Looking back in time: Geological perspectives on Canadian Rockies

If you are in the Canadian Rockies, you must be wondering, why are the colors of these lakes so blue? Why are some of the cliffs so sharp and some are blunted? What is the difference between a Glacier and an Icefield?

Formation of the mountains

  • 500 million years ago, this area was by the ocean and by the equator. This is where Pacific oceanic plate and American continental plates met. Heavier oceanic plate colliding with lighter continental plate created something like a ‘big bang’ 500 million years ago, causing sedimentary rock to rise up like a ‘fold’. If you look closely towards the bare cliffs around you, you can see clearly visible layers. The extreme pressure of the tectonic shift caused the whole sea bed, which had layers and layers of sediments over the ages, to rise up. The top most layer is the most recent, albeit millions of years old.
  • Since it was the tropics back then, an abundance of sea life and fossils can be found in the layers of sedimentary rock here. Different layers have different colors and texture from different types of rock like brittle shale, softer limestone or sandstone. Some contained hydrocarbons due to vegetation (forming into coal) and animals (forming into petroleum).
  • What is currently British Columbia, was formed during this tectonic collision from magma. But the Rockies were created from sedimentary layers pushed up; that is why you will not find any igneous rocks, like granite, here.
  • If you look carefully, the sedimentary layers are not parallel which it was when it was formed. The layers also seem to have broken along a vertical line. Due to high pressure from the weight of the rocks above, a fault develops which is essentially a crack. The rocks on either side of the faultline, slide up or down, thereby creating a phase shift. Other types of faults, caused by tectonic movements and glacier forces are also visible throughout the Rockies creating shapes.
  • Another factor to consider is the weathering by wind and glacier movement for millions of years, causing some cliffs to be extremely steep and some peaks somewhat blunted.

Color of the Lakes

Heavy and thick glaciers formed most of the lakes in this area. As gravity pulls the glaciers, the incredibly heavy ice grinds the rock into rock flour. It is so fine and light, it takes long time to settle down at the bottom of the lake. Bright sunshine is absorbed by the rock flour and only blue light from the spectrum is reflected. That’s why the color of the lakes are such vibrant blue, especially when the sun shines the brightest.DSC_1812

Glacier vs. Icefield

Best analogy to understand this is to think of the Icefields as a lake and glaciers being the rivers coming out of the lakes. Most glaciers are formed from the icefields, and follows gravity. Movement of glaciers is much slower compared to a river, comparable to growth rate of your fingernails. There are a number of glaciers in the Canadian Rockies, with the Athabasca glacier and Saskatchewan glaciers being the largest and most significant. Most lakes and rivers in this area are fed by one of these glaciers, thereby creating some of the purest form of water. Columbia Icefield is one of the largest ones in the world. It is a staggering 200 square kilometers wide and at areas more than 200 meters deep. You can spot flanks of the icefield on top of peaks and plateaus from the entire stretch of the Icefield Parkway.

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