December 5, 1956
Dear Professor Hess:
I have read with vivid interest your paper on the guyots in the Pacific: I will continue here to think aloud. The size of the guyots is no argument against their volcanic nature. The truncated upper surface of a guyot nine miles wide is larger than the widest known crater on earth, yet certainly smaller than Mauna Loa in cross-section measured half way from the bottom of the ocean. I would not shrink even from thinking of them as gigantic mesas: some of the shapes in your drawings have this form. A great volcanic activity took place in the Pacific at an early age. Large stretches of lava in its bottom (Pettersson), and huge quantities of ashes indicate this. The moon with its large craters and dried seas of lava comes into mind (without agreeing with the theory of the origin of the moon from the bed of the Pacific).
Your idea of the guyots being islands submerged ca. 500 fathoms (3,000 feet) is well supported by the findings of M. Ewing in the Atlantic (sand beaches submerged 3 miles, or 15,000 feet).
The explanation of isostatic subsidence of the oceanic floor weighed with accruing sediment requires enormous amounts of this sediment and, I ask myself, whether the figures would hold this portion of the theory. You assume that the oceanic area would decrease because of submergence of the bottom loaded with the sediment and prisms of it along continental margins. Would not the oceanic area increase in such circumstances? The submergence would be more than compensated by the accrued sediment and the displaced water would encroach on the coasts.
I am not familiar with the calculations concerning loads in relation to isostatic subsidence. I assume that a layer of ten feet of sediment would not lower the bottom by the same amount of ten feet, and probably not even by a single one. An earth crust that is neither elastic (resilient) nor rigid, but only plastic, with magma underneath exerting only a minimal opposition to the pressure from above, would submerge a foot for a foot of load of the specific weight 2.5 (if the ocean does not change its horizontal area). Therefore 2,000 feet of sediment since pre-Cambrian time (Kuenens figure) appear to me not enough to account for the rise of the sea level relative to the upper surface of the guyots by ca. 3,000 feet (p. 296).
Also the land on the bottom of the Atlantic Ocean cannot be accounted for by isostatic movement; Ewing found very thin layers of sediment where he expected hundreds or thousands of feet deposited. All of which indicates that some other causes lifted the crust in some places and depressed it in others.
I offer here those thoughts for whatever they are worth. Since 1947, when your paper was written, you may have thought of the guyots in the light of certain facts made known by Fetters-sons expedition. I assume that his finds support your ideas of volcanic origin and submergence of these formations discovered by you in 1942.
I accompany this letter with a list including seven questions which I would like to see included in the program of the International Geophysical Year. I shall be grateful to you if you will consent to offer their inclusion in the program (a carbon copy is for your files.) Should you wish first to discuss them with me, please give me a ring.
I liked the friendly atmosphere last Friday when I spoke in Guyot Hall.
1. Measurement of the strength of the terrestrial magnetic field above the upper layers of the ionosphere. It is accepted that the terrestrial magnetic field — about one-quarter of a Gauss at the surface of the earth — decreases with the distance from the ground; yet the possibility should not be discounted that the magnetic field above the ionosphere is stronger than at the earths surface.
2. An investigation as to whether the unexplained lunar librations, or rocking movements, in latitude and longitude coincide with the revolutions of the terrestrial magnetic poles around the geographical poles.
3. An inquiry into the magnetic orientation of the lavas erupted in the middle of the second millennium before the present era (e.g. in Thera-Santorin) may establish the recentness of the reversal of the magnetic field of the earth.
4. An analysis of the magnetic inclination (dip) in the clay of the pottery of the Old and Middle Kingdoms in Egypt may disclose substantial shifts, actually reversals of the magnetic field of the earth; similar tests could also be performed on various neolithic pottery.
5. An investigation of the direction of the spirals of fossil snail shells and of the windings of fossil vines which are now usually clockwise in one hemisphere and counter clockwise in the other, may reveal, with the help of radiocarbon analysis, the time of changes or reversals in the direction of the rotation of the earth.
6. Measurement of the gravitational constant within a Faraday cage with varying distances between the attracting bodies in order to exclude the influence of the atmospheric electricity on the obtained results, and thus to verify the inverse square law.
7. Tests in comparing the velocity of fall — and of the acceleration constant — of charged and neutral bodies.