Some mechanical curiosities connected with the Earth's field of force

Increased Caribbean seismicity and volcanism during minima in Earth’s rotation rate: Search for a physical mechanism and a 2030 forecast

“…Early in the last century Wegener (1980) invoked polflucht as a mechanism to move continents from the poles toward the equator (Epstein, 1921;Lambert 1921;Krause, 2007). Although this acceleration and its attendendent forces have been subsequently neglected, they influence Coulomb failure conditions on plate boundaries.…”

“…That is, at great distances from the earth, or beneath the Earth's surface, co-geoids tend to become more spherical, whereas at the Earth's surface they are spheroidal. The origin of the polflucht acceleration is most easily visualized (following the discussion outlined in Lambert, 1921) by imagining a large spherical ball-bearing free to roll upon a smooth, perfectly-horizontal surface, such as a frozen body of Frontiers in Earth Science frontiersin.org water, or a perfectly horizontal airport runway. The base of the ball lies on a co-geoid and its point of contact is thus on an equipotential surface and is in equilibrium.…”

“…As a consequence (in the absence of friction) the ball would roll southward as its center of gravity essentially accelerates "downhill" along this higher geoid, away from the poles and toward the equator. Lambert (1921) calculates that the resulting horizontal acceleration is small (<0.001 µGal) for continents where the center-of-gravity and center-of-buoyancy may be of the order of a few hundreds of meters. The difference in radial separation between the c-of-g and the effective c-of-b of the Caribbean is considerably larger and separated also in a latitudinal sense.…”

An equatorward force acting on large floating ice masses: Polfluchtkraft

“…The force that drives floating icebergs on a rotating Earth towards the equator, the Polfluchtkraft, has been recognized since the beginning of the last century (Kreichgauer, 1902; v. Eötvös, 1913; Epstein, 1921; Köppen, 1921; Lambert, 1921; Schweydar, 1921; Berner, 1925; Wavre, 1925; Wegener, 1929) . In the shadow of the long-lasting debate about its significance for continental drift or plate-tectonics, smaller scale applications like its bearing on the drift of icebergs seem to have been virtually forgotten.…”