Risk of another Crustal Overturn is still high!
I have already shown how the global crust can move, and have a dramaticeffect on the world climate. There is one event that has quite a high probability that could move the poles yet again.
A large area of the Antarctic ice sheet is unstable and could collapse.The collapse of a floating ice shelf doesn't matter - it doesn't effect thecrustal distribution of mass. But should an inland ice mountain collapse,and flow as a glacial surge into the sea, the movement of mass will be fargreater than crustal deformation can compensate for.
The Earth must rotate round its centre of mass. If a sufficiently largemass of the crust moves, then the centre of rotation must move - instantly!The earth's core is not going to shift as it is so vast in relation to thecrust, so if the crust becomes out of balance, it is the crust that has tomove. The crust will move until it is again in balance round the axis ofrotation. If we are lucky this could be a few hundred kilometres, but itcould overturn completely again, with north replacing south, but with theold poles a few hundred kilometres away from the new axis of rotation.
There is plenty of evidence from the past that this can happen repeatedly, with coral reefs replaced by glacier deposits, replaced in turn by coral reefs.Then, the pendulum of the imbalanced crust came to rest with the old poleson the equator, and the old equator now running through the poles. The slowbuild up of ice at the new poles only ended with another major collapse, andthe poles swung to the equator again.
The warm spell in Europe that followed the ice age could have been brought to an end by just such a collapse of an ice sheet. At the end of the crustal overturn that ended the last ice age, the North Pole could have been closer to Siberia and Alaska by several hundred kilometres. The British Isles and Europe would have been in a much warmer climate, but the collapse of one ofthe melting ice caps could have triggered a crustal shift that moved the poleout into the middle of the Artic Ocean, where it is now. The whole of Europefound itself in a colder temperate climate overnight!, and North America warmed.
The collapse of Glacial Lake Missoula released 500 cubic miles of waterin as little as 48 hours. This could have been enough to trigger a crustalshift. .
" The age of the later Missoula floods into southern Washington is limited by the intercalated 13,000-years B.P. Mount St. Helens ash (Mullineaux and others, 1978), which overlies at least 28 flood rhythmites and underlies at least 11 (Waitt, 1980b). A new radiocarbon date from a shelly dune at the top of the third Missoula-flood rhythmite belowthe as bed at Mabton is 14,060 +/- 450 years B.P. (USGS-684). The 11,250+/- 250-years Glacier Peak ash-layer G (Mehringer and others, 1984) postdatesice-sheet retreat in Washington and Montana (Waitt and Thorson, 1983); itoverlies deposits of one huge flood but not those of small floods that followeddeglaciation of the Columbia valley (Waitt, 1982a, 1982b). All considered,the various limits on the ice sheet and floods suggest that glacial LakeMissoula existed for 2,000 to 2,500 years between 15,300 and 12,700 yearsBefore Present."
The repeated collapse of glacial inland seas such as this could have produced the crustal shifts that moved the poles slightly, and resulted in slight variationsin the pattern of ice sheets that we see throughout the last ice age.