Underground Rivers - University of New Mexico

Chapter 14 -- Hollow Earth Geophysics
CHAPTER 14
HOLLOW EARTH GEOPHYSICS
This chapter describes hollow earth geophysical hypotheses based scientific conjecture, as
opposed to a pseudo-scientific hollow globe described in popular fiction.
We'll first take our look at the geophysics of such worlds, and then be made parly to perhaps the
greatest geophysical secret ever, the Polar Hole.
The Geophysics
We first met Edmund Halley (1656-1742) in Chapter 12 where his estimation of evaporation
helped quantify the hydrologic cycle as we now know it. Halley was likewise interested in the
earth's magnetic field, concluding “that the Globe of the Earth might be supposed to be one great
Magnet, having four Magnetical Poles or Points of Attraction” -- Philosophical Transactions of the
Royal Society (1683).
No Magnet I had ever seen or heard of had more than two opposite Poles, whereas the Earth
had visibly four, and perhaps more... [and] these Poles were not, at least all of them, fixt in the
Earth, but shifted from place to place…whereas it is not known or observed that the Poles of a
Load-Stone ever shifted their place in the Stone.
[The cause of geomagnetism must] turn about the Centre of the Globe, having its Centre of
Gravity fixt and immoveable in the same common Centre of the Earth, [but must be] detached
from the external parts.
In order to explain the change of the Variations, we have adventured to make the Earth hollow
and to place another Globe within it; and I doubt not but this will find Opposers enough. I know
‘twill be objected, That there is no Instance in Nature of the like thing; That if there was such a
middle Globe it would not keep its place in the Centre, but be apt to deviate therefrom, and
might possibly chock against the concave Shell, to the ruine or at least endammaging thereof;
that the Water of the Sea would perpetually leak through, unless we suppose the Cavity full of
Water.
The solution: a hollow earth of concentric shells, not unlike the yet-to-beinvented
dynamo. The outer shell is 500 miles thick. Drawing upon his
planetary knowledge, Halley determined that the two inner shells have
diameters comparable to Mars and Venus and the solid inner core is the
size of Mercury.
DRAFT 1122//66//22001122
Uppddaatteess aatt hhttttpp::////www. .uunnm. .eedduu//~rrhheeggggeenn//UnnddeerrggrroouunnddRi ivveerrss. .hhttml l
139