Plate tectonics appears to have no accepted explanation for the widely recognised cycles of kilometre scale uplift and subsidence - why they appear to have such regular periodicity measured in many 10’s million years, why they seem to occur synchronically over widely dispersed geographic domains, and why they so often occur at locations where plate tectonics suggests passive tectonic activity. This short paper reconsiders these cycles of uplift and subsidence so strongly in evidence within the Grand Canyon area, and especially the timing of the onset of new pulses of sedimentation as revealed by the dates of strata immediately above the major unconformities. This suggests that commencement of new pulses of marine sedimentation initiating continuous kilometre scales of burial have a strong periodic signature of circa 130Ma. It is demonstrated that these recommencements of burial of often mega sequences of sediment occur when earth climate is emerging from ice-house to hot-house conditions. Furthermore, it is pointed out that recognised periods of mountain building have similar 130Ma periodicity with phasing closely aligned with periods when earth is experiencing ice-house conditions. Tentative explanations as to why changes in climatic conditions could account for these kilometre scales of uplift and subsidence focus on the associated changes in the surficial disposition of ice and water associated with ice- and hot-house conditions and how this effects the geothermal flux. Changes in geothermal flux will as a result of phase changes at the lower crustal boundary producing changes in crustal thickness and hence crustal buoyancy, accounting for both the massive cycles of burial and those of exhumation.