A paraglacial overview

This morning I had a fabulously sunny and clear flight over the Rocky Mountains as I made my way from Vancouver, BC to Calgary, AB.  It’s spring, and snow still covers much of the higher elevation areas in this part of the world, and it graciously acts to highlight the topography and landforms you can see from above.  It got me thinking about geomorphology, as most things do, and about why exactly I enjoy it so much.

Sometimes it is difficult to explain why geomorphology is important to study.  There are always default examples about sediment budgets and geo-hazards, but as I looked out over the incredible landscape of the Rocky Mountains I thought about how for me, learning geomorphology is about learning a language that can help me read a landscape.  To take the metaphor a bit further, let us consider Arabic.  I think Arabic is a wonderfully beautiful written language.  Almost everybody can appreciate its elegance.  I can’t read Arabic, though, and so although I can appreciate its superficial beauty, the real  meaning of the words is lost on me.  The same thing is true for landscapes, I think.  If I wanted to be really cheesy, I would say that although you may be able to admire Nature’s handwriting, you cannot truly appreciate it unless you understand the meaning .  That’s terrible cheesy though so I wouldn’t say that – what am I, a nerd?  I would simply say that geomorphology is the language you need to know to take your appreciation of a landscape to another level.  I like it because when I look out over a landscape, geomorphology helps me pick up on subtleties and piece together a story.

With all of that in mind, I took some sadly low-res pictures of the landscape as we flew over, and I thought I’d share some of my favourite story arcs with you.

Landscape overview

The Rocky Mountains from the air. A classic paraglacial landscape!

Above is an overview of the Rocky Mountain landscape.  This is a paraglacial landscape, which means that although most of it is unglaciated, the current geomorphic (earth moving) processes are still influenced by the legacy of the previous glaciation.  Because of this, paraglacial landscapes like this one tend to have very wide valleys and lower drainage densities than landscapes that have developed exclusively from running water (fluvial) processes.

Fluvial network development?

Fluvial network development?

In the above image, I have marked in red some channels that are fluvial (running water) in origin.  I deduced that based on how deep they are relative to their width (i.e. they are V shaped valleys instead of U shaped valleys) and because they are very close together, i.e. there is a high drainage density.  Glaciers tend to erode the valley walls between them until the ridge is very knife edged, as can be seen very well in the top of the picture, and tend to be lower density drainage basins compared to fluvial basins.  The relevance of the picture to me is that it shows very well how the landscape is changing now that the glacial influence has receded.


A very clear glacial moraine.

In the above photo, the snow and shadows have highlighted a very beautiful glacial moraine (circled in red).  Moraines are essentially just piles of sediment (rock) that are created when glaciers bulldoze through a landscape.  It looks to me like the moraines in the photo are lateral moraines (moraines on the side of a glacier) that have been left behind by a receding glacier.  You can even see the glacial toe at the top of the circle!!

Some lovely crevasses.

Some lovely crevasses.

Circled in red in the above photo is a glacier with some really neat crevasses.  Crevasses are cracks that form on glaciers from stress as they move.



Ok, this is a terrible picture.  I had to include it though, because we were flying over this lake and it was perfectly dotted with these little deltas!  I circled them in red – don’t worry if you can’t make them out very well, though.  These are areas of sediment deposition that are found where a stream is entering a lake.  The foremost one is probably the best example.  As you can see, the stream is coming in from a very confined valley.  Two things happen to form this depositional landform.  Firstly, the stream is a high energy system that is very confined within its valley.  When it enters into the main valley (where the lake) is, it achieves what is essentially unlimited channel width, which causes it to lose energy and deposit its sediment load.  Typically this kind of landform is called an alluvial fan.

Hanging valleys

Hanging valleys feeding into a main U-shaped valley.

This picture shows some of the really dramatic impacts of glaciation on a landscape.  The main valley to the right of the picture is a huge U shaped valley left behind by a main trunk glacier.  To the left you can see small valleys coming in which look essentially snub-nosed.  These valleys are formed where smaller tributary glaciers joined up with the main glacier, although they did not erode as deeply.  The result is small valleys that are left perched above the main valley.  These valleys are known as hanging valleys.

The checker board pattern of clear cutting.

The checker board pattern of clear cutting.

Finally, you could not really look at the geomorphology of this modern landscape without considering the impact that we humans have on the world around us.  This picture shows the dramatic visual impact of clear cutting on the landscape.  It looks like a checker board, no?  Checkmate, Nature!  Your move.

And there you have it!  A slightly different take on a flight over the Rockies.  Next time you are flying with your kids, you can play spot the landform!  Or if you are in first class, make it a drinking game.

2 thoughts on “A paraglacial overview

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