Dear Michel, cher Michel,

have a look at

Hi Volker,

Thanks for your info.

I also find: Fink, J. H., & Griffiths, R. W. (1998). Morphology, eruption rates, and rheology of lava domes: Insights from laboratory models.

Journal of Geophysical Research: Solid Earth (1978–2012), 103(B1), 527-545.

Cheers.

Best wishes.

Michel

I have done research on a widespred tonstein (altered volcanic ash deposit), i.e. the Fire Clay  tonstein of the Appalachian Basin.  What is preserved covers a large area a of the original deposit that had to be much larger.  As preserved now it covers (in part) four states. Of course it is a widespread stratigraphic marker. The magnitude of the eruption can be measured by the chemical composition of the glass inclusions in the volcanic quartz.  The original volume of the magma that was erupted from  the magma chamber can only be surmised but not accurately. estimated . In  my opinion the amount  of volcanic ash that was erupted from the explosive silicic  volcano had to be considerable. I have no doubt that it was more than 50% because it was a highly explosive volcanic ash eruption. In fact, we have presented evidence that the  aidic volcanicash is found iin the MidContinent of Arkansas. I could send you articles and references, if you like.

Best wishes, Paul Lyons.

Hi Paul,

Thanks for your email.

Yes please send me your paper.

In fact there is some sort of consensus around 10% but I do not understand the rational! That is the reason of my question. For example in Wikipedia (French) you find a sentence saying that 'the volume of the eruption is never more tan 10% of the capacity of the magma chamber'.

https://fr.wikipedia.org/wiki/Chambre_magmatique

"Lors d'une éruption volcanique, la fraction de magma qui s'épanche sur la surface terrestre reste très modérée, ne dépassant pas en général quelques pourcents du volume de la chambre superficielle. Si la vidange atteint de l'ordre de 10 %"

I decided to try to understand more as I do not see any reason especially in big pyroclastic eruptions. So I am now looking for numbers. Of course it is not certain i.e. we do not know the exact size of the magma chamber and we do not know the exact size of the DRE... but we can make reasonable assumptions.

Thanks for your help.

Cheers.

Michel

yes, Michel I will do that as soon as  possible. Best wishes, Paul.

Maybe this book will be helpful for you?

Regards,

Tamara

Tamara,

Many thanks! Certainly very useful.

Cheers.

Michel

Hi Michel,

The geological contention you describe is a purely empirical relationship (with a very high degree of uncertainty) due to work carried out by the USGS during the 1960 and 1970’s by Robert L Smith and co-workers. They collated measurements of the area, erupted ash flow volume and estimated magma chamber volume of calderas on the US mainland in the context of evaluating the geothermal potential of recent silicic eruptive centres, and published the results in a series of USGS professional papers.

Smith (1979, p.8) has the following:

“Because caldera areas span approximately four orders of magnitude, whereas magma chambers that support calderas have a thickness range of perhaps less than one order of magnitude, the volumes of silicic magma chambers can probably be approximated within one order of magnitude if their areas are known. Smith and Shaw (1973, 1975) further suggested that not more than about one-tenth of the chamber volume is erupted during any one pyroclastic eruption. The validity of the assumption in a gross sense seems clearly supported, but the degree to which estimates can be refined is, at present, problematical. We think the volume estimates for silicic magma chambers can be accurate within half an order of magnitude if data on area and ejecta volume are reliable. A first approximation may be obtained by assuming a chamber volume one order of magnitude greater than the volume of the products of the caldera-forming eruption”.

Spera (1984, p.8223) has the following:

“Based on observed sizes and shapes of large mesozonal to catazonal plutons, it has been suggested that during catastrophic ash flow eruptions, less than about 10% of the volume of the chamber is evacuated (Smith and Shaw, 1973,1975)”

Unfortunately, neither of Smith and Shaw’s papers referenced above (the 1973 paper is actually a conference abstract) actually contains the key data (erupted volume) that directly provides support for the 10% volume limit. However it seems clear that Smith and Shaw were drawing on a sizeable body of unpublished USGS data as well as the published tabulations.

Hope this helps

Regards,

Graham

Smith, R. L. "Ash-flow magmatism." Geological Society of America Special Papers 180 (1979): 5-28

Smith, R. L., and Shaw, H. R., 1973, Volcanic rocks as geologic guides to geothermal exploration and evolution: EOS [American Geophysical Union Transactions], v. 54, p. 1213.

Smith, R. L., and Shaw, H. R 1975, "Igneous-related geothermal systems", in White, D. E., and Williams, D. L., eds., Assessment of geothermal resources of the United States—1975: U.S. Geological Survey Circular 726, p. 58-83.

Spera, Frank J. "Some numerical experiments on the withdrawal of magma from crustal reservoirs." Journal of Geophysical Research: Solid Earth (1978–2012) 89.B10 (1984): 8222-8236.

Hi Graham,

Thanks for your answer.

Unfortunately the references are quite old. In my understanding today the relation is not as empirical as you said. There are relations between mass fluxes, size of the bubbles, exsolution ... and it is possible to get some order of magnitude.

Still looking for it.

Cheers.

Michel

Hi Michel,

Yes, I agree with you that there must be a multifactorial causal relationship between maximum eruption volume and caldera size/area. However, hopefully you now understand the origin for the "rational" for the 10% value and can appreciate how poorly constrained that value must be, which I think answers the questions you posed in the first instance.

I'll try to get back to you with some up-to-date relevant research on eruption volume controls in the context of your question.

Best Wishes

Graham

Hi,

Yes we now know the rational of the 10%.

Many thanks.

Cheers.

Michel

I think that the ultraplinian, rhyolitic, high-silica explosive eruptions, which spread volcanic ash over large distances, have to be over 50% of the magma in the magma chamber.  It would no make any sense otherwise.  Although only partly preserved due to unstable depositional areas, the amount of volcanic ash produced from the caldera had to be enormous.

Hi Michel

Further to you request for pointers to current research on this topic, I would suggest you take a look at the recent review article by Cashman and Giordano (2014) and in particular Section 4 on “Storage and eruption from Large Silicic systems”. Subsections 4.4 and 4.5 deal specifically with the controls on eruption in the context of different magma storage models, magma reservoir geometries and eruption triggers. The supplemental spreadsheet contains a world-wide tabulation of caldera characteristics including area and collapse heights and eruptive volumes. Of direct relevance to your original query are examples where eruptions of 100% of estimated total magma reservoir volume are noted. 

Best regards,

Graham

Cashman, Katharine V., and Guido Giordano. "Calderas and magma reservoirs." Journal of Volcanology and Geothermal Research 288 (2014): 28-45.

Hi Graham,

Excellent paper. Many thanks.

Best regards.

Michel