Tectonic Hazards Flashcards
what is the distribution of earthquakes like? (for all three types of focus)
- on plate bounderies (shallow focus)
- lots of intermediate focus earthquakes on the west coast of south america
- deep focus earthquakes in south america and asia
whats the distribution of volcanoes like?
- lots of volcanic activity on the west coast of north and south america
- lots on the north east coast of oceania
- lots on the south east coast of asia
whats the distribution of tsunamis like?
- most highly destructive (around 5m) are in New Zealand, south east Asia and North/South America.
- most moderate (around 2m) are located on the south west coast of Australia along with some under 2m.
- some moderate ones found on the east coast of Africa
how thick is the different parts (oceanic and continental) of the crust on earth?
oceanic- 7km thick
continental- up to 70km thick
how deep is the mantle?
700km to 2890km deep
how deep is the outer core?
2890km to 5150km deep
how deep is the inner core?
5150km to centre
whats the temperature of the crust?
surface temp to about 400*c
whats the temperature of the mantle?
870*c
whats the temperature of the outer core?
4400c to 6100c
whats the temperature of the inner core?
7000*c (radioactive decay)
how dense is the crust?
less dense:
oceanic- 2.7g/cm^3
continental- 3.3g/cm^3
how dense is the mantle?
less dense to medium density
how dense is the outer core?
dense
how dense is the inner core?
very dense
what is the composition of the crust?
granite (continental) and basalt (oceanic)
what is the composition of the mantle?
peridote upper = olivine
lower = magnesium silicate
whats the composition of the outer core?
12% sulphur
88% iron
whats the composition of the inner core?
20% nickel
80% iron
whats the physical state of the crust?
solid
whats the physical state of the mantle?
phases of liquid and solid in layers
whats the physical state of the outer core?
liquid (generate magnetic field)
whats the physical state of the inner core?
solid (generates heat)
what happens at a constructive plate boundary?
they move apart
what happens at a transform (conservative) plate boundary
they slide past eachother
does
- seismic activity
- volcanic activity
occur at a constructive plate boundary?
- Yes (shallow focus + low magnitude)
- Yes (effusive flowing eruptions + low VEI)
what are the features of a constructive plate bounderies (what forms)?
island arc, oceanic trench
does
- seismic activity
- volcanic activity
occur at a destructive (ocean and continent) plate boundary?
- Yes (range of focal depths from shallow to 700km, along benioff zone, often high magnitude 6-8)
- Yes (explosive, moderate to high 5-6 VIE)
what are the features of a destructive plate boundary (ocean and continent)?
fault lines, ridges and surface scarring
what forms at a destructive ocean and ocean plate boundary? (seismic activity and volcanic is the same as o and c)
oceanic trench, fold mountains, volcanic peak
does
- seismic activity
- volcanic activity
occur at a collision plate boundary?
- Yes (shallow focus, moderate magnitude 6-8)
- No (usually none, occasional fissure eruptions)
what features are at a collision plate boundary?
- fold mountains, plateus
does
- seismic activity
- volcanic activity
occur at a transform plate boundary?
- Yes (moderate to high magnitude earthquakes of shallow focus)
- Yes/No (usually none, occasional fissure eruptions)
what features are shown at a transform plate boundary?
fault line (eg. San Andreas Fault)
what is slab pull?
- older colder plates sink at subduction zones (because as they cool, they become more dense than the underlying mantle)
- the cooler sinking plate pulls the rest of the warmer plate along behind it
what is paleomagnetism?
- discoveries were made that oceanic crust showed symmetrical bonds of magnetic stripes, formed either side of mid ocean ridge
- the earths magnetic field reverses approximately every 200,000 to 300,000 years.
- this helped to show that new oceanic crust was formed and helped to date rocks.
what did paleomagnetism prove?
sea floor spreading is a key role in plate boundary movement
whats the most convincing evidence of the theory of plate boundary’s constantly moving?
tectonic hazards (earthquakes, volcanic activity, mountain building along plate boundaries)
name an example of a collision plate boundary formation?
Himalayan Mountain Range
name an example of a constructive plate boundary formation?
Mid Atlantic Ridge- Iceland
name an example of a transform plate boundary formation?
San Andreas Fault
what hazards follow a:
-destructive
-collision
-constructive
-transform
- volcano, tsunami, earthquake
- earthquake
- tsunami, volcano, earthquake
- earthquake
examine why volcanoes aren’t created at all plate boundaries?
no way for magma to rise at a transform boundary
does all tectonic activity occur on plate boundaries?
no, because a few volcanoes are in the middle of the pacific ocean, which is very far from the plate boundaries. Also, many earthquakes are in central Asia, again not near a boundary.
discuss whether you think intra-plate activity can be more or less destructive than activity on plate boundaries?
interplate-
• occurs at plate boundery
• more common
• recognised on the surface
• releases stress but dissipated quickly.
Intraplate -
• not at plate boundary
• less common
• rarely recognised
• release more stresss-dissipates slower
how does focus depth influence the strength of an earthquake?
if a focus is shallow, the strength of an earthquake will be higher because the energy has less distance to travel
how does type of boundary influence the strength of a earthquake?
destructive has the most severe earthquake if its a destructive plate boundary - stronger.
how does distance from epicentre affect the strength of an earthquake?
further from the epicentre is weaker
how does geology influence the strength of an earthquake ?
if the rocks are weaker the energy will dissipate quicker so its a weaker earthquake
(geological fault lines or intraplate)
what is amplitude?
maximum extent of a vibration, measured from position of equilibrium
describe primary waves
- body wave
- highest velocity
- least damaging
- reaches surface first
- travel through solids, liquids, shaking back and forth
describe secondary waves
- body wave
- slower velocity
- higher amplitude
- move slower
- only through solid
- sideways motion
- more damaging than p
describe love waves
- surface waves
- highest amplitude
- move slowest
- most damaging
- shake ground side to side
- larger
- focus all energy on Earths surface
how are tsunamis formed?
• earthquake changes shape of sea floor causing displacement of water
• large waves form and move at up to 800km/h
• waves slow in shallower coastal areas but increase in height
name the 6 hazards of a volcano
- lava flows
- pyroclastic flows
- tephra
- gas eruptions
- lahars
- jokulhlaup
location of the boxing day earthquake/tsunami 2004
• indian ocean
• epicentre just off the coast of sumatra, indonisia
• affected thailand, sri lanka, malaysia and india
• caused by indo-australian plate and subducting under eurasian plate
what type of hazard is a tsunami?
secondary
causes of the boxing day tsunami?
• underwater 9.0 magnitude earthquake
• indo-australian plate subducted under eurasian by up to 20km
• release of pressure along 1200km of fault line/plate boundary
• sea retreated in thailand
• 24km high + 13.5m/s speed waves
• LIDC/ EDC not prepared and struggle to alert and evacuate so more died
hazard/impacts of the boxing day tsunami?
• 290,000 killed
• 1.7 bil homeless
• 2.9 mil economic loss
• oil spill
• effected 12 countries
• infrastructure destroyed
identify the four tectonic plates and the fault closest to there the turkey syria earthquake occured?
anatolian plate, eurasian, african and arabian
• east anatolian fault
explain the factors which made the earthquake so deadly? (turkey syria)
- magnitude of 7.8
- broke along a 100km fault line
- shallow focus
- unsturdy buildings
- occured early in the morn
differences between syria and turkey with the earthquake?
syria at war for many years, less of prep- already trying to recover
both EDCs - bad infrastructure