Primary volcanic hazards lateral blasts 1 2 4

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Unformatted text preview: tely poisons victims) and sulphur and nitrogen oxides that combine with water to produce acids. Primary Volcanic Hazards: Lateral Blasts 1 2 4 horizontally ____________directed cloud of hot gases and rock particles that explode from volcano at high speed. - bulg on the side of volcano, side colapsed, all the gas and pulverized material escaped - the neck was plugged up with material, weak on side 5 Can develop without warning during an explosive eruption 3 Mt6 Helens St May 18 1980 10 Secondary Volcanic Hazards: - snow, warms, then flow as fluid Debris and Mud Flows - very fast man.. not outrun (more deaths from lahars) Lahar = Volcanic debris (ash + other ejecta) & mud saturated with water flows down slope Common on composite cones Water from melting of snow or heavy rain fall Movement is extremely _____ rapid ; Mt St. Helens lahars > 30 km/hr Forecasting Volcanic Activity: Probabilistic: based on detailed study of active volcanic areas and products of recent eruptions. e.g., Hawaii, Montserrat - not build: around the volcano, downhill, down in valleys - magma comes up, change in shape of the volcano (jelly donut) - Methods based on: Historical records Seismic activity Topographic changes Geochemical indicators Remote sensing Forecasting Methods Historical records: Mapping - provides information on type of volcanism, nature of eruptions, thickness and areal extent of ash distribution - low areas: more likely to be effected - Dating - timing of volcanic events Can estimate average severity frequency and ________ of volcanic eruptions 11 Forecasting Methods Seismic activity: - small earthquakes, magma moving up volcano and gasses too Ex. Mount St. Helens • Earthquakes can mark increase in volcanic activity: • movement of _magma _____ within conduit • movement of gas • rockfalls Forecasting: October 2004 Forecasting Methods Topography: Dome profile and active growth Dome map; elevation change e.g., Montserrat As magma moves up into the magma chamber feeding the volcano, the ground the surface will sw...
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This document was uploaded on 02/25/2014.

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