eruption columns
DESCRIPTION
Eruption Columns. Jon 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 - PowerPoint PPT PresentationTRANSCRIPT
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.