Natural Hazards Flashcards
(54 cards)
Define a Natural Hazard
a natural event that threatens people or has the potential to cause damage, destruction and death
Atmospheric Hazard
Created in the atmosphere by the weather, by the movement of air and water eg. Wind
Geological Hazard
Created by the movement of the earth’s tectonic plates or surface rock and souls eg. Earthquakes
Types of Hazards
Floods Hurricanes Landslides Tsunamis Droughts Volcanic eruptions Blizzard
Hazard Risk
This is the chance or probability of being affected by a natural event
Why do people put themselves at risk by living in places prone to natural hazards?
Weigh up advantages and disadvantages
Such events don’t happen very often so they accept this risk
Little choice of where to live or knowledge where they’re living is dangerous
Factors affecting Hazard Risk
Natural factors- height of the land, shape of coastline, softer sediment is more likely to liquefy
Magnitude- size of event have different impacts :different on Saffir Simpson scale and Richter scale
Population density- more people means a greater potential for disaster
Frequency- the more often it happens, the more prepared people are. Rare events such as tsunamis mean people are less prepared
Impacts of magnitude 9 Tsunami in Indian Ocean
13 countries affected- mostly Indonesia Quarter of a million people died Two million people made homeless Short term aid- temporary housing water purification tablets and medical supplies Rebuilding of industries
Plate Tectonics
Theory that tries to explain how the earth is structured and what it is made of
Crust
Outermost later of the earth
Mantle
A layer of rock between the core and crust made of molten rock
Magma
Liquid rock (molten) is called magma.it is liquid because the heat from the earths core has melted it
Core
Dense hot rock at the centre of the earth
Structure of earth
Crust- hard outer shell
Mantle- soft molten rock (3800 degrees Celsius)
Outer core- liquid iron and nickel
Inner core- very hot up to 5000 degrees celsius
What is happening inside the earth?
As heat rises from earths core , it sets of convection currents in the mantle to move. It’s that movement that sets of earthquakes and volcanic eruptions
Convection currents
Happen as a result of radioactive decay in the core. Move as fast as fingernails grow
Oceanic crust
Found under the sea
5-10km thick
Dense
Sinks into mantle when oceanic and continental meet
Forms constantly at constructive plate margins
Destroyed at destructive plate margins
Continental Crust
Found under the land 25-100km thick Less dense Doesn’t sink New crust isn’t formed Can’t be destroyed
Tectonic plate examples
Pacific Mazda African Eurasian Philippine Antarctic South American North American Etc.
Why do earthquakes and volcanoes mainly occur on plate margins?
Because they are caused by the friction between two plates, or the hot molten rock rising to the surface of the earth
What is an earthquake?
They are vibrations in the earths crust that creates shaking at surface. Highly unpredictable but tend to coincide with destructive, conservative, collisions and constructive plate margins
Reasons for earthquakes happening
Stresses build up between the plates
Plates snag and grind past each other allowing energy to build up
When plates move again, energy is released as shock or seismic waves through earths crust
Focus
The point of origin of an earthquake
Epicentre
The point on the ground directly above the focus of an earthquake
