Tectonics Flashcards
What is tectonic activity?
movement of plates
What is a plate?
section’s of the Earth’s crust
What is a plate boundary?
the margin where 2 plates meet
Where are Earthquakes located?
- plate boundaries
- destructive plates - Nazca & South American
- conservative plates - Pacific & North American
- Pacific Ring of Fire
- long, narrow belts
Where are Volcanoes located?
- plate boundaries
- especially on destructive margins e.g. Pacific Ring of Fire
- constructive plate margin e.g. Mid Atlantic Ridge
- some in middle of plates on hot spots
- long, narrow belts
What are the characteristics of Oceanic crust?
- thinner
- more dense
- younger
What are the characteristics of Continental crust?
- thicker
- less dense
- older
What happens at a destructive margin?
- convection currents cause plates to collide
- oceanic crust moves to continental crust
- oceanic is more dense so is subducted
- friction caused by oceanic crust can cause an earthquake
- friction causes oceanic plate to heat up
- as it heats it melts to magma which then makes its way up through cracks in continental crust
- when it reaches the surface it forms a volcano
What happens at a constructive/divergent plate boundary?
- plates are moving apart due to convection currents
- magma then rises from the mantle erupting to the surface of the Earth, accompanied by earthquakes
- repeats many times over a long period
- eventually new rock builds up to form a shield volcano
What happens at a conservative plate boundary?
- 2 adjacent plates move alongside each other
- convection currents cause plates to move in either opposite or the same direction past each other but one at a faster rate
- friction can cause them to get stuck together
- pressure builds until one ‘jerks’ past the other causing vibrations causing an earthquake
- volcanoes don’t occur here
What are the layers of the Earth called?
crust
mantle
outer core
inner core
How deep is the crust?
5-70km
How deep is the mantle?
2885km
How deep is the outer core & inner core?
3360km
How hot is the crust?
0-1000°C
How hot is the mantle?
1000-5000°C
How hot is the outer core?
5500°C
How hot is the inner core?
6000°C
What is an earthquake?
vibrations in the Earth’s crust that shake the ground surface
Where do 90% earthquakes occur?
conservative plate boundary
What is the focus?
place inside Earth’s crust where an earthquake originates
What is the epicentre?
the point on the Earth’s surface vertically above the focus
What are seismic waves?
a vibration in the Earth produced by an earthquake
What is magnitude?
strength of the earthquake, measured using a seismometer
How are earthquakes measured?
the Richter Scale
What factors affect the level of damage of an earthquake?
- location of epicentre
- depth of focus
- wealth of country
- time of day
- earthquake size
How does the location of epicentre affect the earthquake?
the closer you are to it, the more destructive
How does the depth of focus affect the earthquake?
the deeper the focus, the less destructive
How does the wealth of country affect the earthquake?
the wealthier the country, the less potential damage because of stronger buildings, better healthcare & emergency services & more education & planning
How does the time of day affect the earthquake?
earthquakes that occur at rush hour or busier times of day have a higher risk
How does the size of earthquake affect the earthquake?
stronger the magnitude, the more damage will be caused
What are the main feature of a volcano?
crater
lava
cone
magma
magma chamber
main vent
secondary vent
dust, ash & rock
What are active volcanoes?
currently erupting or have erupted in recent history e.g. Mount St Helens
What are dormant volcanoes?
historically active but may not have erupted in the last 10,000 years, expected to erupt in the future
What are extinct volcanoes?
haven’t erupted in the last 10,000 years and aren’t expected to erupt in the future e.g. Mount Kilimanjaro
What are the characteristics of a shield volcano?
- low silicone, non-viscous (runny) lava
- wide base
- gentle slopes
- regular & frequent eruptions
- occur at constructive plates
What are the characteristics of a composite/cone/strato volcano?
- high silica, viscous (not runny) lava
- tall, cone shape
- highly explosive
- irregular eruptions with long dormant periods
- occur at destructive plates
Background information about Montserrat
- tiny island in the Caribbean (100km²)
- economy based on farming, fishing & tourism
- LEDC with average household income only £2,800 per year
- ‘British Overseas Territory’
What were the causes of the Soufriere Hills eruption?
- July 1995 it erupted for the first time in 350 years
- 1 month later, 50% the island was evacuated to the North of the island away from the danger zone
- June 1997 explosive eruptions killed 23 people
- only 39km² was considered safe
- dormant for 100 prior
- destructive plate boundary (North & South American plates slide beneath Caribbean plate)
What were the short term effects of the Soufriere Hills eruption?
- 23 death & over 100 injured
- Plymouth covered in ash
- High % homes, businesses & important infrastructure destroyed
- main airport & port closed
- 75% island covered in ash
What were the long term effects of the Soufriere Hills eruption?
- long time taken to rebuild homes & vital infrastructure e.g. roads, telephone lines
- ongoing problems of respiratory disease
- environmental damage to beaches, forests, wildlife & offshore coral reefs
- population fell from 12,000 (1995) to 1,500 (2001)
- skills shortage due to emigration
- fears of over-dependence on UK ‘handouts’
What were the wider impacts of the Soufriere Hills eruption?
- economy (farming, fishing, tourism) decimated very high levels of unemployment (>50%)
- serious impact on tourism, but because of the volcano last year tourism earned the island over £12m
- evacuees living for a long time in cramped, unhygienic conditions in ‘temporary’ camps
- housing shortages led to 70% increase in rents
- ongoing minor eruptions with more serious lahars following heavy rain
What were the responses of the Soufriere Hills eruption?
- 5,000 people evacuated to the North side of the island from towns such as Salem & Plymouth
- links with UK were vital in assisting the relief and recovery
- Royal Navy sent ships to evacuate 4,000 people to nearby Antigua
- islanders were offered £2500 each to relocate & live permanently in UK
- UK sent £41m in relief & further £75m to assist long term development
- non-governmental organisations (e.g. International Red Cross) organised evacuation camps
- permanent monitoring stations measuring volcanic activity all over the island
- island is promoting ‘volcano tours’ to attract tourists but only 20-seater planes are allowed to land at the new airport so this is difficult
What are the primary hazards of earthquakes
ground shaking - caused by seismic waves can fell buildings, bridges, trees etc. trapping people
What does the intensity of the ground shaking depend on?
- conditions of local geology - solid bedrock will shake less than loose sediment
- duration & intensity of earthquake
- distance from epicentre - further the distance the less shaking
What are secondary hazards of volcanoes?
- tsunamis - sudden shift of tectonic plates under sea can displace large amounts of water triggering massive tsunamis
- fire - earthquakes can break gas cables & knock over ovens & open fires, triggering secondary uncontrolled fires
- liquefaction - saturated soil loses strength & rigidity, causing the ground to behave like water allowing things to sink into it
- landslides/avalanches - seismic waves can trigger them causing them to bury/ kill many people
- floods - damage to flood defences/dams can cause widespread flooding
What are the short term hazards of volcanoes?
- volcanic ash - can cause breathing problems, ash on roofs can cause buildings to collapse, can kill plants leading to food shortages, reduced visibility so difficult to evacuate, disrupted travel & planes can’t fly
- pyroclastic flow - extremely hot, burns buildings, toxic gas so can’t breath, over 200kmph so hard to escape
- lateral blast - volcano erupts sideways so affects a larger area
- lahar - ice melts to form a mudflow, causes drowning, homes destroyed & crops damaged
- volcanic gas - sulphur dioxide is toxic & can contaminate water supply causing breathing issues/death, impacts climate change
- tsunami - causes drowning, kills crops, property damage
What are the long term hazards of volcanoes?
- famine
- disease
How can you predict earthquakes?
you can’t
How can you prepare for earthquakes?
- evacuation routes
- rescue teams on standby
- earthquake survival kits
- educate people about what to do in one
- practice earthquake drills
- warning systems for aftershocks & tsunamis
How do you protect from an earthquake?
- reinforced walls
- don’t build high rise buildings
- pyramid shape buildings
- deep foundations
- rubber shock absorbers
- outer panels flexibly attached to steel structure
- steel frames that can sway
- fire resistant building materials
- foundations sunk into bedrock, avoiding clay
How do you predict a volcano?
- increase in temp. prior to eruption (thermal imaging camera)
- change in shape (tilt meter)
- earthquake prior to eruption (seismometer)
- gases emitted prior to eruption e.g. sulphur dioxide
How do you prepare for a volcano?
- evacuation routes
- emergency survival kit
- rescue teams on standby
Why do people live near volcanoes?
- geothermal power - heat from mantle generates renewable electricity
- fertile soil - can be good for farming, volcanic ash contains magnesium & potassium
- creates new landmasses
- tourism (e.g. Vesuvius, Blue Lagoon) - people can earn money through tourists visiting these places
- sulphur mining - used for: bleaching sugar, vulcanising rubber, soap, explosives
What are primary impacts?
things that happen immediately as a result of a hazard
What are secondary impacts?
things that happen in the hours, days & weeks after the initial hazard
What are short term responses?
a response in the days & weeks after disaster has happened, mainly involve search & rescue & helping the injured
What are long term responses?
responses that go on for months & years after a disaster, it involves rebuilding destroyed houses, schools, hospitals etc.., and restarting the local economy
Why do people live in earthquake regions?
- can’t afford to move away
- lack of education/knowledge
- location of job
- connections to family
What were the causes of the Turkey-Syria earthquake?
- strike slip fault between the Arabian plate, the Eurasia plate and the Anatolian plate
- plates slip, pressure releases a 7.8 magnitude quake
- epicentre was only 18km deep
What factors exacerbated the Turkey-Syria earthquake?
- civil war in Syria for the last 12 years
- Syrians in NW region lived in hastily constructed building that couldn’t withstand earthquakes
- hadn’t been an earthquake here for over 200 years and there were no signs so they weren’t prepared
What were the primary impacts of the Turkey-Syria earthquake?
- over 56,000 killed
- 100,000 injured
- at least 4 million buildings damaged in Turkey
- at least 453 schools damaged in Syria
- runway of Hatay airport was split & uplifted
- large fire at Iskenderun port
What were the secondary impacts of the Turkey-Syria earthquake?
- 2.7m made homeless in Turkey
- trauma & mental health issues
- hypothermia became major risk for people living in makeshift accommodation due to snow & freezing weather
- over $100b damage in Turkey
- over $5.1b damage in Syria
What were the immediate responses of the Turkey-Syria earthquake?
- search & rescue teams worked their way through rubble with machinery & dogs
- teams of 60,000 officials were deployed to help the search
- EU dispatched rescue & medical teams, & €3m to aid Turkey & €3.5m to aid Syria
What were the long-term responses of the Turkey-Syria earthquake?
- removing 210m tonnes rubble in Turkey
- building 500,000 new houses
- hospitals could’t cope with large number of casualties
- Turkey president said he would rebuild all collapsed buildings within 1 year
