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Eruption Columns

This article explores the fundamental features of eruption columns, dividing them into three key regions: Gas Thrust, Convective, and Umbrella. The Gas Thrust region initiates the acceleration of pyroclastic material as cooler atmospheric air mixes and heats up. The Convective region sees the column rise due to a lower density than surrounding air, reaching neutral buoyancy. The Umbrella region is characterized by lateral expansion at this buoyancy level. We also examine ash dispersion patterns, maximum height variations, and the eruptive styles observed during the Eyjafjallajökull eruption.

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Eruption Columns

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  1. Eruption Columns Jon Peterson, Taylor Witcher, Casey Duncan

  2. Basic Features of an Eruption Column Divided into three parts: • Gas thrust region • Convective region • Umbrella region

  3. 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

  4. Convective Region • Density of the column is less dense than the surrounding air then the eruptive column rises • The level of neutral buoyancy Mt. Redoubt, Alaska

  5. Umbrella Region • At the level of neutral buoyancy • the column spreads out laterally forming the umbrella region • The degree of lateral expansion is determined by various factors Santa Maria, Guatemala

  6. 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

  7. 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

  8. Eyjafjallajokull Eruption Column • Eruption column heights varied. • Three distinct phases of eruptive style and column height.

  9. April 14th-17th • Mainly phreatic eruptions. • Column reached maximum height of ~8-10 km.

  10. April 14th-17th

  11. April 18th-May 4th • Magmatically driven eruptions. • Column heights varied between <1 km to ~6 km. • Coarser ash during this period.

  12. May 5th-18th • Explosive activity increased in this period. • Column height reached between 4-6 km, and as high as 8-9 km.

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