describe the causes of earthquakes and volcanic eruptions and their effects on people and the environment

•the causes of earthquakes 

          •features of earthquakes

          •earthquakes are caused by plate movements, either towards each other, away from each other or sliding past each other  

          •the plates don't always move at a constant rate and are often ‘stuck’ in one position

                    •pressure builds up as the plates try to move 

                             •a sudden movement (fault) means that energy is released and vibrations travel through the Earth as an earthquake  

•the effects of earthquakes on people and the environment:

          •effects on people: •people injured and hurt; loss of income

                                         •prevention of communication and transport 

                                         •water supplies may be contaminated 

                                         •break out of disease; killing people; exacerbated by bad transport 

                                         •possible rehousing as refugees or in camps

                                         •closure of shops and increase in theft; loss of investment 

Primary Hazards	Nature of Hazard	Effects
Ground Shaking	•ground shaking during the movement of the Earth’s crust	•damage to property and to the  land and death
Secondary Hazards
Liquefaction	•ground shaking causes water to rise; saturating the soil; sand causing it to flow; becoming liquid	•foundations of buildings collapse as they sink into the ground
Landslides	•fast downslope movement of soil  •occurs when the slope is  unstable	•can destroy buildings, cover roads and break power lines
Tsunamis	•massive wave caused by earthquake can be 10m high	•widespread flooding, damaging everything •it can affect a wide area

•factors affecting level of earthquake damage

          •development of warning systems   

          •the amount of energy released

          •density of the population in the area of an earthquake epicentre 

          •distance from epicentre

          •economic input

          •the depth of the focus beneath the surface 

          •how solid the bedrock is for clays to turn liquify 

          •the resistance the buildings have to the disasters

•the process of volcanic eruptions- from magma chamber, through vent, out of the crater 

          •1. magma rises through the cracks or weaknesses in the Earth’s crust and lower density

                than the surrounding rock

          •2. pressure builds inside the Earth 

          •3. when the pressure is released,as a result of plate movement, magma surfaces, exploding

          •4. the lava from the eruption cools to form the new crust

          •5. after several eruption the rock builds up and a volcano forms

Hazard	Nature of Hazard	Effects on People/ Environment
Ash Falls	•fire and ash is blasted into the atmosphere over a large area •can stay for a long time	•damages both by burying them •hazards to aircraft leading to cancellation  •blocks the sun, affecting plants
Pyroclastic Flows	•very fast 400mph and hot 1000 •hot material travelling fast down slopes •white-hot glowing ash cloud	•impossible for people to outrun •destroys and kills the environment •destroys buildings
Lateral Blasts	•a volcano explodes sideways •can wreck a 40km radius	•destroys property and nature
Lava Flows	•flowing lava that’s very slow allowing for escape by molten rock	•destroys building and nature
Volcanic Gases	•gases are released and can go downhill •carbon dioxide and poisonous gases are also released	•suffocation of people •lung disease •poisonous
Lahars	•ash mixes with water and travels downstream •mud water is very dense and destructive	•density means buildings, roads and bridges are all washed away •can crush and kill people
Acid Rain	•sulphur dioxide and hydrogen sulphide is released	•damages buildings and ruins rock structures •effects ability of plant and animal species to survive
Post Eruption Disease and Famine	•chaos, disruption and disease	•disease is caused by disruption of homes, roads and services means famine and disease especially in LEDC’s
Tsunami	•a massive, distinctive wave •the collapse of volcanoes into the sea can cause a tsunami	•chaos, wreckage and death