earthquakes are caused by the friction, deformation, and melting of the subducting plate as it descends. The Benioff zone provides evidence of plate tectonics and subduction processes.
What’s a tsunami? Where do they occur?
An upward of downward movement of crust below seawater that causes it to be disturbed causing a large wave. This is associated with an underwater earthquake which links to a destructive (form of convergent) plate boundary
What’s an intraplate earthquake?
Earthquakes can happen anywhere the crust is cracked
> usually ancient faults created by previous plate movements
Small movements along these old faults build up friction and strain over time which is then suddenly released causing low magnitude earthquakes
> human activities like fracking and reservoirs can trigger tremors
How does isostatic readjustment link to intraplate earthquakes?
Isostatic readjustment is when the Earth’s crust moves up or down because of changes in weight on top of it. For example, during the Ice Age, heavy ice sheets pushed the land down. When the ice melted, the land slowly rose back up. It’s like a sponge bouncing back after being pressed. This process can also happen when lots of sediment piles up or is washed away.
It can also cause earthquakes as the crust is moved upwards or downwards as a result
What is an intraplate volcano? How is it different for oceanic and continental plates?
Volcanic activity happens in the middle of oceanic and continental plates
- oceanic plates are 7km thick and magma rising through the mantle from the edge of the outer core is able to melt its way through, forcing molten material to the surface. This creates volcanos that grow from the sea bed.
- continental plates are much thicker but get stretched enough in places that allow the magma to break through where there is a hotspot and travel up in a mantle plume
What is a mantle plume?
Molten magma rises from the outer core boundary to about 700km below the crust (lithosphere)
> there are two massive mantle plumes in the earths mantle layer, one under the pacific plate and the other under the African plate
What’s a hotspot? How do they relate to mantle plumes?
Small hotspots are created where magma rises through the asthenosphere (the weak part of the upper mantle below the crust) and sometimes breaks through the crust. Molten material from the outer core/mantle boundary can then rise quickly to the surface.
What is the asthenosphere?
The weak part of the upper mantle below the crust
What are the main parts of the earths structure?
The crust
The mantle
The outer core
The Inner core
How has the earths structure been established?
By studying the movement of seismic waves as they travel at different speeds through different material of different densities and some types, like S waves wont travel through liquid
What is mantle convection?
Heat radiating from the inner core through the mantle causes it to convect (the rising motion of warmer areas of a liquid or gas, and the sinking motion of cooler areas of liquid or gas, sometimes forming a complete cycle) as it behaves like a liquid (sometimes solid under pressure).
The convection cells make contact with the base of the crust which causes friction and drags the crust along in the direction of the convection.
What is palaeomagnetism and sea floor spreading?
The outer core is mostly liquid iron and it convects. This movement gives the earth a magnetic field which flips direction every 100 000 years.
When molten rocks cool to form solid rock they trap the magnetic field in the direction of the time they cooled.
Geological records of magnetic directions are symmetrical either side of constructive plate boundaries, proving that oceanic crust has been moving apart in places for a very long time.
What is subduction and slab pull?
At destructive plate boundaries, denser oceanic plates are sub-ducted under less dense continental plates. As a slab of oceanic plate descends it pulls the rest of the plate with it (slab pull).
What is ridge push?
where the new crust formed at constructive plate margins is less dense than the surrounding crust and so it rises to form oceanic ridges
> this may help to move the plates away from the point of divergence
What are mantle super plumes? What are they responsible for?
Mantle plumes that are responsible for pushing up the crust causing it to move or split (perhaps splitting Africa and Europe from the americas)
How do we know continents have moved and rotated over time?
The magnetic field directions locked in rocks
What are the features of destructive (convergent) plate boundaries? (What features are created because of them?)
Trenches, accretion wedges, fold mountains, continental volcanoes, earthquakes (along Benioff zones)
What are the features of constructive (divergent) plate boundaries?
Rifts
Fissures
Faults
Undersea ridges
What are the features of collision (convergent) plate boundaries?
Fold mountains
Shallow earthquakes
What are the features of transform (conservative) plate boundaries?
Major and minor fault lines and frequent earthquakes
Where are the strongest seismic waves created?
At destructive plate margins where there is more friction between two plates causing earthquakes
> tsunamis are also greater at this plate boundary
Why do transform (conservative) faults create earthquakes with strong magnitudes?
Plates try and slide past each other which causes a build up of friction and strain
Where are volcanoes more explosive? (Magma and plate boundary)
Magma that is viscous with high silicone and gas content which are usually found at destructive margins with subduction where the subducted plate is melted under the continental plate
What are the 3 types of earthquake waves?
P, S, and L waves
What are body waves?
P and S waves that travel through the earth
What are surface waves?
L waves that travel along the surface of the crust
What is a primary wave?
Arrives first and moves fast through solid rock and fluids
> compresses and expands like a slinky in the direction of travel
What’s an S wave?
Secondary wave that moves more slowly than P waves and only moves through solid rock
> moves in an up and down motion
What’s an L wave?
Only travels through the surface of the crust, fastest of the surface waves
> moves from side to side horizontally
How do shockwaves move the earth in different ways?
S waves are the most damaging of the body waves due to the high amplitude (up and down) and slow speed
L waves are the most damaging of the surface waves, arriving after P and S waves have weakened buildings
Hazards caused by earthquakes: What is crustal fracturing? What are its effects?
Shockwaves travel fast through solid rock and can increase stress in it especially if there is different rock types. This stress causes strain which will continue until the rock fractures.
This causes faults which can rupture the surface causing subsidence or uplift. Anything on these faults can get moved or damaged.
Hazards caused by earthquakes: ground shaking? Effects?
Shockwave ground movements include pushing and pulling (P), up and down (S) and side to side (L), which all happens in less than 60 seconds.
Buildings that are not aseismic may only survive some types of shaking and will be damaged. If buildings have the same resonance (the occurrence of a vibrating object causing another object to vibrate a higher amplitude) as the seismic energy, the impact is intensified.
Hazards caused by earthquakes: liquefaction? Effects?
Occurs when shockwaves travel through loose unconsolidated material, shaking it so that it acts like a liquid
> Christchurch 2011
Causes buildings to tilt over and collapse or the ground to crack. Underground infrastructure like cables and pipes may rupture.
Hazards caused by earthquakes: landslides? Effects?
Occur when there are steep slopes. Shockwaves loosen rock and cause it to move downwards under the influence of gravity
Landslides may hit settlements directly or destroy and block transport and communications infrastructure
In terms of tectonic hazards what’s the difference between a primary and secondary hazard?
Primary happens as a result of the seismic waves, secondary happens as a result of the ground shaking
Volcanic hazards: ash falls? Effects?
Ash is forced to a high altitude and can be carried around the planet via the atmosphere. A lot of ash falls locally and can cover settlements and cause roofs to collapse. It also gets into electrics and machinery causing it to fail. It may also disrupt the paths of aeroplanes.
Volcanic hazards: pyroclastic flows? Effects?
Consist of superheated solid particles (tephra) and poisonous gases erupted from a crater, moving down the sides of volcanoes at great speed. Any buildings or people in the water are destroyed on impact then buried, incinerated or poisoned. They may also block river channels and cause floods.
Volcanic hazards:
What are gas eruptions? Effects?
One of the common gases to come out of volcanoes is water vapour which may condense locally and mix with other erupted materials. Other gases like sulphur dioxide are poisonous and can cause acid rain which damages buildings, cars and plants. It can also cool the suns heat by blocking its energy.
Volcanic hazards: what are lava flows? Effects?
Molten magma that is erupted from volcanoes flows down the sides until it cools. Basaltic lava flows fastest but people can still get out the way so there is usually not as many deaths unless the eruption is at night or opens on the sides of volcanoes. However structures are often burnt.
Volcanic hazards: lahars? Effects?
These are a mixture of water and erupted volcanic material of various sizes which flow very fast down river valleys. The water may come from rainfall, a crater lake or snow caps on the volcano. These are a major hazard along valleys as lahars can speed up as they enter river valleys.
Volcanic hazards: jokulhlaups? Effects?
Where a volcano erupts underneath an ice cap causing the heat to melt the ice which causes water to build up around the top of the volcano trapped by the surrounding ice. Eventually the ice will be lifted away from the ground allowing the water to burst out and flow rapidly to the ground. Anything in its path is washed away or covered by volcanic and glacial deposits carried in the jokulhlaup.
What are some features of tsunamis?
A sequence of large waves of varying heights.
> the largest wave is not the first
Long wavelength in open ocean but short in shallow water
Very fast in deep water but much slower in shallow water
Low height in deep water but tall in shallow (up to 20x)
What are the causes of tsunamis?
An undersea earthquake at a subduction zone may cause a rapid movement of the seabed. If this movement is up or down then a column of sea water above the epicentre is displaced creating a powerful wave.
Tsunamis can also be caused by:
Violent explosive eruptions of volcanic islands
Major landslides or volcanic cone collapse into the sea
Underwater landslides at the edges of continental shelves
What is a natural hazard? (Word for word)
A natural event that causes a disruption to daily lives or death and destruction
What is a disaster?
When the scale impact of a natural hazard is great. It is measured by the number of deaths or the cost of damage (500+ or millions of $)
What’s a mega disaster?
Over 2000 deaths and a GDP reduction of 5% or more
What is adaptation?
Changes to a way of doing things so future hazards have less impact
What is recovery?
A way of returning to normal after the impacts of a hazard
What’s the hazard risk equation?
Risk (R) = Hazard (H) x Vulnerability (V)
Hazard risk - Potential loss of life and injury, and destruction and damage of buildings and infrastructure
Also considers the degree and frequency of the hazard as well as the vulnerability of the people and their capacity to recover.
What is resilience?
The ability or capacity of a community or society to withstand the effects of a natural hazard through methods of adaption and recovery.
What are some ways to adapt and recover?
Adapt:
Identify the risks of a potential hazard
Plan what to do if the hazard occurs
Implement plans to reduce the impact
Recover:
Stockpile essentials like food, water and medicine
Collect resources for repairing and rebuilding
What is vulnerability?
The extent to which a community could be damaged or disrupted by a hazard. It is based on the human geography of an area.
- location
- people’s knowledge and understanding
- people’s ability to prepare, react and withstand the effects
- the presence of advanced warning systems
- the involvement of people in planning and preparation
What is the PAR model?
Pressure and release model
Has the causes of a hazard (poor governance, political and economic systems) as well as the pressures (things that make it worse - lack of education rapid population growth, high migration and urbanisation rates) and the living conditions on one side and the geography (location, frequency, magnitude, timing, speed of onset) and tectonics (plate movements, earthquake, volcano) on the other side with the hazard risk equation in the middle.
Summarises the link between natural hazards, risk and vulnerability.
How can development be measured?
Economic development - GDP or GNI or capita
Social development - levels of education and healthcare
Social and economic development - HDI
Political development - the involvement of people in decision making
Environmental development - indicates a respect and maintenance of natural systems
What are the trends in deaths from tectonic hazards?
Deaths are a social impact
When characteristics of tectonic hazards are comparable (eg same magnitude) it shows how developing countries have a higher loss of life.
People in developing and emerging countries are more vulnerable due to:
- lower understanding linked to levels of education
- lower levels of technology due to less money to spend on Aseismic buildings, warning systems and emergency rescue and healthcare
Emerging countries like China have rapidly growing cities with denser populations and less land zoning. Corruption in government departments may also reduce the effectiveness of mitigation measures.
What are the trends in costs from tectonic hazards?
This is an economic impact
Again, tectonic hazards are comparable when they have similar characteristics like the same special extent. Developed countries have greater costs of damage than emerging.
Richer countries tend to have more expesive buildings, infrastructure and technology for a hazard to destroy. They also have higher insurance costs after.
Developing countries often only have significant construction in urban areas and if rural areas are impacted by a hazard, costs will be low.
Costs to emerging countries are increasing because they have increased construction and have rapid urban growth. However, even low damage costs can be expensive to poor people who have to buy new construction materials or find a new job because their work has been destroyed.
What are the 4 ways to measure tectonic hazards?
Moment magnitude scale for earthquakes
Mercalli intensity scale for earthquakes
Volcanic exclusivity index
Tsunami intensity scale
What are some characteristics of tectonic hazards which affect the impacts?
Spatial predictability
Areal extent
Frequency
Magnitude
Speed of onset
Duration
What is spatial predictability? How does this affect the impact of tectonic hazards?
Where you can assume a tectonic hazards which affect - usually on a plate boundary
An area that has never experienced an event will have greater impacts as people and places will be unprepared
What is areal extent? How does this affect the impact of tectonic hazards?
The area affected by a hazard
The larger the area the greater the impacts as more people and places are affected
What is frequency? How does this affect the impact of tectonic hazards?
An event that occurs often is more likely to create cumulative impacts (although rare events have more energy)
What is magnitude? How does this affect the impact of tectonic hazards?
The greater the amount of energy released by an event, the greater the impacts are likely to be
What is speed of onset? How does this affect the impact of tectonic hazards?
how quickly the peak of the hazard event occurs, with the starting time at the first point of the process towards it becoming a hazard.
The faster the event occurs the shorter the warning time and the greater the impacts as places are unprepared
What is duration? How does this affect the impact of tectonic hazards?
How long an event lasts
The longer, the more likely there will be greater impacts
What’s the difference between impacts of a tectonic hazard between a developed and developing country?
Developed: incur higher damage costs becasue there is more expensive infrastructure to damage. Even small costs create problems for poorer people.
Developing: incur higher death rates because people are more vulnerable: they lack awareness of hazards and live in buildings that have not been proofed and do not have access to communications or emergency services
How can hazard profiles be compared even if the hazards are different types?
Volcanoes have specific locations and usually give signs that they are about to erupt, but earthquakes are found in broad zones and are unpredictable. Also, not all undersea earthquakes produce tsunamis.
Hazard profiles can also show differences in social and economic impacts between countries at different stages of development.
What are the main influences on vulnerability and resilience?
Unequal access to education
Unequal access to housing
Unequal access to heath care
Urbanisation
Unequal access to income opportunities
Population density
Governance
Accessibility (distance or physical barriers)
How can accuracy and reliability be considered in large data sets?
Data collection method
Recording of costs (inflation means costs are increasing over time)
Multiple databases
Recording of deaths
Change to database content
Geological timescale
What is a mega disaster?
Over 2000 deaths
Over 200 000 people made homeless or
Losses of 5% of national GDP or higher or
Dependence on external aid for one year or longer
What’s an example of a tectonic mega disaster?
Hating 2010 which killed 300 000 people and caused a cost of 100% of GDO
What are some wider economic and human impacts of tectonic mega disasters?
Global energy policies
Global and regional activities
Global pollution
Multi national loss of life
Global temperatures
Regional food supply
How can global energy policies be changed as an impact of a tectonic mega disaster?
nuclear power stations can be damaged releasing radioactivity which makes governments concerned about their countries energy mix
How can global and regional economies activities be impacted as a result of a tectonic mega disaster?
Volcanic ash may disrupt aircraft movements over a large area. This costs airlines money in lost trade and compensation as well as stranding tourists and goods
How can global pollution be an impact of a tectonic mega disaster?
Damaged and destroyed buildings, factories and power stations emit chemicals into the atmosphere, increasing ozone depletion and global warming. Tsunamis may carry debris and contamination into the ocean where currents distribute it more widely.
How can multi national loss of life be a human impact of tectonic mega disasters?
Due to international tourism, foreigners can find themselves in disaster events. Death, upset and grief may be global or a hazard may have a big impact on more than one country
> lots of Swedish nationals were killed in the 2004 Indian Ocean tsunami
How can global temperatures and regional food supplies be an impact of tectonic mega disasters?
Large volcanic eruptions send ash and SO2 particles high into the atmosphere. These particles are carried around the world, especially if the volcano is near the equator. They block and reflect the suns heat energy causing global dimming.
What are the 5 broad groups of hazards?
Meteorological - strong winds
Hydrological - floods
Geophysical - tectonics or mass movement
Climatological - long term drought
Biological - diseases like cholera
What are multi hazard zones?
A country or region that experiences more than one of the 5 hazard groups in a short space of time. This can be deadly.
What are some of the deadliest combinations in multi hazard zones?
Volcanic eruptions may coincide with a rainy season or cyclone. This can cause lahars.
Earthquakes in remote areas of developing countries where there is no health services may cause an outbreak of diseases where there is no clean water and no medicine
How can earthquakes be predicted and forecasted?
predicting the timing of earthquakes is impossible
There is some evidence that animals and birds can seismic waves before they reach a location
Modern seismic monitoring and communications allow for warnings to be given up to a minute before shock waves arrive
Foreshocks can be an indication of a larger event but the pattern can’t be seen until after
The absence of earthquakes along a fault is usually a sign that stress is building up instead of being released by smaller earthquakes
Earthquakes may travel along a fault line over time so it’s impossible to say which area of the fault will be next
Some faults are unknown and catch people by suprise
How can volcanoes be predicted and forecasted?
Volcanoes have a fixed location which allows for constant monitoring
> however, this requires technology which is expensive as a result many are not monitored
Geological evidence of past eruptions provides clues about the type and extent of future eruptions
Measurements include gas emissions (SO2), harmonic tremors, bulging of flanks and composition of magma.
> there are usually changes in these before eruptions which allows accurate predictions and warnings to be given, although the exact magnitude is tricky to forecast
How can tsunamis be predicted and forecasted?
Any sub marine earthquake may create a tsunami, especially if it is large magnitude in subduction zones with mega thrust
Warning systems exist in the pacific and Indian oceans based on seismograph readings locating epicentres and buoys monitoring the movement of the sea
Computer modelling has been used to predict arrival times and wave height but it does not always accurately account for ocean depth or the shape of the sea floor
How do scientists play a role in prediction and forecasting?
There are several groups of people involved. At the forefront is scientists who are working to understand tectonic processes and monitor using the latest technology.
What are the stages of the hazard management cycle? What do they mean?
Mitigation: actions to reduce vulnerability before a natural hazard
Preparedness: ways in which communities can adapt to live with a natural hazard
Resilience: ability to resist, cope with, adapt to and recover from a natural hazard
Response: actions taken during and after a natural hazard to reduce impacts such as evacuation, rescue, medical care and damage assessment
Recovery: rehabilitation and reconstruction through restoring infrastructure, temporary housing, relocation and risk assessment
What’s the role of emergency planners?
The key players in the management of hazards are those involved with planning for emergencies. This may be government departments, rescue teams, NGOs and the community. Expertise and involvement will vary according to the type of country.
What are hazard zoning maps?
Forecast where the biggest dangers are by looking at where a hazard will occur (for example where a volcano is). People can be prevented from living in these areas via land zoning.
How can a tectonic hazard be modified?
Earthquakes: difficult becasue of their power and unpredictability. They can be avoided by not living in hazard zones or designing buildings to withstand waves
Volcanic: hazard zoning maps show where the biggest dangers are and land use zoning stops people living there: draining crater lakes reduces the formation of lahars, lava flows can be diverted using dikes or dams and sprayed with water to slow
Tsunamis: can be modified at the coast to prevent development near the shore by building off shore barriers, higher and stronger walls and using natural defences like mangroves
What is mitigation?
Involves actions and interventions by a community that will reduce the severity of a hazard, such as reducing vulnerability and increasing resilience.
What are adaptations?
Changes or responses to a hazard situation designed to help a community cope with a hazard such as taking precautions.
How can models be used to forecast and modify loss?
Models can be devilled to consider the future and forecast the impacts of a tectonic hazard. Models make it possible to predict the benefits of putting mitigation and adaptation measures in place.
Modifying the loss involves some key players like NGOs and insurance agencies who can help during the recovery stage.
How can vulnerability and resilience be modified?
Hazard risk mapping can help show hazard zones within an area (liquefaction or lahar routes)
Land use zoning
Food supplies
Monitoring and warning systems
Hazard resistant design
Investment in services
Improved evacuation routes
How can modifying the loss be beneficial?
Rescue teams
Emergency relief aid
Community volunteers
Insurance
Evacuation
Development aid
What is a fault?
Rocks (plates) on both sides of the fault move in the same way due to tectonic forces causing a fault to form either by extension, compression or horizontal movement (think of people in a festival crowd: everyone’s being pushed around the same way which could be away towards or horizontal to each other)
What is a rift?
Crust is pulled apart creating rift valleys
What is a fissure?
Small cracks opening in the earths surface
What are ridges?
Elevated, long, narrow bumps formed by tectonic activity. In the ocean they are created by sea floor spreading.
