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