Physical

• Natural hazard


  A natural event that threatens people or has the potential to cause damage, destruction and death
• Types of natural hazards

  • Atmospheric hazards
  • Terrestrial/Geological hazards
  • Water based hazards
  • Biological Hazards
• Atmospheric hazards


  Created in the atmosphere, by the movement of air and water
• Terrestrial/Geological hazards


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


  Created by rivers, sea or oceans
• Biological Hazards


  Any biological substance that poses a threat to the health of people
• Vulnerable


  More susceptible to natural hazards
• Capacity to cope


  Ability to respond to and recover from natural hazards
• Factors affecting natural hazards

  • Natural factors
  • Magnitude
  • Frequency
  • Population density and distribution
  • Level of development
  • Management
  • Education
  • Time
• Natural factors


  Things like rock type (geology) in an earthquake, the shape of a coastline in a tsunami, the height of the land hit by a tsunami can influence the effects
• Magnitude


  The size of the event massively affects the impact it has. Every step up the Earthquake Richter scale represents a 10 fold increase in damage and a 30 fold increase in energy released
• 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
• Population density and distribution


  The number of people in an area and where they are. Generally, the greater the number of people in an area, the greater the potential for disaster
• Level of development


  Determines how much money is available to prepare for and respond to the event
• Characteristics of HICs that help them prepare and respond

  • Stable and democratic governments with emergency agencies
  • Access to technology to predict and withstand hazards
  • Planning laws to prevent building in hazardous locations
  • Well-equipped emergency services
• 3Ps of natural hazard management

  • Predict
  • Prepare
  • Prevent
• Predict


  Some natural hazards are easier to predict than others, e.g. hurricanes can be identified by satellites and tracked
• Prepare


  If a place is well prepared regardless of its level of development this can limit the impact of a hazardous event
• Prevent


  This could be preventing damage to buildings etc. through strict building rules
• Education


  People can be educated to survive natural hazards, e.g. about the risks of contaminated flood water or earthquake drills
• Time


  The amount of time since the last hazardous event can influence the impact, if a long time goes by people can be unprepared. Also, if the hazard occurs when lots of people are asleep, they can also be unprepared
• Plate boundary


  The boundary or margin between two 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
• Plate Tectonics is a theory that tries to explain how the Earth is structured and what it is made up of. The materials that make up our earth slowly gathered together due to gravity. This material has slowly cooled over geological time, forming a crust at the Earth's surface of rocks. These rocks are fractured into huge segments called Tectonic plates
• These tectonic plates are moving about very slowly, pushed, and shoved around from underneath by convection currents
• Types of crust


  • Continental crust
  • Oceanic crust
• Continental crust


  Thicker, older and lighter. Mainly Granite. It is 35 km thick on average and less dense than oceanic crust. Continental crust is formed primarily at subduction zones at destructive plate margins
• Oceanic crust


  Younger and heavier and is mainly basalt and Gabbro. It is mainly formed at constructive margins or spreading mid ocean ridges
• Major tectonic plates


  • Pacific
  • Eurasian
  • African
  • Antarctic
  • North American
  • South American
  • Indo-Australian
• Volcanoes and earthquakes mainly occur along plate boundaries where magma can escape from the Earth's mantle or where stresses build up between 2 plates rubbing together. An exception to this includes Hawaii, which is found in the middle of the Pacific plate over a hot spot
• 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 Margins


  Two plates are moving apart (DIVERGE) from each other in opposite directions. Convection currents moving in opposite directions (caused by the intense heat of the Earth's interior) in the mantle move two plates apart. As these plates move apart this leaves cracks and fissures (lines of weakness), that 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. This can create huge ridges of undersea mountains and volcanoes, and where these mountains poke above the level of the sea, islands are created. Both earthquakes and volcanoes can result at these margins, the earthquakes caused by the movement of magma through the crust
• Conservative margins


  Two plates either slide past each other in opposite directions, or two 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. We know these shock waves as earthquakes
• Destructive


  Two plates move or CONVERGE together and the destruction of some of the Earth's crust results. An oceanic plate (denser) is pushed towards a continental plate (less dense) by convection currents deep within the Earth's interior. The oceanic plate is subducted (pushed under) the continental plate at what is called a subduction zone, creating a deep ocean trench. It is the Oceanic crust which sinks down into the mantle because it is denser (heavier). As it descends friction, increasing pressure and heat from the mantle melt the plate. Some of this molten material can work its way up through the continental crust through fissures and cracks in the crust to collect in magma chambers. This is often some distance from the margin where magma can eventually re-emerge at the surface to create a range of mountains. The movement of the plates grinding past one another can create earthquakes, when one plate eventually slips past the other releasing seismic energy
• Kobe is located in the southeast of Japan, near a destructive plate margin. It is a megacity and has one of the largest container ports in the World. Although further from a plate margin than most of the cities in Japan, Kobe is still found on a fault line
• The earthquake that hit Kobe during the winter of 1995 measured 6.9 on the Richter scale. At this plate margin, the Pacific plate is being pushed under the Eurasian plate, stresses build up and when they are released the Earth shakes. This is known as an earthquake happening along a subduction zone. The focus was only 16km below the crust and this happened on the 17th Jan 1995 at 5.46am. 10 million people live in this area
• Effects of the Kobe earthquake

  • More than 5000 died
  • 300,000 were made homeless
  • More than 102,000 buildings were destroyed, especially older wooden buildings
  • Estimated cost to rebuild the basics = £100 billion
  • The worst affected area was the central part of Kobe including the main docks and port area, built on soft and easily moved rocks
  • Emergency aid was limited due to damaged roads and infrastructure
  • Over 300 fires broke out, taking over 2 days to put out