Natural Hazard Flashcards
What is a Natural Hazard?
Natural hazards are extreme natural events that can cause loss of life, extreme damage to property and disrupt human activities.
What are the different types of Natural Hazards?
- Volcanic Eruptions
- Earthquakes
- Storms
- Tsunamis
- Landslides
- Floods
What is Hazard Risk?
The chance or probability of being affected by a natural event.
Why do people live in ‘Hazard Risk’ areas?
Natural Hazards do not happen regularly, so they decide to take the risk.
- Some people have little knowledge about where they’re living being dangerous.
- People may have little choice on where they can live
What factors affect Hazardous Risk?
- Urbanization
- Climate Change
- Farming
- Poverty
How does poverty affect hazardous risk?
- In poorer countries people are forced to live in Hazardous areas.
- Infrastructure in poorer areas makes them prone to maximal effect from the Hazard.
How does farming affect hazardous risk?
-Rivers flooding leave fertile slit which is good for farming,
How does Climate change affect hazardous risk?
- If a hot place becomes warmer, more energy in the atmosphere= more intense storms and hurricanes
- Places can become wetter leading to an increased risk of flooding
- PLaces can become drier, leading to drought and famine
How does urbanisation affect hazardous risk?
- 50% live in cities making the population density in the area very high, therefore if a natural hazard occured the citizens and city is at major risk
e. g. Hati over 230,000 dead
Where do earthquakes usually occur?
-On plate margins, where plates are moving and enormous pressures are built up and released
What is another less common cause of earthquakes?
Human activity- underground mining or oil extraction
What are the two types of crust?
Dense oceanic crust
Less dense continental crust
How do plates move?
Move in relation to each other due to convection (heat) currents deep within the Earth
Where do volcanoes happen?
-On long belts that follow plate margins e.g. pacific ring of fire
Why is there a pattern of volcanoes?
- Volcanoes feed on hot molten rock (magma) from deep within the Earth.
- The magma rises to destructive and constructive plate margins where there are hot spots which is where the crust is weak so it can break through to form a volcano/erupt
What happens at a constructive plate margin?
- Two plates move apart
- This allows magma to rise and force its way up
- When it breaks through the crusts hot spot it causes an earthquake
- When the magma reaches the surface it forms a flat shield or broad volcano
- The Lava which erupts will flow far before cooling as its very hot and fluid
What happens at a destructive plate margin? (oceanic and continatal plate)
- Two plates move towards each other
- Where the plates meet, a ocean trench is formed
- The denser oceanic plate subduct’s beneath the less dense oceanic plate
- The friction caused between both plates cause an earthquake
- The oceanic plate moves downwards and melts forming magma which breaks through the crust to form a composite volcano
- These eruptions are violent and explosive
What happens when two continental plates meet at a destructive margin?
- Both plates collide
- this makes the crust crumpled and uplifted
- This forms fold mountains and earthquakes
e. g himilayas
Why is there no volcanoes at a destructive plate margin where 2 continatal plates meet?
-theres no magma
What happens at a conservative plate margin?
- Two plates move past eachother in the same direction
- One plate is moving faster than the other
- This causes an earthquake due to the friction build up over many years
- the earthquakes are released suddenly when the plates slips and shifts
What was the magnitude of the Chile earthquake?
8.8 on the richter scale
What plate margin did the Chile earthquake take place at?
Destructive plate margin
Where did the CHile Earthquake happen?
Out at sea creates waves of 800km/hour
What was the magnitude of the Nepal earthquake?
7.9 on the richter scale
What plate margin did the Nepal earthquake take place at?
destructive plate margin
Where did the Nepal earthquake take place?
What is a Primary effect of an earthquake?
Something directly caused by the ground shaking, e.g. damage to roads and buildings, death and injuries
What is Secondary effect of an earthquake?
-A result of the primary effects , so ground shaking causing tsunamis, land slides and avalanches
What were the primary effects of the Chile Earthquake?
- 500 dead
- 12k injured
- 800k affected
- 220k homes destroyed
- Estimated cost of 30bn USD
What were the secondary effects of the Chile earthquake?
- 1500km of roads damaged
- Fires at chemical plants, area had to be evacuated
What were the primary effects of the Nepal earthquake?
- 9000 dead
- 20k injured
- 8 million affected
- 1.4 million needed food and shelter
- Estimated cost of 5bn usd
What were the secondary effects of the Nepal earthquake?
- Ground shaking caused avalanches and landslides, blocking the roads
- Avalanches killed 19 people
- 250 missing due to avalanche
What is a Immediate response?
-Search and rescue and keeping survivors alive by provide medical care, food, water and shelter
What is a Long-term response?
-Re-building and reconstruction, with the aim of returning peoples lives back to normal and reducing future risk.
What were Chiles immediate responses?
- Repairs made to the North-South highway within 24 hours
- Raised 60 usd milliion for 30,000 shelters
What were chile’s long term responses to the Earthquake?
- Government launched reconstruction plan helping 200,000 homes
- re built their economy single handedly by increasing copper exports
What were Nepals immediate responses to the earthquake?
- Sent out search and rescue teams
- water, medical support and food arrived quickly from other countires
- 500k tents provided
- Field hospitals were set up
What were Nepals long term response to the earthquake?
- Roads were repaired
- landslides were cleared
- 7000 schools rebuilt
- Stricter controls on building codes
- They seeked technical and financial support for reconstruction from other countries
Why do people choose to live in tectonically active areas?
- Natural hazards do not happen often
- Building designs can withstand natural hazards
- There is now more effective monitoring of natural hazards
- Volcanoes bring fertile soil, rocks for building and rich mineral deposits
- People in poverty cannot afford to move and need to earn money which is more important to them
Whats it like living on a plate margin? (iceland)
- eruptions every 5 years
- people see the active volcanoes not as a great risk as there is very effective monitoring and awareness of potential dangers
What are the benefits of living on a plate margin? (iceland)
- Hot water from the earths crust provides heat and hot water for 90% of the buildings
- Volcanic rock is used for buildings
- Dramatic landscapes with waterfalls and volcanoes are great tourist attractions bringing 1 million tourists to the country each year
How can risks from tectonic hazards be reduced?
- Monitoring
- Prediction
- Protection
- Planning