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Week 9 Lecture 1 GEOG 2200 2012 Notes.docx

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GEOG 2200
John Milton

Page1Week 9 Lecture 1 Climate Change TodayGEOG 2200 2012How do we see climate change How do we picture extreme weatherLast week Typhoon Haiyan struck the Philippinesthe strongest storm ever to be recordedIs this a preview of what is to come For the mass majority of scientists there is no question that our climate is changing Why are climate is changingwhile again the vast majority of scientists studying our climate seem to agree that it is being triggered by human actions that is it is anthropocentricremains a topic of some debate But we will leave this to next Thursday Today we will look at what is taking place around the world and to consider the implications of these changesDistinguishing between Nature and Humaninduced DisastersCan these be distinguished or are they somehow increasingly interconnected While there are clear examples of a natural disastervolcanic eruptions earthquakes tsunamisand there are examples of humaninduced disasterslandslides caused by hillsidemountainside deforestation flooding caused by changes in watershed in many cases the line blurs Disasters are often amplified by human conditions Where do natural disasters end and humaninduced disasters beginConsider the Indian Ocean Tsunami of 2004 How does a tsunami occur A tsunami is a large ocean wave that is caused by sudden motion on the ocean floor This sudden motion could be an earthquake a powerful volcanic eruption or an underwater landslide The impact of a large meteorite could also cause a tsunami Tsunamis travel across the open ocean at great speeds and build into large deadly waves in the shallow water of a shorelineSubduction Zones are Potential Tsunami LocationsMost tsunamis are caused by earthquakes generated in a subduction zone an area where an oceanic plate is being forced down into the mantle by plate tectonic forces The friction between the subducting plate and the overriding plate is enormous This friction prevents a slow and steady rate of subduction and instead the two plates become stuckAccumulated Seismic EnergyAs the stuck plate continues to descend into the mantle the motion causes a slow distortion of the overriding pelage The result is an accumulation of energy very similar to the energy stored in a compressed spring Energy can accumulate in the overriding plate over a long period of timedecades or even centuries Earthquake Causes TsunamiEnergy accumulates in the overriding plate until it exceeds the frictional forces between the two stuck plates When this happens the overriding plate snaps back into an unrestrained position This sudden motion is the cause of the tsunamibecause it gives an enormous shove to the overlying water At the same time inland areas of the overriding plate are suddenly loweredTsunami Races Away From the Epicentre The moving wave begins travelling out from where the earthquake has occurred Some of the water travels out and
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