Eruption Columns
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Transcript of Eruption Columns
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Eruption ColumnsJon Peterson, Taylor Witcher, Casey Duncan
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Basic Features of an Eruption Column
Divided into three parts:• Gas thrust region• Convective region• Umbrella region
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Gas Thrust Region● Cooler atmospheric air is
mixed into the column ○ the air is heated and
expands● The gas thrust region is
the initial acceleration of the erupted pyroclastic material and gas expansion
● The nozzle velocity Eyjafjallajokull, Iceland
Mount St. Helens, Washington
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Convective Region• Density of the
column is less dense than the surrounding air then the eruptive column rises• The level of neutral
buoyancyMt. Redoubt, Alaska
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Umbrella Region• At the level of neutral
buoyancyo the column
spreads out laterally forming the umbrella region
• The degree of lateral expansion is determined by various factors
Santa Maria, Guatemala
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Ash Dispersal• Max column height of 10
km• Main wind direction at 5
km over crater in a southeast to east direction.• Average wind speed was
20 m/s
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Ash Fallout• Bulk ash fallout volume
for first 3 days of eruption compared to the whole eruption• 0.05-.075 km3 first 3
days• 0.2-0.35 km3
accumulation for whole eruption in Mainland Europe• Total airborne tephra
produced: 270 x 106 m3
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Eyjafjallajokull Eruption Column• Eruption
column heights varied.• Three distinct
phases of eruptive style and column height.
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April 14th-17th
• Mainly phreatic eruptions.• Column
reached maximum height of ~8-10 km.
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April 14th-17th
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April 18th-May 4th• Magmatically driven
eruptions.• Column heights varied
between <1 km to ~6 km.• Coarser ash during
this period.
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May 5th-18th• Explosive
activity increased in this period.• Column height
reached between 4-6 km, and as high as 8-9 km.