Sunday, June 6, 2010

Vancouver Island's Ice Ages

I know I said earlier that there were two processes involved in the geologic development of Vancouver Island, but there were really three, although the third is external to the earth's crust. 1. Was the volcanic activity out in the Pacific ocean, and elsewhere. 2. Was the collisions and subduction of the plates and 3. Was ice, or perhaps more correctly, the forces of ice, wind and water, as our entire continent is gradually being ground down and flattened out once again, while others are still forming.

Interestingly, one of the arguments frequently deployed by the oil and coal industry proponents who are in denial about climate change, is the undisputed fact that ice age cycles have frequently come and gone over much of the globe's surface. (This fact has of course little to do with the carbon dioxide caused, greenhouse gas effect which results to a major degree from man's carbon burning fuel activity, which has increased so dramatically since the era of the industrial revolution).

It is difficult to visualize a layer of ice so thick above our island paradise that it could be measured in kilometers, or to imagine the North American continent, with only the peaks of the mountains showing above the ice layer. Obviously these enormous ice blankets, together with the rocks that they drag across the earth's surface, and the force of the melt water as they retreat, jointly grind down, and cut through mountains. One of the other less obvious effects of ice sheets is to depress the earth's crust under their enormous weight, so that land masses would sink and rebound, above and below the sea level, which itself would rise and fall in accordance with the relative volumes of ice and water.
This glacier is on the steep slope of a mountain high above the Nisga'a highway, North of Smithers, BC.

Paleoclimatologists - there's another of these melodramatic scientific designations for you - have discovered a strangely regular pattern of glacial cycles. The timing of the cycles is apparently set by minor changes in sunlight caused by slow variations of the Earth's orbit, which is elliptical rather than circular.There have been at least 5 major ice ages in the history of the earth plus many lessor ones. The most recent cold period peaked at a glacial maximum some 20,000 years ago, when extensive ice sheets lay over large parts of the North American and Eurasian continents. (Fossil evidence indicates that homo sapiens has been around for some 200,000 years, which means that the earlier members of our species must have figured out how to keep themselves warm without the benefits of oil or coal)

So when will we return to one of these extended ice ages? Well, I don't know about you, but I'd be more inclined to worry about earthquakes, tsunamis or another volcano like Mount St Helens suddenly springing back to life... if I was the worrying type.

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