Talk:Lava

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This is the talk page for discussing improvements to the Lava article.
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[edit] High iron lavas

No mention is made of the fact that both aa and pahoehoe are strictly high-iron lavas, which are much less viscous than high-silica lavas. Ideally I'd like to see a chart of the ferromagnesium silicate range (from ultramafic to ultrasilicic), identifying the ranges which produce each type of lava. Also, the section 'composition of lavas' is not actually about the composition of lavas. It should be. --Leperflesh 01:09, 7 December 2005 (UTC)

[edit] Compositions

I added a new section at the beginning to describe compositions of lava, and made the discussion of mafic lava flows a subsection of that. I also renamed the section about rocks formed by lava, and removed from it the extraneous comments about the use of obsidan and how pretty the rocks of vesuvius are. That discussion properly belongs in articles about igneous rocks, their types, and uses... not an article about lava.--Leperflesh 22:43, 28 December 2005 (UTC)

The section on composition of lava is particularly poor, and needs more work. The section explaining the physical behaviour of lava misses the whole point, namely composition + temperature = viscosity. Will have to deal with this at some stage. Rolinator 23:52, 23 January 2006 (UTC)

I think it is trying to say that, but is too much of an outline presentation and missing some temperature facts. - Marshman 01:22, 24 January 2006 (UTC)
I should have been doing a report at work. Instead, I fixorised the composition section. I think, basically, whoever wrote most of the previous stuff was fixated on Hawaii, which is fair enough for Americans, but there were some sever factual errors, for instance that phenocryst size implies long cooling times (it does not; equigranular, phaneritic texture implies this), that magma is composed primarily of Si, Fe & Mg (ignoring the fact its the aluminosilicates which predominate, not Fe-Mg-Si which is olivine), and didn't seem to have learned in the HVO that aluminosilicates form highly polymerised melts, which is the primary cause of viscosity in magmas. So now it's fixed. Its long, wordy, technical, I do admit that. And because I'm an Aussie, I only know of definite sheeted flows from Australia. But I'm sure there are others around the world.
Chin-chin! - Rolinator 05:58, 24 January 2006 (UTC)
Actually, a very good contribution. Where it needed to be taken. - Marshman 21:32, 26 January 2006 (UTC)
I'm afraid I introduced a couple of those errors; I'm glad you've fixed them (sorry about your report!). I've done a copyedit, linked most of the new technical terms, and fixed a couple of tiny problems. I still don't like the prose beginning with 'Lava Formations' and including the subsection 'Lava cascades and fountains'. It's written in a romantic style that doesn't fit with the scientific-orientation of the rest of the article. I want to remove the enitre paragraph beginning with 'There are few things not made of rock that can resist...' - it just feels inappropriate. Anyone else agree? --Leperflesh 22:46, 27 January 2006 (UTC)
I suspect some of that prose may be old 1911 Encyclopedia stuff, meant to be deleted (in my mind) as soon as we can get our own stuff together - Marshman 23:30, 27 January 2006 (UTC)
Landforms is done. I left the cascades bit because its so poetic! No, actually, I ran out of terminology and give a shit factor. There's also another term for the cones formed by liquid lava...but it escapes me right now. And besides, a fountain of lava is hardly a landform or a formation, its more an event. Meh. Rolinator 02:40, 28 January 2006 (UTC)
  • Sometimes, you know, vandals can prompt good things. Rarely. This was the idiot who added in lava lamp; thanks, anonymous moron, it is a useful illustration of the process of diapirism.Rolinator 07:02, 1 February 2006 (UTC)

[edit] Composition vs flow morphology

Following up on Leperfish's comment of nearly a year ago, I notice that in the article, Pāhoehoe is noted as "basaltic", and that under certain flow conditions it can turn into 'a'a. Nothing is stated about the composition of 'a'a, but this statement about Pāhoehoe implies that 'a'a is also basaltic. The third kind of lava mentioned is pillow lava, with no mention of composition.

But the section on lava composition seems to be quite at odds with this; mafic, ultramavic, felsic, etc; are all these basaltic? Not clear as it appears the the basalt composition distinguishes these. Can any of these compositions be found in the form of 'a'a? Of Pāhoehoe? Of pillow lavas? Or is the composition independent of the form? Not being a geologist I don't know the answer.

Is the problem here due to the "volunteer" mention of "basaltic" in the discussion of Pāhoehoe? I think that this needs to be clarified...does form follow composition, are they somewhat independent, or completely independent, or what?

I'll leave it to you experts to resolve this. Bill Jefferys 23:09, 14 October 2006 (UTC)

Done; its in the lava viscosity section. Well spotted. But just in case it's still opaque, yes, pahoehoe, a'a and pillow lava are basaltic flow morphology. Rolinator 00:05, 15 October 2006 (UTC)

[edit] Ol Doinyo Lengai

• Ol Doinyo Lengai is an active volcano in Tanzania. According to National Geographic (January 2003 p.44) the lavas at the site "have the lowest viscosity of any lava, roughly the same runniness as olive oil." IMO, this information should be included into the article, but I'm not sure where to put it. There is a good section on the chemical composition of different lavas but I (with my limited knowledge on this topic and the English language) can't find any information explaining why the lava at Ol Doinyo Lengai got approximately the same viscosity as ultramafic lavas at half the temperature.
• Also, some information about block lava still needs to be included.
/ Mats Halldin 17:55, 25 February 2006 (UTC)

Block lava is pretty much covered by a'a and the sheeted flows sections. Its lava...which is blocky. Its not neccessary to mention it more than that, I think.
Oldinyo Lengai and the carbonatite lavas it produces are difficult to place into this scheme as it stands because it is only one volcano which is a unique example of its class. Basically...if we were to put it in alongside felsic/intermediate/mafic/ultramafic in that scheme we would first have to explain what a carbonatite is. Which is best left to elsewhere, really. What I will do is simply state the unusual lavas in a little section so people can go read about them in their respective areas.

Rolinator 02:06, 26 February 2006 (UTC)

Ok, looks great! Sorry for delayed answer, I still plan to translate this article to Swedish but I'm working seven days a week at the moment.
/ Mats Halldin 05:45, 6 May 2006 (UTC)

[edit] Deaths from lava flow

It is my understanding that a number of USGS scientists have died at deceptively fast lava flows, Any word on speed of flows (which can be pretty fast) or deaths from lava flows. They should be notable considering most deaths in a volcanic eruption are due to ash and noxious gases, and are rarely attributed to lava flow.Angrynight 11:32, 5 March 2006 (UTC)

Uh...not as many as from pyroclastic flows or debris flows and lahars. I think the record stands ar 22,000 for the former from Pelee, and 20,000 from the one in Colombia. Actual lava flows? If you could famine caused by lava covering pastures, it'd be 10,500 in iceland. Otherwise, no idea.Rolinator 01:20, 6 March 2006 (UTC)

[edit] Lava Types

A simple and widley used chemical classification table is available based on the content of Si02 in the lava. This has been recognised by the International Union of Geological Sciences (IUGS) and maybe should be added as it's really easy! It's as followed

  • %Sio2 wt%
  • <53 basalt
  • 53-57 basalt andesite
  • 57-63 andesite
  • 63-67 dacite
  • >67 rhyolite

What do you think?

Morbid amber, thanks. The TAS, normative mineralogy and silica classification of lavas via geochemistry are generally useful for aphanites and porphyritic lavas in which the composition of the rock is not neccesarily abundantly clear. Particularly metamorphic or ancient lavas. As you would well know.
However, yon average wiki user may not be able to look at a rock in the field and say "Yeah, I think it's 62% silica, 11% combined alkalis, and is a trachy-andesite." Which, I would presume, is why the TAS classification system isn't discussed here yet. If you want to, you can ferret out whether or not the TAS or other geochemistry related subjects on lavas are complete, fill in the (gaping) blanks, and link into there from here. Me, I think it's fine as it is at the moment, and until geochemistry pages get a good working up, it is premature to get too complicated on such a general page. Rolinator 05:02, 18 May 2006 (UTC)

[edit] Speed of Lava Flows

I notice the article doesn't elaborate much on how rapidly lava-flows usually move. (There is mention of a few catastrophic incidents ~60 mph). What's the average speed? Are humans usually at risk? I get the feeling that most flows are pretty slow, long-term events, not exactly Hollywood disasters. Any numbers on average flowspeed? Nimur 00:04, 10 June 2006 (UTC)

Google resulted in the USGS description - however, I'm hesitant to cite it (even though it's a reputable source) because I am not a geologist... can someone with expertise verify this information and update the article? Nimur 00:07, 10 June 2006 (UTC)
Aren't they usuallly very slow (<1 km/h)? - jlao 04 07:48, 30 October 2006 (UTC)
The lavas which erupted from Mount Niyarogongo reached 60mph / 97kph, estimated. Mount Pele had similarly catastrophic highly fluid lava; it could have gone just as fast, but no one took stock. Or if they did they probably said "Mon dieu, that ees some fast lava! Sacre Bleu I am dead!"
Komatiite, well, maybe even faster - how fast is a flash flood? It is a highly subjective thing, really; it depends on slope, elevation, volume, viscosity, the roughness of the terrain, any number f things. But most usually, yes, they are fairly slow in their advance across wide swathes of the countryside, but can be much faster if the volume of lava is concentrated into one aperture or valley or tunnel. I personally don't see much real use in putting a figure in there; it will be woefully misquoted and misrepresentative at the best of times. I think it's fine as it is; slow enough you can walk away. Pyroclastics on the other hand...Rolinator 08:37, 30 October 2006 (UTC)

[edit] Good article?

Should this article be nominated for good article status? - jlao 04 07:54, 30 October 2006 (UTC)

I should fricking think so, after all the effort I've put into it, with others of course.Rolinator 08:31, 30 October 2006 (UTC)
Although it was vandalized almost 5 times in a row, it's good enough. Conundrumer 22:22, 19 November 2006 (UTC)
It probably needs more references. --Eyrian 22:50, 19 November 2006 (UTC)

More references and add a section for them. FullMetal Falcon 22:50, 21 December 2006 (UTC)

[edit] Aegirine

Yes, Vsmith, you were right that aegirine was the correct word.[1] That's what it was when I rechecked the original with a magnifying glass. (SEWilco 03:37, 27 December 2006 (UTC))

[edit] Photograph captions

Could someone in the know add the countries to the photograph captions, please? 82.32.238.139 17:07, 15 March 2007 (UTC)

[edit] Lavas indirection

Isn't "lavas" the common name of the spice "Levisticum officinale" ? I'm no native English speaker, so I didn't want to change it. —The preceding unsigned comment was added by 88.159.74.100 (talk • contribs).

I think that would be "lovage". But it seems the common name is indeed "lavas" in Dutch. -- Avenue 09:39, 24 May 2007 (UTC)

[edit] Composition of volcanic rocks

Removed the 1911 section with the above title to the short volcanic rock article. It was redundant with the lava composition here and fits better there. Still in need of re-working there. Vsmith 21:04, 4 August 2007 (UTC)

[edit] Photographs

Great article. However, all but one (possibly two) of the pics are of American lava flows / volcanoes: 11 are from the US, one from Japan and one from an un-named geographical location. This is an international encyclopaedia - I'm sure there must be some available photos of non-Us lava flows that could be used. The bias as it stands is unacceptable. 86.158.131.45 (talk) 17:37, 14 December 2007 (UTC)

Doesn't matter much where the examples are from as long as the subject (a kind of rock) is documented. Try adding a picture request template if more on the subject is needed. What do we need, a photo of the Deccan Traps perhaps? -- SEWilco (talk) 18:13, 14 December 2007 (UTC)
Respectfully, SEWilco, I think it does matter. Lava is found worldwide; the readership of English Wikipedia is found worldwide. A bias towards any one country or area is unfortunate and should be avoided. I'd quote the relevant policy if I could find it. A photo of the Deccan Traps would be great. How about some of lava in Iceland, or Saudi Arabia, or the Phillipines, or Indonesia, or New Zealand? Lots of scope for choice.86.158.131.45 (talk) 10:08, 15 December 2007 (UTC)
You should certainly feel free to find and add public domain or other acceptable images from around the world, if they are more instructive to this article. Personally I don't think the Deccan Traps would be appropriate, as this article is about lava, the fluid form of the material. Hawaii happens to be probably the most accessible location for modern lava flows - hence the abundant photos. It is not because of US bias, but because of a great abundance of excellent examples that have been photographed from Hawaii. Cheers Geologyguy (talk) 15:36, 15 December 2007 (UTC)
Hawaiian lava flows are not only accessible, but relatively safely approachable. And another reason why we can show so many good US photos is that works created by federal employees are in the public domain.
While I don't think it matters too much where each photo is from, a little more diversity in the photos might be more informative. I've added a couple more from outside the US. -- Avenue (talk) 03:01, 16 December 2007 (UTC)

[edit] Vesicles

The article states that highly viscous material tends to entrap gas creating vesicles. However, is it not basalt that tends to have these? Basalt is mafic and much less viscous than felsic rock. If I'm right, this should be corrected. Mais (talk) 00:55, 22 February 2008 (UTC)

Just above the point you criticise, our article says that cool basalt can be highly viscous. I've seen many basalt lava flows which contain few vesicles, except near the top (which was presumably much cooler). It is also not just basalt that can have vesicles; pumice is a good counterexample. -- Avenue (talk) 10:52, 22 February 2008 (UTC)

[edit] Addition to Lava Landforms

Would it also be useful to put littoral cones and tumuli (plural of tumulus) in this section? They're fairly common features at Hawaiian volcanoes. Farristry (talk) 14:25, 30 April 2008 (UTC)