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90 Cards in this Set
- Front
- Back
Describe and comment on the global distribution of earthquakes, volcanic eruptions and tsunamis |
All three tectonic hazards occur on or near plate boundaries. All tectonic hazards occur on convergent plate boundaries. Earthquakes only on transform and volcanoes and earthquakes on constructive |
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Describe and explain the distribution of plate boundaries and compare divergent convergent and conservative plate movements. |
Convergent - One plate is bring subducted under the other Divergent - two plates are moving apart Transform - two plates are moving past each other |
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Determine the cause of intra-plate earthquakes |
Nuclear weapons - atomic bombs release lots of energy that can send seismic waves through the earths crust. Fracking - by recovering natural gas and injecting water to replace it. This injection creates cracks and if a crack is created near a fault it can release the strain built up along the fault. Intra-plate faults - New Madrid fault was formed from a break up of the supercontinent Rodinia. The break up failed leaving a permanent scar on the earths crust, a intra-plate fault.q |
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Determine the causes of intra-plate volcanoes |
Mantle plumes - When superhot liquid rock in the mantle is hot enough it can punch through the earths crust creating a hot spot that can be located in the middle of a plate e.g. Hawaii. |
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What are the four types of volcanoes and give an example? |
Shield e.g Mauna Loa, Hawaii Cinder done e.g Mount Zion, Israel Composite cone e.g. Mount St Helens |
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What is the inner core made of? |
Solid iron nickel ball |
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What is the outer core made of? |
Liquid semi-molten rock |
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What is the mantle? |
Upper part is the Asthenosphere has plastic properties allowing convection currents to occur. |
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What is the lithosphere? |
The crust and the immediate upper rigid part of the mantle |
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What is the crust? |
Floats on top of the asthenosphere. Two types of crust continental crust and Oceanic crust |
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What is the difference between continental crust and oceanic crust? |
Continental crust - less dense, older and lighter Oceanic crust - more dense, younger and heavier |
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What happens at a divergent plate margin? |
- 2 plates are moving apart - can form shield volcano when rising magma cools and solidifies or islands such as Surtsey in Iceland. - When 2 oceanic move apart = ocean ridges - When two continental move apart = rift valley |
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What happens at a destructive plate boundary? |
- subduction occurs where an oceanic plate is forced under a continental plate - volcanoes and deep sea ocean trenches are formed -2 oceanic plate meet = island arc - 2 continental meet = fold mountains |
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How are fold mountains formed? |
Fold mountain is formed where two plates meet at a geosyncline as these plates come together the geosyncline the sediments get compressed. As the sediment become even more compress the geosyncline begins to disappear and a new mountain ranges formed like the Himalayas. They are equally formed at subduction zones as well like the Andes in South America |
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How is an island arc formed? |
When two oceanic plates come together one plate can subduct under the other. This oceanic plate will be melted and become molten magma. This molten magma will reach the surface creating a volcano as time passes. Except as the plate moves the magma chaebol will move in the process causing the volcano to be extinct as it willno longer have a chamber to fuel it this will create an island arc like the Caribbean and Hawaii. |
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What happens at a conservative plate margin? |
Two plates sliding against each other e.g San Andreas. |
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What are convection currents? |
Convection currents are what drive plate movement. 1) Heat produced by radioactive decay in the earths core heats the lower mantle. 1) Hot molten rock rises in the mantle heated by the earths core 2) Below the crust, the molten rock spreads sideways, beginning to lose heat 3) Eventually the cooler rock sinks back down filling the gap left by the rising rock. 4) Through this process the crust is dragged very slowly (3 to 5 cm a year) 5) This process of moving the crust over very long period of time from a supercontinent called Pangaea to the current day is known as Continental drift |
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What was Alfred Wagner's theory on continental drift? |
Where can I believe that all continents were once all joined together Pangaea opposing the idea at the time that they were connected via land bridge is long since sunk. It was not generally accepted at the time by scientist he didn't have enough evidence but he did notice that there was similar fossils of animals located in Africa and South America |
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What was Harry Hess theory on continental drift? |
Dr Hess believed that hot magma would rise from under the crust at the global rift. When it cooled it would expand and push tectonic plates apart. We know this today as convention currents in the mantle. He discovered Sea floor spreading. Wegener theory started to become more accepted. |
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What was Morley, Vine and Matthews theory on continental drift? |
They believed that magnetic anomalies under the earths surface. When lava cools and becomes rock manual inside the rock lineup with the earth's magnetic direction at the time. Every 400,000 years the earths poles change direction. They metallic elements within the magma are attracted to the earths magnetic field. Over time both sides of the mid Atlantic ridge demonstrated exact changes in polarity at the same time. |
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What is palaeomagnetism? |
The study of past changes in the earth's magnetic field (determined from rocks and sediments or archaeological records) |
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What further evidence is their for continental drift? |
Biological - fossil formations found on either side of the Atlantic) for example mesosaurus freshwater reptile) found both in south-west Africa and in Brazil Climatological - coal and oil deposits found in Antarctica suggest that it was once in a different climatic zone for these to have form Geological - same type age and formations of rock found on two sides of the Atlantic Appalachian mountains in North America and Caledonian Mountains in Scotland both have igneous and sedimentary rock sequence |
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What is basaltic lava and what are the characteristics |
Laugher it formed commonly a constructive plate boundaries low silica content, low viscosity and very hot |
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What is Andesitic lava and what are the characteristics? |
Formed commonly at destructive plate margins medium silica content and viscosity and temperatures roughly 800°C |
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What is Rhyolitic lava and what are the characteristics? |
Formed commonly at destructive plate margins high silica content and viscosity low temperature. E.g Yellowstone |
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What are the characteristics of a Shield volcano? |
Liquid Lafaette emitted from a large central vent or group of vents, gently sloping, flat shape and low lying. Eruptions are gentle, frequent and predictAble. |
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What are the properties of a Cinder cone volcano? |
Explosive liquid lava, small in size, central vent, pyroclastic material composed of ash and cinders |
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What are the properties of a composite cone volcano? |
Explosive and unpredictable eruptions, steep sided, viscous lava, explosive pyroclastic eruptions |
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Montserrat, Caribbean - 1995 (LEDC) |
Info: Part of Island arc formed from from two oceanic plate meeting, Caribbean and North American Until 1995, economy based on farming, fishing and tourism Primary effects: Pyroclastic flows & floods as valleys were blocked by ash Vegetation and farmland destroyed 20 villages and 2/3 of homes were destroyed by pyroclastic flows Tourism came to a halt Health problems from harmful gases and ash Secondary effects: Forest fires caused by pyroclastic flows 23 people died as a result of pyroclastic flows burning them alive More than half of Montserrat uninhabitable Ageing population as many young people left the island (4,000 people went to the UK) 7000 (2/3 of people) have left the island Destroyed capital city Short term responses: Abandons capital city of Plymouth By November 1997 population fell from 12,000 to 3,500 Long term responses: Volcanic observatory built in 1996 to monitor the volcano British government gave £200 million for compensation and redevelopment. Presence of volcano = growth in tourism |
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Eyjafjalljökull, Iceland - 2010 (MEDC) |
Info: On Mid-Atlantic ridge Shield volcano surrounded by ice and water (ice cap) Underwater ice cap mean a eruption similar to composite volcano as hydrogen in water mixes with lava making it thicker and acidic.
Main effects: Less demand for air fuel = loss of money for oil industry Stock market sharing air travel and tourism agencies dropped 40% Airspace closed across much of Europe more than 7000 flights a day cancelled Increased use of Eurostar train services ships and ferries Flash flood damage to fields and homes in Iceland but increased tourism Increased spending by people who are stranded in the UK for hotels and food Tec
Responses: Launched a massive Europe wide review of safety of planes going through ash clouds |
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What is an earthquake? |
An earthquake is a motion of the ground surface, ranging from a faint tremor to a wild motion capable of shaking buildings apart. |
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How is an earthquake caused? |
Produced by sudden slip movements along faults, volcanic activity or man made influences (digging, building, mining etc) such as cracking which has been known to cause tremors. |
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Where are earthquakes common? |
Along ocean trenches (at subduction zones) In regions where continental plates are colliding (Nepal) Along ocean ridges (Iceland) Transform faults (San Andreas fault) |
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What is the focus? |
The point where the fault ruptures first |
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What is the epicentre? |
Above the focus on the surface, where seismic energy is strongest |
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What are seismic waves and how are they caused? |
They are waves of energy that are caused by sudden breaking of rock within the Earth or an explosion. |
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What are the effects of earthquakes |
Primary: Ground Shaking
Secondary: Soil liquefaction (seen in Japan 2011) soil loses mechanical structure and behaves like a liquid Landslides (slope failure due to ground shaking) Collapse of infrastructure - buildings, transport systems, power lines etc Destruction of utilities - water, gas, electricity along with internet connections Fires - ruptured gas mains, fallen power lines Flooding - from groundwater & mains water Disease and food shortages Knock on effect -> start a tsunami e.g. Japan 2011 |
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What are the main types of seismic waves? |
Body waves Surface waves |
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What are body waves? |
Waves that travel through the earths inner layers |
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What are surface waves? |
Waves that only move along the surface of the planet |
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What are the two types of body waves? |
Primary waves Secondary waves |
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What are primary waves? |
Push waves, they can travel through liquid and solid
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What are secondary waves? |
Shear waves, can only travel through the surface |
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What are the three types of surface waves? |
Longitudinal waves Transverse waves Love waves |
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What are longitudinal waves? |
Up and down movement (like a worm) |
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What are transverse waves? |
Side to side movement |
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What are love waves? |
A combination of transverse and longitudinal waves in a circular motion |
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How are earthquakes measured? |
Mercalli scale Richter scale Moment magnitude scale |
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How does the mercalli scale work? |
12 point scale that measures the intensity of the impact of an earthquake on people and envitonemnt |
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What are the advantages and disadvantages of the mercalli scale? |
Advantage - Useful for people to measure the actual damage rather than magnitude Disadvantage - not scientifically accurate, it's based on subjective observation. |
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What is the Richter scale? |
A logarithmic scale measuring the magnitude or energy released of an earthquake based on seismograph readings |
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What are the advantages and disadvantages of the Richter scale? |
Advantages - accurate scientific measurement useful for comparison Disadvantages - not useful for people to know how deadly an upcoming earthquake is if predicted |
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What is the moment magnitude scale? |
Takes in both previous measurements into account. Measures mostly magnitude but also takes in the intensity of the earthquake into account. |
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How do seismometers work? |
Seismometers are placed in the ground and detect vibrations in the ground which are then displayed on seismographs |
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What are the 3 P's? |
Prediction, prevention and protection |
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What are the problems with predicting earthquakes? |
Very difficult, regions at risk can be identified but attempts to predict are unreliable |
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Can we prevent an earthquake? |
No |
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How can we protect people from an earthquake? |
Build earthquake proof buildings e.g. Transmerica pyramid in San Francisco Educate people about earthquakes Emergency planning - computer programmes in Japan alert people via media Insurance - people urged to take insurance to cover loses as it can be very expensive Aid - emergency aid sent after event e.g medical tents, food and rebuilding (long term) |
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What is a tsunami? |
Any wave created by a geological stimulus e.g. an earthquake |
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How is a tsunami generated by an earthquake? |
Underwater earthquakes cause the sea floor to become deformed, triggering a vertically displaced volume of water with waves moving outwards |
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Port Au Prince, Haiti 2010 (LEDC) |
Caused by Caribbean plate moving against american plate at a transform plate boundary
Impacts: Quarter of a million died Thousands of buildings collapsed Prison destroyed leading to criminals escaping Cholera outbreak Forced mass migration 1.2 million homeless
Responses: Only 1 ambulance service run by a volunteer No international aid, security concernsq Armed forces and military arrived as they anticipated violence Global relief effort people relocated to site with tents Shortage of drinking wager. Government stopped some aid arriving at the airport |
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Japan tsunami -March 2011 (MEDC) |
Cause: 9.0 on MMS Impacts: Earthquakes so massive it lower coastline by 1 meter 20,000 dead Over 100,000 buildings destroyed Fukushima nuclear plant overheated. Releasing radioactive substances leaving 35,000 homes uninhabitable |
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Indian Ocean Tsunami - December 2004 (LEDC) |
No warning system, no preparation (barely any)
Causes: plate subducting under Pacific plate 9.2 earthquake 35 meter high waves Epicentre just off Sumatra coast
Impacts: 14 countries affected all poor 280,000 dead 1,500 villages destroyed 2 million homeless Deforestation of mangroves before tsunami, loss of natural defence
Responses: 60% of fishing industry destroyed July 2006 DART system set up Provided sanitation to help contain spread of disease Medical and monetary aid given ($1 billion worldwide) Rapid burial of bodies due to disease Food aid to 1.3 million people affected
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What is a natural hazard? |
A naturally occurring process or event that has the potential to affect people |
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What is a natural disaster? |
A major natural hazard that causes significant social environmental and economic damage |
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What are the primary effects of earthquakes? |
Ground Shaking Crustal fracturing |
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What are the secondary effects of earthquakes? |
Liquefaction Landslides and avalanches e.g Nepal 2015 mount Everest Tsunami e.g 2004 & 2011 |
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How are aftershocks caused? |
Aftershocks occur in ephemeral area of the original earthquake, and are a result of the Earth 'settling down' or readjusting along the part of the fault that slipped |
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What are the primary hazards of volcanoes? |
Lava flows Pyroclastic flows Tephra and ash fall Gas eruptions
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What are the secondary hazards of volcanoes? |
Lahars Jökulhlaup - heat of a volcanic eruption can melt snow and ice in a glacier causing heavy and sudden floods. |
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How do we measure volcanic eruptions? |
Volcanic Explosivity Index (VEI)
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How does the VEI scale work? |
Volcanos are categorised by around and height of volcanic material injected How long the eruption lasts Qualitative descriptive terms like gentle or explosive |
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How can we predict a volcanic eruption? |
Seismometers - when a volcano is about to erupt it generates loads of small as the magma tries to break through the crust. Scientists can detect these on seismographs Thermal imaging - when a volcano is about to erupt the magma is very close to the surface causing the ground temperature to increase. Scientists can use thermal imaging to detect this increase in temperature Tiltmeter - as the magma moves inside the volcanoes it changes the slope and angle or tilt of the volcano |
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How is a tsunami generated? |
When land is uplifted due to the earthquake the ocean is displaced. Waves begin to radiate out from the source in all directions. As the tsunami reaches shallow waters e.g. the coast the eaves begin to slow down and increase in height to produce high waves. |
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What is the hazard risk formula? |
Risk = (Hazard x Vulnerability) divided by capability to cope |
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What human factors affect vulnerability and resilience? |
Quality of existing infrastructure (Mexico 2017 bad infrastructure) Existence of disaster preparedness plans Efficiency of emergency services Existence of public education Level of corruption of government Wealth affects people's ability for them to protect themselves Quality of health care Population density |
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What is resilience? |
The ability to overcome a natural hazard |
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What are the geophysical trends since 1960? |
Number of deaths increased More people affected More damage caused by tectonic events |
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Why have geophysical disasters increased? |
Global population in 1960 = under 3 billion Global population in 2016 = 7.3 billion This increase in population has meant that even more people are living in poverty and are vulnerable. Therefore more people occupy more hazardous spaces and there is an increase in population density in megacities like Mexico City
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What is a disaster hot spot? |
A disaster hotspot is when hydrometeorological and geophysical hazards strike a vulnerable population. For example, the Philippines |
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What are hydrometeorological hazards? |
Natural hazards caused by climatic processes (including droughts, gloods, hurricanes and storms) |
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What makes the Philippines a disaster hot spot? |
The Philippines sits across a major convergent plate boundary creating volcanoes, earthquakes and tsunamis Northern and eastern coasts face the Pacific ( world's most tsunami prone ocean) The Philippines lies within South East Asia's major typhoons belt 47 volcanoes 22 of which are active Landslides are common due to a combination of steep typography high levels of deforestation and high rain fall. |
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Why is the Philippines vulnerable? |
Fast growing population High population density Many of the country's poor live in coastal areas where sea surges flooding and tsunami are made worse by poorly constructed housing and infrastructure. 25% of population live in poverty |
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What is the Hazard management cycle? |
The hazard management cycle is the mitigation and preparation before an event and the response and recovery after an event. |
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What is the park model (hazard-response curve) |
The park hazard-response curve is a model that shows how a country or region might respond after a hazard event |
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What is hazard mitigation? |
Strategies meant to avoid, delay or prevent hazard event like land use zoning, diverting lava flows, GIS mapping and hazard-resistant design and engineering |
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What is hazard adaptation? |
Strategies designed to reduce the impacts of hazard events like high-tech monitoring, crisis mapping, modelling hazard impacts, public education and community preparedness. |
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What is land-use zoning? |
Land-use zoning is the process in which local government planners regulate how land in a community may be used. In areas at risk from natural hazards land use zoning is an effective way to protect people and property. This was done by New Zealands government with Mount Taranaki |
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What is GIS mapping? |
GIS mapping is used to identify the locations of highly populated areas, sizes of major towns and cities, areas affected by the earthquake and the locations of airports and airstrip and key evacuation routes. This was used in the Nepal earthquake 2015. |
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What are the key players in managing loss after a tectonic event? |
Aid donors Governments Non governmental organizations Communities |