Inside Earth

Scientific Basis of Knowledge on Earth's Composition

Correcting an Institutionalized Blunder

J. Marvin Herndon (2005) Scientific Basis of Knowledge on Earth's Composition. Current Science, 88, 1034-1037. Click here for pdf

Just a few hundred years ago, people did not know what is inside Earth or whether the inside is solid, liquid, or gas. Many people thought the Earth is made of rock, because rock is everywhere, and even comes out melted from volcanoes.

In 1897 Emil Wiechert, pictured at left, realized that the Earth is too dense to consist wholly of rock. In museums Wiechert had seen meteorites made of iron, made of stone, and made of both stone and iron, like those pictured at right. He made the bold suggestion that the Earth has at its center a core, like the metallic iron of meteorites, which could account for Earth’s great density.

In 1906 Richard Oldham, pictured at right, found that beneath the crust the velocities of earthquake-waves increase with increasing depth, but only to a particular depth, below which their velocities become abruptly and significantly slower. Oldham thus discovered the Earth’s core.

During the next twenty five years, the dimension of the Earth’s core was determined precisely and its state was shown to be liquid due to its failure to support S-type earthquake-waves. By 1935, the inside of the Earth was thought to consist of a fluid iron core surrounded by a solid rock mantle. But how can that be known? Studies of earthquake-waves can only determine structure and state (liquid or solid), not composition. Deep-Earth composition is inferred from the compositions of meteorites, sometimes incorrectly.

When P-type earthquake-waves enter and leave the core, they change speed and direction. Consequently, there is a region, called the shadow zone, where earthquake-waves should not be detectable.

But in the early 1930s earthquake-waves were in fact detected in the shadow zone. In 1936 Inge Lehmann discovered the inner core by showing that a small solid object, within the fluid core, could cause earthquake-waves to be reflected into the shadow zone. The inner core is an object slightly smaller than the Moon and about three times as massive and is at the center of a very great geo-mistake.

In 1940 Francis Birch, pictured at right, pronounced the composition of the inner core to be partially crystallized nickel-iron metal, like an ice-cube in a glass of ice-water. Birch envisioned the Earth to be like an ordinary chondrite meteorite, the most common type of meteorite observed to fall to Earth. He ignored the rare, oxygen-rich carbonaceous chondrites, which contain little or no iron metal, and he ignored the rare oxygen-poor enstatite chondrites, which contain some minerals, such as oldhamite (CaS), that are not found in the surface regions of the Earth. Birch thought that nickel and iron were always alloyed in meteorites and he knew that the total mass of all elements heavier than nickel was too little to comprise a mass as large as the inner core. Birch therefore assumed that the inner core was nickel-iron metal that had begun to crystallize from the melt. That assumption, which underlies much geophysical and geochemical development over the past six decades, is unfounded and set the geoscience community on a "wild goose chase" for more than half a century.

From discoveries made in the 1960s, J. Marvin Herndon, pictured at left, realized a different possibility for the composition of the Earth’s inner core, which he published in the Proceedings of the Royal Society of London in 1979, click here for pdf.

The abstract in its entirety states: “From observations of nature the suggestion is made that the inner core of the Earth consists not of nickel-iron metal but of nickel silicide”.

Whereas Birch had thought that nickel and iron were always alloyed in chondrites, Herndon realized that elemental silicon, found in the metal of enstatite chondrites, under appropriate conditions could cause nickel to precipitate as nickel silicide, a compound of nickel and silicon, which had been discovered in enstatite chondrites. Significantly, a fully crystallized inner core of nickel silicide would constitute a mass virtually identical to the observed mass of the inner core; no such predictability exists for Birch’s concept of a partially crystallized nickel-iron metal inner core.

So what did Inge Lehmann, the discoverer of the Earth's inner core, think about Herndon's idea of the inner core being composed of nickel silicide? She wrote to him, "I admire the precision of your reasoning based upon available information, and I congratulate you on the highly important result you have obtained". To see a copy of her letter, click here. And, what about the response from other geophysicists? Silence. They systematically ignored the idea. But is that really science?

When a contradiction to an important concept arises in science, the new idea should be discussed and debated; experiments and theoretical calculations should be made. If the new result is found to be wrong, it should be refuted in the scientific literature, ideally in the journal of original publication; otherwise, it should be cited in subsequent publications on the subject. This is because real science is about discovering the TRUE nature of the Earth and the Cosmos. So-called scientists who do not adhere to that ethical standard do a great disservice to humanity and to themselves, trapping themselves in a logical cul-de-sac, keeping themselves from progressing logically to the next level of discovery.

So what is the logical progression of understanding here? The nickel silicide inner core concept led to the enstatite-chondritic-endo-Earth concept, which led to the concept that the matter at the core mantle boundary consists of low-density, high-temperature precipitates from the core, and further led to the understanding of why uranium would be expected to exist in the core, which then led to the idea of a nuclear fission georeactor at the center of the Earth as the energy source for the geomagnetic field.

Read the details: J. Marvin Herndon (2005) Scientific Basis of Knowledge on Earth's Composition. Current Science, 88, 1034-1037. Click here for pdf and enjoy the deep-Earth representations, left and right, which have come from Herndon's work.

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