state the properties of the core of the earth
Answers
Explanation:
properties of the core of the earth:
1)Seismic wave velocity:The velocity of the S-waves in the core varies smoothly from about 3.7 km/s at the center to about 3.5 km/s at the surface. That is considerably less than the velocity of S-waves in the lower crust (about 4.5 km/s) and less than half the velocity in the deep mantle, just above the outer core (about 7.3 km/s).
2)Size and shape:On the basis of the seismic data, the inner core is estimated to be about 1221 km in radius (2442 km in diameter); which is about 19% of the radius of the Earth and 70% of the radius of the Moon.
3)Pressure and gravity:1)The pressure in the Earth's inner core is slightly higher than it is at the boundary between the outer and inner cores: it ranges from about 330 to 360 gigapascals (3,300,000 to 3,600,000 atm).2)The acceleration of gravity at the surface of the inner core can be computed to be 4.3 m/s2, which is less than half the value at the surface of the Earth (9.8 m/s2).
4)Density and mass:The density of the inner core is believed to vary smoothly from about 13.0 kg/L (= g/cm3 = t/m3) at the center to about 12.8 kg/L at the surface. As it happens with other material properties, the density drops suddenly at that surface: the liquid just above the inner core is believed to be significantly less dense, at about 12.1 kg/L.For comparison, the average density in the upper 100 km of the Earth is about 3.4 kg/L.That density implies a mass of about 1023 kg for the inner core, which is 1/60 (1.7%) of the mass of the whole Earth.
5)Temperature:The temperature of the inner core can be estimated from the melting temperature of impure iron at the pressure which iron is under at the boundary of the inner core (about 330 GPa). From these considerations, in 2002 D. Alfe and others estimated its temperature as between 5,400 K (5,100 °C; 9,300 °F) and 5,700 K (5,400 °C; 9,800 °F).However, in 2013 S. Anzellini and others obtained experimentally a substantially higher temperature for the melting point of iron, 6230 ± 500 K.
6)Magnetic field:In 2010, Bruce Buffett determined that the average magnetic field in the liquid outer core is about 2.5 milliteslas (25 gauss), which is about 40 times the maximum strength at the surface. He started from the known fact that the Moon and Sun cause tides in the liquid outer core, just as they do on the oceans on the surface. He observed that motion of the liquid through the local magnetic field creates electric currents, that dissipate energy as heat according to Ohm's law. This dissipation, in turn, damps the tidal motions and explains previously detected anomalies in Earth's nutation. From the magnitude of the latter effect he could calculate the magnetic field. The field inside the inner core presumably has a similar strength. While indirect, this measurement does not depend significantly on any assumptions about the evolution of the Earth or the composition of the core.
7)Viscosity:Although seismic waves propagate through the core as if it was solid, the measurements cannot distinguish between a perfectly solid material from an extremely viscous one. Some scientists have therefore considered whether there may be slow convection in the inner core (as is believed to exist in the mantle). That could be an explanation for the anisotropy detected in seismic studies. In 2009, B. Buffett estimated the viscosity of the inner core at 1018. which is a sextillion times the viscosity of water, and more than a billion times that of pitch.