A.4 Estimation of radial or centripetal forces on the Earth’s crust

From Appendix 2 consider a 1M³ of crust with an average density of 2.8 x10³ Kg.m^-3.

Taking the same values used in Appendix 2

ρ = Average density of the crust: 2.8 kg.m^-3

M = Mass of 1M³ of element of crust: 2.8 x10³kg

R = Radius of Earth (m): 6.4x10⁶ metres

ω = Angular velocity (rad s^-1): 7.27x10^-5 rads.sec^-1

Thus, Fr = Radial Outward Force (N)

= M ω².R

= 2.8 x 10³ x (7.27 x10^-5)² x 6.4 x10⁶

= 94.71 N

= c 9.65 kgf

Thus, for every 1 Tonne of Crust, the Outward Force at the Equator due to the rotational velocity = 9.65/ 2.8 = c. 3.4 kg

This is equivalent to a 0.034% reduction in weight compared with that at the poles, where the rotational velocity is zero. This is enough to cause the crustal plates to move around the Earth surface on a frictionless mantle.