Tectonics Flashcards
What are the 5 features of a shield volcano?
- Non-viscous
- Domes upwards- wider
- Erupt frequently BUT softly
- Basaltic magma
- Volcano gasses diffuse away easily
4 characteristics of Rhyoltic lava
- Coolest
- High silica
- Thick + stiff flow (high viscosity traps gasses)
- Very violent/ cataclysmic
3 characteristics of Andesitic Lava
- Intermediate
- Slow (intermediate viscosity traps gas)
- Moderately explosive
5 characteristics of Basaltic Lava
- Low silica
- Low has content
- Low viscosity
- Gentle/effusive eruption energy
- Hottest
Are crust fracture is another term for a..?
Fault
What does the term ‘jökulhaup’ stand for?
Masses of ice suddenly released from a glacier by the heat from lava inside a volcano. Can become a mudflow if the ground is unconsolidated.
Glacial outbursts
What does the term ‘Lahar’ mean?
Volcanic mudflows commonly created when ash mixes with snow and ice from a volcano summit. Move down volcano flanks like liquid cement.
3 characteristics of a Strato volcano
- Erupt viscous- ANDESITIC or RHYOLITIC
- Eruptions are explosive
- Deadly pyroclastic flow
What are the 4 variations of wave?
1 Primary First: can travel through
2 Secondary whole world.
3 Love Second: Only move through
4 Rayleigh crust
Why does an intra-plate earthquake occur?
1 Stresses build up along ancient faults causing them to become active again
2 Crust that was once weighed down by glaciers is slowly rebounding from the mantle triggering earthquakes
What is the disaster risk equation?
Hazard (times) Vulnerability (divided by) capacity to cope
What is a hazard?
A physical event which has a negative impact on people causing death, injury, loss of property or destruction of life
What is a disaster?
An event that disrupts normal conditions to a point where the place cannot adjust and there is significant loss of life/injuries or economic cost
How to primary waves flow?
A compression/expanding movement
How to secondary waves move?
A vertical movement
How to love waves flow?
A side to side motion
How to rayleigh waves flow?
A circular/orbital movement
What two plate boundaries do volcanos occur on?
- Divergent
* Convergent
What is magnitude?
The amount of energy released at the epicentre
What does intensity mean?
The earthquakes effect on people, structures and the natural environment
How do you measure intensity?
Via the mercalli intensity scale
How do you measure volcanic magnitude?
Via the volcanic explosively index
Where are shield and strato volcanos found?
- Constructive boundary
* Divergent boundary
What does the term ‘viscosity’ mean?
An internal property of a fluid that offers resistance to flow
ie. low viscosity= runny
What are hot spot volcanos?
Volcanos that exist as isolated points + aren’t a consequence of a movement of a plate boundary
What is a hot spot track?
A chain of extinct volcanos
3 characteristics of primary waves
- Can move through solids + liquids
- Fastest
- Push through crust
3 characteristics of secondary waves
- More damaging
- Can only move through solids
- Arrive after primary waves
What are the 4 theories to explain reasons for mantle convection?
1) mantle convection
2) sea floor spreading
3) subduction
4) slab pull
What are the 2 primary effects of an earthquake?
- Ground shaking
* Crustal fracturing
What are the 3 secondary effects of an earthquake?
- Tsunami
- Fire
- Land slides and avalanches
How are volcanos formed?
Via the extrusion of lava onto the earths surface
What are the two main volcano types?
- Shield
* Strato/composite
What are the first 2 earthquake waves called?
- Primary
* Secondary
What are the 2 seconds earthquake waves called?
- Love
* Rayleigh
What are surface raptures directly in line with?
The focus
What are 3 characteristics of a love wave?
- Produced by body wave
- Fastest surface wave
- Most damaging
What are 3 characteristics of a Rayleigh wave?
- Only move through crust
- Last wave to arrive
- Move crust up and down
What are strato volcanos built up of?
Ash and pyroclastic material
What are shield volcanos built up of?
Layers of solidified lava
What is DART?
A sea floor bottom pressure recording system capable of detecting tsunamis as small as 1cm
What is a rift valley?
When a plate moves apart on continents, crust stretches and breaks into sets of parallel cracks (faults). Land between these fault then collapse, forming steel sides rift valleys.
What the 3 stages of a tsunami?
1) Generation
2) Tsunami run-up
3) Landfall
What is slab pull?
At a subduction zone the defending part of the oceanic plate pulls the rest of the plate with it
What is subduction?
Melting of an oceanic plate as it descends into the mantle at a convergent boundary
What is convection?
Movement of mantle material in cells when heated by radiation from the earths core
What is liquefaction?
Groundwater and lose soul/sediments are shaken during and earthquake- acts like fluid
What is an intra plate earthquake?
An earthquake that occurs at centre of a plate
What is the benioff zone?
Zone where descending oceanic plate is in contact with continental plate as it’s subducted.
Zone of earthquake activity created by friction between the two plates
What is the asthenosphere?
Partially molten part of the mantle on which the earths tectonic plates lie
What is water column displacement?
The movement of a volume of seawater above the point at which the seabed was moved up or down by an earthquake event, such as a thrust.
What is a mantle plume?
Hotter areas of mantle that move upwards underneath crust + push up.
Weak spots= hotspots
What is crustal fracturing?
Occurs when earths crust causes rock to break and fracture under stress and strain caused by seismic stresses
What is magnitude?
Amount of energy released durning a tectonic event
What is lithosphere?
The rigid, outer most layer of the earth from which tectonic plates are formed. Made up of the crust and upper mantle.
What is a hotspot?
Intra-plate location where magma from the mantle has broken through weak point on a crust
What is the definition of a moment magnitude scale?
Most accurate earthquake scale, total energy measurement
What is the mercalli scale?
An earthquake intensity scale based on 12 levels of damage to areas
What is sea floor spreading?
Process in which tectonic plates—large slabs of Earth’s lithosphere—split apart from each other.
What are seismic waves?
Shockwaves created by release of tension at the focus
What is palaemagnetism?
Magmas and lavas solidify, the iron minerals in the rock align with the earths magnetic field.
What is speed of onset?
How slow or rapidly the tectonic hazard develops
What does the term duration mean?
How long the tectonic event lasts
What does the term areal extent mean?
How widespread the hazard is
What does the term spacial predictability mean?
How likely scientists are to estimate where a tectonic event will strike
What is a hazard profile?
A diagram which can be used to show the main characteristics of a hazard.
What are the 3 element on the Deggs disaster model?
- Vulnerable population
- Disaster
- Tectonic event
What is the PAR (pressure and release) model?
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.
What is a multiple hazard zone?
Also known as disaster hotspots, they are an area with vulnerable populations at rick from two or more natural hazards.
What can different natural hazards hazards be categorised as?
Geophysical (earth related including tectonic movements)
Hydrometeorogical (climate related)
What is a mega disaster?
The Un states that a mega disaster is when:
• More than 2000 deaths have occurred
•Over 20 000 homeless
•The GDP of a county is reduced by at least 5%
•Dependence on aid from abroad
lee than a year after an event
In a globalised world it is even more likely…
…that disasters will have a major influence across the planet
What is a context hazard?
Such as climate change, increases the magnitude and frequency of other hazards (especially hydrometrogical hazards)
What are the 4 key titles on the hazard management cycle?
1 Mitigation (prevention)
2 Preparedness
3 Response
4 Recovery
What is involved in the ‘preparation’ of a hazard?
- Developing preparedness plans
- Early warning systems
- Raising public awareness
What is involved in the ‘response’ of a hazard?
- Search and rescue efforts
- Evacuating people where needed
- Restoring critical infrastructure
What is involved in the ‘recovery’ of a hazard?
Long term OR short term
- Rebuilding homes
- Providing food and temporary shelter
- Re opening business, schools etc
What is involved in the ‘mitigation’ of a hazard?
- Zoning and land use planning
- Developing and enforcing building codes
- Protective structures
What is the definition of a hazard management cycle?
The Hazard Management Cycle takes into account preparedness, response, recovery and mitigation. The Disaster Cycle. The disaster cycle or the disaster life cycle consists of the steps that emergency managers take in planning for, and responding to, disasters.
What is the parks response curve (1992)?
The Park model is also known as the disaster response curve. Its aim is to show the effects of a hazard on quality of life over a sequence of time.
What is the shape of the parks response curve related to?
Socio-economic status of the country affected
What are the 3 phases of a hazard event according to the parks response curve?
Pre disaster
Relief > Rehabilitation > Reconstruction
What does the term mitigation mean?
Mitigation means to reduce or prevent the effects of something from happening
What does the term adaptation mean?
Actions taken to adjust to living with tectonic hazards
What are 3 options to take when trying to manage a hazard?
1) Modify the event- change the tectonic processes/hazards
2) Modify the vulnerability- plan strategies to make the area/population more resilient to the hazard
3) Modify the loss- accept or share the losses of from the hazard
What is an example of the option ‘modifying the event’?
Lava diversion
Tsunami defences
What is an example of the option ‘modifying the vulnerability ’?
Preparedness/risk awareness days
Technology monitoring
What is an example of the option ‘modifying the loss’?
Emergency aid
Insurance
Which two plate boundaries create submarine volcanos?
Oceanic-Oceanic
Oceanic-Continental
In which direction are tectonic plates moving at constructive boundaries?
AWAY- divergent
TOWARDS- convergent
Why do continental plates never subduct?
The asthenosphere is denser
Why do conservative boundaries produce no volcanos?
There’s no magma- plate isn’t subducted
Which plate boundary is the most hazardous?
Convergent- destructive
What is a transform fault?
A large scale break in the crust: conservative boundary
What does the Degg Model illustrate?
When a hazard becomes a disaster?
What does the term threshold mean?
The magnitude of a hazard , above which a disaster occurs.
What does the term seismic gaps mean?
Areas that have not experienced an earthquake for some time and are ‘overdue’
What are 2 ways in which an earthquake can be predicted?
Areas at high risk identified, together with those likely to suffer sever ground shaking and liquefaction
Seismic gaps can point to areas especially at high risk
What are 4 methods to predict a volcanic eruption?
Monitoring equipment on volcanos can measure changes as magma chambers fill and eruption nears
Tilt metres record ‘bulging’ as magma rises
Seismometers record minor earthquakes that indicate magma movement
Gas spectrometers analyse gas emissions that can point to increased likelihood of eruption
What are 2 methods to predict a tsunami?
Seismometers can tell that an earthquake has occurred and locate it
Ocean monitoring equipment can detect tsunamis in the open ocean
What are 4 examples of good governance that reduce disaster vulnerability?
Meeting basic needs- providing sufficient food and water
Planning- land use planning/zoning
Environmental management- preventing exacerbating factors such as deforestation, effective monitoring systems
Preparedness- education and community awareness
What 3 other geographical factors influence resilience and vulnerability?
Population density
Isolation and poor accessibility
Degree of unbanisation
What is a hazard profile?
A way of summarising the physical processes that all hazards share to help decision makers determine the places most at risk.
What does the moment magnitude scale measure (MMS)?
The energy released via an earthquake
What does the mercalli scale measure?
The damaging effects (ie shaking) produced by earthquake
What are effusive eruptions of basaltic lava with love VEI associated with?
Constructive boundaries or plumes
What are explosive eruptions with high VEI of andesitic it rhyolitic lava associated with?
Destructive boundaries
What does the term resilience mean?
The degree to which a society or environment can absorb a hazardous event and yet remain within the same state of an organisation- it’s ability to cope with stress and recover.
What are the 4 sources of evidence for continental movement?
Carboniferous glaciation round is southern hemisphere continents
Fossil remains of small fresh water reptile have been found in both S america and africa
Coal found in antarctica: it is unlikely to have formed at its current latitude, and requires tropical climate
Basaltic lava flows are located where continents tear apart
What do volcanos lie on?
Mid-oceanic ridges
Volcanic arcs that border trenches
What does the term subaerial mean?
above sea level (volcanos)
What does the term hot spot track mean?
A chain of extinct volcanos form when the overlying plate moves over a fixed plume
What is the definition of a tsunami?
A series of larger than average waves which are usually caused by submarine earthquakes or volcanic eruptions. Tend to occur along plate boundaries.
What is seismic activity?
Seismic activity is defined as the types, frequency and size of earthquakes that happen over a period of time in a certain area.
Why do disasters happen?
Failures of development which increase vulnerability
What does the term root cause mean?
Political or economic systems that control who has power and access to resources such as money eg. level of development, national debt, government corruption
What does the term dynamic pressure mean?
The effect the root causes might have eg. poor infrastructure, no defences, deforestation
What does the term unsafe conditions mean?
The conditions the dynamic pressures lead to ie. lack of evacuation, illegal housing in unsafe conditions- disease outbreaks etc.
What are the 3 plate boundaries?
Divergent-
oceanic-oceanic
Convergent-
oceanic-continental, continental- continental
Conservative
What does the hypo centre mean?
The point within the earth where an earthquake originates
What does the term epicentre mean?
The point on the earths surface vertically above the focus of an earthquake
What does slab pull mean?
A subduction zone- the descending part of the oceanic plate pulls the rest of the plate with it
What does sea floor spreading mean (or palaeomagnetism)?
The movement of oceanic crust from constructive wave boundary, recorded by magnetic stripes in basaltic rock. Magma fills gaps, solidifies forming new crust.
What does the term mantle convection mean ?
Movement of material in cells when heated by radiation > radioactive elements decay, move through mantle
What are the 3 primary volcanic hazards?
Lava flows
Gas eruptions
Pyroclastic flows
What does the term hazard management mean?
A process in which governments and other organisations work together to protect people from the natural hazards that threaten their communities
What is the definition of land use zoning?
Process by which governments regulate how land in a community may be used (eg industrial, commercial etc). Common in wealthy countries
What is involved in diverting lava flows?
Building barriers, digging channels to try and diverge the lava into a safer direction.
A fairly ineffective method
What is involved in GIS mapping?
Can be used in all stages of the disaster management cycle > eg identify where evacuation routes will be
What is the main cause of death during an earthquake?
Collapsing buildings
How are NGOs a crucial role in disaster management?
Especially important when local government is struggling to respond, or doesn’t have resources to do so. Can provide funds, rescue efforts etc
Why is insurance key in hazard management?
It provided individuals and businesses with the money they need to repair and build
What are the 3 destructive plate boundaries?
oceanic-continental
oceanic-oceanic
continental-continental
