Tectonics Flashcards
1
Q
What are properties of the inner core?
A
- solid iron
- hottest section at 6000°
2
Q
What are properties of the outer core?
A
- semi molten
- liquid iron and nickel
- medium temperature of 4500-6000°
3
Q
What are properties of the mantle?
A
- widest layer
- upper part is solid but lower part is molten and forms aesthenosphere
4
Q
What are properties of the crust?
A
Outer shell of solid rock
- oceanic plate is thin and dense
- continental us older, thicker and less dense
5
Q
What is Wegner’s theory?
A
- 1912, continental drift, conversion currents with the mantle
- around 200 million years ago the continents were merged in a supercontinent called Pangea
- these moved and now assume the position we see today (Laurasia which moved north = North African Asia and Europe) and (Gondwanaland which moved south = south Africa, Australia, Antarctica and India)
- Wegner’s also suggested mountains formed when the edge of a drifting continent collided with another causing the floor to crumple and fold
6
Q
What was Wegner’s opposition?
A
-took 150 years to be accepted as scientists still believed mountains are caused by cooling of the earth as well as it being difficult to find variable evidence
7
Q
What was Wegner’s proof?
A
- fossil records showed desert biome species were ready for the artic so the continents must have moved biomes
- many animals shared home structures and were too alike to have developed separately
- mountain ranges had been separated leading to rock correlations
- land masses fit like a jigsaw
8
Q
What was Hess’s theory on paleo magnetism ?
A
- ocean floor is getting progressively older the closer to the coast and that newer crust must be produced by molten rock rising inside as when more molten rock came to the surface the crust is pushed outwards
- pushing at the ridge and pulling at the convergent margin resulted in the sea floor spreading
- at the Benioff zone, oceanic crust is heavier and gravity pulls it under the continental crust. Gravity helps as once cooled it sinks because it gets heavier
9
Q
Evidence for Hess’s theory
A
- as the world isn’t getting bigger he knew the crust must be destroyed at the edge
- used sonar to survey the sea floor discovering it wasn’t flat but rather there were mountain ranges in the middle
10
Q
Examples of Hess’s discovery?
A
- the magnetic poles flip back and forth often over a long time
- when magma cools tiny magnetic minerals cool in the magnetic field direction
- this means there are parallel strips of cooled magma on the sea floor. A series of magnetic crevasses prove that the ocean floor is spreading because the stripes have been pulled apart
11
Q
What is the theory about subduction and slab and pull?
A
- a magma plume heated by the core rises to the aesthenosphere where it slowly pulls the slabs of crust apart as it cools
- in the centre ridges form
- eventually the slabs are subducted by another, less dense of heavy slab forming a trench
- these currents operate as cells
12
Q
What happens when an oceanic plate meets a continental?
A
- oceanic plate is subducted as it is less dense which creates deep oceanic trenches
- fold volcanos may also be made as the continual crust is pushed up
- Benioff zone creates friction adding to the melting of the mantle which creates an eruption
13
Q
What happens when an oceanic plate means another oceanic?
A
- denser or faster plate is subducted beneath the other
- the subducted plate melts creating magma which can rise through faults
- this creates ocean trenches and submarine volcanoes which can sometimes grow above sea level
14
Q
What happens at a divergent plate margin?
A
When two plates move away from each other
- in ocean magma can break through and build up to make new islands and continents. This creates rift valleys as the crust stretches and land between faults collapses
- it can also form submarine shield volcanos and shallow focus earthquakes
15
Q
What happens at a conservative plate boundary?
A
Two plates found last each other or in the same direction at different speeds
- no crust is made or destroyed here yet powerful earthquakes are created due to a shallow focus
- major breaks in crust can occur however when they move (on a large scale this is a transform fault)
16
Q
What are intraplate earthquakes?
A
- earthquakes that occur in midplate settings usually associated with major ancient fault lines being reactivated by tectonic stresses
- collisions if plates can also fracture crust that is far from the focus
17
Q
What are intraplate volcanos (hot spots)?
A
- volcanos at a distance from boundaries
- isolated plumes of convicting magma (mantle plumes) rise towards the surface creating basalt volcanos that erupt continuously
- the plume is stationary but the plate moved slowly above it
- this produces a chain of volcanic islands called a toll
18
Q
what is the risk damage threshold?
A
refers to the classing of different natural hazards based off their magnitude and scale of damage
- at what point does a risk lead to damage and therefore must be mitigated
19
Q
what us physical and economic vulnerability?
A
- physical vulnerability is when people live in hazards prone areas in buildings that offer little protection
- economic vulnerability is when people risk losing their jobs, assets and money
20
Q
what is social, knowledge and environmental vulnerability?
A
- social is when a household or community Is unable to support the disadvantaged people within it (e.g. political isolation)
- knowledge vulnerability exists when people lack education and training, therefore understanding
- environmental vulnerability Is because of things like population pressure which forces people into riskier areas
21
Q
why is mitigation harder than reduction of vulnerability?
A
it is dependent on the physical environment which is harder to change and alter
-yet vulnerability is predominantly to do with people which are easier to educate and alter
22
Q
where must the greatest initiative for mitigation come from?
A
- largest power and influence to implement reforms
- money to maximise their effectiveness and ability
- for example individuals may not have the social influence to make their ideas widespread or the money to successfully enforce them
23
Q
what is a hazard?
A
a natural process becomes a hazard when people are affected
24
Q
what is a disaster?
A
when a hazard affects a vulnerable population causing over 500 deaths
25
what is vulnerability?
how susceptible a population is to the impacts of a hazard
26
examples of recent megadisasters
- Tohuku (15,900 dead)
| - Haiti (230,000 dead)
27
what's the hazard risk equation?
risk reduction = mitigation of hazard x reduction of vulnerability and increase capacity to cope
28
what is the mercalli scale (MMIS)?
- measures the intensity of the quake using the amounted damage caused by shaking
- usually the stringer the shaking the greater the magnitude yet local factors can modify this
- very subjective based off observation
- measures from X to XII
29
what is the moment magnitude scale?
- based on energy released from all shock waves, the area of rupture and also movement
- more accurate than the original Richter scale as that was only based on P and S waves measured on a seismograph
- logarithmic
- equivalent to Kg of explosive
30
what us volcanic explosively index?
- open ended yet exists from 1-8 at the moment
- logarithmic
- calculated from the volume of ejected tephra
- generally the greater the VEI the less frequent the event occurs
31
what are hazard profiles?
a way of comparing the physical processes and impacts that all hazards share
32
why might hazards profiles be useful?
- they can help areas see what they are most at risk of
- this means they can plan and prepare more effectively helping to mitigate the effects
- this can help to rank hazards which need most attention advising decision makers
- breaks the event down into a variety of factors (e.g. frequency and duration). this means we can critically compare similar hazards in different locations based off more than one way
- if hazards are measured in the same way they will have broadly the same impacts
33
why might hazard profiles not be good?
- difficult to compare two different hazards because it doesn't provide specific values for factors leaving it somewhat open to interpretation
- they have varying impacts and spatial and temporal distributions
- doesn't take sub areas into account
34
what is governance?
the sum of the many ways individuals and institutions manage common affairs
- it is a root cause of vulnerability
- there are three strands of governance; economic, political and administrative
35
what are the effects of poor governance on overseas initiatives?
-concerns about political corruption and mismanagement means organisations are unwilling to channel aid money through it directly instead bringing their own staff at huge costs. This can hamper their ability to be self sufficient
36
what are the effects of poor governance of preparation?
- reduces investment into preparation meaning officials didn't know what to do reducing efficiency
- less money invested into preparation because developing counties spend money on debt to previous colonies (e.g. Haiti)
- poor governance can lead to less prediction systems increasing knowledge vulnerability
37
what is the effect of poor governance on social aspects?
- lack of controls and regulations meant slums were poorly built and lacked structural integrity and couldn't withstand the shaking
- dense urban environment made it harder for evacuation teams to work effectively
- poor investment into social spending and exploitation of the environment is rife which can lead to unsafe living conditions poor infrastructure and lack of preparedness
- leads to high inequality so poor have less of a political voice
38
counter point for influence of governance?
- a country needs to be developed to have good governance and development controls how resilient the economy is
- some hazards will also make a place more vulnerable regardless of governance
39
why are earthquakes more disastrous than volcanic eruptions?
- volcanic eruptions cover a relatively small areas and occur in narrow belts
- small proportion of of human population exposed (1% vs 5%)
- volcanoes are more visible so location of eruption is easier to predict compared to earthquake epicentres
- visual signs tend to be given off when a volcano is erupting
40
why might volcanic eruptions be worse than earthquakes?
- volcanic eruptions can go on for years
- can have global impacts (e.g. Iceland)
- can have long geographical reaches (e.g. ash clouds)
41
what is a fault line?
the boundary between two plates or a crack
42
epicentre
directly above the hypo centre on the surface (the shaking tends to be worse here)
43
hypocentre
the point at which tension and fraction releases seismic waves
44
seismic waves
ripples of energy released from the hypo centre
45
facts about earthquakes
- 95% of earthquakes occur along tectonic boundaries
| - 10,000 deaths a year as a result
46
what are the different types of seismic waves?
- p (primary/pressure) waves are caused bay compression pushing and pulling the direction of travel. they are fastest and have side to side weak movements
- s (secondary/shere) waves are 60% of the speed of p-waves and only more through solid rock (up and down movement)
- L (longitudinal/love) waves only travel through the surface of the crust. unlike the other two body waves these are surface waves moving from side to side as to forward
47
what waves cause the most damage?
L-waves cause most damage due to longer wave length and focus of energy at the surface leading to less reduction
-large side to side movement dragging the earth
48
what is the MMS?
- is equivalent to the KG of explosive
- based on energy released from all shock waves, the area of rupture and also movement
- more original that Richter scale as that was based purely on p and S waves off a seismograph
- logarithmic scale, ten fold increase
49
what is the mercalli scale (MMIS)?
- measures from X to XII
- measures intensity of a quake using the amount of damage caused by shaking
- very subjective as based off observation
- usually the stronger the magnitude the greater the intensity but local factors can modify this
50
what are primary hazards of earthquakes?
- ground shaking which drags infrastructure in many directions and can cause them to collapse
- crustal fracturing which leaves gaps in the earths crust
51
what is liquefaction?
- loosely packed grains of soil are held together by friction
- in the event of a tsunami this pore spaces are filled up with water
- earthquake shaking causes the water pressure to decrease and the soil to lose strength
- the structure is then lost and the soil acts like a liquid bubbling up to the surface
- the upwelling of liquid soil means that the soil underneath the buildings becomes muddy and collapses/sinks
52
what are slope processes like land slides?
- can occur naturally but earthquakes with a magnitude over 4 can increase the likelihood as the shaking puts more stress onto the slope causing it to fall
- soil is loosened by rain or gravity eroding the ground causing rock to fall
53
what physical factors affect earthquakes?
- seismic intensity/magitude
- proximity to the epicentre
- soil/rock substrate (e.g. if its saturated can lead to liquefaction intensifying shaking)
54
peak acceleration
how quickly the ground shock and how swiftly it changed direction
55
how do tsunamis form?
- elastic strain is built up in the Benioff zone due to subduction at a locked fault
- energy is released and the seabed is thrust upwards leading to a wave train which travels across the sea
- the waves can travel over 600 mph in deep sea
- when they reach the shallower sea floor the lower part of the wave slows down due to increased friction
- wave height increases and eventually crashes onto the shore
- once energy is lost, water drags debris back into the ocean
56
physical factors affecting tsunami severity
- wave amplitude, velocity and distance travelled
- physical geography of the coast (e.g. funnel/narrowing/gradient)
- degree of costal ecosystems as a buffer
- timing of the day
- wave refractions (e.g. the Boxing Day tsunami ricocheted of Indonesian archipelago)
57
human faros affecting tsunami severity?
- quality of warning systems
- degree of costal development
- structural integrity
- international relations
58
what is the intensity scale for a tsunami?
- 12 point intensity scale created in 2001
- arranged based of a tsunami's effect on humans, effect on objects and damage to buildings
- rough correlation with wave height
- scale 1 isn't felt, scale 12 is 32+ m high
59
where do volcanos tend to occur?
around the ring of fire (a geological fault belt) and convergent plate margins
- shield volcanos can occur at divergent plate margins
- hotspots
60
rhyolitic lava
- coolest form of lava between 650-800 degrees
- high silica and gas content low mineral content
- formed by lithospheric mantle and slabs of previously subjected plates
- very violent with cataclysmic eruptions
- tend to be at supervolcanos and composite
61
andesitic lava
- medium heat between 800-1000 degrees
- intermediate silica and gas content
- low sulpher dioxide, high water
- forms when subjected oceanic plate melts and mixes with seawater
- intermediate viscosity which is slow and traps gases
- eruption is violent and moderately explosive
62
basaltic lava
- ocean hot spots and shield volcanos
- hottest lava between 1000-1200 degrees
- low silica, water and gases
- high carbon dioxide and minerals
- formed by melting of minerals
- eruptions and gentle and effusive
63
what are primary hazards of volcanos?
- lava eruptions from the crater of the volcano
- ash clouds
- volcanic bombs
- pyroclastic flows
- gas eruptions
64
secondary hazards of volcanos
- ash clouds dispersed by prevailing winds affecting accessibility
- lahars due to ash mixing with rain or melted snow from the top of the volcano
- jokkulhlup as due to the heat of the volcanic eruption snow on the volcano melts which can lead to flooding
65
what is the VEI?
- volcanic explosively index ranks eruptions using terms like gentle to mega colossal
- based off volume of erupted tephra and height or eruption cloud
- logarithmic scale
- generally the greater the VEI the less frequent the event occurs making them less predictable
66
How are tsunamis measured using DART?
uses seabed sensors and surface buoys to measure changes in sea levels and pressure.
- when tsunami waves are detected they send signals via a satellite to warning systems
- using this transmitted information they can predict the size and direction of this wave using computer modelling
67
UN definition - natural hazard
a natural process which affects people
68
UN definition - disaster
a natural hazard becomes a disaster when it affects a vulnerable population causing over 500 deaths
69
UN definition - mega disaster
a disaster becomes a mega disaster when:
- over 2000 die
- 20,000 made homeless
- GDP is reduced by 5%
- dependence on aid for over a year
70
vulnerable
how susceptible a population is to the impacts of a hazard
| -incorporates the ability to anticipate, resist and recover from an event
71
resilience
the ability to bounce back from an event and restore areas, e.g. livelihood and infrastructure
72
what is the PAR model?
- hazard crunch model
- pressure increases from both sides
- two sections to it - Hazards and progression of vulnerability which incorporates Root causes, Dynamic pressures and unsafe conditions
- root causes examples = resources, political and economic system
- dynamic pressures examples= lack of local factors like infrastructure and training, macro forces like pop increase and expenditures
- unsafe conditions examples= physical environment, vulnerable society, local economy levels
73
hazard risk equation
risk reduction = mitigation of hazard x reduction of vulnerability and increased capacity to cope
74
risk damage threshold
refers to the classing of different natural hazards and at what point does a risk lead to damage and therefore must be mitigated
75
human vulnerability categories
- social vulnerability = when a household or community is unable to support the people in it
- knowledge vulnerability = exists when people lack education and training and therefore understanding, no evacuation systems
- economic vulnerability = when people risk losing their jobs assets and money
76
physical vulnerability categories
- physical vulnerability = when people live in hazard prone areas in buildings that offer little protection
- environmental vulnerability = vulnerability based off the geographical location or population pressure which forces people into worse areas
77
physical and environmental vulnerability in developing countries
- high population density due to rapid urbanisation in a short period of time tends to drive prices up and lead to many living in informal settlements with low structural integrity. poor infrastructure can also hamper the effectiveness of evacuation
- it also forces people into more susceptible areas of living. these areas can be less accessible and so be less easy to rescue
78
economic and social vulnerability in developing countries
- if the quality of services is better than people will be more educated about the risks
- affluence of local population impacts structural integrity and a lack of income opportunities affects levels of defence
- areas with poor health care are more affected by epidemics and disease.
79
how does governance affect vulnerability in developing countries
- existence of building regulations and codes determines their structural integrity but also the quality of the building
- existence of disaster preparedness plans influences the speed and effectiveness of recovery
- technological advancements and standards influences how easy it is to communicate and warn the population
- levels of corruption can affect the county's commitment to respond the event but also the funds available for this
80
why is mitigation harder than reduction of vulnerability to implement?
because it relies on modification of the physical environment which is inevitably harder to alter and change
- vulnerability is also more to do with human factors which are easier to educate and alter
- mitigation must come from government most as they have the largest influence to implement reforms but also the greatest funds to maximise their impacts
81
hazard profiles
a way of comparing the physical processes and impacts that all hazards share
82
why are hazard profiles useful
- helps areas to see what processes they're most at risk of
- this means their preparation can be more effective and tailored
- they can also help to rank hazards which need most attention advising decision makers
- breaks an event down into a variety of factors ranging from frequency to duration. this makes it easier to compare events in different locations rather than just relying on one factor. By being measured in the same ways they also have broadly the same impacts
83
why can hazard profiles be difficult to use?
- doesn't provide specific values for factors leaving it somewhat open for interpretation
- different events also have varying spatial and temporal distributions
- they are also time consuming to make
84
counter points for role of governance in determining vulnerability
- arguably it is development which influences the type of governance as a government without access to resources and money will find it difficult to make decisions
- development also controls employment structures in a country and therefore economic resilience. (e.g. one reliant on primary industries would be more vulnerable than one with a variety of industries
- some hazards will make a population vulnerable no matter how prepared they are
85
economic governance
includes the decision making process that affects a country's economic activities and its relationship with there economies
86
political governance
the process of decision making to create policies including national disaster reduction and planning
-the way it brings together the state, non state and private sector players determines the quality of the policy outcome
87
administrative governance
system of policy implementation and requires good governance at both central and local levels
-it requires functioning enforcement of building codes, planning, risk assessments and safety standards
88
governance
the sum of the many ways individuals and institutions manage common affairs
-part of the root cause of vulnerability
89
what impact can governance have on developing countries?
- natural disasters can reinforce the economic crisis
- many were previously ruled by brutal dictators and a succession of colonial powers or military bodies who cared little about the domestic situation.
- this has meant money has been spent on debt to previous colonies rather than development
90
effects of poor governance
- poor governance leads to limited investment into social development and rather tends to lead to environmental exploitation. This can lead to unsafe conditions and a lack of preparedness
- concerns about corruption and mismanagement means organisations are unwilling to channel aid money directly through the economy, instead funding their own staff at huge, off-putting costs. this can hamper their ability to be self sufficient meaning local businesses get less funds
- reduces investment into preparation techniques increasing knowledge vulnerability
- poorly built infrastructure with few regulations and that lack structural integrity and which often have high population density hampers rescue missions and exacerbates impacts
- corruption creates less commitment to restore the economy meaning less money is invested into funding
- poor governance means certain groups I society are often ignored and suffer the worst. for example, settlements which aren't formally registered and therefore don't technically exist often aren't included in the rebuilding process
- creates the initiatives for resilience and future mitigation
91
hazard hot spot
an area susceptible to multiple hazards
- they are likely to be where plate boundaries intersect, in areas with major storm belts and high human concentration
- development also influences this
92
how is the Philippines a hazard hot spot?
- located on a plate boundary creating risks from both earthquakes an volcanos
- archipelago so is susceptible to tsunamis
- climatic hazards due to being in a storm belt region
- mountainous terrain and high levels of deforestation can lead to landslides
- tropical monsoon climate so is subject to heavy rainfall
93
what human factors affect the Philippines hazard hot sport status?
- growing population and 25% in poverty poverty increases vulnerability
- many of the country are forced outwards towards costal regions which are affected by storm surges, tsunamis and flooding
94
challenges of multiple hazard zones
- one hazard can trigger a further as many are interlinked
- different hazards happening within a short period time can make resilience for government hard as it drains resources and stretches the ability of emergency services to respond
- operating a near constant sate of emergency
95
how can the heavy rainfall contribute to a tectonic disaster?
- saturates overlying rock on mountains though percolation and infiltration reducing its stability
- when stalking starts the land has a lesser ability to retain its position so is more likely to slip
- increases water lubricant can also magnify the shaking due to a liquefaction affect
- can also create lahars if there is heavy rainfall at the time of an eruption as it mixes with ash forming landslide like formations
- this funnels the effect focusing it on nearby settlements and blocking access routes
96
how can storm surges contribute to tectonic disasters?
- if a storm surge causes flooding or heavy rain impacts can be exacerbated
- for example poor sanitation exposing the population to disease
- it can also destroy food storages meaning crops are ruined
97
geophysical
caused by tectonics
98
hydrometeorological
caused by weather systems
99
why has the trend of reported natural disasters increased?
- methods of prediction and detection is greater and so even if the amount of hazards hasn't changed that much technological advancements means more are picked up
- greater population density so more people are exposed
- climate change has created more climatic disasters both in frequency and magnitude
- changes to the environment as a result of rapid urbanisation and deforestation which has increased impermeable surfaces and flood risks
100
what reduces the accuracy of statistics?
- meaning of definitions sometimes differ across the world
- mega disasters can upset trends
- difficulty in collecting stats especially in remote areas of low human development of densely populated informal settlements where population wasn't properly recorded in a formal consensus
- no single organisation responsible for collecting data so often organised in different ways
- political bias in reporting deaths (e.g. Thailand post the 2004 tsunami understated deaths to have less of a inference on the tourism economy)
- reported number of deaths might be inaccurate due to indirect deaths following the event (e.g. cholera outbreak not actual event)
101
tectonic mega-disasters
- can have large scale spatial impacts in terms of economic economic and or human impacts making them difficult to manage
- can affect more than one country directly and directly
- recorded as high impact low probability (HILP) events so generally poorly prepared for.
102
global social impacts from tectonic mega-diasters
- families of those affected have indirect physiological impacts
- workers abroad on certain schemes such as remittances can leave families isolated and economically unstable
103
global economic impacts from tectonic mega-disasters
- countries have to sustain those affected through aid placing strain on their economies
- reduced tourism to that country
- transport like airports affected by ash in volcanic eruptions
- damaged of world agriculture and supply chain productions. this impacts the final service/product
- global financial systems are interconnected so major disasters affect insurance industries in many countries
104
natural hazards are caused by natural processes argument
- natural process of radioactive decay leads to the initial hazard
- hydrometeorlogical work in conjunction to magnify the impacts of natural hazards
105
natural hazards caused by human processes argument
- economic development determines their defence mechanisms
- prediction methods influencing knowledge vulnerability
- governance determines the longevity of impacts
106
hazard management cycle
process in which governments and other organisations work together to protect people from natural hazards
-the aim is to avoid or reduce loss of life or property, provide help to those affected and ensure rapid and effective recovery
107
in the hazard management cycle what two stages happen before the hazard occurs?
- mitigation whereby hazards are identified and techniques like zoning, land use planning and protective structures are done
- preparedness involves minimising loss of life and property by enforcing building codes, developing plans and warning systems and raising public awareness
108
in the hazard management cycle what two stages happen after the hazard occurs?
- response whereby you cope with the disaster at hand with the main aim of saving lives and reducing economic loss. this is where rescue efforts come in, infrastructure is restored and essential services emerge
- recovery split into short and long term needs. provides provisions, reopen establishments and look to combat future vulnerability
109
why is it difficult for scientists to accurately predict tectonic hazards?
- hypocentres are inaccessible so seismometers can get to them
- changes in rock properties, water content and local shaking increase with depth and along a fault
- probability is used to forecast when an earthquake of a particular magnitude is likely to occur, reoccurrence interval
- complex processes
110
park hazard response model
- used to understand resilience in the aftermath of a hazard event
- the model suggests if your a developing or emerging country then you are likely to recover to a better QOL than if developed when recovery tends to be back to normal standards
- this also depends if it is a freak incident or likely to happen again
- the model shows how a hazard will inevitably cause a deterioration in QOL and economic activity but the length of time disruption occurs for is dependent on thr success of relief
111
earthquake forecasting
- uses probability to predict an earthquake of a particular magnitude and when it is likely to occur
- e.g. large earthquakes happen less than 1 in 1000 years
- they use patterns of previous quakes
112
four stages of hazard response model
- mitigation
- preparation
- response
- recovery
113
how to modify loss
- education of the population (e.g. brochures in Egypt) as this reduces knowledge vulnerability but also an idea of how to respond (e.g. evacuate) this can modify potential loss of life
- insurance companies can help to modify loss of assets and properties (in cali premium is paid based on risk and won't cover all the costs)
- NGOs can reduce loss of life after the event by providing emergency relief
114
how to modify the event
- dams and dytes
- replanting mangroves
- land use zoning
115
resonance
- the frequency at which the ground shales during an earthquake is in tune with the frequency that a building sways leading to a more violent sway in the buildings
- this increases the likelihood of it falling
