Tectonic hazards Flashcards
Natural hazard definition
A natural event that threatens people or has the potential to cause damage, destruction or death
Factors that affect the impact of a natural hazard (6)
frequency
magnitude
population
3 p’s
location
wealth/development
3 reasons plates move
Convection currents
Ridge push
Slab pull
What is slab pull?
The denser plate sinks back into the mantle under the influence of gravity, pulling the rest of the plate with it
What is ridge push?
Magma rises as the plates move apart, the magma cools, forming new plate material, as it cools it becomes denser and slides down away from the ridge pushing apart tectonic plates
What is continental drift
Continents used to all be together but over time moved apart
Oceanic crust characteristics
Dark colour
Very dense
Continental crust characteristics
Not very dense
Destructive plate margin process
- Continental and oceanic plate are moving towards each other
- oceanic plate is denser - sinks
- Where they intersect a trench forms
- Earthquakes occur at subduction zone - high pressure
- As the plate sinks it begins to melt as it gets closer the the mantle, forming magma
- Becomes less dense so starts to rise
- as it reaches the surface there is an explosive eruption of gases, ash and lava
Constructive plate margin process
- two plates are moving apart due to convection currents and a new crust forms at the boundary
- Rift valleys form on the sea floor
- Magma rises from mantle to fill the gap forming sub marine volcanos, a mid ocean ridge develops at this point
- as the basaltic magma cools it adds new land to the separating plates
Conservative plate margin process
- Conservative margins occur when two plates move parallel or nearly parallel to each other
- there is a build up of pressure
- there is a sudden release of pressure and one plate jerks forward as energy is released in the form of seismic waves, causing an earthquake
an example is the San Andreas Fault line in Colorado
Collision plate margin process
- two continental plates move towards each other and collide
- neither plate is denser so they are forced upwards and downwards
- the upwards makes fold mountains (Himalayas)
- the downwards makes mountain roots
- high magnitude earthquakes as there is a massive build up of pressure
- magma is not created so there are NO volcanos
Distribution of earthquakes and volcanos
Found along tectonic plate boundries
Primary effects of a tectonic hazard
- people are injured or killed
- infrastructure such as water, gas and electricity cables are broken cutting off supplies
- leaking can be ignited causing fires
- buildings, bridges and homes destroyed
- blocked transport hindering emergency services, further casualties
- roads, railways, ports damaged
Secondary effects of a tectonic hazrad
- businesses reduced and unemployment increases, money spent repairing damage so economy slows
- people left homeless and can die of exposure
- shortage of clean water and lack of sanitation lead to spread of disease
- repairs and construction can be expensive so weaken the economy
- tourists put off
How are earthquakes measured
Richter scale
Epicentre
the point on earth’s surface that is directly above the focus of he earthquake
this is where seismic waves are the greatest
seismic waves
waves of energy caused by the sudden breaking of rock within the earth
L’Aquila, Italy - facts and figures
2009
6.3 on the Richter scale
HIC
67,500 homeless
308 killed
immediate help and no taxes for residents the following year
Gorkha, Nepal - facts and figures
2015
7.8 on the Richter scale
LIC
1 million homeless
8841 killed
took 4 days for some people to get help
received aid from other countries
Managing tectonic hazard - 4 ways
Monitoring - can predict general locations, satellites
Planning - prepare emergency aid, evacuation, drills, safety checklist, tie down furniture
Protection - better infrastructure to withstand damage, evacuate homes
Prediction - location and times mapped to predict earthquakes
