The main driver of the 100 Ka and 400 Ka eccentricity (ECC) cycles of the Milankovitch model are orbital perturbations by Jupiter and Saturn (Berger, 1980, Vistas Astron. 24:103). Peale and Cassen (1978, Icarus 36:245) identified another interaction with Jupiter in the form of an evection resonance that can do geological work. This evection resonance with Jupiter can occur only when the lunar orbit is at 53.4 earth radii (ER). For this resonance the perigean cycle (a prograde motion of the perigee point of the lunar orbit) is in step with the mean orbital motion of Jupiter (~12 years). During the lead-in phase of the evection resonance the ECC of the lunar orbit is increased significantly when the semi-major axis (SMA) of the lunar orbit is ~50 ER. This increase in ECC causes higher rock and ocean tides during perigee passages. The lead-in phase is estimated to be ~100 Ma to reach a maximum ECC which is controlled by the deformation properties of the lunar body. If the ECC is increased to 0.28, then the rock and ocean tides at perigee passage are ~2.5 times higher than those tides associated with a circular orbit of 53.4 ER. Davies (1992, Geology 20:963) and Stern (2005, Geology 33:556) have suggested that the modern style of plate tectonics commenced ~1.0 Ga ago. The question is: COULD THIS GEOLOGICALLY LENGTHLY, JUPITER-POWERED EVECTION RESONANCE BE THE PARTIAL CAUSE FOR TRIGGERING SLAB-PULL PLATE TECTONICS?

Venus can cause evection resonances at three times in the history of the lunar orbit. The one of interest for this presentation occurs when the perigean cycle of the lunar orbit is ~10 years long and when the lunar orbit has a semi-major axis ~55 ER. The lead-in for this resonance commences before the effects of the JO-LO resonance are over. Thus, before the lunar orbit is circularized from the JO-LO resonance, the VO-LO resonance increases the SMA of the lunar orbit to ~55 ER while increasing the ECC to ~0.25. This causes perigean tidal amplitudes to be ~2.3x higher than those of a circular orbit of ~55 ER. Perhaps the abundance of tidal deposits in the early Paleozoic (e.g.,Lochman-Balk, 1970, Geol. Soc. Am. Bull. 81:3197; Holland, 1974, Wiley, 456 p; Tape et al., 2003, J. Sed. Res. 73:354) could be caused by such a VO-LO resonance.