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Understanding Earth's Geophysical Crust: Insights from a Geophysicist

Dive into the fascinating world of geophysics through the eyes of a geophysicist. Explore what defines the geophysical crust, the significance of the Mohorovicic boundary, and the factors that determine the speed of seismic waves. Discover the historical milestones in geophysical studies from renowned scientists like Andrija Mohorovicic and Keith Bullen to the complexities of crustal thickness variations across different geological settings. This overview also touches on mineralogical differences related to oceanic and continental crust, enriching our understanding of Earth's structure.

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Understanding Earth's Geophysical Crust: Insights from a Geophysicist

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  1. EPSC 666 Team 3: OliviaA geophysicist's view A geophysicist sees Earth through lenses of various physical parameters. • What defines the geophysical crust? • That outer “rigid” layer of Earth constrained below by a sharp increase in the speed of sound waves. • What determines the speed of sound?  = √( k + 4/3  ) / • The Mohorovicic crust-mantle boundary

  2. Geophysical structure ... diagram Wikimedia Commons

  3. Seismic discovery • Andrija Mohorovicic discovers the “Moho”, the base of the geophysical crust in 1906 • Richard Oldham 1906 • Bernard Bruhnes 1906 • Inge Lehmann 1936 • Harold Jeffreys 1936 ... diagram Wikimedia Commons

  4. An inner-inner core? • Xiaodong Song & Xinlei Sun -- 2008 ... diagram http://www.physorg.com/news124372414.html

  5. ... details upon detail: D'' • D'' (D-double-prime) layer is discovered by Keith Bullen, 1950. The global distribution is difficult to map with seismics or other direct geophysical techniques. ... story: http://www.esrf.eu/news/pressreleases/press_earth/index_html/

  6. Back to the crust... If we accept the Moho as the base of the crust, crustal thickness varies from 0km at spreading ridges to about 7km in ocean basins and to as much a 70km under the Himalayas. ... diagram: USGS

  7. ... beyond geophysics This Moho is correlated with mineralogical differences... • Ocean basins: the crust is mafic (basaltic, gabbroic); the underlying mantle, eclogite? – approximately. • Continents: the crust is largely felsic (granitic, andesitic); the underlying mantle, as above? ... but that is another story

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