Old-earth geologists make the key assumption that the entire earth was once molten. Several lines of evidence refute this assumption.
An earth molten for the first half-billion years of its existence is the key reason why conventional geologists do not try to date the earth even from isochron dating of earth rocks. By definition, an isochron dates from the most recent melt, and so no whole-rock isochron date can be older than about 4.0 billion years before the present. (Mineral isochrons can be slightly older.) But several observations suggest that the earth was never molten, except at the cores.
At present the earth has two very hot cores:
- A solid inner core at a depth of 5600 km, and
- A molten outer core at a depth of 4000 km.
The temperature of the inner core is about 7300 K at maximum; that of the outer core varies from 4700 to 6400 K. Though the inner core is hotter than the outer, the density at the inner core is as high as 12.46 grams per cubic centimeter, or more than twice the planetary average. The dense metals are simply too dense to melt, even at that temperature. The outer core is molten because the metals in it remain light enough to melt. Above the outer core is a mantle layer at a temperature of about 1100 K.
To form the outer and inner core of the earth would require 9.156 undecillion ergs of energy, released as heat. In fact, the potential energy of the entire earth (expressed as a negative) is 2.489 dodecillion ergs, or more than 270 times as much. Thus the formation of the entire mass of the earth from gravitational accretion would have released 270 times the heat required to form the inner and outer core of the earth and bring them to their present temperatures. Thus the entire earth would have had to melt many times over, and produce a far greater heat flux than the present value of about 10 septillion erg/yr. Possibly it would never have cooled, or if it did cool a rapidly as required, even over billions of years, the earth’s surface would still be too hot to walk on.
Another reason why the entire earth cannot have been molten is the presence of certain very dense minerals on the surface. Gold is 70 percent more dense than lead, and melts at 298 K, a colder temperature even than the mantle. Had the earth ever been molten, gold would have sunk, probably to the outer core. Nor is gold commonly found near volcanoes, so gold does not come to the earth’s surface by that route. (But gold will dissolve in very hot, especially supercritical, water, and will precipitate if such water is released.)
Zircons contain a number of trace elements whose presence indicates that the zircons formed at a temperature below 373 K (the approximate boiling point of water). But by radiometric dating, zircons are among the oldest objects on earth, old enough to have formed during the molten period. This is an obvious contradiction, but does not mean that the zircons are actually as old as that. (In fact, they’re not, but then, neither is the earth itself.)
The Hydroplate Theory of the Flood suggests that gravitational settling and friction occurred in the final stages of the Flood event. Brown calculates that gravitational settling alone released 29 undecillion ergs of energy, more than three times the amount needed to form the inner and outer cores. The rest of that energy probably went to heating the cores to their present temperatures. But it would not have been sufficient to melt the mantle and crust, because it was not evenly distributed throughout the earth.
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