Natural Hazards Flashcards
Describe the distribution of earthquakes?
- happen along all three plate margins
Describe the distribution of volcanoes?
destructive and constructive plate boundaries
What are the three types of plate margin?
destructive, constructive and conservative
What are the two types of crust?
continental and oceanic
Describe continental crust?
thicker (30-50km) and less dense
Describe oceanic crust?
thinner (5-10k) and more dense
Why are plates moving?
due to convection currents in the mantel underneath the crust
What are plate boundaries or margins?
the place where plates meet
Describe destructive margins?
two plates moving towards each other
oceanic and continental plate are moving towards each other due to convection current processes in mantle
when they meet the denser oceanic plate is subducted (forced beneath) the lighter continental plate. Earthquakes occur along the subduction zone
increased heat and pressure causes oceanic crust to melt and is destroyed forming a magma chamber
build up of pressure and gas forces magma to surface as a volcanic eruption
Describe constructive margins?
two plates moving away from each other.
- convection currents in mantle rise upwards and outwards causing plates above to be pulled apart
- as they pull apart a gap is created between plates
- this is then filled by rising magma from the mantle, which plugs the gap, cooling to form new crust
- overtime this builds up to form a volcano and becomes a volcanic island if high enough- often happens under the oceans
Describe conservative margins?
where two plates are moving sideways past each other at different speeds.
as they move they get stuck causing friction and pressure to build up
this mounting energy is then released as an earthquake
Explain in basic terms how a volcano is formed?
- oceanic plate moves down into mantel where destroyed and melted
- pool of magma forms
- magma rises through cracks in the crust called vents
- magma erupts onto surface causing a volcano
Explain in basic terms how an earthquake is formed?
- when two plates get stuck
- this causes pressure to build up and when this pressure is released an earthquake occurs
What is the focus of an earthquake?
the point in the earth where the earthquake starts
What is the epicentre?
the point on the earths surface straight above the focus
Where is a HIC that suffered through an earthquake?
Chile
What is a LIC that had an earthquake?
Nepal
What were the immediate responses in Chile?
- emergency services acted swiftly
- temporary repairs made to important Route 5 north-south highway within 24 hours
- aid was able to be transported to affected areas
- power restored to 90% of homes within 10 days
- national appeal raised $60 million
Using one word per point what are the immediate responses in Chile?
- emergency services
- temporary repairs
- power and water restored
- $60 million raised
What were the immediate responses of Nepal?
- Search and rescue teams arrived quickly from countries such as UK, India, China
- helicopters rescued many people caught in avalanches on Mount Everest
- half a million tents needed to provide shelter for homeless
- financial aid pledged from many countries
- field hospitals set up to support overcrowded main hospitals
- 300,000 people migrated from Kathmandu to seek shelter and support with family and friends
- social media was used widely to map damaged areas
Using one word per point what are the immediate responses in Nepal?
- helicopters- avalanches
- search and rescue teams
- water and medical support-other countries
- tents
- financial aid
- field hospitals
- migration occured
- social media
What are the long term responses in Chile?
- month after earthquake, Chile’s government launched a housing reconstruction plan to help nearly 200,000 households affected
- Chile’s strong economy could be rebuilt without the need for much foreign aid
- President announced it could take years for Chile to recover fully from damaged buildings and ports
What are the long term responses in Nepal?
- roads repaired
- landslides cleared
- thousands of homeless people to be re-housed and damaged homes repaired
- 7,000 schools to be re-built/ repaired
- tourism to be boosted
- repairs to Everests base camp and trekking routes
- stricter controls on building codes
definition of an earthquake
-the shaking and vibration of the Earth’s crust due tp the movement of the Earth’s plates
definition of an volcanoes
-an opening in the Earth’s crust through which magma, molten rock and ash are erupted onto land
