the worry is the negative feedback loop
@Mike Richards first of all - Canada hasn't migrated. Some of the plates that make up that part of Canada have migrated in so much as the sediment was laid down and lithified at or around the equator however many millions of years ago and those bits of plate are now up in Northwest Canada. Other bits of Canada will be from other longitudes / latitudes and will be parts of plates that previously or subsequently collided with older bits of "Canada" to make up what is now Canada.
The geology of Great Britain contains bits of rock from all over the world, munged together into what is now this island.
Secondly looking at the timescale of these glaciations is alarming. 5 million years between snowball earth and complete absence of ice points to some interesting feedback mechanisms. Although life on earth today is completely unrecognisable from pre-Cambrian life, there will be some common features such as the presence of organisms that photosynthesize and the presence of organisms that eat the photosynthesizers. By turning sunlight and CO2 into oxygen, body mass and energy it is clear that life on earth has shaped and moulded the planet as much as any other process occuring on the planet's surface. It is also clear that the processes that were around 700mya are, give or take, around at the moment. It would be interesting to note whether subsequent glaciations were immediately preceded by rising temperatures and CO2 levels - which could be measured or at least indicated from foraminifera. If this turns out to be the case then there is probably some sort of feedback loop driving it. Might be something along the lines of:
1.) CO2 increases, temperatures increase, basal ice mass temperatures increase, ice starts melting, salinity of oceans drops.
2.) Decrease in salinity of oceans slows ocean currents which leads to increased variation in temperatures as ocean heat transfer slows down. Atmospheric warming however leads to increased precipitation, higher levels of atmospheric water (to drive the feedback) and accelerates atmospheric heat transfer from equator to poles.
3.) At some point the mass of cold, melted, low-saline water from the poles becomes too great and in a move similar to El Nino, it rushes under the warm equatorial water. At this point there is a massive ingress of cold water at the equator pushing the warm water out to the poles, cooling as it goes. The warm water triggers massive evaporation and subsequent precipitation, as snow, at the poles leading to expansion of icesheets which then leads to consequential high albedo and cooling.
4.) in this way a global warming phase is halted and reverted back to a cooling phase which could see disastrous consequences for us humans.
It is irrelevant what contribution towards that heating-cooling cycle is anthropogenic although the mechanism makes it clear that if there is an anthropogenic contribution, it is only to make the eventual "temperature crash" much worse.
I may of course be entirely wrong, it's been a while since I did much paleoclimatology / paleoglaciation stuff.