Misplaced Pages

Lehmann discontinuity: Difference between revisions

Article snapshot taken from Wikipedia with creative commons attribution-sharealike license. Give it a read and then ask your questions in the chat. We can research this topic together.
Browse history interactively← Previous editContent deleted Content addedVisualWikitext
Revision as of 16:18, 1 March 2010 editAwickert (talk | contribs)Autopatrolled, Extended confirmed users, Pending changes reviewers, Rollbackers10,301 editsm grammar← Previous edit Latest revision as of 19:51, 2 September 2024 edit undoTc14Hd (talk | contribs)Extended confirmed users1,333 edits →topTags: Mobile edit Mobile app edit Android app edit App section source 
(71 intermediate revisions by 59 users not shown)
Line 1: Line 1:
{{about|a discontinuity in Earth's mantle|the discontinuity in the core|Earth's inner core}}
{{Expert-verify|date=December 2008}}
__NOTOC__
[[File:S-wave velocity.PNG|250px|thumb|Velocity of seismic ''S''-waves in the Earth near the surface in three tectonic provinces: TNA= Tectonic North America SNA= Shield North America & ATL = North Atlantic.<ref name=Anderson1> [[File:S-wave velocity.PNG|250px|thumb|Velocity of seismic ''S''-waves in the Earth near the surface in three tectonic provinces: TNA = Tectonic North America, SNA = Shield North America and ATL = North Atlantic.<ref name=Anderson1>


Figure patterned after {{cite book |title=New theory of the earth |author=Don L Henderson |url=http://books.google.com/books?id=KB3KsIPa94sC&pg=PA102 |page=102, Figure 8.6 |isbn=0521849594 |year=2007 |edition=2nd |publisher=Cambridge University Press}}; Original figure attributed to Grand & Helmberger (1984) Figure patterned after {{cite book |title=New Theory of the Earth |author=Don L Anderson |url=https://books.google.com/books?id=KB3KsIPa94sC&pg=PA102 |page=102, Figure 8.6 |isbn=978-0-521-84959-3 |date=2007 |edition=2nd |publisher=]}}; Original figure attributed to Grand and Helmberger (1984)</ref>]]
The '''Lehmann discontinuity''' is an abrupt increase of ] and ] velocities at the depth of {{convert|220|km|abbr=on}} in ], discovered by seismologist ].<ref name=Lowrie>{{cite book |title=Fundamentals of geophysics |author=William Lowrie |url=https://books.google.com/books?id=7vR2RJSIGVoC&pg=PA158 |page=158 |isbn=0-521-46728-4 |date=1997 |publisher=Cambridge University Press}}</ref><ref>Lehmann, I. (1936): P', Publications du Bureau Central Seismologique International, Série A, Travaux Scientifique, 14, 87–115.</ref><ref>{{cite web |author1=Martina Kölbl-Ebert |title=Inge Lehmann's paper: " P' " (1936) |url=https://courses.seas.harvard.edu/climate/eli/Courses/EPS281r/Sources/Inner-Core/Lehmann-1936-extracts+interpretation.pdf |date=December 2001}}</ref> The thickness is 220 km {{Citation needed|date=January 2020}}. It appears beneath ]s, but not usually beneath ]s,<ref name=Stixrude>


⚫ {{cite journal |quote=The first possible explanation is that the Lehmann is not a global feature...the Lehmann is more prevalent under continents and may be absent under all or most of the oceans. |title=Mineralogy and elasticity of the oceanic upper mantle: Origin of the low-velocity zone |author=Lars Stixrude and Carolina Lithgow-Bertolloni |journal=J. Geophys. Res. |volume=110 |doi=10.1029/2004JB002965 |date=2005 |issue=B3 |page=B03204 |bibcode=2005JGRB..110.3204S |doi-access=free |hdl=2027.42/94924 |hdl-access=free }}
</ref>]]
The '''Lehmann discontinuity''', originally referred to the liquid-solid boundary between the outer and inner core of the Earth, was named in honor of ] ], who proposed on the basis of seismic waves that the Earth had an inner core. <ref name=Krebs>


⚫ </ref> and does not readily appear in globally averaged studies. Several explanations have been proposed: a lower limit to the pliable ], a ],<ref name= Condie>
This usage still can be found: see for example: {{cite book |title=The basics of earth science |author=Robert E Krebs |year=2003 |publisher=Greenwood Publishing Company |url=http://books.google.com/books?id=-4ndyH7u6T0C&pg=PA142 |isbn=0313319308}}


⚫ {{cite book |title=Plate tectonics and crustal evolution |author=Kent C. Condie |url=https://books.google.com/books?id=HZrA6OQzsvgC&pg=PA123 |page=123 |isbn=0-7506-3386-7 |publisher=] |date=1997 |edition=4th}}
</ref> Later (1940) it was conjectured that this inner core was solid iron, and its rigidity was confirmed in 1971. <ref name=Lee>


⚫ </ref> and most plausibly, depth variation in the ] ].<ref name=Savage>{{cite book |title=Vertical coupling and decoupling in the lithosphere; ''Volume 227 of special publications'' |page=14 |chapter-url=https://books.google.com/books?id=SBs3o5uWeicC&pg=PA14 |author=MK Savage, KM Fischer CE Hall |chapter=Strain modelling, seismic anisotropy and coupling at strike-slip boundaries... |editor=John Gocott |isbn=1-86239-159-9 |publisher=] |date=2004}}</ref>
{{cite book |title=International handbook of earthquake and engineering seismology; volume 1 |author=William Hung Kan Lee |page=926 |url=http://books.google.com/books?id=aFNKqnC2E-sC&pg=PA926 |year=2002 |publihser=Academic Press |isbn=0124406521}}


<!--
</ref>
==See also== redundant, there is an {{Earthsinterior}} navbox

-->
However, today the Lehmann discontinuity refers to an abrupt increase of ] and ] velocities in the vicinity of 220±30 km depth, as also was discovered by Lehmann.<ref name=Lowrie>

⚫ {{cite book |title=Fundamentals of geophysics |author=William Lowrie |url=http://books.google.com/books?id=7vR2RJSIGVoC&pg=PA158 |page=158 |isbn=0521467284 |year=1997 |publisher=Cambridge University Press}}

</ref> It appears beneath ]s, but not usually beneath ]s,<ref name=Stixrude>

⚫ {{cite journal |url=http://supercronopio.es.ucl.ac.uk/~crlb/RESEARCH/PAPERS/StixrudeCLB05a.pdf |quote=The first possible explanation is that the Lehmann is not a global feature...the Lehmann is more prevalent under continents and may be absent under all or most of the oceans. |title=Mineralogy and elasticity of the oceanic upper mantel: Origin of the low-velocity zone |author=Lars Stixrude and Carolina Lithgow-Bertolloni |journal=J Geophys. Res. |volume=110 |doi=10.1029/2004JB002965 |year=2005 |page=B03204}}

⚫ </ref> and does not readily appear in globally-averaged studies. Several explanations have been proposed; a lower limit to the pliable ], a ],<ref name= Condie>

⚫ {{cite book |title=Plate tectonics and crustal evolution |author=Kent C. Condie |url=http://books.google.com/books?id=HZrA6OQzsvgC&pg=PA123 |page=123 |isbn=0750633867 |publisher=Butterworth-Heinemann |year=1997 |edition=4rth}}

</ref> and most plausibly, depth-variation in the ] ].<ref name=Savage>

⚫ {{cite book |title=Vertical coupling and decoupling in the lithosphere; ''Volume 227 of special publications'' |page=14 |url=http://books.google.com/books?id=SBs3o5uWeicC&pg=PA14 |author=MK Savage, KM Fischer CE Hall |chapter=Strain modelling, seismic anisotropy and coupling at strike-slip boundaries... |editor=John Gocott |isbn=1862391599 |publisher=Geological Society |year=2004}}
</ref> Further discussion of the Lehmann discontinuity is found in Kurato and Kurato.<ref name=Kurato>

{{cite book |title=Deformation of earth materials: an introduction to the rheology of solid earth |author=Shun-ichiro Karato, Shunʼichirō Karato |url=http://books.google.com/books?id=rZC7osgnyyYC&pg=PA318 |page=318 |isbn=0521844045 |year=2008 |publisher=Cambridge University Press}}

</ref>


==Notes== ==Notes==
Line 41: Line 22:


==General references== ==General references==
*{{cite book |title=Advances in geophysics, Volume 12 |author=P Caloi |editor=H. E. Landsberg, J. Van Mieghem |url=http://books.google.com/books?id=_z2uoqkaHAIC&pg=PA167 |page=167 ''ff'' |isbn=0120188120 |year=1967 |publisher=Academic Press |chapter=The “20° Discontinuity”}} – some historic background. *{{cite book |title=Advances in geophysics, Volume 12 |author=P. Caloi |editor=H. E. Landsberg, J. Van Mieghem |chapter-url=https://books.google.com/books?id=_z2uoqkaHAIC&pg=PA167 |page=167 ''ff'' |isbn=0-12-018812-0 |date=1967 |publisher=] |chapter=The “20° Discontinuity”}} – some historic background.


==See also== ==Further reading==
⚫ {{cite book |title=Deformation of earth materials: an introduction to the rheology of solid earth |author=Shun-ichirō Karato |url=https://books.google.com/books?id=rZC7osgnyyYC |page=318 |isbn=978-0-521-84404-8 |date=2008 |publisher=Cambridge University Press}}
*]
*]


==External links== ==External links==
⚫ *, ]
*, About.com
⚫ *, ]
* *

⚫ {{Earthsinterior}}

] ]


⚫ {{Earthsinterior}}
⚫ {{geol-stub}}


⚫ {{tectonics-stub}}
]
{{geophysics-stub}}
]
]
]
]
]
]
]
]
]
]

Latest revision as of 19:51, 2 September 2024

This article is about a discontinuity in Earth's mantle. For the discontinuity in the core, see Earth's inner core.
Velocity of seismic S-waves in the Earth near the surface in three tectonic provinces: TNA = Tectonic North America, SNA = Shield North America and ATL = North Atlantic.

The Lehmann discontinuity is an abrupt increase of P-wave and S-wave velocities at the depth of 220 km (140 mi) in Earth's mantle, discovered by seismologist Inge Lehmann. The thickness is 220 km . It appears beneath continents, but not usually beneath oceans, and does not readily appear in globally averaged studies. Several explanations have been proposed: a lower limit to the pliable asthenosphere, a phase transition, and most plausibly, depth variation in the shear wave anisotropy.


Notes

  1. Figure patterned after Don L Anderson (2007). New Theory of the Earth (2nd ed.). Cambridge University Press. p. 102, Figure 8.6. ISBN 978-0-521-84959-3.; Original figure attributed to Grand and Helmberger (1984)
  2. William Lowrie (1997). Fundamentals of geophysics. Cambridge University Press. p. 158. ISBN 0-521-46728-4.
  3. Lehmann, I. (1936): P', Publications du Bureau Central Seismologique International, Série A, Travaux Scientifique, 14, 87–115.
  4. Martina Kölbl-Ebert (December 2001). "Inge Lehmann's paper: " P' " (1936)" (PDF).
  5. Lars Stixrude and Carolina Lithgow-Bertolloni (2005). "Mineralogy and elasticity of the oceanic upper mantle: Origin of the low-velocity zone". J. Geophys. Res. 110 (B3): B03204. Bibcode:2005JGRB..110.3204S. doi:10.1029/2004JB002965. hdl:2027.42/94924. The first possible explanation is that the Lehmann is not a global feature...the Lehmann is more prevalent under continents and may be absent under all or most of the oceans.
  6. Kent C. Condie (1997). Plate tectonics and crustal evolution (4th ed.). Butterworth-Heinemann. p. 123. ISBN 0-7506-3386-7.
  7. MK Savage, KM Fischer CE Hall (2004). "Strain modelling, seismic anisotropy and coupling at strike-slip boundaries...". In John Gocott (ed.). Vertical coupling and decoupling in the lithosphere; Volume 227 of special publications. Geological Society. p. 14. ISBN 1-86239-159-9.

General references

Further reading

Shun-ichirō Karato (2008). Deformation of earth materials: an introduction to the rheology of solid earth. Cambridge University Press. p. 318. ISBN 978-0-521-84404-8.

External links

Structure of Earth
Shells
Global discontinuities
Regional discontinuities


Stub icon

This tectonics article is a stub. You can help Misplaced Pages by expanding it.

Stub icon

This geophysics-related article is a stub. You can help Misplaced Pages by expanding it.

Categories: