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volhaz-pred - Volcanic Hazards and Prediction EENS 2040...

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This page last updated on 26-Sep-2011 EENS 2040 Natural Disasters Tulane University Prof. Stephen A. Nelson Volcanic Hazards This lecture will begin with a video entitled "Understanding Volcanic Hazards". This video was prepared by the International Association of Volcanology and Chemistry of the Earth's Interior in several languages, and was designed show people living in the vicinity of volcanoes the possible effects of an eruption. Although the terminology may vary slightly from what we have learned in this course, the effects are the same and the footage of volcanic eruptions in progress is spectacular. The video is dedicated to the 23,000 people who died as a result of mudflows (lahars) from the 1985 eruption of Nevado del Ruiz volcano in Colombia, and is intended to help prevent similar disasters in the future. The video covers: z Ash Falls (tephra falls) z Hot Ash Flows (pyroclastic flows) z Mudflows (lahars) z Volcanic Landslides (debris flows and debris avalanches) z Lava Flows z Volcanic Gases Primary Effects of Volcanism z Lava Flows { Lava flows are common in Hawaiian and Strombolian type of eruptions, the least explosive. { Although lava flows have been known to travel as fast as 64 km/hr, most are slower and give people time to move out of the way. { Thus, in general, lava flows are most damaging to property, as they can destroy anything in their path. { Control of lava flows has been attempted with limited success by bombing flow fronts to attempt to divert the flow, and by spraying with water to cool the flow. The latter is credited with saving the fishing harbor during a 1973 eruption of Heimaey in Iceland. Volcanic Hazards and Prediction 9/26/2011 Page 1 of 11
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z Violent Eruptions and Pyroclastic Activity { Pyroclastic activity is one of the most dangerous aspects of volcanism. { Hot pyroclastic flows cause death by suffocation and burning. They can travel so rapidly that few humans can escape. { Lateral blasts knock down anything in their path, can drive flying debris through trees. { Ash falls can cause the collapse of roofs and can affect areas far from the eruption. Althoughash falls blanket an area like snow, they are far more destructive because tephra deposits have a density more than twice that of snow and tephra deposits do not melt like snow. { Ash falls destroy vegetation, including crops, and can kill livestock that eat the ash covered vegetation. { Ash falls can cause loss of agricultural activity for years after an eruption, a secondary or tertiary effect. z Poisonous Gas Emissions { Volcanoes emit gases that are often poisonous to living organisms. Among these poisonous gases are: Hydrogen Chloride (HCl), Hydrogen Sulfide (H 2 S), Hydrogen Fluoride (HF), and Carbon Dioxide (CO 2 ). { The Chlorine, Sulfur. and Fluorine gases can kill organisms by direct ingestion, or
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volhaz-pred - Volcanic Hazards and Prediction EENS 2040...

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