Talk:Azolla event

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Former good article nominee Azolla event was a Natural sciences good articles nominee, but did not meet the good article criteria at the time. There are suggestions below for improving the article. Once these issues have been addressed, the article can be renominated. Editors may also seek a reassessment of the decision if they believe there was a mistake.

first time in its history?[edit]

The article states "This drop initiated a global temperature decline which continued for millions of years; the Arctic cooled from an average sea-surface temperature of 13 °C to today's rather frostier −9 °C,[3] and the rest of the globe underwent a similar change: for perhaps the first time in its history,[9]".

The last phase "for perhaps the first time in its history" is speculative, and it is widely believed (though not yet proven) that the earth went through much colder period around 600 million years ago - see Snowball Earth. It is quite likely that the Earth went through cooler periods before, as our Sun is gradually warming up as it progresses through its life cycle, going Nova in about 5 billion years.

I suggest deleting that phrase.

--J987 17:42, 20 October 2007 (UTC)

I had grappled with the best way to phrase it to a reader unfamiliar with the geological time scale. As per the footnote, it (almost) certainly holds for the Phanerozoic; however, whilst extensive glaciation did occur during the Marinoan, there's no evidence to suggest that it was specifically bipolar (sensu. covering both poles, but not the waters in between). Earlier cold events were unlikely due to the vast quantities of atmospheric CO2, which overwhelms the effect of a "faint young sun". Of course, conclusive evidence is unlikely to be forthcoming. Verisimilus T 19:31, 21 October 2007 (UTC)

Okay - I take your point.

--J987 16:39, 25 October 2007 (UTC)

Taking my cue from other science related articles on wikipedia, I would suggest that the immediate accessibility of the article is of less importance than that the information is complete, specific, and thoroughly verified. For example, wikipedia articles related to the evolutionary development of animal orders regularly refer to anatomical data that is not readily understandable to those who haven't studied biology or anatomy. The lack of accessibility in those cases, however, is offset by assiduously linking inaccessible terms to their corresponding wikipedia entries. Noclock (talk) 21:25, 11 March 2009 (UTC)

gamma spike[edit]

The article uses the term "gamma spike" without defining it, and there is no article at gamma spike.--76.81.180.3 22:01, 20 October 2007 (UTC)

Replaced with gamma radiation spike. Better? Verisimilus T 19:31, 21 October 2007 (UTC)
But what does "This organic matter can also be detected in the form of a gamma radiation spike" mean? The fossil plants emit the "spike"? There was an external "spike" that shows up in the fossils? Thanks. Saintrain (talk) 12:47, 10 September 2008 (UTC)
It would be a borehole logging spike. When a graph of the intensity of gamma rays is plotted against depth down the borehole, a spike appears on the graph, probably due to accumulation of some radioactive material in the organic matter - perhaps uranium. Graeme Bartlett (talk) 13:11, 10 September 2008 (UTC)
Thanks Graeme. Is that a standard technique? <rephrase> What would such a technique usually be used for? What's it called? How should that info be phrased for the article? Cheers Saintrain (talk) 23:21, 10 September 2008 (UTC)
Well (no pun) what do you know. WP has an article on it. Saintrain (talk) 23:23, 10 September 2008 (UTC)
In case you dont get the pun the articles are Gamma ray logging and well logging. Graeme Bartlett (talk) 01:41, 11 September 2008 (UTC)

Icehouse Earth[edit]

The terms "Greenhouse-" and "Icehouse" Earth are widely used to mean "periods in earth history that were continually free of ice / affected by ice ages". Hence I'm not sure the wikilinks and change to "temperate" are ideal. Verisimilus T 19:31, 21 October 2007 (UTC)

Good point. Nigholith 19:51, 21 October 2007 (UTC)

Very worthwhile & well-constructed article, maybe let down by first footnote[edit]

The 8m (or 20m) thickness of the Azolla layer isn't externally cited in the article. That means that the first footnote comes across as a bit deceptive. I can't easily find the evidence for this, so it might count against the articles verifiability (although its a minor point, its the first point presented).

Also, is 'unit' a clearer name than 'layer' or 'stratum'? --Wragge 12:54, 3 November 2007 (UTC)

GA Review[edit]

The article is quite interesting, and mostly reasonably well written (though a good copyedit couldn't hurt, as there's a couple of grammatical and spelling issues). However, I think it falls short of the Good Article criteria with respect to completeness. Most of the article's sections are very short, and the 'alternative explanations' section is but a single sentence. The 'economic' section is also a bit short, only connecting the azolla fossils to oil. Are there any other implications, economic or otherwise, from this. More could possibly be added about the connection of this research with global warming?

The article is also overall insufficiently cited; several of the inline citations are actually just footnotes, and do not satisfy verifiability requirements.

  • Possible spelling error: sceptical --> skeptical. Although the "sc" spelling could be a british variant? Double check this.
  • Some of the section headers could be simplified. For example, 'Geological evidence of the event' could be shortened to simply 'Geological evidence'; 'Conditions encouraging the event' could be shortened to 'Favorable conditions' or something. It might also help to tie the first three sections into one single main 'history' section, since they're all somewhat connected together.
  • Why is 49 million years linked to Template:Timeline Geological Timescale? It's a bit awkward to link to a template by only putting the link in a single number. I think it would make better sense, and provide far more context to the article, to remove this link and put the template at the bottom of the article, so readers get a better sense of where this event occurs in relation to global geological history.

Hope this helps improve the article. Like I say, it's quite interesting, but the biggest issue right now is completeness. I think more info needs to be added, and appropriately sourced, before this can be a Good Article. Good luck! Dr. Cash 21:03, 3 November 2007 (UTC)

Thanks for your review! Yes, sceptical is the British spelling for the word. The template is somewhat bulky to add subtly to the end of the article, so I'm not sure what to do here: linking the number follows the fad of linking years to pages about what happened during that year. A collapsed version may be appropriate but the templates involved in this still have some issues I'm trying to iron out. I can't really think what else can be said about the economic impact; the connection with global warming, or indeed cooling, seems to me to be spelt out in the "global effects" section.
I agree that more citations would be well received; the footnotes are intended to be no more than notes which would disrupt the flow of the text.Verisimilus T 13:36, 10 November 2007 (UTC)

On a related note, I find the article on the Paleocene-Eocene Thermal Maximum to be excellent in terms of citations and completeness. Perhaps it could be used as a template for improving this article, especially since many of its sources directly relate to the Eocene climate and could help to put this event in context and lead to more specifically Azolla event literature. Noclock (talk) 20:42, 11 March 2009 (UTC)

Icehouse Earth conflict[edit]

I highly doubt that the azolla event created an icehouse condition that would last for 49 million years. the Template:Geologic time scale even shows there was at least one greenhouse earth (during the oligocene) between the Azolla event and today's current icehouse earth/ice age. The Icehouse earth article states the present icehouse earth conditions started 1.6 million years ago. I'm going to update the template to show that, but i'll leave this page alone. However, i would like some input from the wiki community on this for consistency among articles. RingtailedFoxTalkContribs 02:39, 25 January 2008 (UTC)

I think you are confusing icehouse earth and ice ages. An icehouse earth is a period in which glaciation can occur. I've undone the mistaken (I think) edit to icehouse earth; however, if you can find papers which do contradict the ones cited in this article, then it would certainly be worth placing details of the controversy in the icehouse earth article. Verisimilus T 08:58, 25 January 2008 (UTC)
Possibly, but from my understanding, an icehouse earth is the climate where ice ages take place, but does not mean they will (such as during long interglacials), which is what you said. Thanks for clearing it up. i'll see if the geologic time scale template needs any re-calibrating to come back inline with the new edits. RingtailedFoxTalkContribs 19:19, 25 January 2008 (UTC)

Cenozoic Cooling[edit]

To me it seems like the Azolla event should be characterized as akin to the Uplift "Hypothesis" as possible explanations for Cenozoic Cooling which is usually cited as starting about 40 - 50 million years ago. They are both very interesting hypotheses that deserve serious note and are generative and explanatory of important climate change concepts.

71.123.91.180 (talk) 22:19, 27 July 2008 (UTC)

Are you able to point out a source which states that the Azolla event may not have caused cooling? If so, this change should certainly be considered. Martin (Smith609 – Talk) 23:48, 10 September 2008 (UTC)

Misleading and misrepresenting sources[edit]

Are there any scientific sources which unambiguosly states that the Azolla event DID cause cooling, like this wiki entry claims?

The brinkhuis 2006 paper does NOT state that Azolla caused cooling. Neither do as far as I can tell any of the other cited papers. I find only papers which say that the Azolla event, IF real, MAY have reduced atmospheric CO2, and MAY thereby have contributed to the subsequent cooling. See e.g. http://www.soest.hawaii.edu/GG/FACULTY/POPP/Knies_et_al_2008.pdf which conclude that "We speculate that biological CO2 sequestration in the Arctic Ocean and enhanced organic carbon burial rates may have contributed to lower atmospheric CO2 subsequent to the early Eocene climate optimum." (my emphasis)

I also find no support for many other statements, such as that "The event coincides precisely with a catastrophic decline in carbon dioxide levels, which fell from 3500 ppm in the early Eocene to 650 ppm[4] during this event.", and the citation for this "Palynological controls and calibration with the high-resolution geomagnetic reversal record allows the duration of the event to be estimated at 800,000 years" is misleading. Actually both the supplied citations seem intentionally misleading to me.

This whole wiki entry is incredibly tendentious and in dire need of words such as "may", "possibly" and "speculation". 213.112.197.51 (talk) 10:06, 6 April 2009 (UTC)


I agree azolla event took place 49 mln years while the transition between icehouse/greenhouse is almost exactly on the E/O boundary 34mA. Atmospheric co2 levels were well into 1000µ atm after azolla event (eg Thomas 2008, Geology 36, no. 2, p. 191-192). The significance of findings is that there was almost no influx of warm water from atlantic during that 800ky interval rather than being the main cause of greenhouse/icehouse transition.--139.166.227.144 (talk) 20:03, 27 May 2009 (UTC)