Tectonics Flashcards
Assess the significant of earthquake hazard profiles in relation to the effectiveness of management strategies. (12)
INTRO
Hazard profiles show the key characteristics of earthquakes, such as areal extent, magnitude, duration and predictability. Hazard management involves a range of strategies to reduce disaster impacts by managing before, during and after a hazard strikes.
Hazard profiles represent the physical characteristics of a hazard but these are not the only factor that determines the impact of management.
Assess the significant of earthquake hazard profiles in relation to the effectiveness of management strategies. (12)
Paragraph 1 magnitude
Magnitude is a key element of a hazard profile and, in general, larger magnitude earthquakes are more likely to overwhelm management strategies. HIgher magnitude events such as the 2011 Japanese earthquake and tsunami showed that even countries with high levels of economic development cannot successfully manage a mega disaster. Deaths amounted to 18,000 and economic losses over $300 billion. Low-magnitude earthquakes can be managed by land-use planning and aseismic buildings. However, in low-income countries such as Nepal, where an earthquake occured in 2015, poverty means that few people live in buildings that can resist ground shaking and secondary hazards such as landslides.
Assess the significant of earthquake hazard profiles in relation to the effectiveness of management strategies. (12)
Paragraph 2 areal extent
Immediate response and rescue is made easier if the areal extent of an earthquake is small. For instance, the sequence of shallow earthquakes in Christchurch and Canterbury in New Zealand in 2010-11 was limited in areal extent, whereas the Kashmir and Sichuan earthquakes in 2005 and 2008 affected much larger areas. However, size or area affected is only one factor. The terrain in the Himalayas hampered the relief efforts in 2005 and 2008 due to rugged mountains and isolated, inaccessible settlements.
Assess the significant of earthquake hazard profiles in relation to the effectiveness of management strategies. (12)
Paragraph 3 frequency
If earthquakes are infrequent, such as the Himalayan ones already referred to, there is a risk that community preparedness will be low because the risks are overlooked. In areas where there is a low collective memory of a recent disaster, preparation and education are likely to be more thorough. It could be argued that this is the case in Japan, where the memory of previous earthquakes such as Kobe in 1995 and the Okushiri tsunami in 1993 meant the preparation for 2011 was reasonable: tsunami sirens were heeded by many and the death toll could have been much worse.
Discuss evidence for plate tectonic theory? [12]
POINT 1 WEGENER
Alfred Wegener’s theory of continental drift from 1912 was based on physical evidence that continents were once joined. The most basic evidence is the ‘jigsaw fit’, best shown by the east coast of South America fitting into the coast of west Africa. This could be a coincidence, but geological evidence such as the Appalachian mountains of the USA being geologically related to the Caledonian mountains of Scotland confirms it. Identical fossil remains of reptiles are also found in South America and southern Africa.
Discuss evidence for plate tectonic theory? [12]
POINT 2 SEA FLOOR SPREADING
This early theory based on evidence needed more convincing material to provide an explanation. The theory of seafloor spreading was developed by Harry Hess in the 1960s. Hess showed that mid-ocean ridges were places where new seafloor was created by eruption at what became known as constructive plate margins. Vine and Matthews confirmed this through the discovery of magnetic strips on the seafloor. This paleomagnetic evidence proved that new oceanic plate close to mid-ocean ridges were younger than seafloor some distance away. This magnetism in basaltic rock recorded periodic magnetic reversals and is mirrored either side of ocean ridges.
Discuss evidence for plate tectonic theory? [12]
POINT 3 TUZO-WILSON
Tuzo-Wilson recognised that iland chains like Hawaii are produced as oceanic plates move over fixed mantle ‘hot-spots’ creating active volcanoes as well as chains of older, extinct ones. In the late 1960s, the idea of convection motion in the mantle was accepted as the power-source for moving tectonic plates. The geophysics of earthquakes and mapping of the sea floor has also helped explain the geology of subduction through the discovery of Benioff Zones (earthquake locations which reveal the form of subducting plates) as well as ocean trenches. Evidence gradually built over the last century to not only confirm the former position of continents, but also to provide an explanation for how they have moved.
What are mega disasters
Mega-disasters are large-scale disasters on either an areal scale or in terms of their economic and human impact.
They pose serious problems for successful management to minimise impact and mitigate the impact of the disaster.
They need often require international management both short term and longer term.
Extreme events are likely to pose serious challenges for any governance, however well-planned, e.g. the 2011 Japanese tsunami
Assess the importance of governance in the successful management of tectonic mega-disasters [12]
POINT 1 - PREPAREDNESS
PREPAREDNESS -
82% of earthquake damage comes from collapsed buildings
Twisting steel structure wrapped around building
Rubber shock absorbers in foundation that allows building to sway (Japan)
Base isolation (San Francisco City Hall)
Assess the importance of governance in the successful management of tectonic mega-disasters [12]
POINT 2 - RESPONSE TRAINING
RESPONSE TRAINING -
Japan school kids practice evacuation drill 1st September every year
Emergency services respond quickly with food, shelter and deal with issue swiftly
Services more advanced MEDCs than LEDCs.
Haiti 2010, no army and only 2 fire stations, roads and transport systems less advanced, 130,000 died
Assess the importance of governance in the successful management of tectonic mega-disasters [12]
POINT 3 - PREDICTION
PREDICTION -
Only partly effective with tsunamis where ocean monitoring equipment can detect open sea tsunamis. On the other hand, volcano detection is accurate where tiltmeters and strain meters record volcanoes ‘bulging’ as magma rises and seismometers record minor earthquakes indicating magma movement. . For instance, the Indian Ocean tsunami of 2004 had a magnitude of 9.2 and due to no ocean monitoring equipment being present in the Indian Ocean, there was no way of warning people and as a result there was 225,000 deaths. In comparison, the 2011 Tohoku earthquake which was magnitude 9.1 killed 21,000
Explain the difference between high and low resilience communities [12]
POINT 1 - INFRASTRUCTURE
The quality of infrastructure can have a large influence on how resistant a community is, with poor roads and housing not only posing a threat to those in and around them, but also making recovery efforts much longer and more arduous. In Port-au-Prince, Haiti (an LHD), 70% of the buildings collapsed including 60% of all administrative buildings severely hindering recovery efforts. As a result of this, it can be judged that on the front Haiti had an extremely low resistance. In contrast, New Zealand is a VHHD, so infrastructure in Christchurch was not hit so badly. However, damage is often unavoidable with earthquakes and 115 people were killed when the Canterbury Television Tower collapsed, more than half the total number of deaths from the whole event came from this. As a result the New Zealand government incorporated earthquake proof buildings in the rebuilding process. It is clear that in terms of infrastructure, Christchurch was much more resilient than Haiti.
Explain the difference between high and low resilience communities [12]
POINT 2 - POPULATION DENSITY
Population density also has a significant impact on resilience of communities. Those with a higher population density are likely to be much less resilient as more people are vulnerable and recovery and evacuation processes are likely to be are likely to be somewhat chaotic. The population density of Christchurch is 270/km2, a low density. This is one of the contributing factors to the relatively low death toll of 185. Port-au-Prince, however, has a population density of over 27,000/km2, contributing to the incomparable death toll of over 200,000 people. More people in a given area will mean more affected by a single event. The earthquake had a similar magnitude, yet the Haiti earthquake was still over a thousand times more deadly than Christchurch 2011, therefore Christchurch is more resilient.
Explain the difference between high and low resilience communities [12]
POINT 3 - HEALTHCARE
Healthcare can also have an impact on the resilience of communities. A prime example of poor healthcare having significant consequences is the outbreak of Cholera that occurred soon after the Haiti earthquake. Poor sanitation and a lack of good healthcare meant that the disease broke out, resulting in an additional 6,000 deaths in and around Port-au-Prince. Comparing this with the Christchurch 2011 earthquake, where there were no real issues with healthcare as good services could be found around the city. Therefore Christchurch is much more resilient in terms of sanitation and healthcare as well as a range of other factors.
Define what is meant by disaster (1)
A major hazard event that causes widespread disruption to a community or region that the affected community is unable to deal with adequately without outside help.
Describe two areas of active volcanoes that are associated with plumes from hotspots rather than inter-plate boundaries.
Some volcanic eruptions are described as ‘intra-plate’. This means they are distant from a plate boundary at locations called mid-plate hotspots (such as Hawaii and the Galapagos Islands). At these locations:
• isolated plumes of convecting heat, called mantle plumes, rise towards the surface, generating basaltic volcanoes that tend to erupt continually
• a mantle plume is stationary, but the tectonic plate above moves slowly over it
• over millennia, this produces a chain of volcanic islands, with extinct ones most distant from the plume location.
Explain two secondary hazards caused by earthquakes (4)
- Tsunami when earthquakes displace the water column creating a bulge of water, waves ripple outwards
- Liquefaction, when ground shaking causes sediment to behave like a liquid/solid surface starts to slide or flow
Explain the tectonic hazards that may result from volcanic activity (6)
PRIMARY HAZARD - PYROCLASTIC FLOW
-Fast-moving current of hot gas and volcanic matter (collectively known as tephra)
PRIMARY HAZARD - ASH FALLS/GASES
-The wide variety of material that a volcanic eruption releases into the atmosphere. Material varies in size with larger fragmentation likely to cover the surrounding environment and result in crop and agriculture damages.
SECONDARY HAZARD - LAHARS
Volcanic mudflows, which occur when rainfall mobilises volcanic ash. They travel at high speed down river systems and cause major destruction
SECONDARY HAZARD - JOKULHLAUPS
Catastrophic glacial outburst flood. Can cause widespread landform modification through erosion and deposition.
Which type of plate boundary that does not lead to tectonic activity. (1)
Conservative, no subduction zone.
Explain the causes of tsunamis. (6)
Tsunami waves are caused by the displacement of large quantities (columns) of water
Earthquakes displace water when movement causes the seabed to thrust upwards, undersea landslides displace water when material falls from a continental shelf on to the seabed
Volcanic eruptions displace water when material ejected from the volcano falls into the sea
Landslides displace water when large quantities of water are displaced by land falling into the sea
The displaced water becomes tsunami waves and as the waves reach shallow water in coastal areas (as the topography of the seabed changes) the waves become higher In shallower water the friction between the tsunami wave and the seabed increases and the tsunami wave slows down, decreasing wavelength but increasing wave height.
Explain the causes of tsunamis. (6) part 1
Tsunami waves are caused by the displacement of large quantities (columns) of water
Earthquakes displace water when movement causes the seabed to thrust upwards, undersea landslides displace water when material falls from a continental shelf on to the seabed
Volcanic eruptions displace water when material ejected from the volcano falls into the sea
Explain the causes of tsunamis. (6) part 2
Landslides displace water when large quantities of water are displaced by land falling into the sea
The displaced water becomes tsunami waves and as the waves reach shallow water in coastal areas (as the topography of the seabed changes) the waves become higher In shallower water the friction between the tsunami wave and the seabed increases and the tsunami wave slows down, decreasing wavelength but increasing wave height.
Assess the factors which influence the effectiveness of responses used by different groups of people to cope with tectonic hazards [12]
POINT 1 ACCESSIBILITY
ACCESSIBILITY
- Rural communities are more difficulty to rescue in times of tectonic hazard due to the poor transport links making rescue efforts more difficult
- e.g. Kashmir 2005 where road closures completely cut off land access to the Jhelum, Neelum, and Kaghan alleys. Landslides were the predominant cause of the closures. The problem was so severe that the army was forced to use 12 tanks purely to address this issue. This also meant efforts from emergency aid such as UNICEF was more difficult
- led to more than 80,000 deaths from the 7.6 magnitude earthquake. Comparatively, the 6.2 magnitude Christchurch earthquake whilst smaller only had 185 deaths due to far better transport in place
- TIES TO GOVERNANCE AND DEVELOPMENT SO NOT AS IMPORTANT FACTOR
Assess the factors which influence the effectiveness of responses used by different groups of people to cope with tectonic hazards [12]
GOVERNANCE/DEVELOPMENT
-Development is the most important factor affecting tectonic hazard vulnerability. Development links to a country’s ability to afford tectonic proof defences. For instance, Japan is a highly developed nation that has the procedures in place to cope with a tectonic event. Every Japan resident practices an evacuation drill on the 1st September each year. Moreover, the country has spent heavily “earthquake-proofing” their buildings and putting strict infrastructure legislation in place. E.g. 54 story Mori Tower in Tokyo has earthquake resistant features including reinforced steel piping, motion absorbing technology and 192 shock absorbers. Whilst such defence systems are an essential form of protection they are also too expensive for less developed countries. As a result, the infrastructure of these less wealthy countries will be unable to cope with the strain of tectonic events and are more vulnerable to the threat.
