Tectonic Processes and Hazards Flashcards
1
Q
LWhat is a natural hazard?
A
A natural hazard is a natural event that has the potential to harm people and their property.
2
Q
What is a disaster?
A
This is the realisation of a hazard.
3
Q
What Model shows that disasters have to involve people?
A
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.
3
Q
Why is the relationship between risks , hazards and people complex?
A
- 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.
4
Q
Which equation can be used to understand the relationship between disasters and hazards?
A
Risk=(hazard x vulnerability)/capacity to cope.
5
Q
What causes the risk of a disaster to rise?
A
If the hazard magnitude rises e.g Higher VEI.
6
Q
What causes vulnerability to rise?
A
- 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.
7
Q
What is a threshold level?
A
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.
8
Q
What is the PAR model and what is its function?
A
The pressure and release model suggests that the socio-economic context of a hazard is important.
8
Q
What are the three components of the PAR model?
A
Root causes,dynamic pressures and unsafe conditions which combine with a natural hazard to form a disaster.
9
Q
Using the PAR model discuss a case studies root causes,dynamic pressures and unsafe conditions.
A
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.
10
Q
What are the three broad impacts of tectonic hazards?
A
Social,economic and environmental.
11
Q
What are some examples of social impacts?
A
Death,injury and wider health impacts
12
Q
What are some example of economic impacts?
A
The loss of property, businesses,infrastructure and opportunities.
13
Q
What are some example of environmental impacts?
A
Damage or destruction of physical systems, especially eco systems.
14
Q
Why is comparing impacts between countries difficult?
A
Because the physical nature of an event and the socio-economic profiles of affected places are different.
15
Q
What are some general observation of tectonic hazards in different places?
A
-The deaths in developed countries are low except for the japan tsunami.
- Volcanic eruptions are small compared to earthquakes and tsunamis.
16
Q
Name one volcanic eruption case study ( developing country)
A
2002 Nyiragongo
17
Q
What were some of the physical characteristics of your chosen case study?
A
Nyiragongo 2002
- constructive margin,continental rift zone
-Basaltic magma
-Stratovolcano
-VEI=1
17
Q
What were some of the responses to the Nyiragongo 2002 volcanic eruption?
A
- 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.
18
Q
What were some of the social impacts of Nyiragogo ?
A
- 147 deaths
-120,000 made homeless
19
Q
What were some of the economic impacts of the Nyriagongo 2002 volcanic eruption?
A
- 15% of the city of Goa was destroyed by lava flows
- US 1.2 billion in economic losses
20
Q
Where do the majority of earthquakes occur?
A
95% of earthquakes occur near plate boundaries.
With many occurring around the ‘ring of fire’ Pacific.
21
Q
What type of plate boundary are powerful earthquakes associated with?
A
Convergent or conservative plate boundaries.
22
Where do intra-plate earthquakes occur?
They are often linked with old fault lines or hot spots.
23
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.
24
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
25
What plate boundary affects the occurence of tsunamis
Convergent boundaries.
26
What is a plate boundary?
Plate boundaries are the locations where two tectonic plates meet .
26
What does the late boundary acronym 'Delightful cold tea' stand for
Destructive,convergent,transform.
27
What takes place at a Divergent plate boundary?
The tectonic plates move apart.
E.g the Mid Atlantic ridge.
28
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.
29
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.
30
What are the three categories of convergent boundaries?
Oceanic-continental
Oceanic-oceanic
Continental-continental - This is known as a collision boundary
30
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.
31
What is a hotspot?
A hotspot is a large plume of hot mantle material rising from deep within the Earth.
32
What is an example of an intra- plate earthquake?
The new Madrid earthquake in 1812 and the 2011 Virginia earthquake.
33
Where do hotspot volcanoes occur?
Over stationary magma plumes in the asthenosphere.
33
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.
34
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.
35
What are the three layers of the earth?
The crust, the mantle and the core
36
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.
37
What does the crust consist of?
Seven major and several minor tectonic plates.
38
Where is the mantle?
Between the crust and the core.
It is the widest layer.
38
What is the outer core made out of?
Liquid iron and nickle. This layer is semi molten.
39
What is the inner core made out of?
This has a solid centre and it is composed of mostly iron.
39
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.
40
What is the Mohorovic discontinuity?
This is the boundary between the crust and the mantle.
40
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.
41
What can cause the lithosphere ( crust and upper part of the mantle) to become thicker?
The formation of fold mountains.
42
42
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.
43
What was the second key discovery that supports the theory of plate tectonics?
The ideas of Arthur Holmes in the 1930s that the earth's internal radioactive heat was that driving force of mantle convection that could move tectonic plates.
43
What was the third key discovery that supports the theory of plate tectonics?
In the 1940s, sonar and radar used to reveal the shape of the ocean floors (Harry Hessi).
44
What was the fourth key discovery that supports the theory of plate tectonics?
The discovery in the early 1960s where magnetic strips in the oceanic crust of the sea bed, these are palaemagnetic signals from past reversals of the earths magnetic field and suggests that new oceanic crust is a result of sea floor spreading at mid-ocean ridges.
( BY WILSON?)
45
What was the sixth key discovery that supports the theory of plate tectonics?
In 1965, Wilson and Hess propose the theory of Plate tectonics by combining sea floor spreading with continental drift.
46
Before theories such as sea-floor spreading and continental drift was used to support the movement of plate tectonics, what theory was used before?
The theory of convection currents was used.
47
What are convection currents?
These are formed from magma rising because of the extra energy it received in the form of heat and cooler molten rock falls because of the low energy state. This forms a current as the magma cools and rises and sinks back to the core. This takes place constantly and the interior of the earth is dynamic rather than static.
48
What was the theory of convection currents?
The heat from the radioactive decay of isotopes such as uraniaum-238 in the core moves upwards into the mantle.
That leads to the formation of convection currents, which push up into spreading mid-ocean ridges, forcing them further apart called the ridge push.
49
What is palaeomagnetism?
This is the record of changes of the magnetic field of the Earth, this is shown in the orientation of the magnetic fields in rocks.
50
Describe a subduction zone?
A subduction zone forms when two plates meets. The heavier denser plate subducts under the lighter less dense plate.
50
Describe the theory of sea floor spreading?
Palaeomagnetism provides evidence that the sea floor has gradually moved apart at a mid-ocean ridge.
Lava cools and solidifies with the minerals lining up with the magnetic field.
The direction of the minerals on either side is a mirror image
50
What is slab pull?
At destructive margins gravity forces the lithosphere to descend into the mantle. The collision with the other plate causes both shallow and deep seismic activity
50
What are deep sea trenches and provide an example.
Deep sea trenches are long,narrow depressions in the ocean floor with depths of over 6km and up to 11km. They are found adjacent to land areas and they are associated with island arcs.
An example of this would be between the Nazca plate and the South American plate.
51
What takes place at a convergent plate boundary?
The plates are moving together.
51
Where does slab pull take place?
At destructive margin.
52
What are the four plate boundary types?
Convergent,divergent,collision and transform.
52
What happens between the oceanic plate and the continental plate at a convergent plate boundary?
The denser, heavier plate subducts under the lighter ,less dense continental plate.
This forms deep ocean trenches in the subduction zone.
53
What type of volcanic eruptions and earthquakes take place here?
They are violent. The narrow aea where earthquakes tend to occur in the subduction zone is known as the Benioff zone.
53
What types of convergent plates lead to the formation of fold mountains.
Oceanic and continental plates lead to the formation of fold mountains.
54
What happens when two oceanic plates meet?
The heavier of the two oceanic plates subduct, forming deep ocean trenches and island arcs.
55
What is an island arc and name an example?
Island arcs are a series of volcanic islands,formed in an arc shape e.g the Carribean.
55
Name an example of a constructive plate boundary.
The Mid-Atlantic Ridge is an example of a constructive plate boundary.
56
What takes place at a constructive plate boundary?
The plates are moving apart at a constructive boundary.
56
Do volcanic eruptions and earthquakes take place at a constructive plate boundary?
Yes.
57
What can happen when two continental plate boundaries meet?
Both may fold and deform e.g the Himalayas which if formed from the collision of the Eurasian and Indian plates.
58
What happens at a collision boundary?
- Two plates of a similar density move together
- Neither can sink into the denser rocks below so they are crushed,crumpled and forced upwards, usually folding in the process.
- This creates collision fold mountains such as the Himalayas, which ascend at a rate of 1cm per annum
- No volcanic activity takes place as there is no subduction
- Earthquakes are the main hazard.
59
What happens at conservative plate boundaries?
The plates move slowly past each other at a different rate of travel in the same direction.
59
What tectonic hazard occurs at conservative plate boundaries?
The plates can become stuck and pressure builds and they snap past each other. These can be called strike-slip faults as they strike/stick and then slip/release past each other.
The friction causes earthquakes but not volcanoes.
60
Why is there no melting of the crust or volcanic activity on a conservative boundary?
Because no subduction occurs, there is no melting of the crust and so no volcanic activity.v
61
Describe earthquakes at divergent boundaries?
Earthquakes at divergent boundaries are milder and shallow
62
Describe eruptions at divergent boundaries?
The eruptions tend to be small and effusive. They are usually of basalt lava and they have a low gas content,low viscosity and a higher temperature.
63
Why are earthquakes strong at the Benioff zone?
Friction and pressure builds up in the Benioff zone and this causes strong earthquakes.
64
What are the earthquakes like at transform boundaries?
They are powerful earthquakes as a result of plates sticking and causing a significant build up of pressure.
64
What are the volcanic eruptions like near the benioff zone?
The volcanic eruptions here tend to be explosive as the magma if moving its way to the surface.
These eruptions are often rhyolite lava:
- And they have a high gas content
- High viscosity
-Lower temperature
65
What is the epi-centre of an earthquake?
The point on the Earths surface directly above the focus.
65
What are the 3 types of waves?
Primary waves,Secondary waves and Love waves.
66
Describe the characteristics of primary waves.
-They are the fastest with a rate of approximately 8km/sec so they arrive first
- They cause the least damage
- S and L waves have a larger amplitude and energy force
- They are vibrations as a result of compression.
66
What is crustal fracturing?
Crustal energy is when the energy released during an earthquake which leads to the Earths crust cracking.
66
Describe the characteristics of S waves.
- Arrive next approximately 4km /sec
- Shakes the ground causing damage.
67
Describe the characteristics of L waves?
- Arrive last as they only travel on the surface - vibration occurring in the horizontal plane
- They have a large amplitude and cause significant damage,including fracturing the ground.
67
What is an earthquake secondary hazard beginning with Land ?
Landslides. This is especially true in area of geologically young and unstable mountains such as the Himalaya.
68
What can large earthquakes do to the Earth?
Fault lines can rupture for up to 1000 km after very large earthquakes such as the 2004 Indian Ocean tsunami.
Such earthquakes can lead to ground shaking that lasts up to 5 minutes, as well as dozens of aftershocks.
69
Describe case studies where the secondary hazards were socially impactful.
In the 2008 Sichuan and 2005 kashmir earthquakes, up to 30% of the deaths were linked to landslides.
70
What is an effect of liquefaction?
An effect of liquifaction is that it causes damages to roads,bridges and telecommunications.
70
What is liqueifaction and where in the world is it a hazard?
Liquefaction takes place when intense intense earthquake shaking compacts the loose sediment together,water comes into the sediment and out and upwards. This undermines building foundations and causes buildings to sink,tilt and often collapse.
Is it hazardous in areas where the ground consists of loose sediment such as sand,silt or gravel that is also waterlogged.
71
A Primary hazard of volcanic eruptions are Lava flows. Describe it.
These are extensive areas of solidified lave which can extend several kilometres from volcanic vents if the lava is basaltic and low viscosity. It can flow up to 40 km/h.
72
Where do Lava flows occur?
At subduction zone volcano (composite).
Or a shield volcano
73
A Primary hazard of volcanic eruptions are Pyroclastic flows. Describe it.
These are very large,dense clouds of hot ash and gas at temperatures of up to 600 degrees celcius. They can flow down the flanks of volcanoes and this can lead to the devastation of large areas.
74
Where do pyroclastic flows occur?
At composite volcanoes.
75
A Primary hazard of volcanic eruptions are Ash falls. Describe it.
Ash particles and large tephra particles can cover areas in ash which can kill vegetation and collapse buildings.
76
Where does Ash fall occur?
Ash fall can occur at constructive plate margin volcanoes
or at composite volcanoes
77
A Primary hazard of volcanic eruptions are Gas eruptions. Describe it.
This is the eruption of carbon dioxide and sulphur dioxide, which can poison people and animals.
78
Where do gas eruptions occur?
At composite volcanoes or shield volcanoes.
79
A secondary hazard of volcanic eruptions are Lahars. Describe it.
These are volcanic mudflows , that occur when rainfall mobilises volcanic ash. It travels at high speed down river systems and causes major destruction.
80
Where do lahars occur?
Lahars occur at composite volcanoes.
81
What can tsunamis be a result of?
Sub-marine earthquakes at subduction zones as a result of sea bed and water column displacement.
81
Where do j..kulhaups occur?
At constructive plate margins.
81
A secondary hazard of volcanic eruptions are J..lhaups. Describe it.
These are floods that are a result from volcanoes eruoting beneath glaciers and ice caps. This forms large volumes of meltwater .These are common in Iceland.
82
83
Name a developed country that has experienced a volcanic eruption?
2010 Eyjafjallajokull.
84
Describe the location of your volcanic eruption case study ( developed)
- On a constructive margin
-Mid-ocean ridge
- Basaltic magma
- Stratovolcano
85
What was the VEI of the Eyjafjallajokull volcano?
4
86
What were the social impacts of your volcanic eruption case study ( Developed)?
The 2010 Eyjafjallajokull volcanic eruption
- no injuries
- no deaths
87
What were the environmental impacts of your volcanic eruption case study ( Developed)?
- Ice melt on the volcano led to some flash flooding.
87
Name one developing country earthquake case study.
2015 Gorkha (Nepal).
88
What was the magnitude, focal depth and continent of the developing country earthquake case study.
- Magnitude- 7.9
- Focal depth - 8.2km
- Continent - continent collision zone.
89
What were the environmental impacts of your volcanic eruption case study ( Developed)
2010 Eyjafjallajokull (Iceland)
Economic impacts:
- Major disruption to European and transatlantic air travel affecting 10 million passengers
- costing 10 million in economic losses.
90
What were the social impacts of the developing country earthquake case study you have selected?
2015 Gorkha (Nepal)
- 9000 deaths
- 22,000 injured
- Many rural villages totally destroyed.
91
What were the economic impacts of the developing country earthquake case study you have selected?
2015 Gorkha (Nepal)
- 5 billion in losses
- Many rural villages totally destroyed
92
What were the environmental impacts of the developing country earthquake case study you have selected?
2015 Gorkha (Nepal)
- Some destruction of forests due to pyroclastic flows
- Avalanches triggered on Mount Everest.
93
Name a developed country earthquake case study.
2010 Canterbury ( New Zealand).
94
What was the magnitude,focal depth and location of your selected developed country earthquake case study?
2010 Canterbury ( New Zealand)
- Magnitude - 7.1
- Focal depth - 10km
- Subduction zone
95
What were the social impacts of your earthquake case study ( developed)?
2010 Canterbury ( New Zealand)
-100 injuries
- No deaths
- A magnitude of 6.3 aftershock in Christchurch killed 185 people.
96
What were the economic impacts of your earthquake case study ( developed)?
2010 Canterbury earthquake
- 28 billion of damage was caused.
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