Tectonic plates and hazards Flashcards
explain the distribution and cause of tectonic hazards
plate boundaries often move in different directions at different speeds creating a variations of plate boundaries which leads to variations in earthquake and volcanic activity
what is a divergent plate boundary
this is when the two plates move towards each other and one plate gets subducted which can cause earthquakes and volcanoes
eg: Nazca plate forced under south american plate
What is a convergent/collision plate boundary
this is when two plates move towards each other and collide forming mountains and tends to be continental rock eg: the himalayas
what is a constructive plate boundary
this is when the plates move apart from each other which can lead to creation of new crusts and when in the sea it can form new sea ridges
eg: pacific plate moving away from nazca plate
what is a conservative plate boundary
this is when two plates slide past each other and due to the friction this tends to form earthquakes eg: San andreas fault
what is convection
convection is when magma rises due to the heat and it being less dense causing denser and colder material to sink this tends to help volcanoes
what is mantle convection
heat produced by radioactive decay heats the lower mantle creating convection currents within the asthenosphere causing plate movements
explain sea floor spreading
judge mid ocean ridges formed (constructive) and magma is forced up and hardens forming new oceanic crust causing the sea floor to spread and push the tectonic plates apart
what is subduction
when two plates move towards each other one slides underneath the other causing a subduction zone
what is a slab pull
newly formed oceanic material at mid- ocean ridges become denser and thicker as it cools causing it to sink into the mantle pulling the plate down (helps subduction)
what are intra plate earthquakes
these occur in the middle (interior) of plates and their cause is most likely stresses from scientists faults becoming active again they have a random distribution
explain the distribution of hotspots
these can be found near the centre of some plates due to upwelling if the hot molten material form the core eg: hawaiian plate
or it can be caused by mantle plumes just under the crust heating the surface above it eg: cape verde islands
what is palaeomagnetism
this is a theory form the supercontinent pangaea and how you can find the same rock types at different coasts eg: south africa and south america and this is due to the magnetic field where either side of the plate the rocks ‘lock in’ forming the same pattern of rocks on either side
what are primary waves
primary waves arrive first and move through solid rock and fluids, they move in a push and pull motion
what are secondary waves
slower than P waves and only move through solid rock. They move in an up and down motion
what are Love waves
the only travel through the surface of the crust and are fast. They move from side to side
what are 3 secondary impacts of earthquakes (include examples)
tsunami- japan 2011 (powerpoint & 15,000)
landslides- movement of severe and rocks faking creating hazards such as road blockage kashmir 2005
liquification- sediments in ground become loose due to shaking. christchurch new z had a shallow earthquake 5.95 on which exaggerated liquification
primary factors from earthquakes
crustal factoring
ground shaking creating hazard
how are tsunamis formed
these tend to be formed when submarine earthquakes at subduction zones as a result of water column displacement
describe balsatic lava
hottest lava (1000-1200)
runny and thin
found at shield volcanoes & ocean hotspots
gentle eruptions
describe andestitic lava
around 800-1000
slow flowing however eruptions are moderately powerful
describe rhyolitic lava
coolest lava (650-800)
very high viscosity
has most violent eruptions
found at compositivo volcanoes/ super volcanoes
describe a shield volcano
found at hotspots or convergent boundary
erupt frequently but not that powerful
balsatic lava
describe a composite volcano
found at destructive plate boundary
erupt infrequently however are very powerful
andesitic/rhyolitic lava
primary impacts from volcano/lava
lava flows: streams of lava move slowly from volcano and can take years to cool however because they’re so slow they’re not that hazardous to humans
example: kilauea volcano, Hawaii
pyroclastic flows: consist of dense rock and lava flowing very quickly (100km) from volcano impossible to get away from making them very hazardous eg: mount sinnabung
secondary impact of volcano
lahars: these are masses of rock, mud and water that vairy in size and speed, they occur when eruption occurs on ice/snow eg: jokulaud
describe a few impacts of tsunamis
they can travel several miles inland sweeping away buildings, trees and bridges
they can change the landscape of small islands/ completely destroy them
cause drowning, buildings to collapse on people and flooding can cause contamination to food and water leading to illnesses
how do you detected tsunamis?
DART sensors are used to monitor changes in sea level
japan is known for having the most extensive warming system for tsunamis in 2011 there was a warning within 3 minutes
describe an earthquake event for a developing country
Haiti: January 12th magnitude 7 (13km)
impacts: half a million deaths
this earthquake turned into a disaster due to:
because it isn’t very wealthy money was spent on reducing poverty rather than earthquake preparation
high levels of government corruption reduced improvements to buildings and living standards
poor buildings due to lack of building regulations
high population density
few peephole knew what to do due to lack of earthquake prep
RECOVERY
In 2016 Haiti was still recovering and $13 billion was donated to help however other countries were hesitating due to the corruption in the government
IMPROVEMENTS
despite 80,000 being in temporary homes (2015)
new roads, buildings and schools are slowly being built along with health statistics improving and a stronger government
describe an earthquake for an emerging country
CHINA
earthquake magnitude 7.9 on 12th May 2008 in SICHUAN
IMPACTS
Over 45.5million were effected (70,000) deaths
and 5 million made homeless
landslides caused 25% of deaths
300,000 injuries
in Sichuan the location was quite rural = fewer deaths
china is wealthier (than haiti) meaning they could ph for rescue efforts
medical services restored preventing disease
government gave $10billion for rebuilding
within 2 weeks temporary houses, roads and building were being built
BECAUSE CHINA HAD A STRONGER GOV
they had tougher building codes and regulations which helped with responding to the event
RECOVERY
they rebuilt affected areas in 2 years
(however several days passed until oversea help was accepted)
Describe an earthquake in a developed country
JAPAN
March 11 2011 magnitude 9 earthquake struck
PRIMARY IMPACTS:
seawater displacement caused 10m high tsunami along with surges
Nuclear power plant was severely damaged releasing dangerous levels of radiation forcing evacuation of 47,000 people yet despite this japan had no deaths and few injuries
PREPARATION
japan had financial resources to prepare for hazards such has strict building regulations meaning their buildings could withstand earthquakes (low levels of corruption also helped)
earthquake education and practise drills (well developed disaster plans eg: 10m tsunami wall)
NUCLEAR PLANT RESPONSE:
electricity prices increased by 20%
government debt rose
green house emissions increased
ice land case study
eyjafallajokull april 2010
no deaths
ash clouds affected northern europe for a week
100,000 flights cancelled affecting 10 million people
airlines lost $1.7 billion
crops destroyed from ash
typhoon hiyan
category 5 November 2013 at 4:30 am
primary impacts:
homes destroyed
ross blocked by debree
5m storm surge - 400mm rainfall
7000 deaths
14.1 million people effected
million tons of crops destroyed
secondary effects:
survivors had to fight fro food causing 8 people to die
sea water and sewerage systems contaminated
responses:
800,000 people evacuated (refugee stadium flooded)
mangroves planted and storm surge warning system put into place for future
