Tectonic Flashcards
Name 3 types of tectonic natural hazard
- earthquakes
- volcanic eruptions
- tsunamis
What is the difference between natural hazards and natural disasters?
Natural disasters are when the natural hazards actually do affect people or their property
What causes the tectonic natural hazards?
The movement of the tectonic plates
Describe the inner core of the earth
A ball of solid iron and nickel
Describe the outer core of the earth
Very hot liquid
What is the mantle?
Semi molten rock moving very slowly around the earths core
What is the outer layer of the earth called?
The crust
How thin is the crust?
20km approximately
What are tectonic plates?
Areas of the crust divided into slabs
What do the tectonic plates float on?
The mantle
Name the two types of crust that the plates are made of
- continental
* oceanic
Describe continental crust
- thicker
* less dense
Describe oceanic crust
- thinner
* more dense
Why do the plates move?
The mantle underneath them is moving very slowly
What are the places where the plates meet called?
Boundaries or plate margins
What is a natural hazard?
A naturally occurring event that has potential to affect people’s lives
Name the 4 types of tectonic plate boundaries
- constructive
- destructive
- conservative
- collision
What happens at a collision plate boundary?
Two plates of similar densities push against each other
What do collision plate boundaries cause for the land between them?
The land between them rises up and form mountains
What natural hazards occur at collision plate boundaries?
Earthquakes and tsunamis
How are earthquakes formed at collision plate boundaries?
They push together with equal force so eventually one will give way and flick up, causing an earthquake.
When are tsunamis caused at collision plate boundaries?
If one of the plates is oceanic
What happens at destructive plate boundaries?
Two plates of different sizes/densities are moving towards each other
What happens when an oceanic plate and a continental plate meet at a destructive plate boundary?
The denser oceanic plate is forced down into the mantle and is destroyed
What natural hazards are often caused when an oceanic and continental plate meet at a destructive plate boundary?
Volcanoes and ocean trenches
What is an ocean trench?
Very deep sections of the ocean floor where the ocean plate goes down
Name an example of a destructive plate boundary
The Pacific and North American plate boundary
What happens at a constructive plate boundary?
The plates pull apart
What natural hazard is always formed at constructive plate boundaries?
Volcanoes
How dangerous are the volcanoes that form at constructive plate boundaries?
Not very, the erupt with very little force and often magma just rises and cools to form new crust
Name an example of a constructive plate boundary
The Eurasian and North American plates are moving away from each other at the mid Atlantic ridge
What is a subduction zone?
The area where an oceanic plate is being pushed under a continental plate
What happens when two continental plates meet at a destructive/collision plate boundary?
They smash together but no crust is destroyed
What happens at conservative plate boundaries?
Two plates are moving sideways past each other or moving in the same direction at different speeds
What is a fault line?
The place where two plates slide next to each other
What natural hazard is caused at conservative plate boundaries?
Earthquakes
Why do earthquakes occur at conservative plate boundaries?
The friction between the two plates moving build up and is released when they give way
Name an example of a conservative plate boundary
The Pacific plate moving past the North American plate on the USA west coast, at the San Andreas fault
What moves the mantle under the earths surfaces?
Convection currents, heats and rises due to extremely hot temperatures then cools and falls in a cycle
How hot is the earths core?
5500*c
How hot is the mantle?
1100*c
How are volcanoes formed at destructive plate boundaries?
The denser oceanic plate subducts under the continental plate and melts to make magma. The seawater also goes down with the plate which makes the magma less dense so it rises and erupts out of the earth as volcanic eruptions, the water gets very hot and can erupt as steam to make very explosive volcanoes
What comes out of volcanoes?
Lava (molten rock)
What happens when the oceanic plate sticks to the continental plate as it subducts? What does this cause?
Huge pressure can build up and when they finally give way a huge amount of energy is released and causes an earthquake
What are the gaps in volcanoes called that magma can rise up and out from?
Fissures
Which plate boundaries to volcanoes form at?
- destructive
* constructive
Which plate boundaries cause earthquakes?
- destructive
- collision
- conservative
- (constructive, not devastating)
Where are the most severe earthquakes usually found?
Destructive and conservative plate boundaries
What is an earthquakes focus?
The movement point of the rock
What is an earthquakes epicentre?
Directly above the focus on the earths surface
What are seismic waves?
The vibrations that cause an earthquake that start at the focus
How can we measure the magnitude of an earthquake?
Using the Richter scale and a seismograph
What type of scale is the Richter scale?
A logarithmic scale
What is a logarithmic scale?
When the value increases by 1, the magnitude increases by 10, eg 6 is 10x stronger than 5
What is the Mercalli scale?
Similar to the Richter scale but is based on observation instead of the seismograph
What are earthquakes caused by?
The pressure and friction that build up at all the types of plate boundary
How does pressure build up destructive boundaries?
Pressure builds up when one plate gets stuck as its moving down past the other into the mantle
How does pressure build up at constructive boundaries?
Pressure builds along cracks within in the plates as they move away from each other
How does pressure build up at conservative boundaries?
Pressure builds up when plates that are grinding past each other get stuck
What happens when the plates eventually jerk past each other?
They send out shock waves, vibrations
What happens to the shock waves that were released at the start of an earthquake?
They spread out from the focus and shake the earths surface
Where is the earthquake the strongest and most dangerous?
Closer to the epicentre
What is an earthquakes magnitude?
The amount of energy released by an earthquake
Why does the oceanic plate go under the continental plate at destructive plate margins?
It is more dense
How are earthquakes formed at destructive plate boundaries?
The oceanic plate goes under the continental plate and melts in the magma, a pool of magma forms and rises through the vents, where it then erupts into the surface forming a volcano
What are vents?
Cracks in the crust that magma rises through
How do volcanoes form at constructive plate boundaries?
The magma rises up into the gap created by the plates moving apart, forming a volcano
What are hotspots?
Where volcanoes can also form over very hot parts of the mantle
Name an example of a hotspot
Hawaii
What are primary effects of an earthquake?
The immediate effects of the ground shaking
What are secondary effects of an earthquake?
Effects caused by the primary effects that happen later on
Name 7 primary impacts of earthquakes
- buildings and bridges collapse
- people are injured or even killed
- roads, railways, ports and airports are damaged
- electricity cables are damaged, cutting off supplies
- gas pipes are broken causing leaks and cut off supplies
- telephone poles and cables are destroyed
- underground water and sewage pipes are broken, causing leaks and cutting off supplies
Name 7 secondary impacts of earthquakes
- trigger landslides and tsunamis that destroy even more
- leaking gas can be ignited, starting fires
- people are left homeless
- suffer psychological problems
- shortage of clean water and proper sanitation
- roads are blocked so aid and emergency vehicles can’t get through
- businesses are damaged causing unemployment
Why is there more of an impact of a severe earthquake in developed areas?
There are more settlements and businesses set up so there are more people and properties that can be affected
Name 4 reasons why the impacts of an earthquake are more severe in ledc’s
- poor quality housing, which is less stable so are destroyed more easily
- infrastructure is poorer so poor quality roads make it harder for emergency services to reach injured people which cause more deaths
- they don’t have much money or education to prepare themselves for earthquakes or to react straight away when an earthquake hits, so more people are affected by secondary impacts
- healthcare isn’t as good so they don’t have the supplies to deal with large numbers of casualties
Name 4 reasons why people continue to live in areas where earthquakes happen in medc’s
- they’ve always lived there, moving away would mean leaving friends and family
- employed in the area
- confident of support from their government
- severe earthquakes are rare so they think it won’t happen whilst they live there so they think they’re safe
Name a reason why people continues to live in earthquake zones in ledc’s
•can’t afford to move away
Name 6 factors that affect the amount of damage caused in an earthquake
- size of the earthquake
- emergency services available
- building design and construction in the area affected
- time of day
- education
- physical landscape
Name 3 factors affecting the damage of an earthquake that are related to the wealth of a country
- emergency services
- building design and construction
- education
Name 5 types of reducing the impacts of an earthquake and a volcanic eruption
- prediction
- building techniques
- planning
- education
- aid
Name 5 ways we can use prediction to reduce the impacts of an earthquake
- tilt metre checks the movement within rocks
- animals can act strangely before an earthquake
- water levels can rise because of cracks in rocks
- foreshocks can measure seismic activity
- predict earthquakes from data from past earthquakes, eg mapping and previous seismic activity compared to current seismic activity
Name a way we can use building techniques to minimise the impacts of earthquakes
•design buildings to withstand earthquakes, eg using reinforced concrete or special foundations that absorb an earthquakes energy
Name 4 ways we can use planning to reduce the impacts of an earthquake and a volcanic eruption
- plan for future developments to be built away from earthquake/volcano zones to reduce number of collapsed buildings
- practise drills and citywide emergency plans and supplies
- emergency services can train for disasters to reduce the number of people killed
- government planned evacuation routes to get people out quickly and safely
Name 2 ways education can reduce the impacts of earthquakes and volcanic eruptions
- governments and other NGOs can educate people on how to react if an earthquake hits/volcano erupts and how to evacuate
- people can be told how to make a survival kit to reduce number of deaths of people are stuck in the area
Name a way aid can help reduce the impacts of earthquakes and volcanic eruptions
•ledc’s that have been affected by earthquakes/volcanic eruptions can receive aid from governments or organisations to help rebuild homes and for food
Why is predicting earthquakes not a sustainable strategy?
It’s not effective or completely accurate
Which strategies for reducing an earthquakes impact are more sustainable and why?
•good planning
•education
Because they are the most cost effective as well as socially and environmentally sustainable
Why can some more expensive strategies for reducing earthquake impacts be more sustainable?
They last much longer and are more effective and are cheaper in the long term
Name 3 reasons people choose to live near volcanoes
- soil around volcanoes is fertile so attracts farmers
- they are tourist attractions, get more economy
- source of geothermal energy, work at power stations
Which type of volcano is the most dangerous?
Dormant, because as it hasn’t erupted in a very long time, there is a lot of pressure building up so when it does erupt, and no one knows when, it will be massive
Which plate boundary causes the biggest volcanoes?
Destructive
What are pyroclastic flows?
The fast moving flows of ash, rock and gas that move down the side of a volcano
Name 4 things a volcano spews out
- lava
- ash
- rocks
- gas (carbon dioxide and sulphur dioxide)
Name 4 primary impacts of a volcanic eruption
- buildings and rocks are destroyed by lava flows and pyroclastic flows, can collapse if enough ash falls on them
- people and animals are injured and killed mainly by pyroclastic flows but also from lava flows and falling rock
- crops are damaged and water supplies are contaminated when ash falls on them
- people plants and animals are suffocated by carbon dioxide
Name 9 secondary impacts of a volcanic eruption
- lahars are formed which causes lots more destruction deaths and injuries
- fires are started by lava and pyroclastic flows which spreads
- suffer psychological problems
- people left homeless
- shortage of food due to damaged crops
- shortage of clean water
- roads etc blocked so aid can’t get through
- businesses are damaged causing unemployment
- sulphur dioxide causes acid rain
What are lahars?
Mudflows that form when volcanic material mixes with water
Name 3 ways we can predict when a volcano is going to erupt
- tiny earthquakes happen before
- escaping gas from the volcano
- changes in the shape, eg bulges in the land where the magma has built up
How does predicting when a volcano will erupt reduce the impact of it?
People have the chance to evacuate so less people are injured or killed
How can we use building techniques to reduce the impact of a volcanic eruption
- strengthen buildings to withstand the weight of the falling ash, can’t be designed to withstand lava and pyroclastic flows
- lava can be diverted away from buildings using barriers
Why are all of the strategies for reducing the impact of a volcanic eruption sustainable?
They are all effective and environmentally friendly
Why is predicting eruptions less economically sustainable but more socially sustainable?
It costs a lot of money to pay for special equipment and trained scientists however it is the most effective way to save people’s lives
Why are building techniques also economically sustainable?
Despite the very large downpayment, it can save the money spent on reparations because it stops the building collapsing and needing reparations
Explain 2 reasons why people live in earthquake zones in medc’s
- their jobs are there, so it could be difficult to find work if they move, meaning they could lose money
- earthquakes don’t happen very often so they feel safe knowing that any severe hazards probably won’t happen whilst they are living there
- full of great opportunities and the climate make you want to stay
- have always lived there so built up communities that would be hard to break
Suggest reasons why hazard impacts are usually worse in ledc’s
•less developed hospitals so more people died as their treatment was insufficient
•more patients per doctor so there were more people to care for per doctor, meaning each person had less attention from the doctor so there was a higher chance of them dying
•no or little preparation, such as kits or evacuation routes, meaning there is no way that they can individually reduce impacts
•limited education on how to act, meaning they don’t know how to protect themselves in the case of an earthquake
•water supply and sanitation could be poor so there is a big risk of disease after the event
•can be remote and difficult to reach to get aid to help them, slower recovery
•poorly built buildings don’t stand up to tremors
•
•ledc’s don’t have suitable technology to be able to predict tectonic events
Name 5 ways we can predict an oncoming earthquake
- laser beams across a fault warn of any initial small movement
- increase in radon gas, suggests movement in a fault
- water levels in wells/lakes changing, water might be escaping into small tension cracks that appear before an earthquake
- seismometers measure movement of the ground, warn of foreshocks
- mapping previous earthquakes may show a pattern
Name 6 ways we can predict a volcanic eruption
- animals may behave strangely
- rising magma can cause a volcano to bulge
- satellite cameras can detect heat released from the volcano
- a tilt meter can measure changes in the slope of a volcano
- moving magma gurgles and belches
- sulphur dioxide increases which smells bad
Name 5 features of an earthquake proof building
- concrete wall, provides strength and resists rocking from earthquakes
- concrete core, provides strength to the core of the building
- moat, gap between the ground and the foundations so the shocks don’t reach the building
- shock absorbers at the base, dampen the shock
- cords bracing diagonal steel bars, reinforce the walls
Name 8 ways to protect housing from earthquakes
- fasten bookshelves to walls to prevent toppling with L shaped brackets
- secure brick chime using brackets
- nail plywood to ceiling joints around chimney for protection against falling bricks
- remove heavy items from above beds and locate away from glass windows
- plywood panels to strengthen the walls that surround the crawl space under the house
- metal connectors to strengthen joints in the houses frame to help the house withstand from shaking
- strap water heater to wall to stop it toppling over and breaking a gas line, learn how to shut off gas, water and electricity
- bolt the house to its concrete foundation to prevent it from slipping off
What are you more likely to have in an medc that will reduce the impacts of an earthquake? Name 8 things
- insurance
- stronger, well built house
- cities have earthquake proof buildings
- have an emergency kit at the ready
- good warning systems
- electricity supplies restored quickly
- better equipped and trained emergency services
- emergency food and shelter
Name 4 factors that affect the impact of a volcanic eruption
- the violence of the eruption
- the density of the surrounding population
- how well it was predicted
- how well prepared the people were
Name the 3 types of volcano
- composite
- shield
- dome
Where are you most likely to find composite volcanoes?
Along destructive plate boundaries
What is a rock plug? How is it removed?
Where rock has been cooled at the top of the vent, the next eruption may blow it out and shower the area in rock and ash
What pH is the sticky lava that escapes from the vents?
Acidic
Why does lava form steep slopes?
It moves slowly and cools quickly
What are the slopes of a volcano made up of? Why?
Alternate layers of ash and lava, because the ash erupts before the lava
What does the viscous magma trap in the magma chamber?
Hot gases
What causes hot gases to be released from the magma chamber?
The sudden release of the built up pressure
What makes the eruption of a volcano even more violent?
The steam contained in the magma chamber
Name the 3 top hazards of a volcanic eruption
- pyroclastic flows
- ash cloud
- lahar
Why are pyroclastic flows so dangerous?
They are destructive and move at 200mph
Why are ash cloud so dangerous?
They cause suffocation and lead to many health problems
What is lahar?
Mudslide made of melted snow and volcanic ash that moves at 60mph
Where are shield volcanoes mostly found?
Constructive plate boundaries and hot spots
Why are hot spots volcanic?
Magma escapes there because the oceanic plate is so thin
Name the 2 types of lava
- acidic lava
* basic lava
What type of volcanoes release acidic lava?
Composite volcanoes
What type of volcanoes release basic lava?
Shield volcanoes
Describe the texture, speed and how fast it cools of acidic lava
Texture: sticky
Speed: slow
Cools: quickly
Describe the texture, speed and how fast it cools of basic lava
Texture: runny
Speed: fast
Cools: slowly
What does the basic lava process form?
Volcanoes with wide sides and gradual slopes
What does the acidic lava process form?
Volcanoes with steep slopes
What may happen to shield volcanoes?
They may form part of an ocean ridge or eventually become an island
Why are eruptions from shield volcanoes not explosive?
The magma from within shield volcanoes is not viscous, so no hot gas is trapped in the magma chamber, meaning there is no build up of pressure and eruptions are not explosive
What do volcanoes throw when it erupts violently?
Volcanic bombs
What are volcanic bombs?
Pieces of rock
What 3 things can form pyroclastic flows?
- hot gases
- steam
- ash
What is a caldera?
A very large crater where the cone of a volcano used to be that was blown out by explosive eruptions from a dormant volcano
Describe three features of a dome volcano
- tall and narrow cone
- steep slope
- thick lava
Explain 5 primary impacts of volcanic eruptions
- volcanic blasts, throw rock at high speeds, cause widespread devastation
- lava flows, melt and bury everything in its path
- ashfalls, ash cloud sinking to the ground, covers everything, suffocates people
- pyroclastic flows, very very hot and fast, extremely destructive, cause a great loss of life
- earthquakes may be triggered
Explain 3 secondary impacts of a volcanic eruption
- lahars, occur only when ash mix with melted glacier, destroy everything in their paths
- landslides on slope of volcano, triggered by violent eruptions
- sulphur dioxide emitted from eruption can cause acid rain
Name 8 ways medc’s are good at responding to volcanic eruptions
- good prediction monitoring gives early warning
- warnings reach everyone at risk
- people are well prepared
- clear evacuation processes
- rapid transport and communication links
- needs of the people affected are prioritised
- rescue services reach area quickly
- suitable aid, shelter, food, medical etc
Name 4 reasons why people live near volcanoes
- fertile land
- tourism
- geothermal energy
- minerals
Explain why people live near volcanoes because of the fertile land
Lava and volcanic rock contain minerals, they break down to create fertile soils, which provide fantastic farming conditions
Explain why people live near volcanoes because of tourism
Millions of people visit volcanoes every year, they are a real business opportunity, can be viewed safely, creates lots of jobs in shops, hotels, restaurants etc
Explain why people live near volcanoes because of geothermal energy
Heat underground can be used to heat houses and water, the power station requires jobs and is renewable
Explain why people live near volcanoes because of minerals
Many minerals found in magma, like copper and gold, can be mined after the magma cools
Name 3 ways people can use education to help minimise the impacts of a volcanic eruption
- schools can teach students how to react
- drills can train the community how to respond and evacuate
- people given advice on what to do if there is an eruption, even tourists are given information packs
Name 5 ways forward planning can help to reduce the impacts of a volcanic eruption
- stock up on necessities
- concrete shelters built to protect from volcanic bombs and pyroclastic flows
- concrete lahar channels to divert mudflows
- clear road evacuation signs
- take out insurance to replace their homes and other possessions
Name 4 ways emergency action can be used to decease the impacts of a volcanic eruption
- danger zones sealed off
- frequent news updates
- loud sirens
- no planes flying
What substance in ash causes lung disease?
Quartz
