Eruption ColumnsJon Peterson, Taylor Witcher, Casey Duncan

Basic Features of an Eruption Column

Divided into three parts:• Gas thrust region• Convective region• Umbrella region

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

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

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

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

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

Eyjafjallajokull Eruption Column• Eruption

column heights varied.• Three distinct

phases of eruptive style and column height.

April 14th-17th

• Mainly phreatic eruptions.• Column

reached maximum height of ~8-10 km.

April 14th-17th

April 18th-May 4th• Magmatically driven

eruptions.• Column heights varied

between <1 km to ~6 km.• Coarser ash during

this period.

May 5th-18th• Explosive

activity increased in this period.• Column height

reached between 4-6 km, and as high as 8-9 km.