June 30, 2016

The Chocolate Milk Event: a Glacial Outflow Mystery

A few days ago, we had an afternoon off, and planned to hike to "Iceberg Lake," up above Bow Glacier Falls. This hidden lake sits just below the Bow Glacier, and has an old, unofficial trail to its shore. The only tricky bit is that you have to ford a glacial creek to get there.

The Bow River under normal conditions
On the way up towards the falls, everything was looking pretty normal. The upper Bow River, coming down from the falls, was its normal steely, glacial blue. We turned to look at the mountains, and when we turned back a moment later, the colour of the river had changed to that of chocolate milk. We looked down river, and there was a tsunami of brown heading towards the lake!

Needless to say, when we got to the ford, it was impassable, so we followed the trail parallel to our chocolate milk stream, until we could go no further. Our path was blocked by a side stream that was at full boil. There were three other hikers there, who had crossed the side stream an hour earlier, when, they said, "it was a trickle." They'd barely made it back across.

Nadine watching the mystery side stream turning everything chocolate brown
Unfortunately, we didn't have time to bushwhack any further, but we're guessing that a glacial ice dam or moraine dam had given way, and the glacial runoff was... well, off and running.

Back at the delta, there were plumes of brown coming into the lake. As we headed home, we wondered if anyone else had watched this little mystery unfold, and we marvelled at the weird, little curveballs that nature can throw out there when you have an afternoon off in the Rockies!

Runoff coming into Bow Lake