Monday, 21 January 2013
These two photos are from the Ouimet Canyon spillway in Canada -- 2.5 km long and over 100m deep. It has carried a phenomenal amount of meltwater from the glacial lakes that developed at the end of the last glaciation as the Laurentide ice sheet was retreating back to its core area. But this feature is not the result of a single catastrophic event -- the channel has a very complex history, and is now accepted as a "composite" channel which has probably been used many times, over millions of years.....
This is the Red Rock Pass, which carried vast quantities of water from the overflowing of Lake Bonneville in the USA. It's a very impressive feature, and is justly famous -- but again it seems to have been used more than once.
Click on this one and give it careful scrutiny. Beyond the ice edge, this is complex terrain, with many areas of glacial and fluvioglacial deposits among the bedrock outcrops. The terrain is hilly, and there are many meltwater lakes. But note that the water NEVER flows back into or under the ice. On the other hand there are long stretches of ice front where the meltwater flows in well defined streams along the ice edge, going from one lake to another.