Tectonic Hazards Flashcards
Conservative Plate Margin
Tectonic plate margin where two tectonic plates slide past each other. e.g. West Coast of USA, San Andreas fault.
Constructive Plate Margin
Tectonic plate margin where rising magma adds new material to plates that are diverging or moving apart.
Destructive Plate Margin
Tectonic plate margin where two plates are converging or coming together and the oceanic plate is subducted. It can be associated with violent earthquakes and explosive volcanoes. Ground is folded and forced upwards to create mountain ranges.
Earthquake
A sudden or violent movement within the Earth’s crust followed by a series of shocks.
Immediate Responses
The reaction of people as the disaster happens and in the immediate aftermath. Rescue people, treat injured, recover dead bodies, put out fires, set up temporary homes, temporary electricity, foreign governments send aid,
Long-term Responses
Later reactions that occur in the weeks, months and years after the event. Re-house people, repair buildings, roads, bridges. Set up initiatives to help economic recovery.
Monitoring
Recording physical changes, such as earth tremors around a volcano, to help forecast when and where a natural hazard might strike.
Plate Margin
The margin or boundary between two tectonic plates.
Planning
Actions taken to enable communities to respond to, and recover from, natural disasters, through measures such as emergency evacuation plans, information management, communications and warning systems.
Prediction
Attempts to forecast when and where a natural hazard will strike, based on current knowledge. This can be done to some extent for volcanic eruptions (and tropical storms), but less reliable for earthquakes.
Primary Effects
The initial impact of a natural event on people and property, caused directly by it, for instance the ground buildings collapsing following an earthquake. Buildings collapse, homes destroyed, people killed / injured, transport infrastructure damaged, electricity supplies.
Protection
Actions taken before a hazard strikes to reduce its impact, such as educating people or improving building design.
Secondary effects
The after effects that occur as indirect impacts of a natural event, sometimes on a longer timescale, for instance fires due to ruptured gas mains resulting from the ground shaking. Tsunamis, homeless, shortage of clean water, poor sanitation, lost businesses creating higher unemployment,
Tectonic Hazard
A natural hazard caused by movement of tectonic plates (including volcanoes and earthquakes).
Tectonic Plate
A rigid segment of the Earth’s crust which can ‘float’ across the heavier, semi-molten rock below. Continental plates are less dense, but thicker than oceanic plates.
Volcano
An opening in the Earth’s crust from which lava, ash and gases erupt.
Makeup of earth
Inner core, Outer core, Mantle and then Crust
Example of a Constructive Margin
Mid Atlantic Ridge
Where are volcanoes found
At both Destructive and Constructive Plate Margins
Where can earthquakes occur
At all three types of plate margin. Tension builds up. The plates eventually jerk past each and this sends out vibrations.
Centre of earthquake
Epicentre is the point on the earth’s surface straight above the focus.
How are earthquakes measured
Moment magnitude scale; the amount of energy released.
How does a 7 magnitude compare to a 6
Ten times greater magnitude. Each 1 is ten times so a 7 is 100 times more magnitude than a 5.
Primary effects of volcanic eruption
Buildings and roads destroyed by lava flows, people and animals injured, crops damaged, water contaminated, suffocation from gasses.
Secondary effects of a volcanic eruption
Mudflows when lava mixes with water, flooding due to melted ice, or blocked rivers, poor transport links, homeless, disrupted tourism
Why do people choose to live close to volcanoes or earthquakes?
Always lived there (family and friends), got a job there, government support, don’t think it will happen again, rich soil close to volcanoes, tourist attractions.
How can management reduce the effects?
Management strategies include monitoring, prediction, protection and planning.
How can monitoring help reduce effects?
Early warning systems. Seisometers can predict earth movements for earthquakes. Warnings for volcanoes include escaping gas, tiny earthquake, changing shape and bulges.
How can prediction help reduce effects?
Monitor movement of tectonic plates forecast earthquakes. A well monitored volcano can give people time to evacuate.
How can protection help reduce effects?
Buildings built to withstand earthquakes. Strengthen buildings and bridges. Automatic shut off for gas and electricity.
How can planning help to reduce effects?
Avoid at risk areas. Train emergency services. Educating local people. Government planning. Stockpile emergency supplies.
