Tectonics - Final Flashcards
1.1B - Distribution of plate boundaries
Divergent (constructive boundaries)
- Are most clearly displayed at ocean ridges, (so think of them)
- Constructive plate margins involve two plates moving away from each other. Where this occurs magma rises through the asthenosphere to the surface of the Earth.
- Large number of (mostly submarine) shallow focus and low magnitude earthquakes.
Convergent
- Collisions between two plates, deforms the land and is a subduction zone unless its 2 continental plates. Frequent earthquakes and volcanic eruptions
Conservative (transform)
- Tectonic plates slide past each other. There is no volcanic activity associated with conservative plates, though earthquakes can often occur, friction builds up as they slide past and can causes resistance, as pressure builds, the crust can fracture releasing large amounts of energy as an earthquake. e.g. San Sndreas fault
1.1C - Intra plates
Intra plate EQs
- Ancient fault lines reactivated by tectonic stresses create weaknesses in the crust, making it vulnerable to regional tectonic activity
Hotspots
- Mantle plumes are stationary, column-like heat convection areas that generate continuous basaltic eruptions at mid-plate hotspots like Hawaii, forming volcanic island chains as tectonic plates move over them.
1.2A + B The Theory of Plate Tectonics
Tectonic plates move at 2-5 cm per year.
Discuss Alfred Wegener’s Continental Drift Hypothesis (1912), proposing continents were once joined.
Mention Arthur Holmes’ idea (1930s) of radioactive heat driving mantle convection and plate movement.
Explain palaeomagnetism as evidence for seafloor spreading at constructive margins.
Highlight how subduction and slab pull drive plate movements.
If transform zones are in the question, explain shallow focal depths causing high-magnitude, destructive earthquakes. Do not mention volcanic activity.
1.2C: Impacts on Hazards
At constructive Margins
Eruptions are small and effusive, as the erupted basalt lava has a low gas content and high viscosity. Earthquakes are shallow, less than 60 km deep, and have low magnitudes of under 5.0
Convergent margins on the other hand are a lot more impactful:
Destructive Margins:
Explosive eruptions of high gas/silica magma which is formed through wet partial melting when the descending plate begins to melt).
Benioff zone can yield large earthquakes Earthquakes up to magnitude 9.0.
Collision zones
Huge thrust faults that generate shallow, high magnitude earth quakes
1.3A Hazards caused by earthquakes
You can talk about earthquakes in general - a pulse of energy which radiets out in all directions from the focus (point of origin). The epicentre is most effected and this is the point on the earths surface directly above the focus
The overall severity of an earthquake is linked to the amplitude and frequency of the types of wave:
P waves, S waves, and L waves. Remember that P waves have the fastest arrival time, S waves shake the ground causing damage, L waves travel only on the surface with a very large amplitude, causing most of the damage
When earthquakes are mentioned, also mention crustal fracturing within the earth. e.g. 2004 indian ocean ruptured a fault line for 1000km with energy pulses generated along the fault length. Not just the focus.
Then mention secondary hazards such as large landslides in geologically young mountains, accounted for 30% of deaths in 2008 Sichuan EQ.
Mention how liquefaction undermines foundations by making water saturated material to lose strength temporarily under the pressure of strong shaking. and causes buildings to sink and collapse.
1.3B - Hazards from Volcanoes
Firstly state the primary hazards:
Lava flow, pyroclastic flow, gas
eruption and ash fall.
Also be able to indepth explain secondary hazards such as Lahars (volcanic mudflows) and Jokuhlaups
1.3C Impacts from Tsunamis
Firstly be able to recall what a tsunami is: undersea earthquakes that displace water, generating waves. As these waves approach shallow waters, their speed decreases, and their height increases, causing significant flooding. The waves can reach over 30 meters, destroying coastal infrastructure.
Then mention Secondary hazards including coastal erosion, freshwater contamination, and landslides triggered by the wave impact, which can exacerbate impacts from a tsunami
1.4A - Disasters
If a question mentions disasters, you can begin the question with explaining what it is, a natural hazard is an event with the potential to harm people and property, a disaster is a realization of the hazard, if you can remember, use the the UN definition for one ‘a serious disruption of the functioning of a community or a society involving widespread human, material, economic or environmental losses and impacts, which exceeds the ability of the affected community or society to cope using its own resources’.
On a question of disasters, use the Degg Model in some way. This shows the intersection between a hazardous natural event, such as an earthquake, hurricane or landslide and a vulnerable population which experiences human and/or economic loss, to create a disaster.
Now mention how this pairs with risk equation. risk = (hazard x vulnerability)/capacity to cope. Mention how a risk is assessed by an increase in vulnerability of the population (e.g. poverty) or by an increase in the magnitude.
Now talk about resilience - which is the communities capacity to cope, some are prepared than others so a hazard is less likely to become a disaster. It also includes the ability to return to normal following a disaster. Mention ways to increase resilience such as emergency evacuation systems, hazard resistant design or land use planning or education.
1.4B - The PAR model
Pressure and release model!
Might be its own question but can also be for a 12 marker on disasters
A model showing a progression of vulnerability
Root causes - Low access to resources, poor governance and weak economic system
Dynamic pressures - Lack of education, rapid population change due to urbanisation
Unsafe conditions - poor construction standards, poverty or slums.
The PAR model suggests that the socio-economic context of a hazard is important. In poor, badly governed (root causes) places with rapid change and low capacity (dynamic pressures) and low coping capacity (unsafe conditions), disasters are likely.
if talking about vulnerability, its easiest to link to Haiti:
Haiti:
Root causes:
Per capita GDP (PPP) US $1200
50% of the population is under 20 years old
Dynamic pressures:
Lack of education, training and investment
Rapid population change and urbanisation
Unsafe conditions:
25% of people live in extreme poverty
80% of Port-au-Prince’s housing is unplanned, informal slums
1.4C Impacts of Tectonic hazards
Emphasize how the impacts of tectonic hazards are broadly of three types: Social , economic or environmental
On a broader scheme, economic costs in developed and emerging economies are, in some cases, enormous
deaths in developed countries are low, except for the 2011 Japanese tsunami (a very rare megadisaster)
volcanic eruption impacts are small compared with those of earthquakes and tsunami.
Expand on this with case studies.
1.5A - Measuring Magnitude and Intensity
Magnitude can be seen as the size of the tectonic event
MMS
Probably the best as it is easy to compare, an objective measure which is accurate and comparable.
Moment magnitude scale, an updated version of the richter scale and it measures the energy released during an earthquake. It uses a logarithmic scale, so a 6 EQ is 10x stronger than 5
Mercalli
The Mercalli scale measures earthquake intensity on a scale of I-XII. This scale measures what people actually feel during an earthquake, e.g. intensity of shaking effects, rather than the numerical energy released. Not as good as its harder to compare earthquakes as shaking experienced depends on building type and quality, ground conditions and other factors, not tbe intensity of the actual earthquake, this is more human centered
VEI
Volcanic explosivity index which ranges from 0-8. This is the used index as it is a composite index combining eruption height, volume of material and duration of the eruption. Any scored from 0-3 are typically associated with shield volcanoes, balsaltic eruptions at constructive boundaries and hotspots. scores from 4-7 are associated with high viscocity, high gas and silica eruptions art destructive margins. VEI is basically impossible so dont worry about that. Supervolcanoes
1.5B - Hazard Profiles
Firstly talk about how you can compare the characteristics of earthquakes, volcanoes and tsunamis (magnitude, speed of onset and areal extent, duration, frequency and spatial predictability) through hazard profiles.
These give more information in comparisons rather than just ranking their size on the VEI or MMS as it shows the difference between each event.
Now talk about how different profiles present higher risks such as:
High magnitude + low frequency
Rapid onset with low spatial predictability, which could occur in numerous places without warning
Regional areal extent - affecting large amounts of people in a wide range of locations.
1.5C - Profile examples
If a question asks about how profiles differ between developing and developed nations. it is referring to this part of the spec.
for this use haiti and japan
Haiti (2010 Earthquake - Developing Country)
Magnitude: 7.0
Frequency: Rare in this area (last major earthquake was in 1751).
Spatial Predictability: Haiti was in an area known for seismic risk but had insufficient risk education and preparedness measures.
Japan (2011 Earthquake and Tsunami - Developed Country)
Magnitude: 9.0
Frequency: Seismic activity is frequent in Japan, so the country was more prepared for earthquakes.
Spatial Predictability: The region is within a seismically active zone, and public awareness and preparedness were higher, but the tsunami impact was harder to predict.
1.6A - Inequality
Theres a direct correlation between earthquakes causing more damage in less developed nations due to inequality of access to education, housing, healthcare and income opportunities. This can influence vulnerability and resilience
Try and remember these 5 recent events with a 7.7 magnitude, compared to their HDI
2007 - Chile - 0.83HDI - 2 Deaths
2013 - Khash, Iran - 0.77 - 35
2010 Indonesia - 0.68 - 711
2015 Nepal - 0.55 - 9018
2013 Pakistan 0.54 - 825
Explain how higher HDI links to lowered death counts
But emphasize how there are other factors such as population density, duration of ground shaking, secondary hazard’s and response which can affect death toll.
If relevant in a longer question, you would talk about factors which increase risks and which mitigate them. And how these are affected by development.
In some locations with very low human development (below 0.55), vulnerability is usually high because:
many people lack basic needs of sufficient water and food even in ‘normal’ times
much housing is informally constructed with no regard for hazard resilience
access to healthcare is poor, and disease and illness are common
education levels are lower, so hazard perception and risk awareness is low
1.6B - Governance and Geographical Factors
Remember that governance is most important in coping capacity and resilience in the event of a natural disaster.
e.g. meeting basic needs, land use planning, education, corruption, monitoring equipment
When reffering to geographical factors, mention population density, degree of urbanisation and isolation
Can link them quite nicely with this example
A specific example to talk about includes landslides being made worse by deforestation, bad governance can deforest some areas and therefore increase the impacts, reducing resilience and capacity to cope.
1.6C Disaster Context
Fairly self explanatory - Mention how the development level of countries affects the significance of the event, compare developing - Haiti, to emerging - Sichuan, and developed - don’t include Tohoku as it was an anomaly, but the USA and Chile have advanced insurance allowing recovery to be easier, disaster prevention education, monitoring and planning systems
1.7A - Trends since 1960
Hydrological hazards have become more common
Tectonic disasters have remained constant over time. On a whole, number of deaths increases, but number affected increases remember indonesia 2010
Better response management and preparation has reduced death counts over time, also the reported disasters have increased as improvements in data coverage allows us to identify more disasters. However the number of people affected increased due to population growth.
For earthquakes, theres been no tectonic change but The trend for earthquake economic losses is upwards, averaging about $20-40 billion per year but, once again, this is affected by very few large events.
Indonesia 2010 - numbers affected can be very large because of the mass evacuation of people around an erupting volcano, e.g. 350,000 affected (evacuated) with the eruption of Mt Merapi in Indonesia in 2010, but only 300 deaths
1.7B - Megadisasters
Tectonic mega-disasters can have regional or even global significance in terms of economic and human impacts.
Know these case studies inside out:
Eyafjallajokull
Tohoku
2004 Asian tsunami
1.7C - Multiple Hazard Zones
Multiple hazard zones are places where two or more natural hazards occur, and in some cases interact to produce complex disasters. Examples are California, Indonesia and Japan
Mostly because they are tectonically active (on plate boundaries) so earthquakes and eruptions are common. But also geologically toung mountains prone to landslides.
Can also link to areas prone to global climate pertubations such as el nino - making storm attacks frequent. Can also link to storm attacks mid latitude.
1.8A - Prediction and Forecasting
Earthquakes
- Cant be predicted however areas at high risk (risk forecasting) e.g. prone to liquefaction. Use risk forecasting for land use zoning purposes to mitigate impacts
- Or even mention seismic gaps in areas which are overdue an earthquake
Volcanic eruptions
- Predicted by sophisticated monitoring equipment which can measure changes as magma chambers fill
- Prediction is successful as there is a very minimal death toll from volcanic eruptons directly, despite 60-80 eruptions annually.
Tsunami
- Can be partly predicted, but seisometers can locate the earthquake and identify areas at risk, and evacuate them if theres time
Also worth mentioning that rural areas are harder to reach and inform in developing nations due to a lack of communication infrastructure
1.8B - The Hazard Management Cycle
Gotta learn this:
1 - Response - Immediate help in the form of rescue to save lives and aid to keep people alive, emergency shelter, food and water.
2 - Recovery - Rebuilding infrastructure and services, rehabilitating injured (physically and mentally) people and their lives
3 - Mitigation - Acting to reduce the scale of the next disaster: land-use zoning, hazard-resistant buildings and infrastructure.
4 - Preparedness - Community education and resilience building including how to act before, during and after a disaster, prediction, warning and evacuation technology and systems
Recovery stage can vary massively due to the magnitude of the disaster, development, governance and aid.
1.8C - Park’s Model
Response curve, if used in an exam, link the curve which takes ages for QOL to reach normal, if it ever does, to Developing Countries.
“It could be argued that the 2010 Port-au-Prince earthquake fits profile C because the devastation was still not ‘fixed’ by 2015 and incomes, health, housing and food supply remained worse than pre-disaster. Developed countries are more likely to correspond to profiles A or B, developing ones to C”
1.9A+B - Modifying Vulnerability
Know advantages and disadvantages of high-tech monitoring, education and community preparedness and adaptation as ways to improve a nations vulnerability
heres one for community and education:
Advantages
- Low cost, often implemented by NGOs
- Can save lives through small actions
Disadvantages:
- Does not prevent property damage
- Harder to implement in isolated rural areas
1.9C - Modifying Loss
Stratigies to modify loss include emergency, short and long term aid.
Short-term Emergency Aid refers to
Search and rescue followed by emergency food, water and shelter
Long Term Aid may take the form of reconstruction plans to rebuild an area and possibly improve resilience.
Know the advantages and disadvantages of long term aid, short term aid and insurance.
