99. Is volcanism related to magnetic changes?
Is there any study that correlates the change in movement of the earth's magnetic field with the quantity, size etc. of volcanoes, or even change in land elevations? It appears that if the solid core 'wobbles' and causes eddies and change in flow in the liquid core, that there should be some consequence on the surface of the earth.
Reply
Volcanoes do not come from the core, but from relatively shallow depth. The core is molten and so is lava, but its density (obtained by various means, e.g. earthquake waves) is something like 10 times that of water, maybe more, as expected from iron under pressure, which also conducts electricity, as required from a source of the Earth's magnetic field.
Lavas have different compositions at different locations, but all of them are stony, they do not conduct electricity and have a density of maybe 3 times that of water.
Lavas come from the crust of the Earth, where also most of the heat sources seem to be, namely, long-lived radioactive substances. Lava collects in relatively shallow reservoirs, say 50 km deep, the depth where earthquakes occur. A few sources of volcanism, so-called mantle plumes (e.g. below Hawaii) do go deeper, but you need cross the entire mantle--about 3000 km more--to reach the molten core.
So I do not think volcanism and magnetism are related on the short
term. On the long term--tens of thousands of years, maybe--volcanism may be related to the uneven distribution of heat generation in the earth's crust, and by the uneven escape of heat from the Earth. If the flow of molten core material is driven by heat flow from the Earth, then magnetism may be affected by the pattern of heat flow, too, as suggested by the work of Coe, Hongre and Glatzmeier, but it is probably a slow process.
100. Nuclear reactor at the Earth's Center?
[This follows a phone call from Marvin Herndon on 25 July 2007. He is the author of a theory, arguing for a fission reactor near the center of the Earth. He later sent a link to his new paper "Nuclear Georeactor Generation of Earth's Geomagnetic Field," submitted to Current Science and posted in PDF format at
http://www.arxiv.org/ftp/arxiv/papers/0707/0707.2850.pdf
The fission regon which he proposes is very compact, with radius around 7 kilometers. He sidestepped the question how it is that most evidence suggests that almost all the heating of the Earth's interior originates in the Earth's crust.]
Reply
Dear Marvin
I looked very briefly at your paper. Some comments
(1) Loadstone is not ordinary magnetite. See
http://www.phy6.org/earthmag/lodeston.htm
(2) Gauss did not prove that the Earth's magnetic field originated at or very near the center. All he showed is that it predominantly originated inside the Earth, not outside it
In fact, the Gauss analysis suggests it would be very difficult for the field to originate within 10 km of the center, as you seem to imply. The reason is that the dipole field goes like 1/r3, so extrapolating a surface field of 0.5 gauss to a distance of 10 km gives you something like 100,000 gauss. No permanent magnet can produce such a field--besides, the center is too hot for permanent magnetism. The source therefore must involve electric currents, and the force on that current would be enormously large.
(3) I am not familiar with geochemistry, but understand you seem to say that the core of the Earth is not mostly iron, but maybe silicate. Most geophysicists I know assume otherwise, arguing that dense iron sinks to the bottom, as in a blast furnace, and that iron is a very common element (based on observations--e.g. red Mars--and also on iron having the most stable nucleus).
But there is more. We know the moment of inertia of Earth (0.33 m RE 2, against 0.4 m RE2 for a sphere with uniform distribution) suggesting that it is considerably more dense near the middle. See under "moment of inertia of Earth" in Google. The value observed fits with a core consisting mostly of iron.