Pressure earth crust structure

EARTH CRUST STRUCTURE AS A RESULT OF ROCK FRACTURING AT HIGH PRESSURE AND TEMPERATURE CONDITIONS... 

The global structure of the Earth crust is in accordance with residual states of rocks in an active tectonic regime, that is, when the shear intensity is reaching the rock limit strength at high temperatures and pressures. 

There are four commonly occurring states of stress, shown in Fig. 3.2. The simplest is that of simple tension or compression (as in a tension member loaded by pin joints at its ends or in a pillar supporting a structure in compression). The stress is, of course, the force divided by the section area of the member or pillar. The second common state of stress is that of biaxial tension. If a spherical shell (like a balloon) contains an internal pressure, then the skin of the shell is loaded in two directions, not one, as shown in Fig. 3.2. This state of stress is called biaxial tension (unequal biaxial tension is obviously the state in which the two tensile stresses are unequal). The third common state of stress is that of hydrostatic pressure. This occurs deep in the earth s crust, or deep in the ocean, when a solid is subjected to equal compression on all sides. There is a convention that stresses are positive when they pull, as we have drawn them in earlier figures. Pressure,... 

Limestone varieties differ greatly from one another in their texture and the impurities they contain, and consequently they also differ in color. The color of limestone may vary from white (when it contains practically no impurities) to off-white and even to intensely colored. Minor inclusions within the limestone structure are often of silica, usually in a concentration below 5%, as well as feldspar and clay in still lesser amounts. Many types of limestone also include embedded fossils. Much limestone deposits in the outer crust of the earth are altered during geologic metamorphic processes that involve mainly pressure and heat but also liquids and gases. Marble, for example, a metamorphic rock derived from calcium carbonate, is white when composed only of this substance colored metal ions and other impurities impart to marble a wide range of colors such as red, yellow, and green and also give... 

Table 1.1. Abundance of the metal in the earths s crust, optical band gap Es (d direct i indirect) [23,24], crystal structure and lattice parameters a and c [23,24], density, thermal conductivity k, thermal expansion coefficient at room temperature a [25-27], piezoelectric stress ea, e3i, eis and strain d33, dn, dig coefficients [28], electromechanical coupling factors IC33, ksi, fcis [29], static e(0) and optical e(oo) dielectric constants [23,30,31] (see also Sect. 3.3, Table 3.3), melting temperature of the compound Tm and of the metal Tm(metal), temperature Tvp at which the metal has a vapor pressure of 10 3 Pa, heat of formation AH per formula unit [32] of zinc oxide in comparison to other TCOs and to silicon...

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. 

Because of the contraction in the Fe-donor atom distance, the HS LS conversion is favored by an increase in pressure. From both solution studies and crystal structure determinations the decrease in molecular volume has been estimated as typically 20 A. Thus, an increase in pressure generally results in an increase in the transition temperature, but changes in the width of the hysteresis loop, the steepness of the transition curve, and changes in the residual fractions of HS and LS species at the extremes of the temperature range for the transition are also observed. Relatively simple species such as FeO and FeS in addition to some iron(II)-containing minerals have been shown to undergo pressure-induced HS LS transitions and these are relevant to the behavior of iron-containing minerals under the pressures experienced in the Earth s crust and mantle. 

The planet Earth was thus formed. Heat was created as the coalescence (of planetesimals) proceeded due to gravity, and heat also came from radioactivity of several radioactive elements such as aluminum-26. So the newly formed body was heated and the core was melted. As the material becomes liquid (as a result of melting), the materials contained in the liquid separate out according to their densities. The more dense material would sink closer to the bottom (core). Thus, the present layer structure of the Earth formed. The innermost core is a dense solid of about 1,200 km radius, whose density is about 12.6 g per cubic centimeter (12.6 x 10 kg/m ). It is made of mostly iron metal and a small amount of nickel. By the way, the density of iron metal is only 7.8 x 10 kg/m under the ordinary pressure. The next layer is the outer core (up to 3,500 km from the center of the Earth), which is liquid and has a density of 9.5-12x10 kg/m. The chemical composition seems to be about the same as that of the inner core. There is an abrupt change in density in the next layer, mantle. The width of mantle is about 2,900 km (3,500-6,380 km from the center). Its density ranges from 4 to 5.5 x 10 kg/m. The mantle is made of mostly magnesium-iron silicates (silicon oxides). The outermost layer is the thin crust of about 35 5 km on the land portion, and about 6 km under the ocean portion. 

---