tectonic hazards Flashcards
what is a natural hazard and give some examples
A natural hazard is a natural event which puts people and their property at risk.
examples:
-volcano
-earthquake
-drought
What does tectonic hazard mean?and give some examples.
Tectonic hazards occur when the Earths crust moves.
e.g,
-earthquake
-tsunami
-avalanche
-volcanic eruption
layers of the Earth
There are 4 layers of the Earth:
inner core
outscore
mantle
crust
How do earthquakes occur?
The plates move and friction causes them to become stuck.
Tension builds up until the plates release causing an earthquake to happen.
Destructive plate boundaries
Form when oceanic and continental plates move towards each other due to convection currents. Convection currents occur in the Mantle and friction causes plates to move. When they reach the Benioff zone (point where 2 plates meet) the oceanic plate subducts under the continental plate as it is more denser so more heavier. As it sinks into the mantle it melts and forms magma because of heat current and creates a lot of pressure. when the pressure gets too high it starts building up and releases the magma upwards as magma can escape through weaknesses in the rock and rises up into a composite volcano and explodes.
Constructive plate boundaries
Constructive margins are where 2 plates are moving away from each other.magma rises from the mantle to fill the gap and cool it creating new crust.
Conservative plate boundaries.
Plates moving sideways past each other.
plates can move in same directions at different speeds.
no crust is created or destroyed.
Why do plates move?
due to pressure and friction
Case study:
Newzealand Earthquake 2016
date: 14th November 2016
plate boundary: destructive and conservative
magnitude: 7.8
Primary effects:
-2 people died
-50 people were injured
- tens of thousands home damaged
- costs of damage was $8.5 billion
-60 people needed emergency housing
-200 roads and 190km rail destroyed
-water, sewages and power supplies were cut off
seconday effects:
-debris unto 250m in land
-earthqauek genersted a tsunami
- major land slide blocked the river
-triggered unto 100,000 landsides
immediate responses:
-hundreds of people in emergency shelter
-200 people evacuated in a helicopter
-power was restored in a few hours
-international warships sent supplies
long term responses;
-water supply being restored
-heritage sights reopened
-roads were opened
Case study:
Nepal earthquake 2015
date: 25th November 2015
plate boundary: destructive
magnitude: 7.8
Primary effects:
-2 million people left without access to clean water
-water tanks and pipes destroyed
-approximatly 9000 people died
-more than 22,000 people were injured
-estimated 800,000 buildings destroyed
-4 million people left homeless
-roads, bridges destroyed
- cost of damage was over $5 billion
Seconday effects:
-roads blocked by landslides
-triuggered avalanches killing 18 people.
immediate responses:
-searching for survivors
-setting up emergency preparations
-sending out support teams
long term responses:
-WHO (world health organisation) set up free healthcare facilities and retrofitted hospitals
-road and rail routes repaired
-permamnet water main
what is retrofitting
Retrofitting can be:
-computer controlled weights on proof to reduce movemnt
-automatic window shutters to prevent glass falling
-rubber shock absorbers to absorb earth tremors
-fire resistant building materials
-open areas where people can evacuate safely
why do people live in a danger zone
-lagoons
-minerals leading to trades
-mining
-job opportunities (tour guides, shops, hotels)
-tourism
-soil vegetation is better
-family might be there
-geothermal energy, renewable and non renewable energy, air quality is better, healthier and cheaper.
Managing tectonic hazards
-monitoring-using scientific- Equipment to detect warning signs of events.
advantages=evacuation more easy, early warning.
disadvantages=expensive,can be faulty
-prediciton- using historical evidence and monitoring- predictions when nd where a tectonic hazard may happen.
advantages=know when it’ll happen
disadvantages=unreliable, villages may not have radios to hear news
-protection- designing buildings that will withstand tectonic hazards
advanatges= provides job, less injuries, less damage done
disadvanatges= expensive for LICs
-planning - earthquake drills- identifying and avoiding places most at risk
advanatges= earthquake drills, prepared
Characteristics of oceanic crust
-made of basalt
-older than continental
-more denser
convection currents
-convection currents create drag onto base causing them to move
-they are found in the mantle
-as they move towards the top they cool down become more dense and slowly sink
-the crust is divided into plates that are moving due to this
