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as 'G'. In his 1942 publication of his model, the entire lower mantle was the D layer. In 1949, Bullen found his 'D' layer to actually be two different layers. The upper part of the D layer, about 1,800 km thick, was renamed D′ (D prime) and the lower part (the bottom 200 km) was
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The uppermost section of the outer core is thought to be about 500–1,800 K hotter than the overlying mantle, creating a thermal boundary layer. The boundary is thought to harbor topography, much like Earth's surface, that is supported by solid-state convection within the overlying mantle. Variations
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A seismic discontinuity occurs within Earth's interior at a depth of about 2,900 km (1,800 mi) below the surface, where there is an abrupt change in the speed of seismic waves (generated by earthquakes or explosions) that travel through Earth. At this depth, primary seismic waves (P waves) decrease
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Torsvik, Trond H.; Smethurst, Mark A.; Burke, Kevin; Steinberger, Bernhard (2006). "Large igneous provinces generated from the margins of the large low-velocity provinces in the deep mantle". Geophysical
Journal International. 167 (3): 1447–1460. Bibcode:2006GeoJI.167.1447T.
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in velocity while secondary seismic waves (S waves) disappear completely. S waves shear material and cannot transmit through liquids, so it is thought that the unit above the discontinuity is solid, while the unit below is in a liquid or molten form.
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named D″. Later it was found that D" is non-spherical. In 1993, Czechowski found that inhomogeneities in D" form structures analogous to continents (i.e. core-continents). They move in time and determine some properties of
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do not exist at all in the liquid portion of the core. Recent evidence suggests a distinct boundary layer directly above the CMB possibly made of a novel phase of the basic
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Bullen K., Compressibility-pressure hypothesis and the Earth’s interior. Monthly
Notices of the Royal Astronomical Society, Geophysical Supplements, 5, 355–368., 1949
196:("D double-prime" or "D prime prime") and is sometimes included in discussions regarding the core–mantle boundary zone. The D″ name originates from geophysicist
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233:, a seismologist who made several important contributions to the study and understanding of the Earth's interior. The CMB has also been referred to as the
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WR Peltier (2007). "Mantle
Dynamics and the D" Layer: Impacts of the Post Perovskite Phase". In Kei Hirose; John Brodholt; Thome Lay; David Yuen (eds.).
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is most commonly used in reference to a decrease in seismic velocity with depth that is sometimes observed at about 100 km below the Earth's oceans.
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in the thermal properties of the CMB may affect how the outer core's iron-rich fluids flow, which are ultimately responsible for
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studies have shown significant irregularities within the boundary zone and appear to be dominated by the
African and Pacific
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Creager, K.C. and Jordan, T.H. (1986). Asperical structure of the core-mantle boundary. Geophys. Res. Lett. 13, 1497-1500
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144:, at a depth of 2,891 km (1,796 mi) below Earth's surface. The boundary is observed via the discontinuity in
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237:, the Oldham-Gutenberg discontinuity, or the Wiechert-Gutenberg discontinuity. In modern times, however, the term
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Lekic, V.; Cottaar, S.; Dziewonski, A. & Romanowicz, B. (2012). "Cluster analysis of global lower mantle".
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An approximately 200 km thick layer of the lower mantle directly above the CMB is referred to as the
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Schmerr, N. (2012-03-22). "The
Gutenberg Discontinuity: Melt at the Lithosphere-Asthenosphere Boundary".
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Czechowski L. (1993) Geodesy and
Physics of the Earth pp 392-395, The Origin of Hotspots and The D” Layer
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Dziewonski, Adam M.; Anderson, Don L. (1981-06-01). "Preliminary reference Earth model".
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Lay, Thorne; Hernlund, John; Buffett, Bruce A. (2008). "Core–mantle boundary heat flow".
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velocities at that depth due to the differences between the
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Boundary Has Core-Rigidity Zone
355:Post-Perovskite: The Last Mantle Phase Transition
152:of the solid mantle and the molten outer core.
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446:Physics of the Earth and Planetary Interiors
217:. Later research supported this hypothesis.
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34:Schematic view of the interior of Earth.
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130:) of Earth lies between the planet's
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577:Mineral phase change at the boundary
229:The discontinuity was discovered by
164:mineralogy of the deep mantle named
594:About.com article on the name of D″
277:Earth and Planetary Science Letters
239:Gutenberg discontinuity or the "G"
174:Large low-shear-velocity provinces
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565:The American Geological Institute
555:Audrey Slesinger (January 2001),
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733:D’’ discontinuity (lower mantle)
728:660 discontinuity (upper mantle)
723:410 discontinuity (upper mantle)
115:outer core–inner core boundary
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467:10.1016/0031-9201(81)90046-7
582:Superplumes at the boundary
251:Core–mantle differentiation
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718:Mohorovičić (crust–mantle)
363:American Geophysical Union
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106:Mohorovicic discontinuity
771:Gutenberg (upper mantle)
752:Regional discontinuities
280:. 357–358 (1–3): 68–77.
510:10.1126/science.1215433
286:2012E&PSL.357...68L
256:Ultra low velocity zone
235:Gutenberg discontinuity
820:Structure of the Earth
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711:Global discontinuities
182:Earth's magnetic field
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204:as 'A' and the inner
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738:Core–mantle boundary
365:. pp. 217–227.
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124:core–mantle boundary
111:core–mantle boundary
743:Inner-core boundary
666:Lithospheric mantle
502:2012Sci...335.1480S
496:(6075): 1480–1483.
459:1981PEPI...25..297D
433:doi:10.1111/j.1365-
323:2008NatGe...1...25L
150:acoustic impedances
637:Structure of Earth
599:2008-10-06 at the
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170:Seismic tomography
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75: lower mantle
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372:978-0-87590-439-9
310:Nature Geoscience
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389:|work=
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815:Geophysics
809:Categories
700:Inner core
695:Outer core
682:Mesosphere
570:2011-03-24
262:References
162:perovskite
142:outer core
96:inner core
85:outer core
534:206538202
518:0036-8075
475:0031-9201
391:ignored (
381:cite book
339:1752-0894
194:D″ region
188:D″ region
176:(LLSVP).
794:Category
597:Archived
585:Archived
561:Geotimes
526:22442480
245:See also
211:hotspots
132:silicate
498:Bibcode
490:Science
455:Bibcode
319:Bibcode
282:Bibcode
158:S-waves
18:D"
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514:ISSN
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393:help
367:ISBN
335:ISSN
213:and
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122:The
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