Mohorovicic boundary

Abstract The well-known features of the Earth s crust are interpreted as the result of rock fracturing under deep thermodynamic conditions. For this aim, triaxial failure data are scaled up to the crust taking into account temperatures and rock types. The critical depth of hydraulically permeable cracks coincides with the Mohorovicic boundary and that relates to the crust genesis. The annihilation of a crack system at this depth is in accordance with seismic velocity jump known from geophysical exploration. The features of crust floors as well as total thickness, fault inclination, etc, are explained by the suggested mechanical approach. 

In 1978 discussion about the limit depth of cracks inside the Earth s crust took place in our Institute. The participants were J.R. Rice, B.V. Kostrov, the authors of this presentation, et al. The answer was found later when the rock testing data were collected, Nikolaevskiy (1979) and it was simple the Mohorovicic boundary is the limit depth for an open crack system. This conclusion contained, as one can see, also the genesis of the crust itself. The result of the following study is given below. 

Figure 3.1 A cross section of the crusts, rigid upper mantle, and plastic mantle asthenosphere of the Earth. The Mohorovicic Discontinuity is the boundary between the crust and upper mantle. The lithosphere includes the crusts and the upper mantle.

Mohorovicic Discontinuity The boundary between the lower crust and the upper mantle. 

This table gives the density p, pressure p, and acceleration due to gravity as a function of depth below the earth s surface, as calculated from the model of the structure of the earth in Reference 1. The model assumes a radius of 6371 km for the earth. The boundary between the crust and mantle (the Mohorovicic discontinuity) is taken as 21 km, while in reality it varies considerable with location. 

The profile of the crustal thickness of parts of West and East Antarctica in Fig. 15.11 indicates the complementary depth to the Mohorovicic Discontinuity (Moho) and illustrates the increase of the crustal thickness at the boundary between West and East Antarctica. The structure of the crust of Antarctica was also investigated by Dewart and Toksoz (1965), Jankowski and Drewry (1981), Kurinin and Grikurov (1982), and by... 

The sharp boundary existing between the bottom of the Earth s crust and the upper mantle that was first identified in 1909 by the Croatian seismologist Andriaja Mohorovicic by a clear change in the velocity of P seismic waves is called the Mohorovicic discontinuity or simply Moho. 

Andrija Mohorovicic in Zagreb discovered the existence of zones with distinct boundaries within the earth. He analyzed seismic records after an earthquake in cen-... 

What Mohorovicic originally discovered was the boundary between the earth s crust and the upper mantle. This boundary was named Mohorovidc s discontinuity or simply Moho. 

The crust extends from the surface of the earth to the Mohorovicic s (Moho) discontinuity, which is the first plane of unconformity, or boundary, between the mantle and crust. The crust is divided into the oceanic cmst and the continental crust. The oceanic crust is mainly composed of basic and ultrabasic rocks (e.g., basalt, gabbro, and peridotite) overlain by marine sediments. Continental crust is more siliceous (av. Si02 66 %) than the oceanic crust (av. Si02 50 %) and the average chemical composition of the oceanic crust is roughly equivalent to basalt granite = 1 1. It is also composed of various types of rocks (igneous rocks, metamorphic rocks, sedimentary rocks). 

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