Explore the types and levels of challenge posed by varying forms of tectonic activity.
Research contrasting locations to draw out the range of tectonic activity and the different impacts produced on communities.
Explore the types and levels of challenge posed by varying forms of tectonic activity. Explore, meaning the background concepts, processes, theories and models involved where relevant. Models Theories Processes Concepts
Research contrasting locations to draw out the range of tectonic activity and the different impacts produced on communities. Research, meaning the geographical places, case studies and examples illustrating these.
Explore the types and levels of challenge posed by varying forms of tectonic activity.
3.1 The reasons why people live in tectonically active areas and how this might relate to the level of economic development. 3.2 The range of hazards associated with different types of tectonic activity. Research contrasting locations to draw out the range of tectonic activity and the different impacts produced on communities. 3.3 The specific impacts of a range of tectonic hazards at a range of scales and at locations in countries at different stages of development. 4.1 The varying approaches of individuals and governments to coping with tectonic hazards in countries at different stages of development. 1.1 Tectonic hazards and disasters and what makes tectonic activity hazardous. There is a range of tectonic hazards associated with both volcanoes (lava, pyroclastics, ash, lahars, etc) and earthquakes (ground shaking, displacement, liquefaction, tsunamis, etc). 3.4 Trends in frequency and impact over time. Tectonic Hazards 1.2 Event profile of hazards, including frequency, magnitude, duration and areal extent. 4.2 Specific strategies involved in adjustment: modifying loss burden, modifying the event and modifying human vulnerability; and the range of approaches and strategies used in locations at different stages of development.
Discuss the challenges posed for communities by different tectonic hazards. (70)
Examine the impacts caused by tectonic activity and explore the reasons for these vary. (70)
"The severity of a hazard is determined by the economic situation in which it occurs". How far do you agree?
1.1 Tectonic activity and causes
Tectonic activity can produce a very large range of hazard events
Not all of these events are ‘disasters’
A natural hazard event becomes a disaster when the event causes a significant impact on a vulnerable population.
These impacts could be human (death, injury) and / or economic (property losses, loss of income).
Definitions vary, but ‘significant’ losses usually means 10+ deaths / 100+ affected / $1 million losses.
The Dregg disaster model
1.2 Event profiles
Not all tectonic hazards are the same
Event profiles are a common way of comparing different hazards
In this example the 2004 Asian Tsunami and ongoing eruption of Kilauea on Hawaii are compared
Hazard profiles can be drawn for any event.
Tectonic settings and plates
Most tectonic hazards are concentrated at plate margins (boundaries), although ‘hotspots’ are a notable exception.
Different types of boundary generate very different tectonic hazards.
The range of volcanic hazards
Dangerous volcanic hazards are found along subduction zones at destructive plate margins
The most dangerous volcanoes are themselves multiple hazard areas.
Volcanoes at constructive plate margins (Iceland) and oceanic hotspots (Hawaii) are much less hazardous and destructive.
Magma, molten rock in the earth’s crust, has an important relationship with volcanic explosivity and hazard level
Andesitic magmas, formed by wet partial melting at subduction zones produce highly explosive and destructive composite volcanoes
Magma type Generation Tectonic setting Hazards Basaltic Low silica, low gas, low viscosity. Dry partial melting of upper mantle Oceanic Hot spot (Hawaii) Constructive (Iceland) Lava flow Andesitic Intermediate Wet partial melting of subducting plates Destructive plate margin (Andes) Island arc margin (Montserrat) Lava flow, ash and tephra, pyroclastic flow, lahar, gas emission Rhyolitic High silica, high gas, high viscosity. In situ melting of lower continental crust (very rare eruptions) Continental Hot spot (Yellowstone) Continent collision zone (Himalayas) Cataclysmic explosion, pyroclastic flow
Measuring volcanic explosivity:
The Volcanic Explosivity Index (VEI) is used to measure volcanic power.
VEI measures: Volume of ejecta Height of the eruption column Duration of the eruption.
Modern humans have never experienced a VEI 7 or 8
Earthquakes are a very common, sudden release of energy that generate seismic waves
Most occur along faults (cracks in the earth’s crust) which become ‘locked’
Opposing tectonic forces push against the locked fault, building up strain, which eventually gives way releasing stored energy
This energy spreads out rapidly from the earthquake origin (the focus) reaching the surface at the epicentre, and then spreading horizontally.
Tsunami are relatively rare events.
They are generated by submarine earthquakes, volcanic collapse, and coastal landslides, which suddenly displace huge volumes of water
The 1993 Okushiri tsunami (Japan), 2004 Asian Tsunami and 2009 Samoa events are all useful as case studies.
Tsunami waves are radically different from normal wind generated ocean waves.
When a tsunami hits a coastline, the effect is more like a devastating coastal flood than a single breaking waves
3. Tectonic hazards human impacts
A surprising number of people live in areas of active tectonic processes
Major tectonic hazards can strike with devastating force
The 2005 Kashmir Earthquakes killed around 85000, the 2008 Sichuan ‘quake over 65,000 and 200,000+ died in the 2004 Asian Tsunami
It is important to consider why people live, in such large numbers, in areas of great risk
Every hazard event is different, and therefore the specific impacts of disaster vary
When researching case studies , it is important to be able to identify specific impacts and be able to explain these
Some impacts are tangible and can be given a financial value. Others are intangible , such as the destruction of a temple or artwork.
Many losses are direct and immediate such as property damage, but others are indirect – these come later and are harder to quantify, such as stress and psychological damage.
Impacts are often considered as human (death, injury, illness), economic (property loss, loss of income, cost of relief effort) and physical (changes to landscape and topography).
Examine the two earthquakes below and consider how factors such as economic development, building types, the geography of the area affected and the relief effort may have affected the impacts
(South Asian) Earthquake October 2005, Kashmir (Wenchuan) Earthquake May 2008, Sichuan, China Details Magnitude 7.6 . Huge number of landslides accounting for 30%+ of deaths Magnitude 8.0 . Thrust fault at continent continent convergence Fault displacement Largely horizontal displacement of up to 10m Up to 5m vertically and 4m horizontally at the surface Focus depth 10 km 19 km Aftershocks 900+ over magnitude 4.0 250+ aftershocks over magnitude 4.0 Deaths 80,000 70,000 People affected 8 million 3-4 million homeless 15-30 million 5 million homeless Injuries 200,000+ 380,000 Damage estimate US$5 billion US$150 billion Buildings Around 1 million damaged/ destroyed / severely damaged Over 2 million damaged 200,000+ buildings destroyed
Developed versus developing world
It is often said that disaster impacts in the developed world are largely economic, whereas in the developing world they are human (death).
You should carefully consider if this generalisation is true. (see the table, right)
The 1995 Kobe earthquake in Japan and 1991 eruption of Mt Pinatubo in the Philippines are useful examples to consider
Death Toll Event Location Date 5,115 Mount Kelut eruption Indonesia 1991 23,000 Nevado del Ruiz eruption Colombia 1985 25,000 Spitak Earthquake Armenia 1988 30,000 Bam earthquake Iran 2003 35,000 Manjil Rudbar earthquake Iran 1990 36,000 Krakatoa eruption tsunami Indonesia 1883 66,000 Ancash earthquake Peru 1970 69,197 Sichuan earthquake China 2008 86,000 Kashmir earthquake Pakistan 2005 100,000 Tsunami Messina, Italy 1908 105,000 Great Kanto earthquake Japan 1923 230,000 Indian Ocean tsunami Indian Ocean 2004 245,000 Tangshan earthquake China 1976
Impacts over time
A simplified version of Park’s hazard response model is shown below
Different hazard events have different impacts, shown by the speed of the drop in quality of life, the duration of the decline, and the speed and nature of recovery.
The differences in the 3 lines might be related to type of hazard, degree of preparedness, speed of the relief effort and the nature of recovery and rebuilding.
4. Response to tectonic hazards
People cope with natural hazards in very different ways
The chosen ways are often related to wealth and access to technology
Humans do have a capacity to ignore or seriously underestimate risk, even when it seems obvious to others
Often it may seem obvious that people should move out of harms way, but in reality this may be impossible.
Several different approaches can be taken to reduce the impacts of tectonic hazards:
Modify the event ( hazard mitigation ) Modify human vulnerability Modify the loss Tsunami Coastal defences and engineering
Warming and prediction systems
Coastal zone management and landuse planning
Provision of emergency kits
Loss modification involves immediate rescue efforts, followed by relief efforts which focus on food, shelter, water and sanitation. Insurance can help recovery. Long term reconstruction is needed. Earthquakes Not possible
Ground shaking and liquefaction risk mapping
Earthquake education and drills
Prediction not possible
Volcanoes Lava diversion
Monitoring, prediction warning and evacuation systems