what effect would the loss of the Greenland ice sheet and the Antarctic ice sheet have on the tectonic plates

Question

i know that scotland and northern england is still rising because of the loss of the ice sheets that once covered them. but what affect would ther be in countries like new zealand, canada and the u.s.

Answer 1

Well, it would not change anything on the order of subduction, volcanism, earthquakes, etc. But you are right, there would be uplift, but it is not tectonic, it has to do with the bouyancy of the plates. It is called isostatic rebound. It would highly uplift Greenland, and might have a small effect on Canada. Canada, of course, still has its own isostatic rebound, mostly near Hudson Bay.

Answer 2

There would be several effects arising from the loss of the world's two main ice-sheets - some local and some global in scale. Obviously there would be a world-wide rise in sea-level of the order of 70-80m (about 250ft) and locally there would be very substantial 'isostatic' rebound of the Earth's crust in the areas previously weighed down by the thick ice.

Taking Greenland's icecap first - much of the centre of Greenland lies below present sea-level - I'm talking here of the rock surface and not the ice surface of course! This would rise once the weight of the overlying ice had been removed and would emerge above sea-level. This rise would involve some 'plastic' flow of underlying rocks and some brittle fracturing ie fault activity = earthquakes/tremors, over a long period of time - many tens of thousands of years and beyond.

Now this activity would take place within the confines of the tectonic plate of which Greenland forms a part but it is hard to see how it might influence the lateral movement of the plate which is a westward movement away from the mid Atlantic ridge spreading zone.

The situation would be similar in Antarctica.

Incidentally the higher global sea-levels would have not only the effect of flooding the lower lying margins of the worldd's continents and of course many oceanic islands but would have a similar effect to the ice on the land which they submerged - the extra weight would cause the flooded land to sink even further.. To compensate for this sinking there would be a rise in the land surface just beyond the areas which were inundated - after all the volume of the 'solid' earth cannot change appreciably. this would be achieved by the slow flow of lower custal rocks and mantle from beneath weighted areas to areas that were unweighted. The whole thing would be rather complicated to work out due to the fifferences in rock types and structures from place to place, the intricacies of the coastline etc etc

Answer 3

I wouldn't be so quick to dismiss an impact on plate movement as some respondents.

The argument that the isostatic rebound is "vertical" and wouldn't affect the "horizontal" plate movement is a bit misleading. The plate movement is also in many ways vertical; the older, colder lithosphere at the subduction zones sinks, while the new crust at the ridges is rising. The plates are in effect "sliding downhill". So greatly changing the weight distribution on a plate could accelerate or decelerate this slide, depending where on the plate the weight was.

The idea that the global tectonics is largely independent of surface environment, which is in effect superimposed on it, is becoming increasingly discedited. The effects of erosion, glaciation etc directly influence things like available water on faults and mass distribution, and thus they are as much the drivers as the driven.

Answer 4

The chances are very little to areas outside the direct effects. It may cause some extra Earth quakes or volcanoes to erupt in the area concerned but as the uplift is so slow, Scotland has been rising for thousands of years and Southern England is still sinking still waiting for the rebound down here. I would be more concerned with the effect that losing the sheets would have on the oceans and the worlds climate.

Answer 5

Isostatic related to IceSheets weigth is one theory and have no relation to Tectonic plates movement. Are two separeted events, linked only into a general context of Isostatic theory.

The formation of ice-sheets can cause the Earth's surface to sink. Conversely, isostatic post-glacial rebound is observed in areas once covered by ice-sheets which have now melted, such as around the Baltic Sea and Hudson Bay. As the ice retreats, the load on the lithosphere and asthenosphere is reduced and they rebound back towards their equilibrium levels. In this way, it is possible to find former sea-cliffs and associated wave-cut platforms hundreds of metres above present-day sea-level. The rebound movements are so slow that the uplift caused by the ending of the last Ice Age is still continuing.

.. meanwhime tectonic plates can have influence from isostatic theory in special events.

Answer 6

If the ice sheet metled a given load of ice would be removed, this would result in isostatic rebound. As the weight on the crust is removed the rocks can "fluff up". Isostacy is related to the buoyancy of the lithosphere on the asthenosphere below. Loading results in subsidence as seen in active sedimenetary basins and removal of material results in exhumation.

There would be no direct effect on the tectonics themselves but the plates may show isostatic rebound (land will rise).

Answer 7

With regard to "tectonic plates" -- probably nothing. The ice sheets are technically floating -- so, it's not like it directly touches the ocean floor (where tectonic activity is). If you are asking about water levels, that's a completely different matter.

Answer 8

The isostatic rebound probably would not rebound up to the height of the original ice elevation since rock is much heavier than ice.

Answer 9

No effect, other than a slight one due to the excess weight of water with higher sealevel.

Answer 10

There would be a catastrophic imbalance in pressure, causing Canada to be jettisoned from Earth at a tremendous speed, before landing somewhere around Jupiter.