Talk:Continental crust
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The crust is mostly andesite not granite
editWhile there is plenty of granite in the upper crust, the composition of the crust is andesitic. The confusion is around the word granitic. Geologist divide the igneous rocks into ocean crust (mafic) and continental crust (granitic or felsic). Granite is one of the much broader class of granitic rocks which include andesite. So saying the continental crust is granitic, while technically accurate is likely misleading for the average reader who may believe that this means the crust is mostly granite. http://www.tos.org/oceanography/issues/issue_archive/issue_pdfs/19_4/19.4_tatsumi_stern.pdf Yes, I know that you can find references that say its granitic, but look to the more fundamental references and there is no disagreement. 96.252.103.113 (talk) 18:43, 11 December 2008 (UTC)
Continental crust not "mostly above sea level"
editThe continental crust extends down 30 km from the land surface and most of it is below sea level. This could be corrected by adding the word "surface". The surface of the continental crust is mostly above sea level. But complete rewriting is probably a better choice. 96.252.103.113 (talk) 22:03, 10 December 2008 (UTC)
Origin
editMore on the origin, please! 213.47.144.254 (talk) 20:32, 6 August 2010 (UTC) I did enter the notion that is entirely possible that the volume of continental crust has not changed much over time. As the article by Armstrong states there is little reason to assume that the differentiation between lighter and heavier minerals did not happen very soon after Earth was formed and also Mars and the Moon show a clear distinction between higher (continental crust) area's and lower area's (oceanic crust) without ever having gone through the process of plate tectonics. So the main effect of plate tectonics on the continental crust might just be the clustering of thin, wide spread sections of crust into the thick proto-continents we call cratons today. The parts of the crust that formed the cratons have a far better chance of survival, become the robust building blocks of plate tectonics, which may explain the age-differences found. I'm not a specialist myself but I do find his reasoning to be very compelling and I do not see how, when Mars has clearly formed a lot of continental crust without plate tectonics, this would not have happened on Earth also (even easier, as Earth would have taken longer to cool to a solid state and thus creating more time for gravity based differentiation). I do wonder though whether the oxidisation of the atmosphere would not create more light (weathered) silicates over time. Or is this being reversed as plate tectonics start to recycle parts of the continental crust?--Codiv (talk) 13:31, 5 May 2021 (UTC)
Article history
editHere is an attempt to sort out the references listed in the article:
- Saal et al. 1998, the first reference added to the article, was added 23 December 2005. Only "The height of mountain ranges is usually..." is left.
- von Huene et al. 1991 was added 29 January 2006 by an IP who "fixed some oversimplifications". Only the sentence "It is a matter of debate whether the amount of continental crust has been increasing, decreasing, or remaining constant over geological time." is left from that edit.
- Taylor and McLennan 1995 was also added 29 January 2006. This reference is a simple diagram still present in-line.
- Butler 2006 was added the same day as a reference to the next sentence, still present in-line.
- Bowring et al. 1999; Armstrong 1991; Cogley 1984; Condie 2002; and Clift et al. 2004 were added 2 December 2007. What's left of those edits, as far as I can see, (1) the "Importance" section; (2) first para of "Forces at work" section except first sentence; (3) last para of same section up to "...continental crust formation and destruction."
- Hawkesworth, the only in-line ref, was added 17 April 2010 after "Continental crust makes up about 70% of the volume of Earth's crust."
- Unreferenced section "Origin" was added 5 May 2010.
I'll try to make in-line references of these as much as possible. --Fama Clamosa (talk) 13:34, 31 January 2011 (UTC)
I think I've managed to attribute most content to one ref or another. References added December 2 2007 are only tentatively sorted to match article content (only abstracts were available to me). --Fama Clamosa (talk) 15:53, 31 January 2011 (UTC)
Could be more helpful
editI have spent a lot of time trying to understand the exact process of continental crust formation. This article is not helpful in understanding current theory. There's only a few sentences on crust creation. I understand a lot of that information could go into the section on cratons and/or shields, but a better explanation here might be helpful and educational. An explanation of differention and how it relates to continental crust formation would be nice. An explanation of how island arcs could have accreted over time to form the core of continents would be nice. An explanation of subduction mechanics vs the role hot spots (plumes) in the origin of continental crust would be nice. Did objects hitting the earth play a role in the creation of continental crust? — Preceding unsigned comment added by 15.195.201.89 (talk) 16:22, 15 December 2011 (UTC)
The basic concept is one of gravitation acting to differentiate between lighter and heavier components in a molten earth. The heaviest metal components formed the iron/nickel core and the silicates differentiate between the more dense mantle and less dense crust silicates. Object hitting the earth just added extra building blocks (the entire Earth has been made out of this), the composition of asteroids are either metallic (siderites) or silicates (chondrites) or a combination of both. They would just become a part of our planet, a process that is still in process every day (which you can see happening across the night sky every night), although a metallic meteorite hitting the earth today will have little or no chance of ever becoming a part of the core. --Codiv (talk) 14:24, 5 May 2021 (UTC)
"Importance"
editI'm looking for citations for the "Importance" section, and it looks like it was lifted right off of a blog post.[1] I'm not sure which came first, though. I'm looking through various sources to try to corroborate the bit about metazoan life. I figure that would be a good start for possibly expanding this section. Skolithos (talk) 02:27, 30 November 2013 (UTC)
- Never mind, I found a good source for it. I didn't expand it as much as I would have liked, but I've added it to my watchlist and would be interested for any input anyone else could offer. Skolithos (talk) 02:36, 30 November 2013 (UTC)
External links modified
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More content
editHello editors,
Because of you we have many made many topics for us to learn So I request you to please add more content to this topic 😊 Thank you
Yours sincerely, Princess Anu (*I can not tell my real name*) PrettyPrincessAnu (talk) 16:15, 26 June 2021 (UTC)