Tectonics Flashcards
What is the starting point of an intra-plate earthquake?
Ainchent rift or faults
How does an intra-plate earthquake form?
Ainchent rifts or faults with building tectonic strain causing a fracture and ground shaking
How does an intra-plate volcano form?
A tectonic plate moves over a stationary hotspot and intense heat and pressure is exerted on the lithosphere and submarine volcano erupts and causes a volcanic island to form
What % of earthquakes happen at the ring of fire?
70%
What are the two types of plate TYPES?
Oceanic and continental
What are the three types of boundry types
O-O
O-C
C-C
What are the three types of plate movement?
Divergant, convergant, conservative
What is the magma type of an Oceanic-Oceanic plate?
Balsaltic
What is the magma type of an Oceanic-Continental plate?
Andesitic
What is the magma of an Continental-Continental plate? (Rare)
Rhyolitic
What is the example of an Oceanic-Oceanic plate type? (place)
Iceland 2010
What is an example of an Oceanic-Continental plate? (place)
Mt St Helens 1980
What is an example of an Continental-Continental plate? (plate)
Yellow stone
What is an example of a divergant plate movement?
SW Iceland 2000
What is an example of a convergant plate movement?
Nepal 2015
What is an example of a conservative plate movement?
Hati 2010
What is the depth of an oceanic plate?
7km
What is the depth of a continental plate?
40km
What is the explosivity of a Oceanic-Oceanic plate?
Not very
What is the explosivity of a Oceanic-Continental plate?
More explosive
What is the explosivity of a Continental-Continental plate?
Very explosive
What is an example of a intra-plate volcano?
Hawaii
What is the core?
A liquid middle of the earth which is 6,000°
What is the mantle?
The second layer of the earth which is semi-ductile
What is the lithosphere?
Outer layer of the Earth
What is slab pull?
The enormous weight of subduting slab causes it to sink into the mantle and cools
What is the Wadetti Benioff zone?
Different speeds and movement of crustal rock generate strain and fractures at varying focal depths.
What is the focal depth important in determining?
The magnitude of the ground shaking
What is a P wave?
Vibrations caused by compression
What is a S wave?
They vibrate at right angles to the direction of travel
What is an L wave?
Responsible for the ground shaking
What distance do L waves travel?
Surface
What wave arrives first?
P wave
What is a Landslide caused by?
A steep slope of the side of a hill or mountain
What happens in a landslide?
Geound shaking cuases cuases loosly packed sediment to fall downhill
What is a case study for a landslide?
Elsavador 2001 with a magnitude of 7.6 and killed 585 people
What causes waterlogged ground?
Liquifaction
What happens in liquefaction?
Ground shaking caused the ground to act like a liquid causing building collapse
What is the case study for Liquifaction?
Nigatta 1964 with a magnitude of 7.5 caused 3,500 houses to be destroyed
Where does landslides affect communities?
When they are located at the bottom of a steep slope
Where does liquefaction affect communities?
When they are located on loosely packed waterlogged ground
What happens in a fracture below the sea floor?
A Tsunami
What happens at a tsunami?
A displacement of water creating a ripple reaching land
What is the case study for Tsunamis?
Indian Ocean 2004 boxing day tsunami with a magnitude of 9.1 and killed 225,000 people
Where does tsunamis affect communitites?
Located at a convergent o-c boundary with the upward movement of crust along a fault
What are the four primary hazards on a volcano?
Pyroclastic flows
Tephra
Lava flows
Gas eruptions
What are pyroclastic flows?
Large clouds of hot ash with material being deposited
How fast do pyroclastic flows move?
700km/h
What is the example of a pyroclastic flow?
Momtserat 1997
What is tephra?
Rock fragments and lava bombs being ejected into the air
What is the example of tephra?
Eyjafjallajökull 2010 with a VEI of 4
What is a lava flow?
Lava erupting from the volcano affecting houses, people and land
On a steep slope with basaltic lava, how fast can it travel?
15m/s
What is an example of gas eruptions?
Lake Nyos 1986 killed 17,000 people
Why are gas eruptions bad?
They are colourless and odourless and so can kill easily
What is a Lahar?
Particles of ash forming condensation nuclei triggering rainfall which leads to volcanic mudflow
What is the example of Lahars?
Pinaturbo 1991 with a 24km high ash cloud with 3km2 of sediment dropped
What is a Jokullhalwp?
Rapid discharge of meltwater (ice) causing destruction
What is the example for a Jokullhalwp?
Eyjafjallajökull 2010 with discharge of 3,000m3/s
How does an earthquake form?
Build up of tectonic strain -> pressure exceeds the strength so fractures -> seismic waves released -> the crust rebounds causing it to shake
What are the 2 secondary hazards associated with volcanoes?
Lahars and Jokullhlawp
What are the 3 secondary hazards associated with earthquakes?
Landslide, Liquefaction, Tsunami
What is a hazard?
A geophysical event that has the potential to cause threats to life and property
What is a disaster?
A serious disruption of land and life which exceeds the ability of the affected community to cope
What does the Deggs Model state?
A disaster will not occur unless a vulnerable population is exposed to hazards effects
What does the Deggs model show the interaction of?
The geophysical hazard and the vulnerability of a population
What is the case study of the Deggs model?
Pinatubo 1991 with a VEI of 6 with a 24km high ash cloud and they had flat roofs causing 300 deaths
What is the hazard risk formula?
It breaks down the individual components of risk and can be broken down to show the different influences that make risk
What is the case study for the Hazard Risk Formula?
Hati 20120 with a magnitude of 7 and was at risk as 25% of the population were just 25km from the epicentre with weak buildings and poor governance with 230,000 deaths
What is the Disaster Age Index?
States that age is a determining factor in levels of risk and that elderly people cause more risk
Why are elderly people more at risk?
They have less mobility, weaker immune systems and low coping capacitates
What is the case study for the Disaster Age Index?
Tohoku 2011 with a magnitude of 9 with 15,000 deaths with 23% of the population over 65
What is the PAR Model?
Shows the progression of vulnerability in the form of pressure and how growing pressure from each side cause a bigger disaster
What is the case study for the PAR Model?
Hati 2010 with a magnitude of 7 with both poor governance and weak buildings caused an increased scale of disaster
What 2 measures measure the intensity of tectonic hazards? (models)
Volcanic explosivity index and the moment magnitude scale
What is the volcanic explosivity index?
A relative measure of explosivity calculated from the volume erupted
What is the moment magnitude scale?
It describes earthquakes in term of energy realised
What is the speed of onset?
Time from detection to hazard occuring
What is areal extent?
How far and wide a hazard affects are felt
What is spatial predictability?
Ease of predicting where a hazard may take place
How can low access to education can increase vulnerability?
No qualifications lead to less secure income lead to less educated on evacuation leads to increased vulnerability
How can poor quality housing lead to increased vulnerability?
Weak buildings made out of weak concrete can’t withstand ground shaking causing building collapse leading to increased vulnerability
How can poor healthcare lead to increased vulnerability?
In a disaster spread of disease and injury likely due to contamination of water sources to less likely to recover from disease
How can low income increase vulnerability?
Inability to send the children to school so affording hazard proof housing and can’t afford good nutritious food
How can poor nutrition increase vulnerability?
Lead to a weaker immune system and malnourishment and so disease spread and those with weak immune systems will die
How can high levels of development lead to an increased resilience?
High levels of financial and human capital so has aseismic building codes so less damage occurs and they can recover quickly
How many children in Hati go to school?
50%
How many houses in Hati are made from weak concrete?
90%
How many % of Hati’s population have access to healthcare?
40%
What is the poverty risk nexus?
Low income households suffer a share of disaster due to inequality
Why might disaster statistics be questioned?
Open to political bias, no universally agreed definition of a disaster
What are 2 reasons that we must question recorded disaster statistics?
Data collection methods will vary, open to political bias e.g may make them worse for more aid
What is meant by a multiple hazard zone?
An area that exposed to both tectonic and hydro-meteorological hazards
What is an example of a multiple hazard zone?
Pinaturbo / Philippines
How can you predict or forecast a Volcano?
Giving some form of warning that can be detected with equipment. Tilt metres are a good use
How can you predict or forecast an Earthquake?
Areas at high risk are identified with those likely to suffer severe ground shaking and seismic gaps can point to areas of high risk
How can you predict or forecast Tsunmais?
The earthquake cannot be predicted but the waves can be and you can use seismometers and ocean monitoring equipment can detect tsunamis
What is the hazard managment cycle?
It illustrates the different stages of managing hazards in an attempt to reduce the scale of a disaster
What are the 4 stages in the Hazard amnagment cycle?
Recovery
Response
Mitigation
Preparation
What is mitigation in the hazard management cycle?
Building back better and adapting for future hazards
What is the PARKS model?
Shows the time dimension of resilience so the time it takes from a place disrupting and it recovering
What does a bigger curve in the PARKS Model show?
A more vulnerable place and a bigger dip
What is a prediction?
Provides a % chance that a hazard will occur relating to past trends
What is a forecast?
Knowing when and where a natural hazard will take place
How can we reduce earthquakes affect on an area?
Creation of aseismic buildings
Cross bracing
Base Isolation
What is an example of base isolation systems?
Apple HQ sits on 700 bases and can move 4-5 feet
How can we reduce tsunami effects on an area?
Engineering defences
Planting of Mangroves
What is an example of a reduced effect of a Tsunami on an area?
Tohoku 2011 built 245 mile sea wall with 4 feet of reinforced concrete
How can we reduce the effects of a volcano on an area?
Diverting lava flows
How can we detect an earthquake? (2)
Seismometers
Community preparedness and education
How can we detect a Tsunami?
Tsunami warning systems
How can we detect a Volcano?
Diagnostic precures with an increase of gas emission and tremors
What is short and long term aid?
Search and rescue, water and shelter
What is insurance?
Covering the cost of the earthquake damage
