Talk:Oceanic crust
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[edit] Thickness of oceanic crust
Under the continents "oceanic crust" should be thinner than it is in the ocean basins, do to isostasy. --Bejnar 01:40, 1 February 2007 (UTC)
[edit] Density changes
Editor Karl07 added the sentence: "When the crust becomes dense enough it subducts into the mantle at what is known as a convergent boundary." Unfortunately the rocks cannot change their density as they are pulled/pushed away from the oceanic ridges. One theory has it that the convection currents in the mantle formed early in the earth's history and their current locations are more a matter of history than mechanics. --Bejnar 22:14, 15 February 2007 (UTC)
[edit] Inaccuracies in the edits of 16 March 2007
This is just to address a couple of the inaccuracies present in the edits of 16 March 2007 that I reverted. (1) The Oceanic crust and the SIMA are not the same, they are related. The SIMA can be solid or molten, the crust is solid. (2) The lava that solidifies at the mid-oceanic ridges may not come from as deep as the asthenosphere. It is considered by some authors much more likely that the circulating heat from the asthenosphere melts the rock above it. (3) The lava does not pour out at the crests. The crests are an erosional feature that are pushed upwards by magma domes. Additionally, the magma can solidify without being extruded as lava. (4) The edit added send magma into the rock cycle, which is inaccurate as the differentiation between lighter and heavier elements in the Earth has been going on for a long, long time. The magma has been in the rock cycle since very early in the process. (5) The edit added [such magma] are the origins for all the Earth's materials. This statement is both overbroad and incorrect. One simple counter-example is limestone. I don't think that I need to go on any further. --Bejnar 03:00, 17 March 2007 (UTC)
[edit] Conrad Discontinuity
Om February 2008 Cmapm added a sentence about the Conrad Discontinuity, indicating that it was the sial/sima boundary. This was what some thought before deep drilling below the Kola Peninsula found no such switchover. No one knows what the Conrad Discontinuity represents. It doesn't signal a change in rock type; neither is there a fault or boundary of any kind. It is important to find out what is wrong here, because much of modeling of the unseen structure of the earth's crust depends upon a realistic interpretation of seismic records. Monastersky, Richard (1989) "Inner Space" Science News, 136: p.266. Is there an update in the last 18 years? Isostasy predicts that there will still be lighter sial at the depth of the Conrad Discontinuity, but it is possible that there is a phase change due to pressure effects at that depth. --Bejnar (talk) 00:40, 19 February 2008 (UTC)
- It sometimes appears in scientific papers up to this day (I've found one paper of 2007, mentioning it, in springerlink), but is quite a mystical thing I'd say:) with too few sources. I seriously doubt if we can find enough inf. for the article on this, just for a short stub.Cmapm (talk) 09:29, 19 February 2008 (UTC)
