✅🟢Natural and Tectonic Hazards Flashcards
Natural Hazard meaning
A natural event that threatens people or has the potential to cause damage
Natural hazard examples
Earthquake / volcanic eruption / flood / tropical storm
Factors that affect natural hazard risk
Magnitude
Frequency
Location (steep slopes / active plate boundaries)
Population (high population = more people at risk)
Level of development / wealth - poorer communities = less money to prevent / invest in disaster management
3P’s
What are the 3P’s and what do they do?
Protection (planning / preparation)
Prediction
Prevention
If the 3Ps are good = less of an impact from natural hazard
What’s the plate tectonic theory?
The movement of the plates, and the activity inside the Earth, is called the theory of plate tectonics.
Describe the Crust of the earth
Earths crust is broken into plates, either oceanic or continental. Once believed the convection currents in the mantle slowly moves the crust around, now though that a mechanism called slab pill drives the movement of tectonic plates.
Describe earths structure
Inner Core - centre / hottest part of the earth - made of iron / nickel, temps up to 55°
Outer core - liquid layer surrounding inner core made of iron / nickel
Mantle - thickest section of the earth (2900km) molten rock - magma
Crust - outer layer of the earth - think (0-60km) either continental or oceanic
What’s the slab pull / when does it occur?
Slab pull occurs where older, denser tectonic plates sink into the mantle at subduction zones. As these older sections of plates sink, newer and less dense sections of plate are pulled along behind. Sinking in one place leads to plates moving apart in other places.
Tectonic plate meaning
Section of earths crust which land + oceans are above
Plate margin meaning
Boundary between 2 plates
A plate margin marks the point where 2 of the earths tectonic plates meet. At these points the earths crust of either destroyed / creates / collides / slides past
Oceanic vs Continental Crust
Oceanic is less than 200 years old
Continental is 1500millipm years old
Oceanic is thiner by 10x
Oceanic is denser therefore can sink
Oceanic - basalt
Continental - granite
Oceanic - can be removed / destroyed
Continental- can’t be removed / destroyed
Destructive / convergent plate margins
Move towards eachother
Can be continental and oceanic
Oceanic and continental plates move together. The oceanic plate subducts under the lighter continental plate. Friction causes melting of the oceanic plate and may trigger earthquakes. Magma rises up through cracks and erupts onto the surface.
Earthquakes are violent here
Constructive / divergent plate margins
occurs when 2 continental plates move apart / diverge. Volcanoes are formed as magma wells up to fill the gap, and eventually new crust is formed.
An example of a constructive plate boundary is the mid-Atlantic Ridge.
Gentle earthquakes
Mid Atlantic Ridge
Collision zone
Collision zones form when two continental plates collide. Neither plate is forced under the other, and so both are forced up and form fold mountains.
Conservative / transform margin
Sideways
Oceanic + continental crust slides past each other, presssure + friction from plate movements can build up if they get stuck due to friction. When they break apart energy is sent through the earth as shock waves in the form of an earthquake.
No margin crust created / destroyed
Sam Andreas fault
What’s the global distribution of earthquakes / volcanic eruptions and their relationship to plate margins?
Earthquakes - along all types of plate margins.
Volcanoes - only constructive and destructive plate margins.
What are the primary physical effects of a tectonic hazard - Christchurch?
Ground deformation
What are the secondary physical effects of a tectonic hazard - Christchurch?
Liquifaction - 400,000 tons silt
Cliff collapsing
Tsunami
What are the primary social effects of a tectonic hazard - Christchurch?
185 people killed
4000 injured
What are the secondary social effects of a tectonic hazard - Christchurch?
1293 died in aftermath
Outmigration of 1/5 of population
Physiological impacts
What are the primary economic effects of a tectonic hazard - Christchurch?
Pine Court Corpiration / CTV building fell
£40 billion total repair
Church fell down
What are the secondary economic effects of a tectonic hazard - Christchurch?
Impact on school
Rugby World Cup impacted
Peoples money lost
Financial problems - people couldn’t work
What are the primary environmental effects of a tectonic hazard - Christchurch?
Roads fractured
Debris / rubble on roads
Water pipes / telephone wires not working
Bridges broken
What are the secondary environmental effects of a tectonic hazard - Christchurch?
80% of pipes / sewage couldn’t work properly
Roads filled with debris - unaccessible
Primary responses to Christchurch earthquake?
Rescue crew Firefighters Survivors helping Media + news Farmer army clean up Domestic help 300 Australian police came
Secondary responses to Christchurch earthquake?
Community groups
Structural engineers
Green / orange / red / white zones
Temporary homes
Compare : Christchurch New Zealand 2011 Kathmandu Nepal 2015
Christchurch - disaster plans in place / well trained emergency services / disaster drills / evacuation routes clear / food amount of equipment / well trained emergency crews - Death toll lower 185 / no one homeless / £40 billion repair cost
Kathmandu - disaster plans not in place / people unaware / people waiting for equipment to be flown in / poorly trained service crews- death toll higher 9000 / homeless = 3.5million / £10 billion repair cost
Give economic reasons why people continue to live in areas at risk from a tectonic hazard
- A good job / way of life May keep you in a danger zone
- Sulphur can be mined in some volcanically active areas
- The worlds best coffee is grown on volcanic soil in Columbia
- Poor people (LIC’s) can’t afford to live away from volcanoes as they provide jobs (tourism)
- Engineering can make people feel safe in these areas in richer parts of the world. Buildings can be made to be earthquake proof like the Bird’s Nest stadium in Beijing
- Volcanic soils are very fertile - in Italy olives / vines / bits / lemons / oranges are grown near Mount Vesuvius
Give social reasons why people continue to live in areas at risk from a tectonic hazard
- Some places are well prepared for hazards so people feel safe
- People in Mount Merapi (Indonesia) worship ancient spirits believing they will warn them of an eruption, on a full moon they throw items into the volcano crater to calm the volcanoes spirits
- People believe the chance of the volcano erupting is slim
- Many volcanic / earthquake events are infrequent so people don’t think they will experience a natural disaster
- Volcanoes provide jobs / families and friends live there
- A good way of life May keep you in a danger zone
Give environmental reasons why people continue to live in areas at risk from a tectonic hazard
- Some settlements have grown into enormous cities and would be hard to move anywhere else
- In Iceland volcanoes provide cheap geothermal power (28% of all its energy) - can be used to heat pavements in the winter
- Volcanic soils are fertile as the weathering of volcanic rock releases potassium into the soil which is essential for plant growth.
What’s monitoring +How does it reduce the risks from a tectonic hazard?
Using scientific equipment to detect warning signs of events such as volcano / earthquake
Remote sensing - satellites detect heat / shape changes of volcano
Seismicity - seismographs record earthquakes
Gas - instrument detect gases related to magma rises
Ground deformation - laser beams measure volcano shape change
Why are earthquakes harder to detect than volcanoes?
Usually they occur without warming but there’s evidence of water pressure changes / ground deformation / minor tremors prior earthquake
Scientists are yet to discover reliable ways to monitor / predict earthquake
What’s prediction + how does it reduce the risks from a tectonic hazard?
Using historical evidence + monitoring scientists predict when / where a tectonic hazard may occur
Use scientific data / historical records on frequency
Prediction relies on monitoring
What’s protection + how does it reduce the risks from a tectonic hazard?
Designing buildings that will withstand tectonic hazards
Volcanoes :
Embankments / explosives to divert lava away from property
Earthquakes:
Rolling weights on roof - control movement
Safe open areas for people to gather
Shutters that automatically shut
Rubber shock absorbers between foundations / above ground
What’s planning + how does it reduce the risks from a tectonic hazard?
Identifying + avoiding places most at risk
Volcanoes:
Hazard maps for worlds most dangerous volcanoes - restrict certain land areas + identify land that needs to be evacuated + where to go if volcano erupts
Earthquakes:
Hazard maps for areas where earthquake will effect - high value land uses (hospitals / reservoirs) ab be protected in these vulnerable areas
