|
Today the most widespread model of the Earth structure is the Gutenberg-Bullen model, and the most widespread model of the inner structure and property is the Haddon-Bullen model.
According to this model, the value of acceleration of gravity increases with depth, reaching its maximum value (1046.7 cm/s2) on the Gutenberg discontinuity (3000 km), then smoothly decreases in the direction to the center of the Earth, and has the zero value in the center of the Earth. At the same time, the pressure increases smoothly with depth, without any sudden changes, and reaches its maximum value (3.608x1011Pa) in the center of the Earth. Density also increases smoothly from 2.46 to 12.46 g/cm3, having sharp increase on the Mohorovièiè and Gutenberg discontinuities.
In our opinion, pressure in the center of the Earth is also equal to zero. By the Newton's second law, net force is equal to the mass of the material particle times the acceleration of it; when the acceleration of gravity is equal to zero, the net force is also equal to zero, and pressure is nothing but the net sum of forces acting upon the certain area (or point).
Besides, the effect of horizontal forces (the derivatives of vertical forces), which take all the pressure on the archs upon itself, is not taken into account. Therefore, the density of matter in the inner core of the Earth, must not exceed the value of density of chondrites, which serve as a "constructional material" of the terrestrial planets.
The value of density gradually increases with depth and reaches its maximum in the Gutenberg discontiniuty, then decreases sharply. In the transition zone of the core, pressure decreases because of the cancellation of the forces inside the core and increases from 3.57 to 5.86 g/cm3 in the center of the Earth.
The Earth, except for the transition zones, is in solid, but very heated state. It is because of strong static pressure, because of it, matter heats up greatly, but does not melt down because of high pressure, resulting in the increase of longitudinal seismic waves' velocities. That process shows up especially in lower mantle. One may assume that the primeval space cold remains in the center of the Earth as a rudiment of the initial stage of the Earth formation.
Terrestrial magnetic field is the result of ferromagnetic materials in its core. Ferromagnetic materials of the mantle, because of their temperature, which exceeds the Curie point, turned into paramagnets and did not take part in the formation of the magnetic field.
|
