The Challenge of Natural Hazards (part 1) Flashcards
What are the two types of tectonic plates and what are their properties?
- Continental - won’t melt, thicker but lighter, mostly granite
- Oceanic - can be destroyed, heavy and thin (will sink), basaltic
How are earthquakes caused?
Tectonic plates are moved by convection currents in the mantle. At some plate boundaries, plates get stuck, pressure builds. When pressure is released, there is a jolt, which is an earthquake
Name the four plate boundaries
- Conservative
- Collision
- Constructive
- Destructive
Describe conservative plate boundaries
Describe collision plate boundaries
Plates slide past each other (either in different directions or different speeds), only cause earthquakes
Continental plates move towards each other, crust crumples and forms fold mountains, only cause earthquakes
Describe constructive plate boundaries
Describe destructive plate boundaries
Plates move away from each other, magma fills the gap, causes shield volcanoes and earthquakes
One oceanic, one continental plate move towards each other. Oceanic is more dense so subducts underneath, oceanic plate melts in mantle. New, hot magma breaks through surface, causes composite volcanoes and earthquakes
Why do people live in earthquake-prone areas?
Trust in government to keep them safe Insurance will pay out Family and friends live there They have jobs there / have no choice Trust in the rebuilding process Financial compensation
How can you reduce the impacts of earthquakes?
Predict
Protect
Prepare
Describe Predict of the three Ps of earthquakes
Watch animals for strange behaviour
Measure radon gas levels
Predictions using seismometers
Describe Protect of the three Ps of earthquakes
Build earthquake-proof buildings
Bendy pipes to prevent gas/water leaks
Steel poles in walls to make them stronger
Improve quality of infrastructure
Describe Prepare of the three Ps of earthquakes
Prepare emergency services Stock up on supplies Evacuation training / earthquake drills / education Have earthquake survival kits Create disaster plans
What are the general facts around the Nepal earthquake?
What are the general facts around the Chile earthquake?
2015, 7.9 magnitude, collision plate boundary between the Eurasian and Indo-Australian plates
2010, 8.8 magnitude, destructive plate boundary between the Nazca and South American plates
What were the primary impacts of the earthquake in Nepal?
- 9000 deaths
- 20,000 injured
- 1/3 population affected
- Cost of damage US $5 billion
- 3 million homeless
What were the secondary impacts of the earthquake in Nepal?
- Avalanches blocked roads + disrupted rescues
- Avalanche on Mount Everest killed 19
- Landslide blocked a river, caused flooding
What were the short-term responses to the earthquake in Nepal?
- Search + Rescue teams from UK, India, China
- 1/2 million tents for the homeless
- Many countries gave financial aid
- Financial compensation for victims
What were the long-term responses to the earthquake in Nepal?
- Roads repaired, landslides cleared
- Lakes formed from landslides damming rivers drained
- International conference for aid and support
What were the primary impacts of the earthquake in Chile?
- 500 deaths
- 12000 injured
- 800,000 affected
- Cost of damage US $30 billion
- 270,000 homes destroyed
What were the secondary impacts of the earthquake in Chile?
- 1500km roads damaged
- Tsunami devastated coastal towns
- Fire at a chemical plant in Santiago
- Remote communities cut off
What were the short-term responses to the earthquake in Chile?
- Emergency services very quick
- Temporary repairs to the main highway in 24 hours
- Power + water restored to 90% homes in 10 days
- Whole population given food
- All children given supplies for education
What were the long-term responses to the earthquake in Chile?
- 1 month plan helped 200,000 households
- Wood houses for temp shelter until all rebuilt in a year
- Main economy (copper) rebuilt without financial aid
- Aid from charities like Unicef
What is a tropical storm?
An area of extreme low pressure with extreme winds (at least 74mph) spiralling around an eye (calm centre)
What are the characteristics of a tropical storm?
- Up to 480km across and 14km high
- Spiralling winds get weaker towards the edge
- Eye is where cold air sinks so calm conditions
- Eye wall is where strongest conditions are felt
What are the conditions for a tropical storm to form?
- Must form over an ocean in the tropics
- Ocean must be 60m deep
- Ocean must be 27 degrees C
- Must be far enough away from equator for the Coriolis Effect (correct spin of the earth) to work
How does a tropical storm form?
Strong upwards movement of air (low pressure) draws moisture from ocean
Evaporated water cools, condenses, forms thunderstorms
Condensing air releases heat, draws up more vapour
Several small storms join to form one spinning storm
Storm carried cross ocean by prevailing winds, gets stronger
When it reaches land, energy supply cut off, it dissipates
How can the impacts of a tropical storm be reduced?
Predict
Protect
Plan
