moraine

A murrain on my brain. As Bugs Bunny would say, what a maroon I am. I should have remembered you need more rain to make an esker from snirt. And so a commenter who goes by Rain, Rain informed me that there’s a rhyme geologists use to recall the difference between eskers and moraines:

The melt that flows
Into the drains
Leaves behind eskers
Not moraines.

But dirty snow
That just retreats
Leaves small moraines
Upon the streets.

I knew of moraine, of course. When I was a kid, we would often go hiking above Moraine Lake, near Lake Louise in Banff National Park. We’d go in early fall to Larch Valley, where there is a stand of (guess what) larch: deciduous conifers – they look like evergreens but their needles turn orange in the fall and fall on the ground. My parents, being from western New York State, were used to very colourful falls, and autumn in Alberta is for the most part basically a few days of yellow followed by the browns and greys of early winter. So we would go for larch and lunch. But first, or last, or both, we would climb the moraine.

That pile of moraine at the mouth of the lake gives you a million-dollar view. Well, OK, it gives you a 20-dollar view, at two dollars per peak. You see, it used to be featured on the back of Canadian $20 bills, and the valley the lake is in is the Valley of the Ten Peaks. The lake is kept a lovely colour by constant influx of rock flour. Rocks just keep coming down from those peaks. And the glaciers that feed the lake grind rocks, and rocks fall into them and so on. There are glaciers all around there, and when they move on or melt away they leave piles of rock in their wake, sort of like the slime a snail leaves, only completely different. Those piles of rock, like large versions of those dirt piles left at the end of the winter, are moraine (a word which comes to us from Savoyard French).

But that pile of moraine at the mouth of Moraine Lake is not a pile of moraine. It’s more irony: the lake is surrounded by moraine and partly filled with it, but the moraine for which it is named is actually the debris from a rockslide. A big pile of rocks came down from one of the surrounding peaks and dammed off the end of the valley, causing the lake to form. The lake is more rain and runoff than moraine! Might as well call it Maureen Lake – to make a set with Louise and Agnes nearby.