What are the distribution of volcanoes?
volcanoes are mainly located along the rim of the pacific plate and joining plates on the ring of fire.
- these ring of fire volcanoes are active
- these are linear
Volcanoes are also located within plates as intraplate volcanoes these occur when random plumes exist.
What are the distribution of earthquakes?
earthquakes are found most commonly along tectonic plate faults.
These can also be formed at intraplate occurrences as the older faults are reactivated allowing tectonic energy to occur.
What are the distribution of tsunamis?
tsunamis are all formed over oceanic currents when the ocean has enough energy and current to carry a strong wave
These waves are mainly located along the ring of fire because tectonic activity is most common there therefore, there is a greater chance that a secondary hazard (tsunami) will occur.
What are the differences between convergent divergent and conservative plate boundaries?
convergent - destructive plates colliding
divergent - constructive plates moving apart
conservative - transform plates sliding past each other
What happens at a convergent (oceanic+oceanic)?
give an example of a land form or occurrence
- the denser basaltic oceanic slides underneath the other creating a ocean trench and earthquakes in the benioff zones
- if the earthquakes are powerful then a tsunami is formed
- the mantle is melted as the crust is forced down this then creates underwater volcanoes (submarine)
- the volcanoes can grow creating island arcs
This is evident in the line of volcanoes, known as the Aleutian Islands
What happens at a convergent (continental+oceanic)?
give an example of a land form or occurrence
- the oceanic is sub-ducted underneath the lighter continental plate as its sub-ducted this creates
- creates fold mountains as continental is pushed backwards
- earthquakes occur int he Benioff Zone due to extreme friction
- friction also melts mantle = volcanoes due to upthrusting magma through faults
Eg fold mountain The Andes range
What happens at convergent (continental+continental) (collision)?
- plates are same density (buoyant) so neither are sub-ducted and both are less dense then asthenosphere
- So they collide forcing rocks upwards in high fold mountains
2b (if they are subducted then it causes an earthquake with a shallow focus)
Eg Fold mountains in the Himalayas
What happens at a divergent boundary?
oceanic
example?
- when 2 plates move apart making new crust in the water this makes trench
- minor shallow focus underground and submarine volacnoes are formed as ridges can grow to make volcanic island eg Iceland
- volcanoes have runny lava basaltic
- non explosive (effusive)
What happens at a divergent boundary?
continental
example?
- when 2 plates move apart from each other making rift valleys parallel cracks and faults.
- the land between faults collapses creating steep valleys with water
Eg East Africa Valley
What happens at a conservative boundary?
example?
- 2 plates slide past each other
- major break in the crust (transform)
- potential shallow focus earthquakes causing major damage
- earthquakes magnitude 8.5, daily tremors
Eg San Andreas
What happens at a intraplate earthquake?
example?
- occur along middle or interior of tectonic plates
- along old faults which reactivate
- also fracture crust
eg tibetan plateau
What happens at a intraplate hot-spot volcano?
example?
- up welling of molten magma in random area (mantle plume)
- high heat and pressure at lithosphere base = melting rocks causes magma to rise through cracks
- This then moves across the mantle causing new volcanoes from the moving plates as a chain
Eg Hawaii (atoll= previous volcano)
What is convection current theory?
1) constant magma plates in mantle pulling away and towards each other
2) this is at divergent margins
3) radiated heat rises from radioactive nuclear core
4) pulls apart plates sinks at convergent margins as if subducts making ocean trenches.
What is sea floor spreading theory?
That magma forced up by convection currents creates a ridge in ridge push on an oceanic plate
This then sinks due to be denser than the continental plate subducts at an oceanic trench
Slab pull occurs when applied by gravity it sinks to the warmer core turning back to magma
This cycle is repeated and pushes plates apart.
What is paleo magnetism?
1) This a way to prove sea floor spreading
2) This is a study of changes in magnetic field of the earth
3) These magnetic poles flip every couple of years
4) The symmetrical polarity patterns in the varied igneous rock show age of different magnetic fields over time
What is meant by the term plate boundary?
it is a tectonic zone where 2 or more plates interact with each other which has the potential to alter the surrounding earth. This is shown as the Eurasian plate meets the north american plate creating land forms each mid Atlantic ridge at divergent
What are the 4 types of plate boundary?
convergent (destructive) eg Chile (Nazca and South American plate)
divergent (constructive) eg Mid-Atlantic-Ridge
conservative (transform) eg San Andreas
collision (convergent) eg Himalayas Indo-Australian plate and Eurasian plate
What two plate boundaries are earthquakes most powerful?
Conservative (transform) eg San Andreas
Convergent (destructive) eg Chile (Nazca and South American plate)
What are hotspot volcanoes and where do they occur?
These volcanoes are intraplate tectonic hazards where a mantle plume upwells through the lithosphere and above the crust. This magma then abruptly is forced above the crust solidifies which is a constant process which eventually forms island arcs such as Hawaii as plates keep moving however the plume remains stationary (pacific)
What did Harry Hess discover?
That the Mid-Atlantic-Ridge existed and that older rock was nearer the coastline which proved that new land was being formed from a constructive margin (a submarine volcano). This led to the discovery of sea floor spreading and ideology that the earths crust was on a constant ‘recycling’ process. Eg Eurasian plates moving east and the North American Plate moving west.
Why are some locations more at risk from tectonic hazards then others?
- low lying land (tsunamis, Indian-ocean 2004)
- tectonic plates boundaries (Eg San Andreas)
- level of development (Eg Haiti vs Christchurch earthquake)
- high focus/hypocenter in ground
How did paleo-magnetism help in the study of plate-tectonics?
Helped prove sea floor spreading
Helped prove that Wegner was correct
Showed that Harry Hess discovered it correctly
What is a locked fault and why is a cause for concern?
It is a fault where there is an extreme amount of elastic energy, tectonic strain, elastic rebound and plates slowly grind along each other.
Can cause deadly quakes, create secondary hazards, hard to research/discover, unpredictable, impact human lives
What is the benioff zone?
A zone where two plates meet in a destructive margin and is where extreme friction, tectonic strain and elastic energy is present from the subduction.
This contributes to sea-floor spreading and where the subducted plate melts in the upper mantle which can fuel volcanoes and earthquakes
