Section A- the challenge of natural hazards

• natural hazard

  “A natural event (for example earthquake, volcanic eruption, tropical storm, flood) that threatens people or has the potential to cause damage, destruction and death.
• atmospheric hazard

  created in the atmosphere by the air, wind and water
• Terrestrial/Geographical hazards

  Created by the movement of the Earth's tectonic plates or surface rock and soils
• water based hazards

  created by the sea, ocean or rivers
• Biological hazards

  Any biological substance which poses as a threat to humans
• Geomorphological hazard-

  A hazard caused by processes which occur on the surface of the earth (or ocean)eg. floods and landslides
• Frequency-

  how often the hazard occurs.  The more often a hazard occurs generally the more prepared people are, and the more used to coping they are.  Large earthquakes and volcanic eruptions are generally very rare events in terms of a human lifespan so when they occur they can surprise.  Floods are often regular events, large parts of Bangladesh flood every year for example.  In this event people can adjust their buildings and lives to cope with the risk associated.
• Population density and distribution-

   the number of people in an area and where they are in comparison to the risk. Generally, the greater the number of people in an area, the greater the potential for disaster.  Therefore, an earthquake in Alaska will have less impact than one which hits a more densely populated area such as San Francisco. The Pacific Ring of fire covers a 40,000km horseshoe shape and has around 90% of the world’s earthquakes and 452 volcanoes which affects millions of people.
• Level of development of areas-

  This determines how much money can be invested to prepare for the event in advance

  predicting the hazard and preparing people to cope with it,

  how the country responds after the event occurs. ( richer countries normally means quicker response)
• Governments in HICs

  Because HICs often are often more stable and democratic, more agencies can be contacted during and emergency.

  Being democratic means the public can put pressure on the government to have buildings which can survive natural disasters. Politicians will listen and attempt to put this in place to gain votes.
• Technology in HICs-

  HCs can afford the technology necessary to predict natural disasters. E.g. the US and their seismometers
• Planning laws in HICs-

  Many HICs have laws that prevent building in hazardous locations. Eg along a low coastline which may be at risk of a storm surge
• Agencies

  Many HICs have agencies that an act quickly to help people after a disaster, such as well-equipped army or fire services, and experts to coordinate short and long term responses
• Predict- some natural hazards are easier to predict than others, hurricanes can be identified by satellites and then tracked. this allows governments to evacuate if needed.
• Preparation- if a place is well prepared regardless of how developed it is, this can limit the impact of a hazardous event. EG. In India, despite its low level of economic development, rounded wooden houses have been designed to be earthquake proof, thus limiting the impact of these hazards.
• Prevent- preventing damage to buildings e.g counterweights for buildings (for earthquakes)
• Education- regardless of how developed the country is, people can still be taught how to survive natural hazards, as this saves many lives. Eg, Earthquake drills
• Time the event takes place- if the time is late at night, then people will be unprepared to face a natural hazard. People can also be unprepared If it has been a long time since the last event. Eg, Christchurch 2011 earthquake happened during the day- work buildings collapsed and many died
• Plate boundary- the boundary or margin between 2 tectonic plates
• 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.]
• The materials that make up our earth slowly gathered together due to gravity, to create a ball of hot molten material. This material has slowly cooled over geological time, forming a crust at the Earth's surface of rocks. 
• slabs of crust pushed apart at constructive plate magins (SLAB PUSH)
• plates increase in density away from these margins get pulled down into the mantle (SLAB PULL) by gravity and local convection cells.
• tectonic plates are moving about very slowly, pushed and shoved around from underneath by currents within the mantle called convection currents.
• Structure of the inside of earth, terms+ explanations

  A) plate margin

  B) solidcore

  C) outer core

  D) convection currents

  E) oceanic

  F) the crust

  G) the mantle

  H) tectonic plates

  I) plate edges -plates sliding, moving together or apart

  J) 3700*C iron+ nickel- solid because of intense pressure

  K) heat currents in molten magma move crust very slowly

  L) under slightly less pressure

  M) continental

  N) 2

  O) a zone of molten+minerals because of earth's inner heat

  
• Continental crust is thicker, older and lighter, and is composed mainly of Granite. Less dense than oceanic crust. Continental crust is more complex than oceanic crust, and is formed primarily at subduction zones at destructive plate margins.
• Oceanic crust is younger and heavier, and is mainly composed of basalt and Gabbro. It is mainly formed at constructive margins or spreading mid ocean ridges.
• Conservative plate boundary - Tectonic plate margin where two tectonic plates slide past each other.
•  Constructive plate boundary -Tectonic plate margin where rising magma adds new material to plates that are diverging or moving apart.
• Destructive plate boundary - Tectonic plate margin where two plates are converging or coming together and oceanic plate is subducted. It can be associated with violent earthquakes and explosive volcanoes.
• Constructive or Divergent Margins

  At this type of plate margin two plates are moving apart (DIVERGE) from each other in opposite directions. Convection currents moving in opposite directions in the mantle move two plates apart. As these plates move apart this leaves cracks, which allows magma from the mantle to escape from the highly pressurised interior of the planet. This magma fills the gap and eventually erupts onto the surface and cools as new land.
• Both earthquakes and volcanoes can result at constructive plate margins, the earthquakes caused by the movement of magma through the crust. A really good example of this is the Mid-Atlantic Ridge, where the Eurasian plate moves away from the North American plate at a rate of around 4cm per year.
• Conservative margins

  At conservative margins mountains not made, volcanoes don't erupt and no crust destroyed. Instead, 2 plates either slide past each other in opposite directions, or 2 plates slide past each other at different speeds. As they move past each other stress energy builds as the plates snag and grind on one another. When this stress energy is eventually released it sends shock waves through the earth’s crust. these shock waves are earthquakes.
• Destructive margins

  Oceanic plate pushed towards continental plate by convection currents. The oceanic plate is subducted under the continental plate at a subduction zone, creating a deep ocean trench. Oceanic crust sinks down into the mantle because it's denser. It descends, increasing pressure and heat from the mantle so it melt the plate. Some of the melted plate can work its way up the continental crust through cracks in the crust to collect in magma chambers. Movement of plates grinding another can create earthquakes, if one plate slips past the other releasing seismic energy. 
• Reasons for living close to volcanoes:

  • Some settlements have grown into enormous cities and would be hard to move anywhere else
  • Some places are well prepared for hazards so people feel safe
  •  People believe the chances of the volcano erupting are very slim
  • Many tourism industry opportunities for good money
  • cheaper to live there as demand to live in those areas is not very high
  • Magma contains a large amount of minerals, such as, copper, gold, silver, lead and zinc.  After an eruption this magma cools and these minerals can be mined.
  • In Iceland volcanoes provide cheap geothermal power
• Management strategies - Techniques of controlling, responding to, or dealing with an event.
• Monitoring - Recording physical changes, such as earthquake tremors around a volcano or tracking a tropical storm by satellite, to help forecast when and where a natural hazard might strike.
• Planning - Actions taken to enable communities to respond to, and recover from, natural disasters, through measures such as emergency evacuation plans, 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 reliably for earthquakes.