Natural Hazards

• natural hazard

  a natural event that has the potential to cause loss of life and/or damage to property
• natural disaster

  a natural hazard that causes extensive destruction of property and often a large number of fatalities
• magnitude

  the size and strength of a natural hazard
• factors that affect damage and fatalities in a natural hazard

  - magnitude

  - population density

  - age of buildings + quality of buildings

  - location

  - LIC / HIC

  - duration
• parts inside the earth

  - crust ~ solid rock broken down into oceanic tectonic plates

  - mantle ~ molten rock slowly moving due to convection currents

  - outer core

  - inner core
• why do tectonic plates moves

  convection currents in the mantle

  - they cause the movement of the plates above it
• how convection currents work

  - hot mantle is closer to the core (less dense)

  - then rises and starts to cool as it becomes further from the core (more dense)

  - as it's more dense the mantle falls and the cycle repeats

  
• continental crust vs oceanic crust

  continental

  - thick

  - old

  - less dense (lighter)

  oceanic crust

  - thin

  - young

  - more dense (heavier)
• 3 types of plate boundaries

  - destructive

  - constructive

  - conservative
• destructive plate boundary

  1. The denser oceanic crust is subducted below the continental crust

  2. The plate that is subducting leaves a deep ocean trench

  3. Friction between the two plates causes strong, deep earthquakes

  4. The oceanic crust is melted as it is pulled deeper into the mantle, creating magma.

  5. This magma causes pressure to build up under the crust.

  6. Eventually the magma pushes out through weaknesses in the crust, creating explosive volcanoes.
• constructive plate boundary

  - 2 plates move away from each other

  - magma rises to form a new crust

  - large amounts of magma can rise up to form underwater mountain ranges and even break the surface to form volcanic islands

  - the volcanoes formed at constructive plate boundaries are shield volcanoes, that have gentle slopes, gases can easily escape and a low viscosity, which causes less destruction
• conservative plate boundary

  - does not create volcanoes, rather earthquakes

  - plates slide past each other, but not smoothly due to friction, which causes the plates to catch and stick

  - the pressure from the convection currents in the mantle builds and eventually the plates violently jolt past each other ~ is felt as an earthquake
• impacts of earthquakes

  - buildings are damaged, means buildings like hospitals are damaged, means amount of aid available decreases and injured people have no where to be treated

  - earthquakes cause violent jolts and movement of the ground which can then lead to landslides or even trigger tsunamis > more death

  - damaged businesses, can lead to unemployment and lost income, can even deter tourists

  - homes are destroyed, leaves people without shelter and can die due to exposure to cold, if not they are still left homeless
• why do people live near volcanoes

  - they volcanoes they live by are not very active

  - shield volcanoes are less destructive (safer to live by)

  - have no choice ~ can't afford to move, no safe places left to live, some even have emotional attachment to the area

  - choice ~ farmers often choose to live nearby as soil is more fertile meaning more food can be produced and the farmers can get more money, geothermal energy can be released there and people can get jobs inside the power plant, locals can get tourism based jobs and make money from tourists, can mine (copper, silver, diamonds and zinc) once lava cools which provides more jobs for locals
• clues a volcano is about to explode

  - changes in size or shape of a volcano

  - increased number of small earthquakes and tremors

  - increased production of gases eg. sulfur dioxide

  - increase in temperature of the volcano
• how can we survive a volcanic eruption

  - lay down barriers to deflect lava flows

  - cool lava using water ~ causes it to solidify
• despite not being reliable, how can we predict earthquakes

  - strange animal behaviour

  - changes of chemical composition

  - seismic monitoring

  - foreshocks

  - earthquake cycles
• protection from earthquakes

  - cross bracing ~ stops buildings from moving left to right, makes them more secure (creates 4 triangles ~ wide base, structurally better)

  - automatic window shutters ~ prevents falling glass as it won't break

  - computer controlled moveable roof ~ balances weight, creates 'standstill
• preparation of earthquakes

  - organise drills and training so people know what to do when an earthquake occurs
• global atmospheric circulation

  how the air above us moves in a circular motion around the world
• latitude

  how north or south something is from the equator
• altitude

  how high u something is above sea level
• fundamentals of global atmospheric circulation

  - warm air is less dense

  - cold air is more dense

  - rising air creates low pressure

  - falling air creates high pressure

  - temperature decreases with rising altitude

  - water exists on earth in 3 states: solid, liquid, gas
• why do temperatures increase towards the equator and decrease towards the poled

  - at the equator, the sun is directly overhead, meaning it doesn't hit the earth at an angle, which then means it hits a smaller area, meaning a higher concentration of heat hits the earth at the equator

  - also at the equator, it has less time travelling through the atmosphere, and when the heat travels through the atmosphere is cools, so spending less time there makes it even hotter at the equator

  - this contrasts at the poles
• anticyclone vs cyclone


  anticyclone

  - air sinks towards the ground and creates areas of high pressure and the wind moves outwards from these areas

  - eg. at the North Pole

  cyclone

  - air rises from the ground and creates areas of low pressure and winds the ground move towards these areas

  - eg. at the equator
• the coriolis effect

  - winds on the ground are distorted by the earth's rotation

  - they curve as they move from areas of high pressure to areas of low pressure

  - surface wind are very important in transferring heat and moisture from one place to another

  - winds are deflected to the right in the northern hemisphere and to the left in the southern hemisphere

  - this is known as the coriolis effect which results in the difference in velocity of the earth spins

  
• tropical storm name variations

  - Atlantic ocean ~ hurricane (USA, Mexico, Haiti)

  - Indian ocean ~ cyclone (India, Myanmar, Thailand)

  - Pacific ocean ~ typhoon (Philippines, China, Australia)
• tropical storms

  - areas of very low pressure (where air rises)

  - average wind speeds of 120kph

  - they do not form on the equator and do not cross the equator

  - they also don't occur in the North and South poles

  - they do not form on land and rather lose power when they hit land

  - they have seasons

  - they get stronger the longer they stay over warm oceans

  - they need warm water (26-27°) to form as there is more evaporation
• formation of tropical storms

  - ocean is at 27°c and evaporates into water vapour

  - this then cools, and condenses into clouds, which creates rain

  - the air rises due to the 'low pressure void' which creates the wind

  - the coriolis effect creates the spin

  
• the eye of a tropical storm

  - in the middle of the storm

  - here the air is cold not hot, meaning it sinks and is calm
• impacts climate change has on distribution and frequency of tropical storms

  - global climate increases

  - means more of the world's oceans are closer to 27°c

  - creates lower pressure, and the formation of more tropical storms begins
• effects of tropical storms

  - heavy rain

  - strong winds

  - storm surges
• prediction of tropical storms

  - hurricane aircraft

  - radar

  - weather balloon

  - meteorologists

  - satellites

  - weather station
• protection from tropical storms

  - board up windows

  - cyclone shelters

  - stilts

  - breakwater

  - storm surge barrier
• preparation for tropical storms

  - evacuation

  - emergency services

  - food, water and medical aid

  - broadcast warning

  - educate population
• weather vs climate

  - climate ~ average weather

  - weather ~ changeable and is what you actually experience
• weather hazards in the UK

  - thunderstorms: Canary Wharf in London, July 2014, heavy rainfall led to a flash flood

  - prolonged rainfall: southern England, winter 2014, heavy rain led to rivers flooding

  - heavy snow and extreme cold: north of UK, winter 2004, heavy snow traps people in buildings

  - drought and extreme heat: most of Europe, summer 2003, droughts led to thirst and malnutrition

  - strong winds: most of the UK, February 2014, caused trees to fall which led to disruptions to power
• why is weather so changeable in the UK

  - NW ~ cold (north) and wet (Atlantic ocean)

  - SW ~ warm (south) and wet (Atlantic ocean)

  - SE ~ warm (south) and dry (land)

  - NE ~ cold (north) and dry (land)
• when does high pressure occur

  - falling air

  - no condensation, no clouds
• impact of high pressure in the summer vs winter

  summer

  - people get burned

  - heatwaves

  - droughts

  - can lead to thunderstorms in random areas

  winter

  - water on roads freezes into ice ~ more dangerous

  - frost is created

  - fog is created

  - people get hyperthermia

  - pipes can burst and then homes can get flooded or have no water