Tetonic Hazards Flashcards
Define natural hazard
Natural hazards are sudden severe events which make the natural environment difficult to manage.
What’s the plate tectonic theory?
- The earths crust is split into seven major and several minor tectonic plates
- There are two types of crust - dense thin oceanic crust and less dense thicker continental crust
- Plates move driven by convection currents within the mantle and under gravity
What is ‘hazard risk’?
The chance of being affected by a natural hazard.
How does urbanisation affect hazard risk?
Densely populated urban areas concentrate those at risk.
How does poverty affect hazard risk?
Expense of housing leads to building on risky ground.
How does farming affect hazard risk?
The attraction of nutrient-rich flood plains puts people at risk.
How does climate change affect hazard risk?
Global warming raises sea levels and generates more extreme weather.
What types of natural hazards are there?
Floods, tropical storms, earthquakes and droughts
What are the plate margins called that the earths crust is separated in to?
Constructive, destructive and conservative
What happens at a constructive margins?
Plates separate forming new crust causing volcanic eruptions
What happens at a destructive palate margin?
Plates collide causing subduction, earthquakes, volcanic eruptions and fold mountains.
What happens at a conservative plate margin?
Plates slide past each other causing earthquakes.
When did the New Zealand earthquake take place?
February 2011
What was the cause of the New Zealand earthquake?
It was a destructive plate margin. Subduction of the Pacific plate beneath the indo Australian plate.
What was the size of the NZ earthquake?
7.1 magnitude
What we’re the PE of the NZ earthquake?
- 181 killed
- 2000 injured
- Hundreds of kilomètres of damaged sewage pipes and water pipes
- Liquefaction caused lots of damage to roads and buildings
- 80% of the city without electricity
What we’re the SE of the NZ earthquake?
- Businesses were out of action for a long period of time causing loss of income
- Schools has to share classrooms due to damage of other school buildings
- Liquefaction made it difficult for people and emergency services to move around
- Christchurch could no longer host rugby matches
What were the IR for NZ?
- Cared for the most vulnerable people and ensured people were safe from dangerous buildings
- Chemical toilets were provided for 30,000 residents
- International aid was provided in the form of money (around $6-7 million) and aid workers
What were the LTR for NZ?
- Paid $898 million in building claims
- Provided temporary housing and ensured all damaged housing was kept water tight
- Water and sewerage was restored for all residents by August
- Roads and houses were cleared of silt from liquefaction by August and 80% of roads/50% of footpaths were repaired
When did the Nepal earthquake take place?
April 2015
What was the cause of the Nepal earthquake?
Indo-Australian plate colliding with the Eurasian plate
What was the size of the Nepal EQ?
7.9 magnitude
What we’re the PE of the Nepal EQ?
- 9000 killed
- 20000 injured
- 8000000 people affected
- widespread destruction of buildings and Infrastructure
- Power water sanitation and communication cut
- $5 billion worth of damage
What we’re the SE for this Nepal EQ?
- Communities cut off by landslides and avalanches
- Avalanches on Mount Everest killed at least 19 people
- Flooding caused by blocked rivers
What were the IR for the Nepal EQ?
- Overseas aid
- Aid included helicopters for search rescue, supply drops in remote areas such as Mount Everest
- 300 000 migrated from Kathmandu for shelter and support from family and friends
What we’re the LTR for the Nepal EQ?
- Roads repaired, landslides cleared and flood lakes drained
* International conference to seek technical and financial support
Why do people continue to live at risk from tectonic hazards?
- Some people have no experience or knowledge of the risks
- Poor people have no choice- money, food and family are seen as more important
- Volcanoes can bring benefits such as fertile soils, rich mineral deposits and hot water.
How are volcanoes monitored?
- Remote sensing- satellites detect heat increase
- Seismicity - seismographs record microquakes
- Ground deformation- laser beams measure changes in the shape of the ground
How are earthquakes monitored?
Earthquake generally occur without warning but a number of events can occur before the quake…
• Microquakes before the main tremor
• Bulging of the ground
• Raised ground water levels
How are volcanoes predicted?
Monitoring is now allowing accurate prediction and effective evacuation.
How are earthquakes predicted?
Accurate predictions are impossible due to a lack of clear warning signs but historical records can help determine probability.
How can protection reduce volcanoes?
Little can be done to protect property but earth embankments and explosives have been used to successfully divert lava flows.
How can protection reduce earthquakes?
Earthquake drills help keep people alert and prepared. But earthquake resistant construction is the best way to reduce risk.
How can planning reduce earthquakes and volcanoes?
Risk assessment and hazard mapping to identify areas to
• protect buildings and infrastructure
• Practise evacuation or restrict building.
