Talk:Core–mantle boundary

Bullen Discontinuity?
On About.com, I saw the D’’ refered to as the "Bullen Layer". I've seen "Bullen Discontinuity" used for the D” as well. However, the orignal Bullen Discontinuity article here described the term as if it were the Lehmann discontinuity (in between outer & inner core). So, which is which? I find myself confused right now. Iotha 02:58, 3 November 2005 (UTC)


 * If you do a Google search on "Bullen Layer" with the quotes, Google returns a grand total of 4 hits including the about.com ref you mentioned and another is an iranian? edu copy of the about.com article. A third is to "Bullen's Layer [C3]... and the fourth is a UK quiz member only site. Given that I'd say the "Bullen Layer" hasn't been overwhelmingly adopted. Vsmith 03:40, 3 November 2005 (UTC)


 * I've googled about and it seems to me now that "Bullen Discontinuity" is just another term for the Lehmann one. The latter returns more results though, so I'll stick to using it either way. Sorry for any mix up. Iotha 04:59, 3 November 2005 (UTC)


 * Lehmann discontinuity is an abandoned term for the inner-core outer-core transition. Nowadays it refers to the phase transition at depths of ~220 km in the upper mantle.

Googling for "Bullen discontinuity" (in quotes) today returns 1,020 hits, whereas "Inner core boundary" returns 155,000 hits. Since Wikipedia has articles on all the other major boundaries but not on this one, I suggest one be created under the name "Inner Core Boundary" and that "Bullen discontinuity" redirect to it. Vaughan Pratt (talk) 19:47, 14 May 2014 (UTC)

What happens after 500million-1billion years
when the core grows to the surface?If it increases each year by 1cm its going to happen. —Preceding unsigned comment added by MidNiteNeko (talk • contribs) 13:38, 6 October 2007 (UTC)


 * Meanwhile that sentence has been deleted. However it only said "order of cm", not "1 cm".  The Earth, in particular the outer core, could well be frozen in two billion years time, so "order of cm" is entirely reasonable.    Vaughan Pratt (talk) 19:57, 14 May 2014 (UTC)

The D’’ layer and the CMB
The phrase "The top of D’’ has been observed in some regions to be marked by a seismic velocity discontinuity (sometimes known as the Gutenberg discontinuity)" is contradicted by a 2001 article: http://www.geotimes.org/jan01/earthsinterior.html. Here, the D’’ layer is NOT part of the CMB but it is rather on top of it. See the last picture to get a visual idea.George Rodney Maruri Game (talk) 03:54, 26 January 2011 (UTC)

Therefore in the sentence it should be changed to "The bottom of D" has been observed ......" which would make it correct. — Preceding unsigned comment added by Martin Hind (talk • contribs) 13:25, 8 March 2011 (UTC)

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= Gutenberg Discontinuity = There is a section currently on the Gutenberg discontinuity being at about 2900 km depth. The Gutenberg discontinuity within geosciences often also refers to a boundary at the lithosphere-Asthenosphere boundary, not near the CMB (see ). It is difficult to find a primary source on the name "Gutenberg Discontinuity" referring to the CMB. A google scholar search on "core gutenberg discontinuity" yields papers from the early 1900's. In fact, this paper (https://pubs.geoscienceworld.org/ssa/bssa/article/54/5A/1299/116273/the-fine-structure-of-the-earth-s-core) affirms that Gutenberg discovered a discontinuity but never refers to it as the "Gutenberg discontinuity" Scootalmighty (talk) 15:16, 3 July 2018 (UTC)

A agree that the Gutenberg discontinuity section leads to confusion because in modern times the 'G' typically refers to a decrease of seismic velocity with depth at around ~100 km. Gutenberg may have discovered the seismic discontinuity associated with the core-mantle boundary, but currently in the field it is never referred to as the Gutenberg discontinuity. It would be interesting to add a section detailing the history of the nomenclature, though. Njmancinelli (talk) 17:37, 4 August 2018 (UTC)

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