Natural Hazards

• a natural hazard is any natural event that has the potential to endanger human life, the economy and property.
• is a tornado a climatic or tectonic natural hazard?

  climatic
• is a blizzard a climatic or tectonic natural hazard?

  climatic
• is a tsunami a climatic or tectonic natural hazard?

  tectonic
• a volcano erupting on a desert is not a natural hazard because there is no potential to harm human life, economic effect or damage to property.
• hazards can have economic, social and evironmental effects
• In an LIC, the death toll of a natural hazard tends to be high but the economic effect tends to be fairly low.
• In a HIC, the death toll tends to be fairly low, but the economic cost tends to be high.
• LIC's tend to be slower at repairing infrastructure, further damaging their economy by limiting things such as tourist income.
• the crust of the earth is 0-70km thick
• the mantle of the earth is just under 3000km thick
• the core of the earth is about 3000 degrees celcius
• the core of the earth is 3500km thick
• oceanic crust is 5-10km in thickness, is denser than continental crust, and is much younger.
• continental crust is 25-100km thick, is less dense than oceanic crust, and is much older.
• when 2 plates meet it is called a plate margin
• oceanic crust can be created and destroyed
• the study of fossils shows us that tectonic plates have moved gradually over time
• convection currents of magma are caused when magma is heated by the core of the earth and rises to the surface, then cooled, causing it to sink again
• the plates on the surface of the earth move in the same direction as the convection currents
• constructive plate margins are when the plates move apart. at these plate boundaries, no earthquakes occur, however volcanoes are formed (shield volcanoes)
• a destructive plate boundary is where an oceanic plate and a continental plate are moving towards each other and the oceanic plate subducts underneath the continental plate because it has a higher density.
• in a destructive plate boundary, volcanoes are active because the oceanic plate melts into the earths mantle, causing an increase in magma to be pushed up through the earths surface
• a conservative plate boundary is where two plates are sliding past each other. Earthquakes happen here because of the force of friction as the plates move against each other. volcanoes are not formed here.
• destructive plate boundaries produce explosive volcanoes
• constructive plate boundaries do not produce explosive volcanoes
• earthquakes are a sudden and violent movement or fracture within the earths crust
• earthquakes happen mainly along the boundaries of the earths plates
• as plates rub against each other friction can cause pressure to build up
• over time pressure builds up through friction and plates can suddenly slip past each other at a weak area (a fault line), and the pressure is released
• the focus is the place underground where the rock actually slips
• the place at the earths surface directly above the focus is called the epicentre
• pressure is released outwards from the fault as seismic waves
• seismic waves cause the earths crust to tremor, causing damage to the earths surface.
• less damage is caused to the earths surface the further you get from the epicentre
• primary waves (p-waves) travel fastest, causing a back and forth movement
• secondary waves (s-waves) are slower and cause a side to side movement
• surface waves cause a sideways and up and down movement, making them the most dangerous because of their likelihood to make buildings fall
• seismic waves are measured by seismometers
• the Richter scale measures earthquakes on a scale of 0-10. It measures the amount of energy released