Natural Hazards Flashcards
Give a definition of the term natural hazard
And event beyond human control that could threaten both life and property.
What are the things you can do to reduce the effects of tectonic hazards?
- monitoring
- prediction
- protection
- planning
What is the definition of prediction?
attempts to forecast when and where a natural hazard will strike
What is the definition of monitoring?
recording physical changes to help forecast when and where a natural hazard will strike
What is the definition of protection?
actions taken before a hazard strikes to reduce it’s impacts
What is the definition of planning?
actions taken to enable communities to respond to, and recover from, natural disasters
What are 9 natural hazards?
- sandstorm
- earthquake
- tsunami
- volcanic eruption
- thunderstorm
- landslide
- drought
- floods
- tropical storm -> hurricane, typhoon, cyclone
What is a secondary hazard?
It is a hazard that occurs because of another hazard
e.g. a tsunami is caused by an earthquake
What are properties of continental crust?
- older
- less dense (than oceanic)
- thick (up to 70km)
- mainly has landmass on it
What are the properties of oceanic crust?
- younger
- denser
- thin (up to 10km)
- mainly has ocean on it
What is the structure of the earth?
(from the inside to the outside)
- Inner core - very hot, solid
- Outer core - liquid
- Mantle - semi liquid/solid
- Crust - rock, thin (7km - 70km deep)
Why do plates move?
(3 key learning points)
- Convection currents, move plates together or apart or slide them past each other
- At constructive plate boundaries, convection currents and ridge push move the plate apart
- At destructive plate boundaries, convection currents and slab pull move the plates together
What are the four types of plate boundaries?
- constructive plate boundary <— —>
- destructive plate boundary —\ <—
- conservative plate boundary //
- collision plate boundary —><— (don’t need this)
What happens at a constructive plate boundary?
- Convection currents in the mantle cause hot magma to rise, heating the rocks above them
- The tectonic plates move apart from each other because of ridge push, the molten magma rises in between, cools and forms new rock. This forms part of the new oceanic plate. The new plate sometimes fractures as it is moved, causing shallow, usually small, more nonviolent earthquakes.
- Much of the magma never reaches the surface, but it can push the crust upwards to form ridge and rift features. Where magma does erupt onto the surface it produces a lava that is runny and spreads out before solidifying. This produces after many eruptions a shield volcano. 🌋
What happens at a destructive plate boundary?
- At a destructive plate boundary plates move together because of convection currents in the mantle and slab pull
- When they meet tension builds up in the plate
- If the plates slip, then energy is released as seismic waves, causing an earthquake
- At destructive plate boundaries oceanic plates meet continental plates
- The oceanic plates subducts because it is denser
- As it sinks into the mantle it melts forming magma
- This magma is formed under pressure so forces its way through cracks in the rock above
- So will explode at the surface as lava forming a violent composite volcano.
- This causes hazards like lava flows and ash clouds 🌋
What happens at a conservative plate boundary?
- Pressure builds up at the margin as the plates are being pulled along by a plate being moved by convection currents. Eventually, the pressure becomes too great, the rock fractures in an earthquake and jolts into a new position. (snag)
- Land is neither created nor destroyed, and so there are no volcanoes.
What is an example of a constructive plate boundary?
The Mid Atlantic Ridge
What is an example of a destructive plate boundary?
The Pacific ring of fire
What is an example of a conservative plate boundary?
San Andreas Fault
What type of crust is the densest?
Oceanic crust
What 3 things makes the plates move?
- Convection currents
- Ridge push
- Slab pull
What is the process where the oceanic crust goes under the continental crust?
Subduction
What is ridge push?
The process where the plates move because of gravity acting on the plate where it is forced up
When plates are moving together, what builds up in the rock?
Elastic energy
How is heat created in the core?
Radioactive decay
What is slab pull?
It is where the plates move faster, because of the weight of the plate and gravity acting on the plate as it is subducted
Where do convection currents occur?
In the mantle
What are primary effects?
(give 3 examples)
They are the immediate impact caused by the hazard itself
death, buildings collapsing and injuries
What are secondary effects?
(give 3 examples)
They happen later on often as a result of the primary effects
starvation, lower economy and spreading disease
What is an immediate response?
A response in the days and weeks immediately after a disaster has happened
What is a long-term response?
Go on for months and years after disaster
What is short term aid?
It is the aid that is given immediately (decreases secondary effects)
What is long term aid
It is the aid that is given weeks or months after after the hazard and should help the country recover
How many people died in the Nepal earthquake?
9,000