Volcanism - Ash Columns

Question 1

What are ash columns

Answer 1

Resultant from explosive solo liv eruptions at destructive margins/ continental hotspot locations when the top of a conduit is breached

Question 2

4 stages of ash Column formation

Answer 2

1) Rising magma reduces pressure at shallow depths, gas bubbles exsolve driving the magma up
2) bubbles grow, forcing material upwards to get more space, travelling at super sonic velocities to explode at fragmentation surface
3) column entrails ambient air heated by rock fragments, ash rises to equal buoyancy height in convective thrust region
4) plume spreads horizontally by winds, blocks and bombs fall - right angle to wind s

Question 3

VEI

Answer 3

Logarithmic measurement

Ash could height depends on VEI which is dependent on magma types and gas

Tephra fall out and ejected form conduit walls

Can view 3D fly by

Question 4

Air problems from ash columns

Answer 4

Ash fragments melt inside planes, corrode and clog up engines
- N America to Asia particularly at risk

Question 5

Example of air problems from ash columns

Answer 5

Indonesia, 1982

From New Zealand lost power in engines and dropped 7.5km

Front panels corroded only 1 left

NO DEATHS

Question 6

Ground problems from ash columns

Answer 6

Blocks and bombs

Close to source can fall on people

Isopachs predictions and show radial manner

Question 7

Ground problems from ash columns example

Answer 7

Tamboura, 1815

VEI 7

61,000 deaths from starvation and disease through crop death and contamination

Question 8

Deposit problems from ash columns

Answer 8

Tephra property destruction underweight

Breathing ash = respiratory problems
Ash = blinds animals, contaminated water and crops

Can mobilise to form lahars and abrasion of machinery

Question 9

Deposited problems from ash columns example

Answer 9

Pinatubo, 1991

VEI 6

Typhoon eruption, ash mixed with water = slurry, concrete roof collapsed

Question 10

Zobin, 2005

Answer 10

Volcan de Colima, Mexico

Most active volcano in Mexico

Done building and destruction, culminating in explosive events

Reached more than 200-220km across
Velocities 50km
Cloud 3860m

Question 11

Forecasting Ash columns

Answer 11

Denlinger, 2010

SEVIRI - enhances infrared images detect Ash

World meteorological organisation examine dispersion and transport = modelling sensitivity and column

Maximum likelihood estimates - include parameters: height, rate, time, altitude, spatial complexity

Icelandic eruption predict and create estimates by SEVIRI and maximum likelihood estimates

Question 12

2010

Answer 12

Denlinger

Question 13

Denlinger

Answer 13

2010

Question 14

1978

Answer 14

Wilson

Question 15

Wilson

Answer 15

1978

Question 16

Wilson, 1978

Answer 16

Controlling ash column heights
AC Height= expresses in total energy required to eject materials to height and ambient conditions

Growth controlled by release of kinetic and thermal energy

Dispersal factors:

1) wind velocity cover eruption
2) variation in wind Iver eruption
3) eruption column height
4) spatial distribution of different size particles in column

Lower part of column mixture dominates motion - modelled as projected slug