geography - global hazards

• hadley cell


  0-30 degrees n+s of equator
• ferrel cell 


  30-60 degrees n+s of equator
• polar cell 


  60-90 degrees n+s of equator
• high pressure


  cold air sinks to create clear skies + warm weather
• low pressure


  hot air rises, cools + condenses to form clouds + precipitation
• el nino


  cooler water off coast of Australia reverses wind direction - leads to high pressure in Australia - hot weather, lack of rainfall, drought
• convectional rainfall


  land warms up, heats air enough to expand + rise. as air rises it cools + condenses. if process repeats, rain will fall
• frontal rainfall 


  warm air meets cool air, front is formed. as warm air rises over cool air, clouds are produced. eventually, steady rain produced.
• relief rainfall


  wind meets mountains, warm air is forced to rise fast and cool - leads to condensation + eventual rainfall. however, when air descends, very little rain falls - creates rain shadow
• shield volcano


  basaltic rock - form gently sloping cones from layers of runny lava. in hot spots + constructive margins. eruptions: gentle + predictable
• composite volcano


  most common type on land. created by layers of ash + lava. found in destructive margins. eruptions: explosive + unpredictable due to pressure within magma chamber
• hotspots


  happen away from plate boundaries. occur because plume of magma rise to eat into plate above. where lava breaks through to surface, active volcanoes occur above hotspot. (hawaii)
• destructive plate margin


  denser oceanic plate subducts under less dense continental plate. friction causes it to melt + become molten magma. magma forces way up to surface - forms volcano. - also responsible for harsh earthquakes
• constructive plate margin


  plates move apart - cause new magma to reach surface through gap. volcanoes formed along the crack cause submarine mountain range like in mid atlantic ridge
• conservative plate margin


  plates slide past each other in opposite or same direction but at diff speeds. responsible for earthquakes like in san andreas fault usa
• collision zone


  two continental plates collide. both forced up to form fold mountains. responsible for shallow earthquakes in himalayas
• e16 causes

  north american + eurasian plates move apart - constructive plate boundary. disruption caused by e16 was result of series of small volcanic eruptions.
• e16 effects


  thick ice cap melted which caused major flooding. no reported deaths. airspace closed across europe, with at least 17,000 flights cancelled. costed insurers 65 million to customers with cancelled flights
• e16 management


  iceland had good warming system, texts sent to residents within 30 min warning. large sections of euro airspace closed down due to ash spreading over continent. airlines develop ash monitoring equipment
• boscastle causes


  caused by 1422 million litres of rain falling in 2 hours. urbanisation in town made flood worse. boscastle is in valley with steep slopes
• boscastle effects

  84 cars destroyed, 32 never found. 58 properties flooded. 20 hotels closed. 25 businesses destroyed. uprooting of trees
• boscastle management


  7 RAF helicopters sent to rescue ppl. sandbags used to stop water. 10 million from environment agency to improve management
• big dry causes


  el nino made aus hotter and drier. over pop in urban areas put stress on water supply
• big dry effects


  rural suicide rates inc. water bills rose by 20%. 10,000 unemployed in agriculture effected. grassland turned to shrub land
• big dry management


  more efficient irrigation. 1.7 million paid from gov to farmers per day. showers limited to 4 mins.
• volcanic hazards - ash cloud


  small pieces of rock and glass thrown into atmosphere
• volcanic hazards - gas

  sulphur dioxiide, water vapour and co2 come out of volcano
• volcanic hazards - pyroclastic flow


  fast moving current of super-heated gas and ash. travel at 450mph
• volcanic hazards - volcanic bomb


  thick viscous lava fragment that is ejected by volcano
• shallow focus earthquake


  usually small and common. seismic waves spread and damage wide area
• deep focus earthquakes


  occur on destructive margins, damage localised as seismic waves travel vertically
• cause of earthquake


  caused when 2 plates become locked, friction build up. from this stress, pressure eventually released, triggers plates to move into new position - causes energy in form of seismic waves to travel from the focus towards epicentre, as result, crust vibrates to trigger earthquake
• richter scale


  scientific measurement based on energy released. measured by seismometers using measurement from 1-10. logarithmic -each point up scale is 10x greater than one before
• mercalli scale


  measures how much damage caused based on observations, not scientific instruments. base from instruments and weak to extreme and cataclysmic. limitations - subjective due to being based on perception