Evolution of the theory of Plate Tectonics
****************DISCONTINUITY**************************
1. MOHOROVICIC DISCONTINUITY-
a point at which a function is discontinuous or undefined
In geology the word "discontinuity" is used for a surface at which seismic waves change velocity.
Mohorovičić Discontinuity - The Moho
The Mohorovicic Discontinuity, or "Moho," is the boundary between the crust and the mantle. The red line in the diagram shows its location.
In geology the word "discontinuity" is used for a surface at which seismic waves change velocity. One of these surfaces exists at an average depth of 8 kilometers beneath the ocean basin and at an average depth of about 32 kilometers beneath the continents. At this discontinuity, seismic waves accelerate. This surface is known as the Mohorovicic Discontinuity or often simply referred to as the "Moho."
How Was the Moho Discovered?
The Mohorovicic Discontinuity was discovered in 1909 by Andrija Mohorovicic, a Croatian seismologist. Mohorovicic realized that the velocity of a seismic wave is related to the density of the material that it is moving through. He interpreted the acceleration of seismic waves observed within Earth's outer shell as a compositional change within the Earth. The acceleration must be caused by a higher density material being present at depth.
The lower density material immediately beneath the surface is now commonly referred to as "Earth's crust." The higher density material below the crust became known as "Earth's mantle." Through careful density calculations, Mohorovicic determined that the basaltic oceanic crust and the granitic continental crust are underlain by a material which has a density similar to an olivine-rich rock such as peridotite.
The map below illustrates the thickness of Earth's crust. Note how the thickest areas (red and dark brown) are beneath some of Earth's important mountain ranges such as the Andes (west side of South America), Rockies (Western North America), Himalayas (north of India in South-central Asia), and Urals (north-south trending between Europe and Asia).
There are a few rare locations where mantle material has been brought to the surface by tectonic forces. At these locations, rock that used to be at the crust / mantle boundary is present. A photo of rock from one of these locations is shown on this page.
source:https://geology.com/articles/mohorovicic-discontinuity.shtml
- 10 'abril 2018 **************** ainqitae ************************** 1. ainsijam mahbubi nuqtat takun fiha alwazifat ghyr mutasilat 'aw ghyr muhadada fi aljayulwjiaa , tustkhdm kalima "altawqf" lisath tataghayar fih almawjat alzilzaliat alsareat. Mohorovicic altawaquf - dha muhu 'iin tawaquf Mohorovicic ، 'aw "Moho" , hu alhudud bayn alqashrat waleiba'ati. yuzhir alkhata al'ahmar fi alrasm albianii mawqieih. fi aljayulwjia , tustkhdm kalima "altawqf" lisatah tataghayar fih almuajat alzilzaliat alsirieatu. yujad wahid min hadhih al'ustuh ealaa eumq 8 kilumitrat taht hawd almuhit waealaa eumq hwaly 32 kam taht alqaraati. fi hadha altawaquf , tatasarae almawjat alzilzaliatu. yuerf hdha alsath biaism tawaquf Mohorovicic 'aw ghalbana ma yushar 'iilayh bbsatt biaism "Moho". kif tama aiktishaf mawhu? tam aiktishaf tawaquf Mohorovicic fi eam 1909 bwastt Andrija Mohorovicic , ealam alzalazil alkurwati. 'adrak muhurufytsh 'an sureat almawjat alzilzaliat murtabitat bikathafat almadat alty tataharak min khilaliha. wafusr tasare almawjat alzilzaliat alty luhizat dakhil alghilaf alkharijii lil'ard kataghyir tarkibi dakhil al'arda. yjb 'an yakun sbb altasare wujud madat dhat kathafat 'aelaa mawjudat fi aleumq. yushar 'iilaa almawadi dhat alkathafat almunkhafidat mubasharat 'asfal alsath alan biaism "qshirat al'arda". 'asbahat almadat dhat alkathafat alealiat taht alqishrat tuerf biaism "eba'at al'ard". min khilal hisabat alkathafat aldaqiqat , qarar muhurufitsh 'ana alqishrat almuhitiat albazltiat walqishrat aljaranitiat alqariat ytmu tahtimuhuma bwastt madatan laha kathafat mumathilat lisukhur ghaniat bazit alzaytun mithl albirutit. kharitat samakat alqishrt: samakat qishrat al'ard bwastt hayyat almasahi aljayulujii al'amrikiat - nzrana li'ana jazirat mawhu taqae fi qaeidat alqishrat , fa'iina hadhih alkharitat tuzhr aydana eumq jaziratan muhu. ma mda eumq almawahu? yumathil tawaquf Mohorovicic alhadi al'adnaa liqashrat al'arda. kama dhakar aelah , yahduth ealaa eumq mtwst hwaly 8 kilumitrat taht 'ahwad almuhit w 32 kam taht al'astah alqari. kan mawhurufitsh qadraan ealaa aistikhdam aiktishafih lidirasat aikhtilafat samak alqushra. aiktashaf 'ana alqashrat almuhitiat laha samak muahad nsbyana , fi hyn 'ana alqishrat alqariat 'athkhan taht salasil aljibal wa'arq taht alshwl. tuadih alkharitat 'adnah samakat qishrat al'ardu. lahaz kayf 'an 'akthar almanatiq samakaan (ali'ahmar walbanii aldaakina) taqae 'asfal bed salasil aljibal almuhimat lil'ard mithl jibal al'andiz (aljanib algharbii min 'amrika aljunawbiati) , rawkiz (ghrib 'amrika alshamaliata) , jibal alhimalaya (shmal alhind fi janub wasat asia) , wal'awral (alshimal waljanub tatajih bayn 'uwrubba wasya). eaba'at, 'iihtaz, 'iilaa، surface :، Ordovician، ophiolite، 'iilaa dakhil, Gros، Morne, alhadiqat alwatania, niufunadlanid, Canada. sakhrat eabaa'atan qadimatan makshufatan ealaa alsath. hal shahid 'ahaduhum mawhu? lm yakun hunak 'ayu shakhs eamiq bma fyh alkfayt fi al'ard liruyat almawhu , walam ytma hafr 'aya biir eamiqat bma yakfi liaikhtiraqiha. hafr abar ealaa hadha aleumq mukalaf lilghayat wasaeb lilghayat bsbb darajat alhararat waldaght alqasiti. kan 'aemaq biar tama hafruh hataa alan fi shbh jazirat kula fi alaitihad alsuwfiti. tama hafruha ealaa eumq hwaly 12 kilumtirin. alhafr limawhu min khilal qishrat almuhitat kama lm tanjah. hnak eadad qalil min almawaqie alnnadirat hayth tama jalb mawadu alwashah 'iilaa alsath bwastt quaa tuktuniat. fi hadhih almawaqie , tujad alsukhur alty kanat mawjudatan eind hudud alqishrat / alwashah. tazhar suratan lihadhih alsakhrat min 'ahad hadhih almawaqie ealaa hadhih alsafhat.
1. MOHOROVICIC DISCONTINUITY-
a point at which a function is discontinuous or undefined
In geology the word "discontinuity" is used for a surface at which seismic waves change velocity.
Mohorovičić Discontinuity - The Moho
The Mohorovicic Discontinuity, or "Moho," is the boundary between the crust and the mantle. The red line in the diagram shows its location.
In geology the word "discontinuity" is used for a surface at which seismic waves change velocity. One of these surfaces exists at an average depth of 8 kilometers beneath the ocean basin and at an average depth of about 32 kilometers beneath the continents. At this discontinuity, seismic waves accelerate. This surface is known as the Mohorovicic Discontinuity or often simply referred to as the "Moho."
How Was the Moho Discovered?
The Mohorovicic Discontinuity was discovered in 1909 by Andrija Mohorovicic, a Croatian seismologist. Mohorovicic realized that the velocity of a seismic wave is related to the density of the material that it is moving through. He interpreted the acceleration of seismic waves observed within Earth's outer shell as a compositional change within the Earth. The acceleration must be caused by a higher density material being present at depth.
The lower density material immediately beneath the surface is now commonly referred to as "Earth's crust." The higher density material below the crust became known as "Earth's mantle." Through careful density calculations, Mohorovicic determined that the basaltic oceanic crust and the granitic continental crust are underlain by a material which has a density similar to an olivine-rich rock such as peridotite.
Crustal thickness map: Thickness of Earth's crust by USGS - since the Moho is at the base of the crust, this map also shows depth to Moho.
How Deep is the Moho?
The Mohorovicic Discontinuity marks the lower limit of Earth's crust. As stated above, it occurs at an average depth of about 8 kilometers beneath the ocean basins and 32 kilometers beneath continental surfaces. Mohorovicic was able to use his discovery to study thickness variations of the crust. He discovered that the oceanic crust has a relatively uniform thickness, while continental crust is thickest under mountain ranges and thinner under plains.The map below illustrates the thickness of Earth's crust. Note how the thickest areas (red and dark brown) are beneath some of Earth's important mountain ranges such as the Andes (west side of South America), Rockies (Western North America), Himalayas (north of India in South-central Asia), and Urals (north-south trending between Europe and Asia).
Mantle rock at surface: Ordovician ophiolite
in Gros Morne National Park, Newfoundland, Canada. Ancient mantle rock
exposed at the surface.
Has Anyone Ever Seen the Moho?
No one has ever been deep enough into the Earth to see the Moho, and no wells have ever been drilled deep enough to penetrate it. Drilling wells to that depth is very expensive and very difficult because of the extreme temperature and pressure conditions. The deepest well that has been drilled to date was located on the Kola Peninsula of the Soviet Union. It was drilled to a depth of about 12 kilometers. Drilling to the Moho through oceanic crust has also been unsuccessful.There are a few rare locations where mantle material has been brought to the surface by tectonic forces. At these locations, rock that used to be at the crust / mantle boundary is present. A photo of rock from one of these locations is shown on this page.
source:https://geology.com/articles/mohorovicic-discontinuity.shtml
- 10 'abril 2018 **************** ainqitae ************************** 1. ainsijam mahbubi nuqtat takun fiha alwazifat ghyr mutasilat 'aw ghyr muhadada fi aljayulwjiaa , tustkhdm kalima "altawqf" lisath tataghayar fih almawjat alzilzaliat alsareat. Mohorovicic altawaquf - dha muhu 'iin tawaquf Mohorovicic ، 'aw "Moho" , hu alhudud bayn alqashrat waleiba'ati. yuzhir alkhata al'ahmar fi alrasm albianii mawqieih. fi aljayulwjia , tustkhdm kalima "altawqf" lisatah tataghayar fih almuajat alzilzaliat alsirieatu. yujad wahid min hadhih al'ustuh ealaa eumq 8 kilumitrat taht hawd almuhit waealaa eumq hwaly 32 kam taht alqaraati. fi hadha altawaquf , tatasarae almawjat alzilzaliatu. yuerf hdha alsath biaism tawaquf Mohorovicic 'aw ghalbana ma yushar 'iilayh bbsatt biaism "Moho". kif tama aiktishaf mawhu? tam aiktishaf tawaquf Mohorovicic fi eam 1909 bwastt Andrija Mohorovicic , ealam alzalazil alkurwati. 'adrak muhurufytsh 'an sureat almawjat alzilzaliat murtabitat bikathafat almadat alty tataharak min khilaliha. wafusr tasare almawjat alzilzaliat alty luhizat dakhil alghilaf alkharijii lil'ard kataghyir tarkibi dakhil al'arda. yjb 'an yakun sbb altasare wujud madat dhat kathafat 'aelaa mawjudat fi aleumq. yushar 'iilaa almawadi dhat alkathafat almunkhafidat mubasharat 'asfal alsath alan biaism "qshirat al'arda". 'asbahat almadat dhat alkathafat alealiat taht alqishrat tuerf biaism "eba'at al'ard". min khilal hisabat alkathafat aldaqiqat , qarar muhurufitsh 'ana alqishrat almuhitiat albazltiat walqishrat aljaranitiat alqariat ytmu tahtimuhuma bwastt madatan laha kathafat mumathilat lisukhur ghaniat bazit alzaytun mithl albirutit. kharitat samakat alqishrt: samakat qishrat al'ard bwastt hayyat almasahi aljayulujii al'amrikiat - nzrana li'ana jazirat mawhu taqae fi qaeidat alqishrat , fa'iina hadhih alkharitat tuzhr aydana eumq jaziratan muhu. ma mda eumq almawahu? yumathil tawaquf Mohorovicic alhadi al'adnaa liqashrat al'arda. kama dhakar aelah , yahduth ealaa eumq mtwst hwaly 8 kilumitrat taht 'ahwad almuhit w 32 kam taht al'astah alqari. kan mawhurufitsh qadraan ealaa aistikhdam aiktishafih lidirasat aikhtilafat samak alqushra. aiktashaf 'ana alqashrat almuhitiat laha samak muahad nsbyana , fi hyn 'ana alqishrat alqariat 'athkhan taht salasil aljibal wa'arq taht alshwl. tuadih alkharitat 'adnah samakat qishrat al'ardu. lahaz kayf 'an 'akthar almanatiq samakaan (ali'ahmar walbanii aldaakina) taqae 'asfal bed salasil aljibal almuhimat lil'ard mithl jibal al'andiz (aljanib algharbii min 'amrika aljunawbiati) , rawkiz (ghrib 'amrika alshamaliata) , jibal alhimalaya (shmal alhind fi janub wasat asia) , wal'awral (alshimal waljanub tatajih bayn 'uwrubba wasya). eaba'at, 'iihtaz, 'iilaa، surface :، Ordovician، ophiolite، 'iilaa dakhil, Gros، Morne, alhadiqat alwatania, niufunadlanid, Canada. sakhrat eabaa'atan qadimatan makshufatan ealaa alsath. hal shahid 'ahaduhum mawhu? lm yakun hunak 'ayu shakhs eamiq bma fyh alkfayt fi al'ard liruyat almawhu , walam ytma hafr 'aya biir eamiqat bma yakfi liaikhtiraqiha. hafr abar ealaa hadha aleumq mukalaf lilghayat wasaeb lilghayat bsbb darajat alhararat waldaght alqasiti. kan 'aemaq biar tama hafruh hataa alan fi shbh jazirat kula fi alaitihad alsuwfiti. tama hafruha ealaa eumq hwaly 12 kilumtirin. alhafr limawhu min khilal qishrat almuhitat kama lm tanjah. hnak eadad qalil min almawaqie alnnadirat hayth tama jalb mawadu alwashah 'iilaa alsath bwastt quaa tuktuniat. fi hadhih almawaqie , tujad alsukhur alty kanat mawjudatan eind hudud alqishrat / alwashah. tazhar suratan lihadhih alsakhrat min 'ahad hadhih almawaqie ealaa hadhih alsafhat.
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