The Challenge of Natural Hazards: Tectonic Hazards Flashcards
Natural hazard
Natural hazards are extreme natural events that can cause loss of life, extreme damage to property and disrupt human activities.
There are 4 different types: geological, biological, meteorological and geomorphological.
Examples of geological hazards:
Earthquakes
Tsunamis
Volcanoes
Landslides
Examples of meteorological hazards:
Tropical storms
Drought
Wildfires
Extreme temperature
Examples of biological hazards:
Disease epidemics
Insect/animal plagues
Examples of geomorphological hazards:
Avalanches
Floods
Hazard risk
The probability of being affected by a natural event. Factors affecting hazard risk include location in world, stage of economic development, urbanisation, time of event and climate change.
Factors affecting hazard risk: vulnerability
- People living in coastal regions more at risk of tropical storms
- People in LICs less prepared for natural hazards
- People living in urban areas more at risk from earthquakes
- People living in low-lying areas more at risk from flooding
- People more at risk if an earthquake happens during rush hour
Factors affecting hazard risk: capacity to cope
HICs tend to be better prepared for natural hazards because they can monitor, predict and evacuate areas at risk. They also have enough money after a hazard for repairs and hospitals.
Factors affecting hazard risk: nature of natural hazard
- The higher a tropical storm is on the Saffir-Simpson scale, or an earthquake is on the Richter scale, the higher the risk will be
- If an earthquake at a destructive plate boundary caused a tsunami, more people would be at risk
Oceanic crust
Found underneath the oceans
Mostly made of igneous rock which is very dense
Thinner than the continental crust but heavier
Can be subducted
Continental crust
Has land on top of it
Mostly made of granite which has low density
Lighter than oceanic crust but also thicker
Floats higher on the mantle and doesn’t sink
Generally older than oceanic crust
Less often destroyed
Crust
The crust is the solid rock layer upon which we live. It is the outer layer of the Earth and also the thinnest. It is either continental or oceanic. The earth’s crust is broken into plates. Heat rising and falling inside the mantle creates convection currents generated by radioactive decay in the core. The convection currents move the plates.
Mantle
The mantle is the thickest section of the Earth and makes up for nearly 80% of the Earth’s volume.. The mantle is made up of semi-molten rock called magma.
Outer core
The outer core is the layer surrounding the inner core. It is so hot that it is always molten, also made up of iron and nickel.
Inner core
The inner core is in the centre and is the hottest part of the Earth. It is solid and made up of iron and nickel with temperatures of up to 5,500°C.
Lithosphere
It’s made of the crust and the solid upper mantle.
Asthenosphere
The layer below the lithosphere where it’s less solid and convection happens.
Plate tectonic theory: convection
- convection currents occur in the mantle layer
- the molten rock is heated by radioactive decay in the core and then it rises
- when it meets the crust it cools and sinks back down
- this process repeats, either pulling the plates apart or pushing it together
Plate tectonic theory: ridge push
- When plates move apart at a mid-ocean ridge, magma rises from the mantle to create hot new rock (less dense so floats to top).
- As the rock cools and ages it becomes more dense (so sinks) and is pushed out of the way as new magma emerges behind it.
- This creates a ridge in the crust.
Plate tectonic theory: slab pull
- Because the oceanic plate is denser than the hotter mantle beneath it, it is heavier so gravity pulls it into the mantle.
- The process of a tectonic plate descending into the mantle is termed subduction.
Constructive plate boundary
- 2 plates move apart due to convection currents in mantle
- As the plates move apart, magma rises through crust then cools and solidifies
- Process repeats until new rock builds up, forming volcano
- Earthquakes can also occur
E.g. Mid Atlantic Ridge
Destructive plate boundary
- Denser oceanic plate is pushed under continental plate (subduction)
- Friction where the plates slide causes earthquakes and melts oceanic crust into magma
- Magma rises through gaps in continental plate and forms a volcano if it reaches the surface
E.g. Nazca plate forced under South American plate
What is the global distribution of earthquakes and volcanoes?
- Along plate boundaries.
- On the edge of continents.
- Around the edge of the Pacific.
(Earthquakes found along all types of plate margins.
Volcanoes only occur at constructive and destructive plate margins.)
Conservative plate boundary
- 2 plates slide past/move in same direction at different speeds
- Pressure builds along a fault
- Friction when the plates suddenly jerk free causes earthquakes
- No volcanoes
E.g. San Andreas Fault, California
Earthquake in a HIC case study: Christchurch, New Zealand 2011
Causes
- Destructive + conservative plate boundary between the Pacific Plate and the Australian Plate
- 6.3 magnitude earthquake
- Epicentre 10km from central business district
Earthquake in a HIC case study: Christchurch, New Zealand 2011
Primary effects
- 185 people killed
- 3,000 injured
- 10,000 homes destroyed
Earthquake in a HIC case study: Christchurch, New Zealand 2011
Secondary effects
- 350,000 homeless
- Cost of damage was $50 billion
- No disease
Earthquake in a HIC case study: Christchurch, New Zealand 2011
Immediate responses
- Full emergency response plan in place within 2 hours
* Electricity companies worked around the clock to restore power
Earthquake in a HIC case study: Christchurch, New Zealand 2011
Long-term responses
- Strict building terms enforced
- Demolished buildings to stop them collapsing
- Temporary housing set up
Earthquake in an LIC case study: Port au Prince, Haiti 2010
Causes
- Conservative plate boundary between the Caribbean Plate and the North American Plate
- 7.0 magnitude earthquake
- Epicentre 25km from capital (Port au Prince)
Earthquake in an LIC case study: Port au Prince, Haiti 2010
Primary effects
- 220,000 people killed
- Too many injured to record
- 100,000 homes destroyed
Earthquake in an LIC case study: Port au Prince, Haiti 2010
Secondary effects
- 1.3 million homeless
- Cost of damage was $14 billion
- Cholera outbreaks
Earthquake in an LIC case study: Port au Prince, Haiti 2010
Immediate responses
- Survivors pulled from wreckage
- Dominican Red Cross sent the first medical aid
- Widespread crime in camps
Earthquake in an LIC case study: Port au Prince, Haiti 2010
Long-term responses
- Received $1 billion in aid
* 1 year later 98% rubble was still there
Why do people continue to live in areas at risk from volcanoes?
- Fertile soil
- Hot springs for bathing in (Iceland)
- Cheap geothermal energy can be generated from heat (Iceland)
- Minerals in the soil
- Mud used for skin care
- They build new land (Iceland)
- Copper, silver + gold can be found in land
- Tourist attractions (Iceland)
- Beautiful landscape
Why do people continue to live in areas at risk from earthquakes?
- Cheap geothermal energy can be generated from heat (Philippines)
- Many earthquakes are close to the coast, which is a good area for fishing + farming (Philippines)
- People have learnt to deal with earthquakes
- Earthquake-proof buildings can be built (Philippines)
- Large earthquakes are rare, so people are willing to take the risk
Why are the risks of hazards greater in LICs than HICs?
•HICs have more money to prepare for hazards and repair damage
•Organisations such as Mountain Rescue are only found in HICs
•HICs have better infrastructure, so emergency services can get there faster
•People In HICs are better educated:
-will be aware of hazards + how to prepare
-lots of scientists to warn people of dangers + prepare evacuation plans + monitor for hazards
Reducing the risk of tectonic hazards: monitoring
Seismometer measure earth movement.
Volcanoes give off gases.
Reducing the risk of tectonic hazards: prediction
By observing monitoring data, this can allow evacuation before an event.
Reducing the risk of tectonic hazards: protection
Reinforced buildings and making building foundations that absorb movement.
Automatic shut offs for gas and electricity.
Reducing the risk of tectonic hazards: planning
Avoid building in at risk areas.
Training for emergency services and planned evacuation routes and drills.
