Tetonic Hazards Flashcards
What is a hazard risk?
The probability or chance that a natural hazard may take place
What is a natural hazard?
A natural event that threatens people or has potential to cause damage, destruction and death
What is a conservative plate margin?
Tectonic plate margin where two tectonic plates slide past eachother
What is a constructive plate margin?
Tectonic plate margin where rising magma adds new material to plates which are diverging or moving apart
What is a destructive plate margin?
Tectonic plate margin where two plates are converging to coming together and the oceanic plate is subducted
What is an earthquake?
A sudden or violent movement within the earths crust followed by a series of shocks
What is a rift valley?
Found at a constructive plate margins where two continental plates have pulled apart. Forms a steep valley where the land has dropped
What is monitoring?
Recording physical changes, such as earthquake tremors around a volcano, to help forecast where and when a natural hazard may strike
What is a plate margin?
The boundary between two tectonic plates
What are primary effects?
The initial impact of a natural event on people and property caused directly by it, for example ground buildings collapsing
What are secondary effects?
The after effects that occur as indirect impacts of a natural event, for instance fires due to a ruptured gas mains resulting from the ground shaking
What is a shield volcano and where is it found?
Typically found at a constructive plate margin
They have a wide base and gentle slopes
Erupt frequently and non explosive
What factors affect the impact of a natural hazard?
Population density and distribution
Level of development and wealth
Magnitude
3 Ps
Frequency
Location
What are the three Ps?
Prediction
Prevention
Preparation
How is the earth structured from inside -> outside?
Inner core
Outer core
Mantle
Crust
What are the theories why tectonic plates move?
Convection currents
Slab pull
Ridge push
How do convention currents cause plates to move?
The hot magma rises in the mantle and sinks towards the core when it cools
Convection builds up pressure and carries plates with it
How does slab pull cause plates to move?
The denser plate sinks into the mantle from gravity
Pulls the rest of the plate with it
How does ridge push cause plates to move?
The molten magma rises as the plates move apart
Cools to create new plate
As the lisophere cools it becomes denser and slides down causing plates to move away from each other
What is oceanic crust?
Newest
Less than 10km thick
Very dense
What is continental crust?
Older
Between 25-75km thick
Not very dense
What plates meet at a destructive plate boundary?
Continental
Oceanic
What happens at a destructive plate boundary?
Continental meets oceanic plate
The plates move towards each other due to convection currents
The ocean plate subducts as it is denser
What happens at a contrsuctive plate boundary?
Two plates move apart and now crust is formed
Initially ride valleys from on the sea floor
Magma rises to fill the gap between the plates causing submarine volcanoes
As basaltic magma cools, it adds new land to the separating plates
What is an example of a constructive plate boundary?
Eurasian and north american
What happens at a conservative plate boundary?
As the plates move by each other they stick until pressure builds up
There is a sudden release of pressure as the plates move forward causing seismic waves
What is an example of a conservative plate boundary?
Pacific plate and North American
(San Andreas Fault)
What happens at a collision plate margin?
Two continental plates move together and collide
Neither can be destroyed so they move upwards and downwards
The upwards causes fold mountain and the downwards forms mountain roots
What do you get at collision plate margins?
Earthquakes because of the build up of pressure
No volcanoes due to no magma
What is an example of a destructive plate?
Nazca plate
What is formed at destructive plate margins?
Earthquakes
Volcanoes
What occurs at a constructive plate boundary?
Volcanoes
Few low magnitude earthquakes
What happens at a conservative plate boundary?
Earthquakes
No volcanoes
What are the 3 types of volcanoes?
Cinder cones
Composite
Shield volcanoes
What are the most dangerous volcanoes?
Cinder cones
What is the name of the rock which is formed from cooled lava?
Igneous
What is an active volcano?
Either erupting or likely to erupt in the near future
What is a dormant volcano?
Haven’t erupted recently, but are expected to in the very far future
What is an extinct volcano?
Volcanoes not expected to erupt again
How does a volcano form?
Molten rock originates from the mantle
Driven by buoyancy and gas pressure, it forces its way into magma chambers
This accumulates and exerts pressure on the surface causing it to bulge upwards
The pressure then gets too great that it breaks through weaknesses of the earths crust
What are the features of a composite volcano?
Thick lava
Explosive
Steep sides
What are the features of a shield volcano?
Thin and runny lava
Non explosive
Gentle sloping sides
How can volcanic gases cause the climate to change?
They can cause a rise in global temperatures
What is Lahar?
A mixture of volcanic ash ricks and other debris mixed with either cold or hot water, they can destroy many towns and are too fast to outrun
What are pyroclastic flows?
Mixtures of hot dry ash, rock and gas
They travel about 80km/h and range from 200-700 degrees
What is tephra?
Anything that is blow out of the volcano into the air
What is jökulhlaup?
A glacial outburst where a glacier is ontop of a volcano melts due to an eruption
When was the eyjafallajökull eruption?
2010
What was the location of the eyjafallajökull eruption?
South Iceland
The ash cloud moved to europes air space
How long was the eruption?
From 14th April to 22nd may
What was the magnitude of the eyjafallajökull eruption?
4 on the VEI scale
What were the immediate responses to the eruption?
Iceland declared a state emergency
European airspace was closed
More then 600 people where evacuated 2 hours after the eruption
What were the long term responses of the eruption?
No planes were allowed to fly in and out of Europe until the 21st April
What were the short term impacts of eyjafallajökull?
Ash cloud
Jökulhlaup caused mud flows destroying houses
What were the secondary impacts of the eyjafallajökull eruption?
Ash clouds cancelled thousands of flights and left people stranded
Big econicmal impacts on tourist ocatom
Mud flows destroyed hundreds of homes
What is the focus?
The point of origin of an earthquake within the earths crust is
How thick was the icecap melted in the eyjafallajökull eruption?
120m
What is the epicentre?
The point on the earths surface that us directly above the focus of the earthquake
What are seismic waves?
Waves of energy caused by the sudden breaking of rock within the earth
What are the two ways of measuring earthquakes?
Mercalli scale - qualitive
Richter scale. - quantitive
Where is L’Auila?
Western region in Italy
When was the L’Aquila earthquake and what size was it?
6th April 2009
6.3 Richter scale + mechalli
Focus 5.88 miles
What is the GDP of L’aquila?
37,226 USD
What were the causes of the L’Aquila earthquake?
Faulting on the paganica fault
What were the primary effects of L’Aquila earthquake?
308 killed
1500 injured
67500 homeless
$11,434 million damage
15000 buildings collapsed
What were the secondary impacts of the L’Aquila earthquake?
Landfalls damaged houses and ricks
Mudflows caused burst water
Some city cordoned off reducing business
What were the immediate responses to the L’Aquila earthquake?
10000 sheltered at hotels
7 dog units searched
40000 tents given
What were the long term effects of the L’Aquila earthquake?
Torch lit procession every year
No taxes during 2010
university fees waived
Where is Gorkha?
North nepal
When was the Gorkha earthquake?
28th April 2005
What size was the Gorkha earthquake?
7.8 richter
10 Michalli
9.3 focus
What is the GDP of Gorkha?
902 USD
What was the cause of Gorkha earthquake?
Convergent plate margin
Between Eurasian and Indian plates
What were the primary effects of Gorkha earthquake?
8841 died
16800 injured
$5 billion damage
1 million homeless
What were the secondary impacts due to the Gorkha earthquake?
Landslides and avalanches killed 19 on Mt Everest
Tourism declined
Food shortages
Blocked roads slowing aid
What were the immediate responses to the Gorkha earthquake?
500000 tents provided
Field hospitals
Facebook set up a safety feaure
What were the long term responses to the Gorkha earthquake?
$274 million aid money
Stricter building controls
New trekking routes
