Saturday, June 5, 2010

The traumatic origins of Vancouver Island (VI - II)

This blog will follow up on the prior one about the Pangea blob and its various moving parts:

Collisions were inevitable, and the results dramatic. Prairies were pushed, tipped, stacked, compressed and folded into mountain chains such as the Rockies and their foothills. In fact at one time our west coast was actually more or less where we now have the BC / Alberta border. From coast to coast to coast was rather less impressive distance wise in those days, eh? We are now told that the Vancouver Island we know and love, is a combination of three distinctly different fragments of the Earth's crust, which came together in stages as a result of three discrete land mass collisions.

That's one part of the story, and the other is referred to as subduction. No not seduction you dummy, but every bit as traumatic, because it results in the earth really moving... as in earthquakes. Great big ones. You see, most of BC sits on the westward moving, North American plate, whereas our little Island rests on the leading edge of the eastward moving Juan de Fuca plate... right where it slides under the N. American one. Doesn't sound at all like a really great place to live the idyllic stress-free life of an islander, does it? And this information becomes even harder to digest, when you realize that about once every 500 years or so (the scientists estimate the time lapse between major quakes to be between 200 and 1000 years, which seems rather vague to me) the friction between the two plates builds up to a point where it suddenly lets go... and we suffer a really catastrophic "big one".

Another of the snow covered mountains in the
central spine of Vancouver Island .

When is the next one due, you may well ask? Well, the last one with a magnitude of greater than 9 was in January of 1700, so your guess is as good as mine, but we may be OK for a while yet... if we keep our fingers crossed. However, we should certainly be prepared for a few smaller ones, perhaps like the 6.3 magnitude Gold River event in 2004. And lets not forget the tsunami potential. Remember Alaska's 9.2 magnitude quake in 1964, caused a wave which did considerable damage to houses and mills in down town Port Alberni. Both of these events were altogether too close for comfort.

The following website provides a record of Canadian quakes which have struck during the past decade.

I do believe it's time to go revisit my insurance agent, to re-examine the earthquake coverage specifications... before they have a chance to read these last two blogs.

No comments:

Post a Comment