[Havoc]

This assumes there have always been ice caps or that there has always been an excess of water. River channels under the ocean and extending well down toward the sea floor have never been explained. Like on the surface of Mars, it is significant; but, often sidestepped, ignored or otherwise avoided in science. From what I've read, no explanation given to date has held up under scrutiny. Mudflows do not create the friction needed to do the job. Currents are in the wrong direction and don't have the force needed, etc.

If they were worn by natural river flow as would have to be a primary consideration, then the problem presents itself. Where did the extra water mass come from. This is not a stand-alone issue. There is a vast tropical forest submerged under the northern ice sheets at roughly 1 mile below sea level if memory serves. An Ice mass that large would have to be explainable in some manner; but, that too is problematic in that in this case, we are talking not about pack ice like in ice bergs or snowcaps, etc. It's Rock ICE and apparently would have to have formed where it sits. Rock ice forms from sleet or freezing rain and does so rapidly. So where does several thousand cubic miles of rock ice come from if it precipitates into place and a forest preceeded it's location? If a forest was there before the ice, where did the excess mass of water come from that made the ice. Keep in mind that this much mass of ice would really screw with the planet if it were at the poles to begin with.

Where'd it come from.

[Cronos]

Ice -- would form at the coldest places -- high altitudes and high latitudes. This occurred during the ice ages when glaciers stretched over land and sea. When the ice age ended and the glaciers melted, the water went to the lowest spot due to gravity -- the oceans. the oceans expanded to accommodate this extra liquid H2O and ate into the coastlines.