What is a 'natural hazard'?
A natural event (for example earthquake, volcanic eruption, tropical storm, flood) that threatens people or has the potential to cause damage, destruction and death.
What is hazard risk?
Hazard risk is the chance or probability of being affected by a natural event
List some examples of natural hazards (and their category if you can)
Tectonic hazards (e.g. earthquake, tsunami, volcanic eruption)
Atmospheric hazards (e.g. hurricanes)
Geomorphological hazards (e.g flooding)
Biological hazards (e.g. forest fires)
What factors affect hazard risk?
1. Poverty - poorer places will struggle to adequately prepare for a hazard or be able to respond.
2. Magnitude - the severity of the hazard will make the impacts worse
3. Population density- areas that have high populations will experience more destruction.
4. Education - how educated the population are to react and prepare for the hazard
Describe the structure of the earth starting from the outermost layer?
OUTERMOST: 1. Crust - the outermost layer of the Earth, broken into tectonic plates.
2. Mantle - semi - molten part of the Earth.
3. Outer core - liquid iron and nickel
CENTRE: 4. Inner core - solid iron and nickel
What causes the plates to move?
Convection currents in the mantle
What are convection currents?
Circulating movements of magma in the mantle caused 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 more dense than continental crust.
- Oceanic crust is recycled at destructive margins as it subducts under the continental crust.
- Continental crust is thicker (20-200km thick) and is less dense than oceanic crust.
- Continental crust cannot be destroyed.
What is a conservative plate margin?
A plate margin where the tectonic plates are sliding past each other
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 a continental plate collide.
What are tectonic hazards?
Threats posed by earthquakes, volcanoes etc
What is subduction?
The transformation into magma of a denser tectonic plate as it dives under a less dense plate
The point on the ground directly above the focus (centre) of the earthquake
The point of origin of an earthquake
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
The way in which people react to a situation eg. an earthquake
What are secondary effects?
The after effects of a disaster eg. disease spreads or economic losses
Huge waves caused by earthquakes under the sea
List two characteristics of an oceanic crust
- 5-10 km thick
- Destroyed at destructive plate margins
- Forms constantly at constructive plate margins
- Geologically young compared to continental crust
List two characteristics of a continental crust
- 25-100km thick
- Less dense (than oceanic)
- Cannot be destroyed. New crust is not formed
- It is geologically old 3-4 billion years old
What is an earthquake?
Earthquakes are vibrations in the Earth's crust that create shaking at the surface. They are highly unpredictable and often occur suddenly without warning, mainly on the plate margins