Tectonics (EQ1, EQ2 and EQ3) Flashcards
What are the 5 main types of plate boundaries, and give an example for each
1) Divergent plate boundaries ( Constructive )
- Mid Atlantic Ridge
2) Convergent plate boundaries ( Destructive )
- Nazca and Pacific Plates
3) Transform plate boundaries ( Conservative )
- San Andreas Fault
4) Collision plate boundaries
- Altiplano and South American Plates
5) Complex plate boundaries
- Northeast of Caribbean Plate
What causes an earthquake ?
When there is friction within a plate boundary strain builds up. Over time this strain is released in the form of seismic waves which are felt at the Earth’s crust.
What causes a tsunami ?
An upwards or downwards movement of the crust, most commonly caused by seismic waves which displace a large volume of water to produce a tsunami.
What are the main causes of intra-plate earthquakes, and give an example of a country which regularly experiences intra-plate earthquakes.
Intra-plate earthquakes are associated with ancient faults situated within the interior of tectonic plates. Small movements along these faults can initiate a relatively low magnitude earthquake. These movements can be caused by hydraulic fracturing ( fracking ), the mass of water within a reservoir, large explosions and isostatic readjustment.
The UK is situated 1500km away from the nearest tectonic plate boundary, however, it experiences on average 25 small-scale earthquakes per annum.
What are the main causes of intra-plate volcanoes, and give an example of one.
Intra-plate volcanoes tend to be associated with mantle plumes. These are areas within the Earth’s mantle which consist of significantly hotter magma in comparison to other areas within the mantle. There are two main known mantle plumes, one of which is located underneath the Pacific plate, and the other underneath the African plate. Mantle plumes can give rise to hot spot areas, where the unusually hotter magma from mantle plumes rises from the outer core, through to the top of the mantle where it breaks through the Earth’s crust to form a volcanic eruption.
Over time, as these mantle plumes and hotspots are stationary within the Earth’s mantle, the moving tectonic plate above it can lead to the formation of a chain of volcanic islands. For example, the Hawaiian islands which consist of 15 volcanoes.
Name and explain the four stages of the plate tectonic theory.
1) Earth’s interior structure and characteristics
Inner core : - 5200 degrees celsius
- Very dense - Solid Iron and Nickel
- Produces heat through either of 2 ways.
One of which would be through the
radioactive decay of unstable elements,
and the other of which would be through
left over heat from planetary formation.
Outer core : - 4500 to 5000 degrees celsius
- Less dense - Liquid Iron and Nickel
Mantle : - 1000 to 3700 degrees celsius
- Both solid and liquid ( liquid at mantle plumes
and plate boundaries )
- Mostly consists of silicon and oxygen
compounds, such as peridotite, as well as some
magnesium oxide.
2) Mantle Convection
Heat produced at the inner core of the Earth’s internal structure rises upwards through the outer core and to the mantle. Here it drives convection currents which operate in different convection cells. Convection currents rise through the mantle until they reach the Earth’s crust-mantle boundary, as they cannot pass through the Earth’s crust they move underneath it, creating friction which ultimately causes the Earth’s crust to move in the same direction as those convection currents.
3) Paleomagnetism and Sea Floor Spreading
Magma which rises at divergent plate boundaries to fill in the space or gap left by diverging plates eventually cools to form solid rock. Within this rock there are minerals which trap and almost record the direction of the Earth’s magnetic field at that current time. Scientists have studied rocks at either side of a diverging plate boundary to find that the order of previous magnetic field directions trapped within rocks is exactly symmetrical either side as you progress from a divergent plate boundary. This observation can only occur if new rock is continously being depositied at these specific plateboundaries, thus confirming the theory that the Earth’s seafloor’s have been spreading for a very long time.
4) Slab pull and Subduction
Convection currents cause oceanic plates to subduct underneath continental plates at convergent plate boundaries. As this oceanic plate desends, mostly under the influence of gravity, it pulls the rest of it’s plate with it .
Name all 6 volcanic hazards, and explain each briefly.
1) Ash Falls (PRIMARY HAZARD)
Small and light fragments of glass, rock and minerals which are ejected in the event of a volcanic eruption. These are light and so ascend into high altitudes, where they can be transported globally, thus giving rise for potential global impacts. They can irritate eyes and cause respiratory problems. Ash can get into machinery, such as aircraft engines, thus causing them to stop working. It can also deposit on roofs, until it eventually causes roofs to collapse due to the heavy amount of ash which has been deposited.
2) Gas eruptions (PRIMARY HAZARD)
Gasses of the likes of HCl, HF, SO2, CO2 and H2S are erupted within a volcanic eruption event. SO2 can react with H20 to form weak sulphuric acid rain which is corrosive and can wear away buildings and other infrastructure. SO2 also blocks the Sun’s heat, thereby causing global cooling, however, this is not permanent and so eventually disappears. HCl can lead to ozone depletion within the Earth’s atmosphere. CO2 is a greenhouse gas and can contribute towards global warming and climate change.
3) Lava flows (PRIMARY HAZARD)
Lava is essentially molten magma which is ejected during a volcanic eruption and flows slowly down the sides of a volcano. The speed at which lava flows at depends on its viscosity, with less viscous lava such as basaltic lava flowing fastest and being most deadliest and andesitic lava being more viscous, and therefore less dangerous. Lava can burn, burry and destroy anything in its path, however, as mentioned before it is very slow and so can be easily fled from by humans, yet buildings and infrastructure are left to bare the consequences.
4) Pyroclastic flows (PRIMARY HAZARD)
These are extremely hot “density currents” comprised of heated rock debris, ash and poisonous gasses which flow rapidly down the sides of volcanoes during the event of a volcanic eruption. These cannot be evacuated by people and so tend to be the most deadliest hazard linked to volcanoes. They incinerate, destroy, poison and burry anything in their way.
5) Lahars
Lahars are a mixture of erupted volcanic material and water which flows down the sides of volcanoes or river valleys at an extremely fast pace. The water may come from rainfall, or melted snow caps which mix with volcanic materials to produce lahars. Lahars are similar to floods, however, they tend to be more viscous and so can be more deadly. It floods, burry’s and washes away anything in its path, for example, crops and buildings which are unsupported.
6) Jokulhlaups
This is essentially meltwater, formed when a volcanic eruption melts the volcanoes constituent ice cap to form melt water. This meltwater is supported and held in place by surrounding ice, however, the meltwater eventually melts this and moves underneath it until it bursts out from underneath the ice, flooding anything in its path.
Explain the link between risk, vulnerability and hazard.
When a more vulnerable community or population are exposed to a hazard, the risk is far greater than when a less vulnerable community is exposed to a hazard. This is portrayed by the pressure and release model, as well as the hazard risk equation.
What Is the hazard risk equation.
Risk = ( Hazard x Vulnerability ) / Capacity to cope
Explain how resilience links to risk.
The less resilient a community is the less able they are to withstand the effects of a natural hazards, and so the greater the risk.
Name and explain the 7 factors which contribute to vulnerability and resilience within a community.
1) Unequal access to education
Increases vulnerability as less people within the population know what to do before, during and after a tectonic hazard occurs. This affects decision making, and therefore weakens a community’s preparation in the run up to a hazard, as well as response and recovery immediately after the tectonic hazard occurs.
2) Unequal access to housing
Many people within vulnerable communities only have access to weak houses which have been built in unsafe areas and lack the ability to withstand tectonic hazards. However, there are also richer people who live in developed countries such as the USA and who have houses on the coasts which are vulnerable to tsunamis.
3) Unequal access to healthcare
Within the event of a tectonic hazard, many people are injured and need be treated fastly and effectively to prevent the occurrence of death. Some countries may lack access to healthcare and people with severe injuries are left unattended to, thereby increasing the potential death toll, and therefore a community’s vulnerability.
4) Unequal access to economic opportunities
Some people may lack a formal and secure source of income, and therefore are unable to save money which may be vital for paying insurance for properties, buying medical supplies, water and food for stockpiling purposes and for saving to implement safety improvements into homes. This increase the potential economic and social costs which are experienced by a community, thus increasing their vulnerability. However, they also have less resources from which could be used to cope with tectonic hazards, therefore, decreasing their resilience.
5) Governance
There tends to be poor governance within developing countries, and this may be due to corrupt political parties and systems which run their countries. This may result in the lack of investment into hazard-resistant buildings, the legislation of building codes or land-use policies and the exploitation of natural resources such as wood from mangrove forests. The above may occur as economic interests may outweigh those of preparing for a tectonic hazard, whose occurrence is not guaranteed. Consequently, the potential for impacts to occur increases significantly, and therefore so does a communities vulnerability.
6) Accessibility
Some places which are prone to tectonic hazards may be isolated, either due to mountainous terrain or by sea. This makes it hard for aid to be delivered these areas, which is crucial to communities especially if their healthcare systems are overwhelmed for example. This could potentially increase death tolls and increases vulnerability within a community.
7) Population density
The more people there are within a given area of risk from tectonic hazards, the greater the number of people which could be potentially impacted by the tectonic hazard, thus increasing vulnerability.
Name the four stages of the hazard management cycle and explain each one.
1) Preparedness
This stage involves firstly identifying the natural hazard before it occurs (e.g through prediction) and preparing for the potential implications it is likely to give rise to. This can be achieved through stockpiling food, water and medical supplies, installing early warning systems, increasing public awareness through hosting drills and establishing evacuation routes.
2) Response
The response stage involves responding to the natural hazard which has just occurred through saving as many lives as possible and preventing the further loss of lives, as well as restoring critical infrastructure. This tends to be achieved through search and rescue teams which search for bodies which could potentially be trapped underneath collapsed buildings or rubble, treating those found injured people, constructing temporary safety shelters for those whose homes have been destroyed and repairing any damaged power lines or generators and water pipes.
3) Recovery
Recovery from a natural hazard consists of reconstructing all infrastructure, restarting economic activities and getting the country’s economy up and running again, as well as relocating and rehabilitating injured people and their lives. This tends to be achieved through rebuilding houses, schools, hospitals, roads and rail networks, re-opening businesses and providing insurance for those protected people.
4) Mitigation
Mitigation focuses on taking experience and knowledge from past events and acknowledging weaknesses and mistakes in the management of the natural hazard which just occurred and improving to establish a better management of the next natural hazard which aims on eliminating or reducing significantly the implications brought about by future natural hazards. This can be done through legislating land-use policies, incorporating hazard proof designs into the construction of new infrastructure and completing frequent risk assessments.
Explain Park’s model for disaster response.
Before the natural hazard or disaster the quality of life is normal and people are preparing for potential natural hazards which may occur in the foreseeable future.
At the time of the natural hazard there is a deterioration of the quality of life as it suddenly drops. The greater or deeper the curve the greater the magnitude or scale of the natural hazard event.
Straight after the natural hazard has occurred, for the next hours to days, is the relief stage. This stage consists
of providing emergency aid to injured people, as well as searching and rescuing people, preventing further fatalities. As the natural hazard event is over and people are now being treated, the quality of life stops decreasing and starts to increase very slowly.
The rehabilitation stage follows after the relief stage, and typically occurs days to weeks after the natural hazard. This stage involves the local and national government, as well as NGOs who provide food, water and medical supplies and shelter to those people who have been displaced
The recovery stage occurs weeks to years after the original natural hazard. Within this stage all infrastructure is repaired or rebuilt and displaced people are eventually resettled into new homes. The quality of life at this stage tends to return back to normal or even becomes better for most developed nations, however, most developing nations tend to struggle with this and so usually end up with a worse quality of life than before. There are many reasons to this, however, one of the main would be the fact that these nations tend to experience natural hazards quite frequently and so tend to be in debt from all the external aid they’ve had to receive. Consequently, these nations become quite poor and so lack enough money to reconstruct all that has been lost, essential in bettering the quality of life.
Name 4 ways in which a natural hazard can be modified, and suggest whether they are an example of mitigation or adaptation strategies.
1) Land - use zoning
2) Hard engineering defences
3) Diversion of lava flows
4) Hazard proof buildings
Name 3 ways in which a communities vulnerability or resilience can be modified, and suggest whether these are an example of adaptation or mitigation strategies.
1) Hi - tech monitoring systems
2) Raising public awareness
3) Impact modelling
