TECTONICS! Flashcards
what are the three types of plate margins?
conservative
constructive
destructive
what are oceanic tectonic plates made of?
basaltic rock
destructive plate margins:
the oceanic plate slides beneath continental rocks catch against one another pressure between plates build plates slip past each other ground shakes
what causes plates to move?
movement in the mantle
what thickness are oceanic and continental plates?
oceanic: 7-10km
continental: 25-75km
three types of tectonic hazard:
earthquake
tsunami
volcano
what is a cause of intra-plate earthquakes?
stresses reactivating ancient fault lines
formation of intra-plate volcanoes:
isolated plumes of concerting heat rise towards surface
plume remains stationery but tectonic plate above moves
plate movement continues to produce chain of volcanic islands
what is a hazard
a natural/geophysical event that has the potential to threaten both life and property
how are hotspots made?
hot mass of rising heat
a weakness in a plate
magma rises to the surface
what is the name given to the impact of the Indo-Australian plate with the Eurasian plate?
collision zone
the inner and outer core are made from…
iron and nickel
what process happens at collision margins?
fold mountains are formed
what is true of the earth’s structure?
the core is a source of radioactive heat
the lithosphere is 80-90km thick
outer core is more liquid than inner core
what proves new crust is created by sea floor spreading at mid-ocean ridges?
paleomagnetic signals
what can be expected at constructive plate margins?
basaltic eruptions
low viscosity lava
low magnitude, shallow-focus earthquakes
order of earth’s structure
inner core outer core mantle asthenosphere lithosphere crust
what are some plate tectonic discoveries?
Wegener’s continental drift hypothesis
seafloor spreading creates new crust
slab pull drags down high density ocean floor at convergent boundaries
gravitational siding at divergent boundaries
internal radioactive hear drives convection currents
what happens at the Californian San Andreas fault?
transform margin: high magnitude, shallow focus earthquakes are common but no volcanic activity
what do higher altitudes of oceanic crust at ridges create at divergent plate boundaries?
gravitational sliding
how is energy released from the focus of an earthquake ?
seismic waves
what type of earthquake wave causes the least damage?
p-waves
what are the causes of deep-focus earthquakes?
previously subducted crust moving towards earth’s core
previously subducted crust heating up
previously subducted crust decomposing
what is the point directly above the centre of an earthquake on the earth’s surface?
epicentre
when an earthquake happens, what waves have the ability to shake the ground violently, but what cause more damage?
s-waves
l-waves
what are shallow focus earthquakes?
where the focus is 0-70km under earth’s surface
types of earthquake wave:
l-waves: only across surface, cause most damage
p-waves: fastest, cause least damage
s-waves: shake ground violently, only produced by some earthquakes
why are deep focus earthquakes less damaging than shallow focus earthquakes?
shock waves have to travel further so cause less shaking at surface
what are the main secondary hazards of earthquakes?
liquefaction
tsunamis
landslides
two primary hazards of an earthquake:
ground shaking
crystal fracturing
what happened in Pompeii in AD79?
Mount Vesuvius erupted and covered the city with pyroclastic flow
what is a jökulhaup?
type of glacial flooding caused by melting ice caps and glaciers (secondary hazard of some volcanoes)
what is true of pyroclastic flow?
very hot and high velocity
what is a lahar?
fast mudflows that happen when rain mobilises deposits of volcanic ash
primary hazards of volcanoes:
ash falls
pyroclastic flow
lava flows
volcanic gases eg. CO2, carbon monoxide
what follows the vertical displacement of the seabed?
water column displacement
characteristics of tsunamis:
often preceded by drawback reaches coast as wave-train very short amplitude at sea very long wavelength at sea high velocity (speeds of up to 700ph)
the Boxing Day tsunami:
epicentre in Banda Aceh
magnitude of 9.2
happened in 2004
what is a drawback?
when water is sucked up and away causing a localised drop in sea level
which direction is the seabed displaced after a submarine earthquake?
vertically
what is the probability of a hazard happening and creating a loss of lives/ livelihood
risk
how is a populations ability to cope with a natural disaster increased?
emergency evacuation, rescue and relief systems
what is vulnerability?
the risk of exposure to hazards combined with an inability to cope with them
what does the PAR model say?
risk is a function of vulnerability and nature of tectonic hazard
what is a disaster?
when a hazard has a significant impact on people: the consequence of a hazard happening
what is the hazard risk equation?
risk = (hazard x vulnerability) / capacity to cope
what does the PAR model show?
the connections between the nature of a hazard and its wider context
what does the PAR model stand for?
pressure and release
why is it difficult to compare impacts between countries?
the hazard itself will be different
socio-economic characters are different
deaths in developed countries usually low, but high in developing countries
what are some social impacts of a hazard?
deaths, injuries, physical health impacts, psychological health impacts
measuring tectonic hazards:
volcanoes: VEI, magnitude
earthquakes: MMS, mercalli scale
what was the areal extent of the Kashmir 2005 earthquake?
1000km2
what would be associated with high risk natural hazards?
low frequencies large areal extents rapid speeds of onset low spatial predictability high magnitudes
information contained in hazard profiles:
magnitude speed of onset areal effect duration frequency spatial predictability
hazard profile of Kashmir earthquake:
areal extent of <1000km2 MMS 7.6 aftershocks of MMS 6.4 damage centred on Muzaffarabad ground shaking lasted 30-45 secs
what magnitude and frequency would a high risk event have?
high magnitude and low frequency
what do hazard profiles summarise?
the physics processes shared by all hazards so that decision makers can determine which areas are most at risk
which of the following are characteristics of places with a low HDI (<0.55)?
low education levels
people lack basic things in ‘normal’ time
poor access to healthcare
informal housing
why are death tolls from natural disasters higher in urban areas than rural?
high concentration of people at risk
what should governments be doing after a disaster?
meeting basic needs by proving sufficient food and water
tackling corruption and making sure aid money is not taken by officials
zoning
splitting up land use between different areas of a city to make sure there are no houses on unstable land
what does HDI stand for?
human development index
what counts as having a low HDI score?
less than 0.55
immediate response to the Tohoku earthquake and tsunami
search and rescue
preventing nuclear disaster at Fukushima
evacuating people from the Fukushima area
what kind of tectonic zone did the Tohoku earthquake and tsunami occur on?
subduction
statements about the 2011 Tohoku earthquake:
16,000 known deaths economic losses were US$300bil magnitude MMS 9.0 tsunami travelled up to 20km inland happened on a subduction zone
what was he government post disaster report for the Tohoku earthquake and tsunami focused on?
future safety measures
features of the Gorkha earthquake:
MMS 7.9
90km NE of Kathmandu
9000 deaths
22000 injured
how much financial aid did the Asian Development Bank provide for reconstruction work?
US$200million
aid post-earthquake:
ADB gave US$200 million
1mil needed emergency food
severe gender discrimination
statements about the 2015 Gorkha earthquake:
NE of kathmandu
2.8mil people displaced from kathmandu valley
9000 deaths, 22000 injured
magnitude MMS 7.9
statement about the 2010 Mount Merapi eruption:
large pyroclastic flows caused damage
eruption came from a composite cone
a lahar caused devastation
the volcano is at a subduction zone
things delivered by government aid post-eruption:
food
water
hygiene kits
what was the VEI of the 2010 Mount Merapi eruption?
4
Mount Merapi eruption:
VEI of 4 large clouds of ash 353 deaths 350000 successfully evacuated rice harvest lost forest destroyed by pyroclastic flows
Mount Merapi 2010 eruption responses:
pre-eruption: evacuated everyone within 20km of the volcano
post eruption: government aid (food, water, hygiene kits), local airports shut, refugee shelters
statements about earthquakes since 1980:
15-40 disasters per year
large disasters have skewed death numbers
economic losses have increased
what % of earthquake deaths since 2005 can be accounted for by Kashmir (2005) Sichuan (2008) and Nepal (2015)?
40%
characteristics of multiple hazard zones:
at risk from global climate perturbations eg. ENSO
geologically young eg. prone to landslides
on major storm tracks eg. mid-latitudes or on tropical cyclone tracks
tectonically active eg. earthquakes and volcanoes are common
what does ENSO stand for?
the El Niño Southern Oscillation
examples of large tectonic disasters in the himalayas:
Kashmir 2005
Sichuan 2008
Nepal 2015
how many volcanic eruptions have killed more than 100 people since 1980?
7
what would you use to record volcanoes ‘bulging’ as magma rises?
tilt meter
equipment to monitor volcanoes:
gas spectrometer: analyse gas emissions that can point to increased eruption likelihood
seismometer: records minor earthquakes that indicate magma movement
tiltmeter: record volcanoes bulging as magma rises
what does forecasting mean?
giving a percentage chance of a hazard happening
what does prediction mean?
knowing when and where a natural hazard will strike so that meaningful action can be taken
the hazard management cycle stages:
response (immediate rescue help)
recovery (rebuilding infrastructure and services
mitigation (trying to reduce scale of next disaster)
preparedness (community education and resilience building)
what does the Park Disaster Response Model show?
the different stages of disasters
impact of disaster on quality of life
usefulness of management strategies
response curve (depends on preparedness and economic development)
how can land use zonin be used?
to prevent building on low lying coasts to avoid tsunami damage
avoid building on areas where liquefaction is likely
what would be used in an earthquake-proof building?
cross-bracing
what are examples of emergency aid?
search and rescue
emergency food water and shelter
how can vulnerability to natural disasters be modified?
using hi tech monitoring to monitor volcanoes and predict eruptions
through community preparedness and education
why would you build a building with deep foundations, cross-bracing and counterweights?
to resist earthquake damage
