Lecture 5 Volcanos - Lecture5Volcanoes An...

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Lecture 5 Volcanoes
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An oceanic-continental convergent plate boundary
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An oceanic-oceanic convergent plate boundary
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A continental-continental convergent plate boundary
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The San Andreas fault  in southern California Conservative margins Transform faults
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Divergent boundaries are located mainly along oceanic ridges
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The East African rift   a  divergent boundary on land
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Hot Spots ?
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Volcanic eruptions Factors that determine the violence of an eruption Composition of the magma Temperature of the magma Dissolved gases in the magma Viscosity of magma Viscosity is a measure of a material's resistance to flow
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Volcanic eruptions Viscosity of magma Factors affecting viscosity Temperature (hotter magmas are less viscous) Composition ( silica content ) High silica – high viscosity (e.g., rhyolitic lava) Low silica – more fluid (e.g., basaltic lava) Dissolved gases ( volatiles ) Mainly water vapor and carbon dioxide Gases expand near the surface
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Volcanic eruptions Viscosity of magma Factors affecting viscosity Dissolved gases ( volatiles ) Provide the force to extrude lava Violence of an eruption is related to how easily gases escape from magma Easy escape from fluid magma Viscous magma produces a more violent eruption
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Materials associated with volcanic eruptions Lava flows Basaltic lavas are more fluid Types of lava Pahoehoe lava (resembles braids in ropes) Aa lava (rough, jagged blocks) Gases One to five percent of magma by weight Mainly water vapor and carbon dioxide
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This note was uploaded on 10/22/2008 for the course EAS 2600 taught by Professor Ingalls during the Fall '08 term at Georgia Institute of Technology.

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Lecture 5 Volcanos - Lecture5Volcanoes An...

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