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Terms in this set (36)
Name the four types of plate boundary.
1. Divergent (constructive)
2. Convergent (destructive)
Name the two plate boundaries where the most powerful earthquakes occur.
Name the two plate boundaries where the most volcanoes occur.
What are hotspot volcanoes and where do they occur?
Where the crust above a plume is weak, the magma breaks through and volcanic activity occurs, as in the Hawaiian islands.
They occur at locations on the Earth's surface where there are rising currents of magma (plumes).
They are not associated with plate boundaries.
Describe the origins of the Mid-Atlantic Ridge and its associated tectonic hazards.
It marks a divergent or constructive plate boundary running the length of the Atlantic. It is in effect a submerged mountain range made up largely of extruded basaltic rocks. In places, the volcanic mountains rise above the ocean surface as islands.
So the hazards are volcanic eruptions and occasional earthquakes.
Distinguish between the TWO different types of the Earth's crust.
Oceanic crust: underlying ocean basins; thin; composed mainly of basalt.
Continental crust: underlying the continents; thicker; composed mainly of granite.
Name 3 processes at work along a destructive plate boundary.
What is paleo-magnetism and how does it help in the study of plate tectonics?
It results from cooling magna locking in the Earth's magnetic polarity. From this locked in magnetic alignment, scientists can work out:
- When there were periods of large-scale tectonic activity in geological history
- The directions and speeds of present and past plate movements
When is a locked fault and why is it a cause for concern?
A fault that is not slipping. It is stuck because the friction along it is greater than the shear stress across it. The strain in the fault builds up. Eventually the frictional resistance is overcome and the strain is suddenly released.
Such a release usually results in a large magnitude earthquake with devastating consequences. The 2004 Indian Ocean tsunami .
What is the Benioff zone?
It is the boundary between an oceanic plate which is undergoing subduction beneath an overriding continental plate.
The sinking oceanic plate is colder than the crust into which it is sinking. This causes sudden stresses that may trigger earthquakes.
It is within this zone that the subjecting oceanic plate is melted.
Distinguish between the hypo-centre and epicentre of an earthquake.
Hypocentre is the point within the Earth where an earthquake rupture starts.
Epicentre is the point on the Earth's surface directly above the hypocentre.
Distinguish between the magnitude and intensity of an earthquake.
Magnitude relates to the amount of movement or displacement in the Earth's crust and to the amount of energy released.
Intensity is a measure of the amount of ground shaking. This is a critical factor affecting the amount of damage that an earthquake causes.
Describe the THREE different types of seismic wave.
Primary or P-waves: vibrations caused by compression; they spread very quickly.
Secondary or S-waves: they vibrate at right angles to the direction of travel; they move more slowly than P-waves.
Long or L-waves: surface waves with high amplitude.
Describe 3 secondary hazard associated with earthquakes.
Tsunamis: large sea waves caused mainly by earthquakes, especially those with epicentres under the sea.
Landslides: occur where and when earthquake vibrations cause slopes to weaken and fail. Heavy rain is often a contributory factor.
Liquefaction: earthquake tremors cause sands, silts and clays to lose their load-bearing capacities, so that buildings literally sink into the ground.
Name 3 PRIMARY volcanic hazards and describe how each threatens people.
Pyroclastic flows; tephra; lava flows; volcanic gases.
Pyroclastic flows and tephra are fast moving currents of hot gas and rock. People in their path are unable to escape. They are asphyxiated by gas or simply overrun. These are the most lethal of the hazards.
Lava flows may be slower and escape is possible, but they can do immense damage to property and farmland. They often create devastating fires.
Volcanic gases can be quite lethal; sometimes they are not readily detectable.
What is meant by vulnerability in the context of hazards?
The likelihood of a community being unable to absorb and recover from the impacts of a hazard.
What is meant by resilience in the context of hazards?
The ability of a community to cope with the effects of a hazard.
What is the hazard-risk equation?
risk = hazard x exposure x vulnerability
Name the pressure in the pressure and release model.
The natural hazard event and the vulnerability of the people experiencing the hazard.
What are the impacts of earthquakes generally greater than those of volcanoes?
Volcanic primary hazards are more localised; earthquakes can affect much larger areas. The same applies to secondary hazards, especially to tsunamis.
What does VEI stand for, what exactly does it measure
Volcanic Explosive Index
It measures the volume of material ejected, the height of the eruption cloud and qualitative observations (using terms ranging from 'gentle' to 'mega-colossal').
It is of no use in connection with non-explosive eruptions of lava.
Name the SIX characteristics commonly used in producing a tectonic hazard profile.
2. Speed of onset
4. Areal extent of damage
Mean Stags Don't Allow Frequent Practice
Explain the value of compiling hazard profiles
They can inform decision making in hazard planning by helping to identify: levels of risk; the likely scale and impacts of hazard events; the relative threats posed by a number of different hazards.
Identify the inequalities that make low-income households and communities carry a disproportionate share of disaster 'costs'
- Asset inequality: lack of proper housing and means of livelihood; difficult to recover from any loss of limited assets.
- Access to services inequality: education, healthcare, policing, etc.
- Political inequality: not able to fight their corner or protect their interests.
- Social status inequality: lack of status also means an inability to reduce inequalities.
In what ways does poor governance increase vulnerability to the impacts of tectonic hazards?
Resources not invested in mitigating the possible impacts, as for example by quake-proofing homes and buildings.
People and businesses are not 'educated' about what to do in the immediate aftermath of a hazard event.
Lack of proper investment in infrastructure — unsafe and lack of proper sewage disposal increases the risk of post-event disease;
Inadequate transport links prevent prompt access to disaster areas.
Identify the factors that made ONE specific earthquake event into a disaster.
Haiti - poor governance.
identify TWO ways in which disasters can create development opportunities.
1. More willingness to invest in hazard mitigation so that future hazard events cause less disruption.
2. The need for reconstruction provides a great opportunity to make a fresh start (e.g. better housing, new businesses and new development directions).
Spatial scale is one characteristic of a mega disaster. What are the others?
1. Large economic and human impacts
2. Scale poses a serious challenge in terms of effective management
3. Strong likelihood of needing international support from NGOs and IGOs; high-impact
4. Low probability.
Name THREE examples of tectonic Mega-Disasters
2004 Asian tsunami
2011 Tohoku (Japan).
What are the 4 main stages of the hazard management cycle.
Give 3 examples of the human factors affecting the response to a tectonic hazard .
Degree of community preparedness
Education and training
Quality of governance
Identify the 4 stages in Park's model of the disaster response curve.
Describe how the Park's model can help in the study of tectonic disasters.
It is possible to compare the curves of two or more tectonic hazards and gain a better understanding of their relative resilience — what makes one place more resilient than another.
So the model can be used to help plan and understand not just resilience but also risk. It also allows places at risk to prepare better for future events.
What is a mitigation strategy?
A set of actions and steps aimed at reducing the impact of a hazard event and/or the probability of its occurrence.
Name an example of a micro approach to improving protection from earthquakes
Strengthening individual buildings against stress and shock waves.
Name an example of a micro approach to improving protection from Volcanoes
Spraying cold water on, or physically diverting a lava flow.
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