Tectonic Processes and Hazards Flashcards
LWhat is a natural hazard?
A natural hazard is a natural event that has the potential to harm people and their property.
What is a disaster?
This is the realisation of a hazard.
What Model shows that disasters have to involve people?
Deggs model highlights the intersection between a hazardous natural event ( such as an earthquake) which experiences human and or economic loss, to lead to a disaster.
Why is the relationship between risks , hazards and people complex?
- The unpredictability of the hazards timing and magnitude.
-Lack of alternatives- people staying due to a lack of options ( work , lack of space and skills)… Case study: Sichuan 2008 as- 78% of the families that were engaged in both agricultural and livestock farming.
- Dynamic hazards- threats that can change over time and can be affected by human influence.
Which equation can be used to understand the relationship between disasters and hazards?
Risk=(hazard x vulnerability)/capacity to cope.
What causes the risk of a disaster to rise?
If the hazard magnitude rises e.g Higher VEI.
What causes vulnerability to rise?
- Poverty- Haiti 2010 earthquake - GDP Per capita of 343.89 dollars.
- Lack of Preparedness - Kashmir 2005 earthquakes- no local disaster planning, poor infrastructure and not earthquake resistant.
- Lack of awareness of potential hazards - Nyiragongo 2002 volcanic eruption- there was political unrest at the time so monitoring of the volcano was difficult. Not many people were warned.
What is a threshold level?
A threshold level is used to determine whether the impact of an event is large enough to be considered a disaster.
Such as:
- 10 or more deaths
- 100 or more people affected
- US 1 million in economic losses.
What is the PAR model and what is its function?
The pressure and release model suggests that the socio-economic context of a hazard is important.
What are the three components of the PAR model?
Root causes,dynamic pressures and unsafe conditions which combine with a natural hazard to form a disaster.
Using the PAR model discuss a case studies root causes,dynamic pressures and unsafe conditions.
Haiti
root causes- Per capita GDP (PPP) US1200$
50 Percent of the population is under 20 years old
Dynamic pressures - lack of education, training and investment,
rapid population change and globalisation.
Unsafe conditions
- 25% of people live in extreme poverty
- 80% of port au prince’s housing is unplanned, informal slums.
What are the three broad impacts of tectonic hazards?
Social,economic and environmental.
What are some examples of social impacts?
Death,injury and wider health impacts
What are some example of economic impacts?
The loss of property, businesses,infrastructure and opportunities.
What are some example of environmental impacts?
Damage or destruction of physical systems, especially eco systems.
Why is comparing impacts between countries difficult?
Because the physical nature of an event and the socio-economic profiles of affected places are different.
What are some general observation of tectonic hazards in different places?
-The deaths in developed countries are low except for the japan tsunami.
- Volcanic eruptions are small compared to earthquakes and tsunamis.
Name one volcanic eruption case study ( developing country)
2002 Nyiragongo
What were some of the physical characteristics of your chosen case study?
Nyiragongo 2002
- constructive margin,continental rift zone
-Basaltic magma
-Stratovolcano
-VEI=1
What were some of the responses to the Nyiragongo 2002 volcanic eruption?
- Major international aid response launched
- The UN sent 260 tonnes of food to the affected area within a week of the eruption
- The UK OXFAM sent 33 tones of water cleaning equipment for 50,000 people in refugee camps.
What were some of the social impacts of Nyiragogo ?
- 147 deaths
-120,000 made homeless
What were some of the economic impacts of the Nyriagongo 2002 volcanic eruption?
- 15% of the city of Goa was destroyed by lava flows
- US 1.2 billion in economic losses
Where do the majority of earthquakes occur?
95% of earthquakes occur near plate boundaries.
With many occurring around the ‘ring of fire’ Pacific.
What type of plate boundary are powerful earthquakes associated with?
Convergent or conservative plate boundaries.
Where do intra-plate earthquakes occur?
They are often linked with old fault lines or hot spots.
Where are most volcanoes concentrated?
Most volcanoes are located near or on plate boundaries.
About 75% are around the Ring of Fire surrounding the pacific ocean.
Where are tsunamis typically located?
Over 70% are located around the pacific ocean.
15%- Mediterranean sea.
9%- Carribean sea and Atlantic ocean
6%- Indian ocean
What plate boundary affects the occurence of tsunamis
Convergent boundaries.
What is a plate boundary?
Plate boundaries are the locations where two tectonic plates meet .
What does the late boundary acronym ‘Delightful cold tea’ stand for
Destructive,convergent,transform.
What takes place at a Divergent plate boundary?
The tectonic plates move apart.
E.g the Mid Atlantic ridge.
What takes place at a Convergent plate boundary?
Give an example
The tectonic plates move together.
For example the collision of the Indian plate with the Eurasian Plate.
What takes place at a Transform plate boundary?
The tectonic plates will move past each other or in the same direction at different speeds.
e.g The San Andrea’s fault and Queen Charlotte fault.
What are the three categories of convergent boundaries?
Oceanic-continental
Oceanic-oceanic
Continental-continental - This is known as a collision boundary
What are two theories that explains the occurrence of intra-plate earthquakes?
Tectonic stresses causing ancient fault lines to reactivate.
or
The plates are moving over a spherical surface and this causes zones of weakness.
What is a hotspot?
A hotspot is a large plume of hot mantle material rising from deep within the Earth.
What is an example of an intra- plate earthquake?
The new Madrid earthquake in 1812 and the 2011 Virginia earthquake.
Where do hotspot volcanoes occur?
Over stationary magma plumes in the asthenosphere.
What happened for the hawaiian chain of volcanic islands to form?
The tectonic plate moves over the plume leading to a form of a chain of volcanic islands.
What happens at mid-plate hotspots?
Isolated plumes of convecting heat, called magma plumes,rise towards the surface, which generates basaltic volcanoes that tend to erupt continuously.
A mantle plume is stationairy ,but the tectonic plate above moves slowly over it.
This leads to the formation of volcanic islands.
E.g the Galapagos islands.
What are the three layers of the earth?
The crust, the mantle and the core
What are the two types of crust?
The first type of crust is the continental crust and this is thicker (45-50km), it is less dense and composed of mostly granite
The denser and thinner crust is the oceanic crust and this is between (6-10km) and made up of mostly basalt.
What does the crust consist of?
Seven major and several minor tectonic plates.
Where is the mantle?
Between the crust and the core.
It is the widest layer.
What is the outer core made out of?
Liquid iron and nickle. This layer is semi molten.
What is the inner core made out of?
This has a solid centre and it is composed of mostly iron.
What are the two layers of the upper mantle?
The rigid layer above the asthenosphere,which together with the crust,makes up the litosphere.
The asthenosphere is a semi-molten, which moves under high pressure.
The lower mantle is hotter and denser than the upper mantle.
What is the Mohorovic discontinuity?
This is the boundary between the crust and the mantle.
What can cause crust to become thinner in some places?
As the plates move crustal stretching can take place and cause thinning. As plates move at a speed of 2-5cm per year the thinning willl happen gradually.
What can cause the lithosphere ( crust and upper part of the mantle) to become thicker?
The formation of fold mountains.
What was the first key discovery that supports the theory of plate tectonics?
Alfred Wegner’s continental drift hypothesis in 1912 that postulated that now-separate continents had once been joined.
