A: Natural/tectonic hazards Flashcards
Define natural hazard
A natural process which could cause death, injury or disruption to humans or destroy property and possessions.
What are the two types of natural hazards
Meteorological
Geological
What’s s geological hazard
Caused by land and tectonic processed
E’g. Volcanoes
Earthquakes
Landslides
Avalanches
What’s a meteorological hazard
Caused by weather and climate
Tropical storms Extreme weather Heatwaves Cold spells Climate change
What’s a natural disaster
Natural hazard which has actually happened
What are extreme events
They do not pose any threat to human activity and there not counted as hazards (drought in an unhabitated desert)
What are different factors affecting hazard risk
Vulnerability
Capacity to cope
Nature of natural hazards
What is hazard risk
The probability that a natural hazard occurs
Explain vulnerability as a factor affecting hazard risk
More people in areas exposed to natural hazards the greater probability they will be affected by a natural hazard - hazard risk is higher
Explain capacity to cope as a factor affecting the hazard risk
Natural hazards have to affect human activities to count as a hazard. The better a population can cope with an extreme event, the lower the threat
HICs are better coping
Explain the nature of natural hazards as a factor affecting the hazard risk from a natural hazard
Type - the hazard risk from some hazards is greater than others
Eg tropical storms can be predicted and monitored giving people time to evacuate safely
But earthquakes happen very suddenly no warning
Frequency - some natural hazards occur more often than others increasing the hazard risk
Magnitude - more severe natural hazards cause greater effects than less severe natural hazards
What is the earths surface made of
Huge floating plates that are constantly moving called tectonic plates
What are the layers of the earth from the inner to the outer
Inner core
Outer core
Mantle
Crust
What’s the core of the earth like
Ball of solid (inner) and liquid (outer) iron and nickel
What’s the mantle like
Semi - molten rock that moves very slowly
What’s the crust like
Divided into slabs called tectonics plates (they float on the mantle) plates are made of two types of crust — continental and oceanic
What’s continental crust like
Thicker (30-50km) and less dense
What’s oceanic crust like
Thinner (5-10km) more dense
Why are the plates always moving
Because of convection currents in the mantle underneath the crust
What’s it called where plates meet
Plate margins or plate boundaries
What are the three types of plate margin
Destructive
Constructive
Conservative
What are destructive margins
Two plates move towards each other
Oceanic meets continental. Denser oceanic is late if rocked down into the mantle and destroyed
Often creates volcanoes and ocean trenches (very deep sections of the ocean floor where the oceanic plate goes down)
Two continental meet. Plates collide. Ground is golden and froorced up creating mountain range
E.g. West coast of South America
What are constructive margins
Two plates moving away from eachother
Magma (molten rock) rises from the mantle to fill the gap and cools, creating new crust
Eg mid Atlantic range
What are conservative margins
Two plates moving sideways past eachother or moving in the same direction at different speed
Crust isn’t created or destroyed
Eg along west coast of USA
What happens at destructive plate margins to form volcanoes
The oceanic plate goes under the continental plate because it is more dense.
The oceanic plate moves down into the mantle where it’s melted and destroyed
A pool of magma forms
The magma rises through cracks in the crust called vents
The magma erupts onto the surface (where it’s called lava) forming a volcano
What happens at constructive margins to form volcanoes
Magma rises up into the gap created forming a volcano
Where are volcanoes found
At destructive and constructive plate margins
Where can some volcanoes also form?
Over parts of the mantle tht are really hot (hotspots)
Eg in Hawaii
Which plate margins do earthquakes occur at?
All three
What are earthquakes caused by
Tension that builds up at all three plate margins
How’s an earthquake formed at destructive margins
Tension builds up when one plate gates stuck as it’s moving down past the other into the mantle
How do earthquakes form at constructive margins
Tension build up along cracks within the plates as they move away from each other.
How do earthquakes from at conservative margins
Tension build up when plates that are grinding past each other get stuck
What exactly is the earthquake during tension build up?
The plates eventually jerk past each other sending out shock waves (vibrations) which is the earthquake
What do shock waves do
Spread out from the focus - the point in the earth where the earthquake starts. Near the focus the waves are stronger and cause more damage
What’s the epicentre?
Point on the earths surface straight above the focus in an earthquake
What are earthquakes measured with
Linen magnitude scale
What does the moment magnitude scale measure
The amount of energy released by an earthquake (called the magnitude)
It’s scale is logarithmic - so a magnitude 7 is ten times more powerful than a 6
What is the magnitude of earthquakes which normally only cause slight damage to buildings although they can be worse in very built up areas
Magnitude 6 and below
What size earth quakes cause major damage and deaths
Magnitude 7 and above
Global distribution of earthquakes and volcanoes
…
What are the two earthquakes we studied
Haiti
Japan
When was the Haiti earthquake and what magnitude was it
January 2010
Magnitude 7
What were the primary effects of Haiti earthquake
Prison was destroyed releasing 4,00 imprisoners
Buildings and homes destroyed
1-5 lost jobs
Injuries or killed from collapsed buildings and falling debris
Secondary impacts of the Haiti earthquake
250,000 buildings were destroyed meant that people couldn’t work, roads became blocked disrupting any rescue attempts, trade difficult
Deaths of 250,000 people
Cholera spread
1.3mill lost there homes
Food rationed
Where is Haiti?
19.19N 73.30W
72.5 longitude 18 Latitude
Caribbean
Impacts only from Haiti earthquake
Mag 7 250000 dead Mercali 8 No defences 280,000 destroyed buildings 4000 prisoners escaped 1.1 billion damage 1/5 lost jobs 1300 schools damaged 1.3mill homeless
Impacts from Japan earthquake followed by tsunami 🌊
Up to 12000 peiple dead Magnitude 8.9 40m high wave 🌊 £200 billion damage Had defences but we’re destroyed Nucleur meltdown Shifted earth on its axis 10cm Mercali 9 Water reached 6 miles into land
Impacts both on Japan and Haiti
Caused by earthquakes Affected major cities Had help from other places Natural hazards Houses/buildings + livelihoods destroyed Occurred just if coast Diseases from dirty water (cholera)
Haiti is a Lic what were its responses to its earthquake
3/4 damages buildings were inspected + repaired
200,000 peiple recieved cash or food for public work
World bank pledged $100 m to support reconstruction + recovery programmes
Japan is a HIC what was its responses to its earthquake following with a tsunami
+ 100,000 soldiers deployed in search and rescue
Blankets food and water distributed
Specialised search and rescue teams flown in from overseas
Exclusion zone set up around fukushima nucleur plant and peiple were evacuated from the area
What was the earthquake in Japan and when and where is the area
The Sendai earthquake in Japan 201
Sendai is in the continent of Asia in the stat Thoku
What was the cause of the Sendai earthquake
Tremors were result of a violent uplift of the sea floor 80mikes off the coast of Sendai where the Pacific tectonic plate slides beneath the plate Japan sits on. Tens of miles off the coast is Sendai, where the Pacific tectonic plate slides beneath the plate Japan sits on. Tens
Monitoring volcanoes and earthquakes
Volcanoes
Remote sensing - satellite detect heat and changes to the volcano shape
Seismicity - seismographs record earthquakes
Gas - instruments detect gases realeased as magma rises
Earthquakes - generally occur without warning there’s some evidence of changes in water pressure, ground deformation and minor tremors prior to earthquakes
How can you predict volcanoes
Based on scientific monitoring
In 2010 an increase in earthquake activity beneath an ice cap in Iceland enabled scientists to make an accurate prediction about the eruptions that took place in March and April that year
How can you predict earthquakes
Impossible to make accurate predictions about earthquakes due to the lack of clear warning signs
How can you protect areas from earthquakes
Construct buildings and bridges to residue ground shaking
Reinforce concrete columns strengthened by steel force
Regular earthquake drills
Construct tsunami walls
How can you protect an area from volcanoes
Earth bankments or explosives to divert lava flows away from property
How can you plan for volcanoes
Hazard maps show sangered places
Used in planning to restrict certain land uses or to identify which areas need to be evacuated when an eruption is due
How can you plan for an earthquake
Maps produces to show effects of an earthquake or identify those areas most at risk
High - value land uses a.g. Hospitals can be protected in these vulnerable areas
Why do people still live in areas at risk from tectonic hazards
They’ve always lived there don’t wanna naive from friends and family
Employed in the area
Confident in support from government after a tectonic hazard
Think Severe hazards won’t happen again in area
Soil around volcanoes is fertile because it’s full of minerals from volcanic ash and lava attracts farmers
Volcanoes are tourist attractions - live/ work in tourist industry
Management strategies can
Reduce the effects of tectonic hazards
Monitoring tectonic hazards
Networks of seismometers and losers monitor earth movements, and can be used in early warning systems to give a small but vital amount of warning before a large earthquake occurs
Scientist can monitor the tell-tale signs that come before a volcanic eruption, such as tiny earthquakes, escaping gas, and changes in the shape of the volcano (eg. Bulges in the land where magma has built up under it) all mean an eruption is likely
Predicting tectonic hazards
Earthquakes cannot be realisable predicted but by monitoring movement of tectonic plates scientists can forecast which areas should be prepared for one to occur
Volcanic eruptions can be predicted if the volcano is well-monitored, predicting when a volcano is going to erupt gives people time to evacuate this reduces number of injuries and deaths
Predicting tectonic hazards
Buildings can be designed to withstand earthquakes eg by using materials like reinforced concrete or building special foundations that absorb an earthquakes energy
Existing buildings and bridges can be strengthened (eg by wrapping pillars in steel frames) so they’re less likely to collapse under the weight of falling ash or due to shaking from an earthquake
Automatic shutoff switches can be fitted that turn off gas and electricity supplies to prevent fires if an earthquake is detected by a monitoring system
Planning for tectonic hazards
Future developments can be planned to avoid the areas most at risk from tectonic hazards
Emergency services can train and prepare for disasters eg by practising rescuing people from collapsed buildings or setting up shelters this will reduce deaths
People can be educated so that they know what to do if an earthquake or eruption happens
Governments can plan evacuation routes
Which reduces number of deaths by fires, pyroclastic flows or mudflows
Emergency supplies like blankets, clean water and food can be stockpiled, if a natural hazard is predicted the stockpiles can be moved close to affected areas potentially
