Challenge of Natural Hazards Flashcards
What is a natural hazard?
A natural event (e.g. earthquake, volcanic eruption, tropical storm, flood) that threatens people or has the potential to cause damage, destruction and death.
What is a hazard risk?
The chance or probability of being affected by a natural event.
List the categories of natural hazards and some examples
- Tectonic hazards: earthquake, tsunami, volcanoes
- Atmospheric hazards: hurricanes, drought
- Geomorphological hazards: flooding, erosion
- Biological hazards: malaria, ebola
What factors affect a hazard risk?
- Poverty - poorer places will struggle to adequately prepare for a hazard of be able to respond
- Magnitude - the severity of the disaster will make the impact worse
- Population density - areas that have high populations will experience more destruction
- Education - how educated the population are to react and prepare for the hazard
Describe the structure of the earth starting from the outermost layer
- Crust - the outermost layer of the Earth, broken into tectonic plates
- Mantle - semi-molten part of the Earth
- Outer core - liquid iron and nickel
- Inner core - solid iron and nickel
What causes plates to move?
Convection currents in the mantle
What are convection currents?
Circulating movements of magma in the mantle causes by the heat of the core
Describe the global distribution of earthquakes
Earthquakes occur in lines which coincide with plate margins. There are many along the western coast of North and South America.
Describe the global distribution of volcanic eruptions
Volcanoes are found both on land and in the sea. They tend to be found along plate margins. Some volcanoes are found in the centre of plates. These are known as hot spots. There is a large band of volcanoes around the Pacific Ocean known as the Ring of Fire.
What is oceanic crust?
The part of the Earth’s crust which is below the oceans
What is continental crust?
The part of the Earth’s crust that makes the continents
What is the difference between oceanic and continental crust?
- Oceanic crust is thinner (5-10km thick) and continental crust is thicker (20-200km thick)
- Oceanic crust is recycled at destructive margins as it subducts under the continental crust
- Oceanic crust is denser than continental crust
- Continental crust cannot be destroyed
What is a conservative plate margin?
A plate margin where the tectonic plates are sliding past eachother
What is a constructive plate margin?
A plate margin where the tectonic plates are moving apart
What is a destructive plate margin?
A plate margin where an oceanic and continental plate collide
What are tectonic hazards?
Threats posed by earthquakes, volcanoes etc
Define epicentre
The point on the ground directly above the focus (centre) of the earthquake
Define focus
The point of origin of an earthquake
Define magnitude
The size of an earthquake
What is an ocean trench?
A deep depression on the ocean floor formed at the subduction zones of destructive plate margins
What are tectonic plates?
The large pieces of broken crust that cover the earth
What is a plate margin?
The boundary between two tectonic plates
What are primary effects?
The impacts of a natural disaster that happen immediately or soon after the event
What are secondary effects?
The events that occur as indirect impacts of a natural event
Define tsunami
A long, high sea wave caused by an earthquake or other disturbance
List 2 characteristics of oceanic crust
Oceanic crust is thinner and more dense than continental crust. This is because it has been compressed by the weight of the ocean
What is an earthquake?
A sudden violent shaking of the ground caused by movement in the earth’s crust or volcanic action
Do earthquakes happen on all four plate boundaries?
Yes
Why do earthquakes occur?
Tectonic plates are constantly moving, sometimes they get stuck and friction/pressure builds up as the plates are still trying to move. This pressure is eventually released in the form of an earthquake.
List some characteristics of a composite volcano
- Acidic lava
- Steep sides
- Alternate layers of ash and lava
- Violent eruptions
- Long periods between eruptions
List some characteristics of a shield volcano
- Runny lava
- Gentle sides
- No layers (pure lava)
- Less violent eruptions
- Shorter periods between eruptions
Can we predict volcanic eruptions and earthquakes?
Volcanic eruptions: Yes
Earthquakes: No
List some reasons why people live in areas at risk from tectonic hazards
- Fertile land
- Income from tourism
- Lack of other alternatives
- Mining precious minerals
How do we measure the size of an earthquake?
Richter Scale (scale of 1-9)
At which plate margins can earthquakes occur?
All plates margins
At which plate margins can volcanoes occur?
Shield volcanoes at constructive margins and Composite volcanoes at destructive margins
What type of plate margin does Haiti lie on?
Conservative
What type of plate margin does Japan lie on?
Destructive
What was the magnitude of the Haiti earthquake?
7
What was the magnitude of the Japan earthquake?
9.1
What were the primary effects of the Haiti earthquake?
- 316,000 deaths
- 1.3 million homeless
- Destruction of buildings
What were the secondary effects of the Haiti earthquake?
- Port-Au-Prince (capital) needed rebuilding
- Cholera outbreak
- New homes being build to a higher standard
- Became dependant on overseas aid
- 1 million people still displaced after 1 year
What were the primary effects of the Japan earthquake
- 16000 deaths
- 131000 homeless
- Destruction of buildings
What were the secondary effects of the Japan earthquake?
- Tectonic plate shifts
- Tsunamis
- Coastal changes
- Transport disruptions
What was the recovery of the Haiti earthquake like?
- Crucial aid was very slow to respond
- Land was offered by Senegal
- Dominican Republic accepted refugees
- The EU donated $330 million
What was the recovery of the Japan earthquake like?
- Crucial aid responded almost immediately
- Introduced rescue services
- Rebuilt destroyed buildings
- International aid donated $1 million
What is meant by ‘monitoring tectonic hazards’?
Using scientific equipment to detect warning signs of events such as a volcanic eruption
What is meant by ‘prediction of a natural event’?
Using evidence and monitoring information to make a judgement about when an earthquake or volcano is likely to happen
What is meant by tectonic hazard protection?
Designing buildings to withstand tectonic hazards
What is meant by planning for tectonic hazards?
Identifying places at risk of tectonic hazards and ensuring people know what to do in the event of an earthquake
How can we monitor volcanoes?
Satellites and amp: laser beams detect changed to the volcano’s shape. Increased amount of gases such as carbon dioxide and hydrogen sulphide are given off before an eruption
How can we monitor earthquakes?
There is no reliable way of monitoring and predicting earthquakes
How can people plan for tectonic hazards?
Identify areas at risk and don’t build on these areas, as well as planning to evacuate high risk areas.
How can we protect against volcanic eruptions?
Divert lava away from built up areas by using explosives
How can we protect against earthquakes?
Building with reinforced foundations, shock absorbers, automatic shutters and rolling weights on roofs
