Flashcards in Natural Hazards- Earthquakes/volcanoes Deck (25):
How are convection currents created
By heat and pressure within the mantle causing the plates to move
What occurs at constructive boundaries and how does this happen?
Only volcanoes form here and this is when the plates move away from eachother leading to magma rising up the mantle and erupting. When this magma cools it forms surface of igneous rock and this is repeated until a volcano forms.
Where are constructive boundaries found?
Under the sea
What happens at destructive boundaries
Mainly volcanoes as the plates move together leading to the dense oceanic crust going under the continental crust at the subduction zone. The oceanic plate then melts to form magma which rises up cracks in continental crust and erupts at surface
At conservative boundaries only...
Earthquakes as the 2 plates stick and when pressure builds there is a sudden release of friction resulting in seismic waves being released
Give 3 reasons why people live near plate edges
Become settled before risks known
Ignore the danger
Well prepared for disasters
How do the usa protect against earthquakes
Seismometers monitor path of earthquake
How do India protect against earthquakes
As they are an LEDc they use houses built on concrete slabs in order to keep them grounded when the earthquake strikes.
Give three uses of volcanoes
Produce fertile soils for farmers as they are Rich in minerals
Provide tourism as many people want to see a dormant volcano or a thrill at seeing an active one
Provide health spas due to the naturally hot water e.g bath 49*
What is the medc example of an earthquake and what were the effects?
Japan March 2011
3 nuclear reactors exploded
4 million no electricity
All ports closed
Radio active gas leaks
What is an LEDc example of an earthquake and what were the effects?
Yogyakarta Java may 2006
Led to volcanic eruption of merapi
Hindu temple damaged
1.5 million homeless
Loss of income from tourism
What is the medc example of an volcano and the effects?
Eyjaffalokull March 2010
Volcanic ash released
Six day travel ban
0.15 million tonnes of co2 released daily
Shortage of importation
Air travel disruption
What is the LEDc example of a volcano and how does it affect the people?
Tungrahua Ecuador 2006
Lava destroyed 7 villages
Hundreds killed by falling rocks
Lava covered fertile land
Local airport shut
Give three reasons why more people die in ledcs than in medcs
Buildings not proof against dangers
Corrupt politicians invest money into other areas
Emergency services are not as well prepared or funded to deal with them
How does prediction help reduce effect s of earthquakes
By studying plate tectonics you learn the most at risk areas and so can invest more money there into prevention
How does preparation reduce the effects of earthquakes
Earthquake drills educate the local public on how to deal with an earthquake
How does planning reduce the affect of an earthquake
Earthquake shaking maps show areas that need aid.
Give three ways to reduce the affect of a volcano
Prediction- use seismometers
Planning- first aid kits and evacuation
Preparation- filter systems and glass roofs to shed ash from them.
What is the point where pressure from an earthquake is released
The point directly above the focus is the
Epicentre and this is where most damage is felt
Give three factors affecting the impact of an earthquake
Distance from epicentre
Medc or LEDc
Define magma chamber and crater
Magma chamber- stores magma below volcano
Crater- forms at top after eruption
Where are shield volcanoes found and what do they look like?
They are found at constructive boundaries and have low sloping sides and are formed by frequent gentle eruptions of lava
Where are composite volcanoes found and what do they look like?
Found at destructive boundaries and made of pyroclastic flow of lava at 400* above