40 minutes read
From the ashes: a 150th anniversary review of the Askja-1875 tephra
Funders:
Stockholm University
Language:
English
Reviews
Version 2
David Lowe
General comment:
Alice Carter-Champion
General comment:
Version 1
Alice Carter-Champion
General comment:
Sections comments:
Where there’s smoke: discovering a volcano
Alice Carter-Champion: The scene setting is really great, but it would be helpful to also have a map of Iceland, to help contextualise some of the places that you mention - either a reproduction of one of the historical maps that I'm sure exist, or a modern one!
irst mapping of the crater-depression and the plain of Askja by Lieutenant Caroc of the Danish Navy
Alice Carter-Champion: Again, this sounds very interesting, is there any chance to reproduce/photograph this and include it?
which in
Alice Carter-Champion: which began in?
separate plumbing systems
Alice Carter-Champion: three separate plumbing systems you mean? Askja, northern lava flow, southern lava flow? Or two plumbing systems, one for the explosive stuff and one for the effusive lava flows?
produce a map of the ashfall
Alice Carter-Champion: Again, would be really nice to include a reproduction of this if it's possible!
Figure 3:
Alice Carter-Champion: It would be nice to include the proximal data from Askja-1875 from Meara, R.H., Thordarson, T.H., Pearce, N.J.G., Hayward, C. and Larsen, G., 2020. A catalogue of major and trace element data for Icelandic Holocene silicic tephra layers. Journal of Quaternary Science, 35(1-2), pp.122-142.
Figure 4:
Alice Carter-Champion: It's interesting that there is a clear distinction based on Na2O for the samples from Borge (I think?) - could there be some issue of sodium migration? Or a different probe used compared with the other data?
The reason for the Lake Getvaltjärnen subgroup’s separation from other Askja-1875 tephra findings thus remains uncertain.
Alice Carter-Champion: Maybe it would be nice to mention the potential for trace elements to distinguish whether this is the case or not?
David Lowe
General comment:
Sections comments:
David Lowe: Excellent topic and abstract
1830’s,
David Lowe: 1. Remove appostrophe 1830s 2. 'widened to a caldera' - is this a true caldera which is a major collapse feature (that arises because of large volume of ejecta, unlike a crater). Please check and reword to 'large crater' if appropriate.
David Lowe: Add space before 'N' and 'W' lat/long
David Lowe: Lake level must fluctuate with evaporation etc hence suggest add approximately or similar
David Lowe: This scenario has, however, been...
David Lowe: although
David Lowe: interpretation ie This interpretation has been
was
David Lowe: were
Thi
David Lowe: This process caused...
David Lowe: Please record if the volume estimates are as loose material or dense rock equivalence
migration
David Lowe: insert 'human' ie affected human migration (initiallly I read this as volcanic migration)
Öskjagá caldera
David Lowe: Ok it seems it is a caldera
David Lowe: add comma after Sweden
This
David Lowe: This pattern of deposition was in agreement...
ash particle
David Lowe: examined ash particles (i.e. glass shards) under...
David Lowe: ash particles is misleading here as 'ash' is a grain size term technically - the particles in the image are glass shards and should be described as such. Also, in more proximal deposits 'ash particles' can also contain crystals and lithic fragments, not just glass, So the term 'ash particle' is not synonymous for glass particles.
David Lowe: ....becoming dark or black
David Lowe: delete 'the'
David Lowe: Although modern geochemical analyses were unavailable at the time, tentative..
David Lowe: in, for example,... add commas
David Lowe: Need to note if the values are normalised or not
David Lowe: use 'locations' rather than 'findings'
David Lowe: now referred to as...
lkali-Silica
David Lowe: alkali-silica
it is
David Lowe: I am
).
David Lowe: Could add here if desired a citation Lowe et al., 2017 QSR Lowe, D.J., Pearce, N.J.G., Jorgensen, M.A., Kuehn, S.C., Tryon, C.A., Hayward, C., 2017. Correlating tephras and cryptotephras using glass compositional analyses and numerical and statistical methods: review and evaluation. Quaternary Science Reviews 175, 1-44.
his
David Lowe: relationship
entred log-ratio transformed published Askja-1875 tephra major-element oxide compositions,
David Lowe: compositions of glass shards, as principal.... (add 'glass shards' as they were analysed, not whole tephra)
data
David Lowe: selection of glass-shard analytical data...
of
David Lowe: delete 'of'
David Lowe: than to the majority...
David Lowe: ..measured contents of
David Lowe: Could insert sentence before "Looking..": Problems in analysing Na2O in glass using the electron probe, usually showing reduced totals, have been well documented (e.g. Lowe et al., 2017)
ll numbers presented as weight percentages.
David Lowe: Need to add that data are normalised.
Pub
David Lowe: Also add after percentages... All iron represented as FeO.
Looking
David Lowe: Before "Looking.." could insert sentence That Na2O totals are somewhat low reflects the well known problems associated with the analysis of glass shards using the electron microprobe (e.g. Lowe et al., 2017).
ephra shards
David Lowe: tephra-derived glass shards the shards are not "tephra shards", they are glass shards
first detailed ash dispersal ma
David Lowe: first for Icelandic tephra or globally?
David Lowe: ...geochemical analyses of glass from the ...
David Lowe: ..raw data (i.e. not normalised) from...
David Lowe: ..tephra-derived glass-shard major...
David Lowe: ..tephra-derived glass-shard
David Lowe: tephra-derived glass-shard
David Lowe: ..raw glass-shard analytical
Reviewers:2