The first calculation of the force of the drift from the poles was carried out by P. S. Epstein.[1] He found the expression for the force K in the geographic latitude π to be
Kπ = β 32mdπ2sin 2π,
where m is the mass of the continental block, d half the difference in altitude between the floor of the ocean and the surface of the continental block (or, equal to the difference in level of the centres of gravity of the block and of the displaced sima), and π is the angular velocity of the earth.
He used this equation in order to calculate the coefficient of viscosity π of the simasphere from the velocity of displacement of the continental blocks (according to the general formula K = π vM, where M is the thickness of the viscous layer), and obtained
π= πsdMπ2v,
where π is the specific gravity of the block and s its thickness. Using now the following numerical values, which are certainly very extreme,
| π | = | 2.9 |
| s | = | 50 km. |
| d | = | 2.5 km. |
| M | = | 1600 km. |
| π | = | 2π86164 |
| v | = | 33 m. per annum, |
he found the coefficient of viscosity of the sima to be
π = 2.9 Γ 1016 g.cm.β1 sec.β1,
thus being three times as great as that of steel at room-temperature. He concludes from this that βwe can summarize the results thereof in the state-
- β P. S. Epstein, βΓber die Polflucht der Kontinente,β Die Naturwissenschaften, 9, Part 25, pp. 499β502, 1921.
