Global Hazards

• Atmospheric circulation

  Large scale movement of air by which heat is displaced on the surface of the earth
• Cells in order from equator to poles

  hadley

  ferrel

  polar
• how does the global circulation system control temperatures?

  by influencing precipitation and the prevailing winds.
• what does the global circulation system create?

  distinctive climate zones
• Temperature climate: where, what, e.g.

  mid-latitude, 50°-60° north and south of equator, air rises and cools to form clouds, creating frequent rainfall, e.g., UK
• Tropical climate: where, what, e.g.

  Along equatorial belt, experiences heavy rainfall and thunderstorms, e.g., Brazil
• Polar Climate: where, what, e.g.

  Within the polar zones, cold air sinks causing dry, icy, and strong winds, e.g., Antartica
• Desert Climate: where, what, e.g.

  30° North and South of equator, sinking dry air leads to high temperature without conditions for rainfall e.g., Libya
• What causes High pressure

  cold air sinking
• what does high pressure cause

  clear and calm weather
• what causes low pressure

  hot air rising
• what does low pressure cause

  stormy, cloudy weather
• what is wind

  movement or air from an area of high pressure to area of low pressure
• What are trade winds


  Winds that blow from high pressure belts to low pressure belts
• What are katabatic winds

  winds that carry air from high ground down a slope due to gravity, e.g., Antartic
• jet stream winds

  winds that are high in the atmosphere travelling at speeds of 225km/h
• what is precipitation

  water vapour is carried by warm air that rises. As it gets higher, the air cols and the water vapour condenses to from a cloud. As water molecules collide and become heavier, the water will fall as rain
• convectional rainfall

  when the land warms up, it heats the air enough to expand and rise. As the air rises it cools and condenses. If this process continues then rain will fall
• frontal rainfall

  when warm air meets cold air a front is formed. As the warm air rises over the cold air, clouds are produced. Eventually, steady rain is produced
• relief rainfall

  when wind meets mountains, the warm air is forces to rise quickly and cool. this leads to condensation and eventually rainfall. When the air descends however, very little rainfall falls, creating a rain shadow
• how the patterns of tropical storms are changing

  global warming is having an impact on the strength and frequency on tropical storms. This may be due to an increase in ocean temperature
• how is the pattern of droughts changing

  severity has increased, may be due to changing rainfall patterns related to gradual climate change
• distribution of droughts

  Most frequent between the tropics of cancer and capricorn but can happen anywhere
• what is el nino associated with creating

  dry conditions
• el nino vs normal year

  
• distribution of tropical storms

  occur in a band that lies between tropics. Some form just outside the tropics, but always in areas where sea temps are +27°
• temp the sea need to be to form tropical storm

  27° (26.5°)
• why tropical storms start spinning

  trade winds going one way, earth spinning (coriolis effect) going the other way
• what is the eye of a tropical storm

  as storm spins, cool air sinks in the centre of the storm, creating calm, clear conditions
• why does the storms die out over land

  the warm sea is its energy source so on land it runs out of energy and eventually 'burns itself out'
• structure of the crust

  5-10km deep. Made of several large plates
• structure of the mantle

  2900km, Heat and pressure means the rock is in liquid state and in a state of convection (causing convection currents)
• inner and outer core

  hottest part (5000°) made of mostly iron and nickel and 4x denser than the crust. Inner section is solid whereas outer layer is liquid
• where are tectonic plates and why do they move

  they are in the lithosphere and move due to convection currents in the mantle
• how convection currents work

  mantle generates a lot of heat. When they are heated they get less dense and rise. As they get towards top they cool and sink again. These circular movements of semi molten rock are convection currents. these create drag on the base of the tectonic plates and this causes them to move
• describe what happens at a destructive plate boundary

  denser plate (oceanic) subducted under other, friction causes it to melt and become molten lava. magma forces its ways up to the surface to form a volcano. also causes earthquakes when friction is released quickly
• describe what happens at a constructive plate boundary

  two plates move apart causing new magma to rise to the surface through the gap. volcanoes formed along this crack cause a mountain range like mid atlantic ridge
• what happens at conservative plate boundary

  plates slide past each other in opposite directions or the same direction at different speeds. This is responsible for shallow earthquakes e.g. san andreas fault
• what happens at collision plate boundary

  two continental plates move towards each other and collide. neither is more dense so neither subducted so both forced upwards and make fold mountains. these cause shallow earthquakes. e.g. himalayas are fold mountains
• features of shield volcano

  made of basaltic rock and form gently sloping cones made of runny lava. occur over hotspots and constructive plate boundaries. eruptions are gentle and predictable