tectonic hazards Flashcards
where do earthquakes occur?
at plate margins
how do the plates move at constructive plate margins
they move away from each other
how do the plates move at destructive margins
towards each other
where do volcanos occur
volcanoes occur in long belts that follow plate margins
at which type of plate margins can volcanoes occur
- constructive and destructive
what is a hot spot
parts of the mantle which are really hot
how do the plates move at conservative plate margins
where the two plates are moving sideways past each other, or moving in the same direction but at different speeds
what is magma like at constructive margins?
very hot and fluid and lava will flow a long way before cooling - usually forms shield volcanoes
what happens at destructive margins
when an oceanic and continental plate meet, the denser oceanic plate sub ducts ( forced into the mantle) and destroyed creating magma - ocean trenches occur here
when two continental plates meet the ground is folded upwards making fold mountains
what happens at a constructive margin?
when the two plates move away from each other magma rises to fill the gap and cools, creating new crust.
what is the key information on the New Zealand ( HIC)
- (5 things)
- kaikoura ( new zealnd)
- 14th of November 2016
- GPD per captia - US 40,331
- plate boundary - destructive and conservative - the pacific plate sub ducts beneath Australian plate to the north and sliding past in the south
- 7.8 magnitude
what were the primary affects of new zealand eatrthquake
HIC
- 2 people died
- 50 people were injured
- tens of thousands of houses were destroyed and damaged
- 60 people needed emergency housing
- US 8.5 billion - cost of damaged
- over 200km of road destroyed
- communications,water and power supplies were cut off
what were the secondary affects of the New zealand earthquake
- triggered up to 100,000 land slides which blocked major roads and rail routes
- a major landslide blocked clarence river leading to flooding and evacuation of 10 farms
- generated tsunami with wave of 5 m
what were the immediate responses for the New Zealand earthquake?
- tsunami warning - residents of coastal areas told to go to higher ground
- people housed in emergency centres
- 200 vulnerable people evacuated from kaikoura by helicopter
- power restored to most places
- temporary water supplies set up
- international warships were sent with supplies e.g food medicine, portable toilets
what were the long term Reponses of the New Zealand earthquake
- most road are rails were opened within 2 years
- the kaikoura mayoral earthquake relief fund was set up to support residents who couldn’t afford basic supplies
- 5.3 million of funding was provided by kaikouras district council to help with rebuilding
name the 3 layers of the earth
the core, the crust and the mantle
Tectonic plates move according to the movements below in the _______
mantle
where do convection currents happen
in the upper mantle
What are the potential products of volcanic eruptions?
- gas
- ash
- lava
- pyroclastic flows
what is the key information of the Nepal earthquake 2015
- 25th April 2015
- 7.8 magnitude
- destructive plate margin
- the indo Australian plate subducts beneath the Eurasian plate
- GDP - US 690
what were the primary affects of the Nepal 2015 earthquakes
- 9000 people died
- 20000 injured
- 4 million people left homeless
- overall cost of US 5 billion
electricity and water effected - roads and bridges were destroyed
what were the secondary effects of the Nepal 2015 earthquake?
- land slides + avalanche causing road blockages
- avalanche in mount Everest kill 18 people
- landslide blocked river causing river to flood making people evacuate
what were the immidiate responses of the Nepal earthquake 2015?
- search and rescue
- half a million tents to provide shelter to the homeless
- financial aid
- feild hospitals
what evidence is there that Nepal is poorer than New Zealand?
the HDI and GDP shows that nepal is lower than New Zealand in the rankings.
why was such a vast area of Nepal affected?
the earthquake in Nepal triggered landslides and avalanches which went on for miles increasing the amount of land that was affected by the earthquake
why do people choose to live in hazardous areas?
- poverty
- they might not be aware
- favourable areas ( coasts - ports)
- volcanoes can bring benefits - fertile soil
- earthquakes and volcanoes dont happen often so people do not worry about them
- they have always lived there
- wealthy countries might have effective monitoring which reduces risk
how can we reduce the risk of hazards?
- monitoring - scientific equipment to detect warning
- planning - avoiding places at risk
- protection - building that will withstand
- prediction - historical evidence
what are some warning signs of volcanoes?
- steam erupting
- heat melts the snow
- gases from the rising magma
what are different types of monitoring?
- remote sensing - satellites that detect heat
- seismicity - seismographs
what two types of crust are plates made up of?
- continental - thicker and less dense
- oceanic - thinner and more dense
why do plates move
because of convection currents in the mantle
what are the places where plates meet called
plate margins or plate boundaries
what are the three different types of plate margins
- destructive
- constructive
- conservative
give an example of a conservative plate margin
San Andreas Fault
the pacific plate is moving in the same direction as the north american plate but faster
give an example of a destructive plate margin
- west coast of south america
- Nazca plate sub ducts under south american plate creating the Atacama trench
give an example of a constructive plate margin
- the movement of the Eurasian plate and north american plate away from one another creates the mid Atlantic ridge
how do volcanoes occur at destructive plate margins
- denser oceanic plate moves down into the mantle where it melts
- a pool of magma forms which rises through the cracks in the crusts called vents
- the magma erupts forming a volcano
how do volcanoes occur at constructive plate margins
- the magma rises into the gap created by the plates moving apart creating a volcano
which plate margins do earthquakes occur at?
all three of them
what are earthquakes caused by?
by the tension that builds up at the plate margins
how do earthquakes occur at destructive plate margins
- tension builds up when one plate gets stuck as it moves across the other
how do earthquakes occur at constructive plate margins
the tension builds along cracks in the plates as they move away from each other
how do earthquakes occur at conservative plate margins
tension builds up when plates that are grinding past eachother get stuck
plates eventually jerk past eachother, sending out ______ ____. these vibrations are the ____________
shock waves
earthquake
where are shock waves spread out from
the focus
what is the focus
the point in the earth where the earthquake starts
- waves are stronger near the focus and cause more damage
what is the epicentre
the point on the earths surface straight above the focus
how can we monitor earthquakes
- seismometers and lasers monitor earth movements and can give a small amount of warning
how can we monitor volcanos
- tiny earthquakes
- escaping gas
- changes in shape of a volcano
how can we predict earthquakes
they cant be reliably predicted but scientists can forecast where they may occur by monitoring the movement of plates
hwo can we predict volcanos
is scientists monitor volcanos closley
how can we use protection to reduce the effects of earthquakes
- new buildings can sue reinforced concrete that absorb an earthquakes energy
- existing buildings and bridges can be strengthened
- automatic shut off switches can turn off gas and electricity to stop fires
how can we use protection to reduce the effects of volcano
- buildings strengthened so they are less likely to collapse under the strength for ash
- trenches and barriers can be used to try and divert lava away from buildings and settlements
what methods can be sued to plan fro volcanoes and earthquakes
-emergency services can prepare by practising e.g practise rescuing people from collapsed building
- people can be educated to know what to do in the event of a hazard
- government plan evacuation routes
- emergency supplies can be stockpiled
What type of hazard are earthquakes and volcanoes examples of?
geological
What factors affect the severity of natural hazards?
frequency
predictability
magnitude
what are the two layers of the core
inner metallic core - solid
outer outer - liquid
what are the characteristics of volcanoes at destructive plate margins?
- highly explosive
- produces alot of gas
- produces alot of lava
What do we call the event when a volcano erupts, produces lots of ash, and blocks the sun?
a volcanic winter
what are lahars
Lahars (mudflows) can destroy everything in their path, including buildings, homes, workplaces.
they re secondary affects of volcanoes
what are overall secondary affects of volcanoes
- flooding and tsunamis
- volcanic winter - crops dont ripen
- lost forests and farm lands
- infrastructure damage
- economic damage
- lahars
- increased soil fertility
what are the overall immediate responses to volcanoes
- temporary infrastructure
- aid
- evacuation
- warning and monitoring
what are the overall long term responses to volcanoes
- relocate
- rebuild infrastructure
- improve local economy
Governments may help people relocate after a natural disaster using _______ programmes
resettlement
