How can a volcanic eruption's energy be Calculated?

[promeus]

The thread title speaks for itself,I am wondering how I would be able to this.

Ex:

Volcano A erupts

Volcano A yielded 1 kiloton of energy.

^^^How would I calculate that? ^^^

 

[Fewmet]

The thread title speaks for itself,I am wondering how I would be able to this.

Ex:

Volcano A erupts

Volcano A yielded 1 kiloton of energy.

^^^How would I calculate that? ^^^

I have never seen the calculation worked out, but it seems like a good first approximation is to calculate the increase in potential energy of the solid material that emerges used E_p=mgh. You could estimate the mass of the magma/lava from its volume and density (which will vary with magma composition). The change in height would be from the magma chamber to the altitude at which it cools.

More refined calculations could take into the mass of tephra in the plume and the heat lost as the lava cools. I suspect those contributions will not change order of magnitude, and perhaps give the same value to one significant figure.

 

[Astronuc]

There is Volcanic Explosive Index - http://volcanoes.usgs.gov/images/pglossary/vei.php
http://en.wikipedia.org/wiki/Volcanic_Explosivity_Index


I believe that one option is to calculate the volume of Earth ejected from a crater (from before and after pictures) then some assumption of the density is made to calculate the mass and how it was ejected.

More recently - "Explosive Energy" During Volcanic Eruptions from Fractal Analysis of Pyroclasts
http://www.earth-prints.org/bitstream/2122/1820/1/subm revised to epsl_Kueppers et al_fractals.pdf

 

[davenn]

I believe that one option is to calculate the volume of Earth ejected from a crater (from before and after pictures) then some assumption of the density is made to calculate the mass and how it was ejected.

yes that's true
one other link I followed the other day was along those lines

they look at the energy required to lift say 10 cubic km of rock of "x" density to 510m


its gives a reasonably definitive result.

cheers
Dave