EESA06H3 Lecture 6: EESA06 Lec6

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13 Feb 2016
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->>>> Natural Disasters
-earthquakes are not very easy to predict, the technology does not exist
->Hazard: something that THREATENS HUMAN INTERESTS
->Risk: how SEVERE a hazard is going to be esp. taking into consideration the human impact (poor communities
vs. rich communities; social vulnerability)
->Disaster: a hazard that affects a SPECIFIC AREA
-Catastrophe: a hazard that affects a LARGE AREA AND MORE PEOPLE
->Two energy sources that drive natural disasters:
-the sun (external source)
-heat from inside the earth (internal source)
->Magnitude-frequency Concept
-large disasters are uncommon, small hazards are frequent
-the larger the disaster, the less likely it is to occur
->>>Volcanoes
-different magmas have different viscosities
-and explosivity is related to viscosity (thick magma = trapped gases = explosive; intermediate to felsic magma)
-the big bad volcanoes come from subduction zones.
->Hazards:
-ash destroys engines and airplanes, destroys homes (can be meters thick near the volcano but it can travel quite
far, even blocking out the sun)
-lava flows are not much of an issues because you can usually just move out of the way
-climate change: send out gases(some are toxic and deadly and cling to the ground and aerosols(result in
cooling) into the atmosphere
-earthquakes: as the magma is rising, the ground may start to shake.
-landslides: esp the big volcanoes are very unstable.
-lahar vs. pyroclastic flow: Lahar can happen at any time and are cold or hot; are superconcentrated mudflows
whereas pyroclastic flows only happen during an eruption and are caused by hot gas mixed with volcanic
sediments
-volcanic explosively index (measures the volume of tephra(ash))
-tiltmeters: measure the tilt/bulge on the side of the volcano
->TYpes of volcanoes:
-composite volcanos: layers of ash and lava
-sheild volcanos: Huge
-cindercones: much smaller
->How to monitor volcanoes:
-seismic activity
-gas output (changes in type of gas)
-heat flow (if its getting hotter, magma is close to surface)
-topography (looking for bulges)
-mudflows (lahars)
-hydrology (surface water and ground water temp, if increasing then maybe magma is flowing up)
-satellites (to monitor remote volcanoes)
->Volcanoes are driven by plate tectonics and mantle convections
->Four tectonic settings of volacnoes:
-continental rift volcanoes
-continental volcanic arc
-hot-spot volcanoes
-volcanic island arc
->volcanoes mostly occur on plate boundaries (all types have shallow earthquakes, only subducting plates have
deep earthquakes)
->The Richter Scale: measuring the strength of earthquakes
->What causes earthquakes:
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