The Challenge of Natural Hazards Flashcards
Define natural hazard
A natural event that posses a risk to people and property
What are the two types of natural hazard?
- Geological
- Meterological
What is a geological hazard?
Hazards caused by land and tectonic processes
Examples of geological hazards [4]
- Volcanoes
- Earthquakes
- Landslides
- Avalanches
What is a meterological hazard?
A hazard caused by weather and climate
Examples of meterological hazards [2]
- Tropical storms
- Extreme weather
Define hazard risk
The probability of people being affected by a hazard in a particular area
What 3 things affect hazard risk?
- Capacity to cope
- Population density
- Nature of hazard
How does capacity to cope affect hazard risk? [2]
- The better a population can cope with an extreme event, the lower the risk of them being severely affected
- e.g. HICs are able to cope with flooding because they can afford to build flood defences
How does population density affect hazard risk? [2]
- The more people there are in an area exposed to a hazard, the greater probability that they will be affected
- e.g. an area with a large population density on a floodplain would be very vulnerable to flooding
How does the type of hazard affect hazard risk? [2 examples]
- Tropical storms can be predicted and monitored, giving people time to evacuate
- Earthquakes happen very suddenly, with little warning, so it’s harder to protect people
How does the frequency of a hazard affect hazard risk?
Natural hazards that occur more often may carry a higher risk
How does the magnitude of a hazard affect hazard risk?
More severe natural hazards tend to have greater effects
What are the 2 types of crust that tectonic plates are made from?
- Continental
- Oceanic
Describe continental crust:
i) thickness
ii) density
i) Thicker (30 - 50 km)
ii) Less dense
Describe oceanic crust:
i) thickness
ii) density
i) Thinner (5 - 10 km)
ii) More dense
What moves tectonic plates in the mantle?
Convection currents
Describe what happens at a destructive plate boundary (2 diff. plates) [2]
- Oceanic and continental plates move towards each other
- Denser oceanic plate subducted and destroyed
Describe what happens at a destructive plate boundary [2]
- Two continetal plates meet
- Ground is folded upwards
What is created at destructive plate boundaries (2 diff. plates)? [2]
- Volcanoes
- Ocean trenches
What is created at destructive plate boundaries?
Fold mountains
Describe what happens at a constructive plate boundary [2]
- Two plates moving away from each other
- Magma rises from the mantle, creating new crust
What is created at a constructive plate boundary?
Ridges
Describe what happens at a conservative plate boundary [2]
- Plates are moving sideways past each other
- OR plates are moving in same direction but at different speeds
What can occur at conservative plate boundaries?
Earthquakes
What plate boundaries do volcanoes occur at? [2]
- Destructive
- Constructive
Explain how volcanoes form at destructive plate margins [3]
- Denser oceanic plate moves down into the mantle and melts
- A pool of magma forms, which then rises through cracks in the crust called vents
- The magma erupts, forming a volcano
Explain how volcanoes form at constructive plate margins [2]
- Magma rises up into the gap, created by the plates moving apart
- Forming a volcano
What plate boundaries do earthquakes occur at? [3]
- Destructive
- Constructive
- Conservative
Explain how earthquakes occur at destructive plate boundaries
Tension builds when one plate gets stuck as it moves past the other
Explain how earthquakes occur at constructive plate boundaries
Tension builds along cracks in the plates as they move away from each other
Explain how earthquakes occur at conservative plate boundaries
Tension builds up when plates that are grinding past each other get stuck
What is the focus of an earthquake?
The point in the earth where the earthquake starts
What is the epicentre of an earthquake?
The point on the Earth’s surface straight above the focus
What are the 2 scales that measure earthquakes?
- Richter scale
- Mercalli scale
What does the Richter scale measure?
Magnitude of an earthquake
What does the Mercalli scale measure?
Damage caused by an earthquake
Why do people continue to live in areas at risk from tectonic hazards? [5]
- Family ties
- Too poor to move
- Farming
- Mining
- Tourism
How can earthquakes be monitored?
Use seismometers and lasers to monitor earth movements
How can volcanic eruptions be monitored?
Scientists can monitor tell-tale signs (e.g. tiny earthquakes, escaping gas and changes in volcano shape)
Protection from earthquakes [3]
- Buildings built with concrete that absorbs shock waves
- Bridges strengthened withs steel frames
- Automatic shutters and shut-off switches