Tectonic Hazards Flashcards
Earthquakes
a sudden or violent movement withing the Earth’s crust followed by a series of shocks
Most occur at the margins of slowly moving tectonic plates. Friction and sticking between the plates creates enormous pressures and stresses which build up to breaking point. However, activities such as mining or oil extraction can cause them.
Volcanoes
they are large, and often cone shaped landforms, formed over long periods by eruptions. They are fed with molten rock (magma) from deep within the earth’s mantle. Like earthquakes, most occur in belts along plate margins (e.g. the ‘pacific ring of fire’ and the mid-Atlantic ridge). But some occur at hot spots where the crust is thin and magma breaks through.
Describe the different types of crusts
Oceanic crust - dense, thin
Continental crust - less dense, thicker
Overview on Plate margins
Plates move, driven by convection currents within the mantle and under gravity.
At constructive plate margins, plates separate, forming new crust, causing massive volcanic eruptions.
At destructive plate margins, plates collide, causing subduction, earthquakes, volcanic eruptions and fold mountains.
At conservative plate margins, plates slide by each other, causing earthquakes.
Constructive Margins
The convection currents move the plates apart. This allows the magma to force its way up. Once it hits the sea, it cools and solidifies forming new land which can be ocean ridges such as the Mid Atlantic ridge in Iceland, cone volcanoes or cause earthquakes.
e.g. Iceland
Destructive Margins
two plates move towards each other due to convetion currents pulling and dragging the plates. The plates are jammed together causing friction. The rocks are constantly against together and the pressure builds up over a large period of time. Once the pressure overcomes the friction, the thin oceanic plate is sub-ducted beneath the thick continental plate. Friction between the plates causes strong earthquakes . The sinking oceanic plate creates sticky, gas rich magma. This results in steep-sided composite volcanoes which erupt violently as the melting crust feeds it.
e.g. Nazca plate sub ducting underneath the South American plate
Conservative Margins
The convection currents move two places in opposite directions or different speeds.
Friction builds up between these two plates and they suddenly move apart. This causes an earthquake.
E.g. San Andreas Fault
The faster moving Pacific Plate is sliding in the same direction next to the slower moving North American Plate.
Collision boundary
Where two continental plates meet there is no subduction, so there is no magma to form volcanoes. The crust crumples and lifts to form fold mountains (e.g. the Himalayas). Powerful earthquakes can be triggered.
Geographical location of Chile
- SW of South America
- west of Chile is the Pacific Ocean
- East is the Andes and Argentina
- Borders with Peru and Bolivia in the north
Contextual information about Chile
Population: 16.7 million
Urban Population: 89%
GDP: 38th of 193 countries
HDI: 41st out of 187 countries
Overview of Chile 2010
Magnitude = 8.8
Feb 2010
Close to the Coast therefore cause Tsunami
Primary Effects of Chile 2010 earthquake
- 500+ died
- 12,000 injured
- Cost estimated US $30 billion
- Widespread power cuts
- 220 000 homes, 4500 schools, 53 ports, 56 hospitals and other public buildings destroyed.
Secondary Effects of Chile 2010
- Tsunami
- 1500km of roads damaged, mainly by landslides – remote communities cut off for many days.
- A fire at a Santiago chemical plant – area had to be evacuated
Immediate Responses of Chile 2010
- Swift and effective response by emergency services
- Key roads repaired within 24h
- Water and power restored to 90% of homes in 10 days
- US$60 million national appeal built 30 000 emergency wooden shelters.
Long Term Response of Chile 2010
- Strong economy reduced the need for foreign aid, based on copper exports.
- Government reconstruction plan to help 200 000 households
- Full recovery estimated took 4 years.
Geographical Information of Nepal
- in Asia specifically in the Himalayas
- Bordering India and China
- Land locked
- On a destructive plate margin. (Indian plate sub ducting the Eurasian plate)
Contextual Information about Nepal
Population: 29million in 2010
GDP: 109/193
HDI: 145/187
Overview on Nepal 2015 earthquake
7.8 on Richter scale. Shallow (only 15km below ground), epicentre was 80km north-west of Kathmandu, Nepal’s capital.
Primary Effects of Nepal 2015
- 9000 people dies and 20 000 injured, over 8 million people affected (1/3 of population) affected.
- 3 million left homeless.
- 50% of shops destroyed, affecting people’s livelihoods and food supplies.
- Cost estimated at over US$5 billion.
Secondary Effects of Nepal 2015
- Landslides and avalanches triggered, they blocked roads and hampered relief efforts.
- Avalanches killed at least 19 people on mount Everest
- 250 people missing after avalanche in Langtang region.
Immediate Responses in Nepal 2015
- Aid included helicopters to reach cut of areas
- Half a million tents needed to provide shelter for the homeless.
- Financial aid pledged from many countries including India
- 300 000 people migrated from Kathmandu
- Local people played a central role in the search and rescue of people
- emergency services were disorganised at times
Long term Responses in Nepal 2015
- Roads repaired, landslides cleared and flood lakes drained.
- In June 2015 Nepal hosted an international conference to discuss reconstruction.
- Tourism to be boosted, by July 2015 some heritage sited reopened.
- in August 2015 Everest reopened for climbers after repairing the Everest Base camp and trekking routes
Why do people live with tectonic risk
E.g. Iceland
- cheap electricity + heating
- hydroelectric power
- Geothermal energy generates 25% of Iceland’s electricity
- Industries: Tourism and Fishing
- Large earthquakes and volcanic eruptions don’t occur that often, so people aren’t so scared.
- Better building design makes people feel less at risk
- More effective monitoring can help evacuations
Others:
- Volcanoes bring benefits: fertile soil, rocks for building, rich mineral deposits and hot water.
- Plate margins often coincide with favourable areas for settlement, such as coastal areas where there are ports.
Managing Earthquakes Strategies: Monitoring
Scientists are yet to find reliable ways to monitor and then predict them. However, they can try with; laser beams, gas, animal behaviour, seismometer, water pressure, ground deformation and minor prior tremors.
Managing Earthquakes Strategies: Prediction
impossible to make accurate predictions but studying historical records can give scientist ideas about areas most at risk.
Managing Earthquakes Strategies: Protection
- Rolling weights on roof to counteract shock waves
- Walls reinforced with steel and concrete to reduce movement
- Automatic shutters come down over windows to prevent glass falling
- Reinforced Foundations and Shock absorbers to absorb ground shaking
- Open areas for evacuation
Managing Earthquakes Strategies: Planning
– maps can be produced to show the effects so areas of high risk can be identified and high-value land uses can then be protected in those areas.
- earthquake drills in school
Managing Volcanoes Strategies: Monitoring
Modern hi-tech equipment is used to monitor volcanoes and give warning signs when necessary. This is done with; remote sensing = satellites that detect heat and changes to volcano’s shape
seismicity = seismography record earthquakes
ground deformation = changes to the shape of the volcano are measure using laser beams
Gas = instruments detect gases released as magma rises
hydrology = measurements of gses dissolved in H2O
Managing Volcanoes Strategies: Prediction
Based on scientific monitoring
Managing Volcanoes Strategies: Protection
their sheer power means that not much can be done, but earth embankments can help divert lava flow.
Managing Volcanoes Strategies: Planning
Hazard maps have been created for the most dangerous volcanoes, which can be used in planning to restrict certain land uses to identify which areas need to be evacuated when an eruption is about to happen.
- drills can also take place
Different types of Management Strategies
Monitoring = using scientific equipment to detect warning signs of events Prediction = using historical evidence and monitoring, scientists can make predictions Protection = designing buildings that will withstand tectonic hazards. Planning = identifying and avoiding places most at risk
