volcanoes usgs volcanoes hazards explosive eruption: mt. saint helens
TRANSCRIPT
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Volcanoes
USGS Volcanoes Hazards Explosive Eruption: Mt. Saint Helens
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VolcanoVolcano: A vent or fissure in the Earth’s surface through which magma and gases are expelled.2 Types Explosive and Nonexplosive.
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I. Volcanic EruptionsA. Volcanic eruptions are both destructive and
constructive forces.
Destructive because they can cause mountains to collapse, and scorch forests and wildlife in surrounding areas.
Constructive because they can help form fertile farmland and create large mountains.
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Where Do Volcanoes Form?
National Geographic: Forces of Nature Slide 3-4
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II. What Makes up Magma?
A. Composition of magma affects how explosive a volcanic eruption can be.The main components of eruption are:
Dissolved Gases (Water Vapor)
Viscocity (Silica Content
National Geographic: Forces of Nature Slide 5-6
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B. Viscosity The viscosity of magma, or how the lava flows,
varies greatly.
Viscosity: a liquids resistance to flow.
The more silica that is present in magma, the greater the viscosity of the magma.What has a higher viscosity
water or maple syrup?
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Magma erupts as lava or pyroclastic material.
A.Explosive eruptions produce
mostly pyroclastic material.
Eruption of Mt. Saint Helens
III. Types of Eruptions
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III. Types of EruptionsB. Nonexplosive eruptions
produce lava.