Yr 12 UCAS Tectonic Hazards Flashcards
where are most earthquakes and volcanoes found
along plate boundaries, 70% of earthquakes found in the Ring of Fire in the Pacific ocean
what is a divergent plate boundary
when two plates move away from each other, 2 continental magma rises to fill the gap creating a rift valley, two oceanic plates it forms a submarine volcano
what is a convergent plate boundary
when two plates move towards each other, when two oceanic the denser plate subducts, when oceanic and continental the oceanic subducts. causes earthquakes due to friction, two continental plates it forms fold mountains
what is a Conservative plate boundary
when two plates slide past each other, sinistral ( left) or dextral (right), causes shallow earthquakes
what is a hotspot
a volcano created in the middle of the plate, caused by a mantle plume which melts the oceanic crust and forms a submarine volcano which grows into an island arc as convection currents cause the plates to move which forms new volcanos e.g Haiwaiian Ridge
what are the three theories of plate tectonics
layers of earth, continental drift, seafloor spreading
what are the four layers of the earth
crust, mantle, outer core, inner core
what is the Benioff zone
an area of seismicity corresponding with a slab being thrust down into the subduction zone
what are p waves
vibrations caused by compressions
what are s waves
vibrate at right angles to direction of travel and can’t pass through liquids
what are love waves
surface waves which can cause large amounts of damage
what is liquefaction
cause buildings to settle, tilt and collapse, lateral spreading causes damage to roads and bridges. Secondary effect
what are landslides
occur when slopes weaken and fail, in Kashmir earthquake 1/3 of all deaths due to landslides. Secondary effect
what is pyroclastic flow
mixture of dense hot rock, lava, Ash and gases that are ejected, 700 degrees and 100km/h, Primary Hazard
what is tephra
pieces of rock and Ash that blast into the air during eruptions, Primary hazard
what are lava flows
streams of lava that are 1170 degrees and take years to cool completely but are slow, primary hazard
what are volcanic gases
water vapour, CO2, sulphur dioxide and can be potentially hazardous, primary hazard
what are lahars
masses of rock mud and water that travel quickly down the flanks of a volcano, 10m/s, when eruption melts ice and snow, secondary effect
what is jokulhaup
heat of volcano melts snow and ice and causes flooding, secondary effect
what is a hazard
a perceived natural event that has the potential to threaten both life and property
what is a disaster
a serious disruption of the functioning of a community, which exceeds the ability of the affected community to cope using its own resources
what is the risk equation.
hazard x exposure x (vulnerability/ manageability)
what is continental drift
there was a super continent called Pangea that became separated, evidence was that Africa and South America looked like a jigsaw, Scotland and Canada have matching rock sequences, Fossils in India and Australia matched
what is seafloor spreading
by studying the age of rocks on either side of the Mid-Atlantic Ridge Harry Hess realised that the Earth’s polarity swaps every 400,000 years (Palaeomagnetism)
how is a tsunami formed
from the displacement of large quantities of water, created by an underwater earthquake, sub-marine volcano erupting or a landslide
what is the pressure and release model
a disaster is the intersection of two processes, on one side its the process generating vulnerability and then the natural hazard event on the other
what are the three earthquake measures
Richter Scale, Mercalli Scale, Moment Magnitude Scale
what is the Richter Scale
measure of the amplitude of the waves produced, good because its an absolute scale, 0-9
what is the Mercalli Scale
measures the experienced impacts of an earthquake, a relative scale because experience different amounts of shaking in different places, based on a series of key responses, such as people waking up or damage to structures
what is the moment magnitude scale
modern measure used by seismologists to describe earthquakes in terms of the energy released, based on the ‘seismic movement’ of the earthquake which is calculated from the amount of slip on the fault, the area affected, and an Earth rigidity factor, 0-9
what is the volcanic measure
the Volcanic Explosivity Index, a relative measure of the explosivenesss of a volcanic eruption, calculated from the volume of the products, height of the eruption cloud and qualitative observations -0-8
what factors contribute to a more vulnerable community
Corruption, Weak political commitment, population density, geographic isolation an accessibility, degree of urbanisation
what factors affect the impacts of a tsunami
the duration, the amplitude, the geography of the coastline, if there is a coastal ecosystem buffer, timing of the event, degree of coastal development
what are the methods of predicting earthquakes
seismometer, animal Behaviour, Magnitude/Frequency analysis
what are the methods of predicting volcanoes
Thermometer, Seismometer, Geometer, Spectrometer
what is Park’s model
can be used as a framework to help better understanding the time dimensions of resilience, can be used to help plan and understand risk and resilience, as well as better prepare for future events through modification of the responses to the event
what is the Swiss cheese model
suggests that hazard and risk can be reduced by reducing the number of weaknesses and gaps in the response system by modifying the hazard event, modifying vulnerability and resilience, and modifying the loss
how can you modify the hazard event
through micro protection techniques such as strengthening individual buildings and structures against hazardous stress, macro protection techniques such as large protective measures designed to protect whole communities
how can you protect against an earthquake
strengthening public buildings and facilities, especially those expected to remain operational during a disaster such as hospitals and police stations. Also strengthening schools and factories so that people can shelter in them, and improving the planning frameworks for private houses
how can we protect against tsunamis
tsunami walls that work for a given amplitude or threshold of wave, replanting of coasts to use as buffer zones
how can you defend against volcanoes
by diverting or shilling the lava flows, land use zoning, GPS and satellite monitoring equipment
what is the ability to predict a hazard
the ability to accurately identify when and where the hazard will take place
what is the ability to forecast a hazard
the ability to predict what type of the hazard will take place where
