Lesson 6: Glaciers - favorite bits

What a fascinating topic. I’ve always wanted to visit a glacier but haven’t yet. I know time is running out for the closest ones, but I’m inclined to avoid that kind of long-distance sight-seeing travel (especially by air) precisely because of climate change. So this segment is next-best, I guess. On the general production values re the labels, I LOVED that the “calve” label fell into the sea along with the ice!

  • Glaciers cover 10% of land area?!? Most of it must be at the poles?
  • Wonderful terms: firn, sintering (knew that one from the fantastic “What I Learned in Avalanche School” essay, highly recommend if you haven’t read it), ablation zone, ogives, aretes
  • Even snow is heavy! The transition from snow to firn to glacier ice was especially well-explained.
  • I had never thought about why the Matterhorn is that shape. More new ways to see the landscape!
  • I didn’t realize there were so many kinds of moraines, or that they are a dynamic part of glaciers - the laterals getting squeezed into medial moraines is especially cool.

I also found it fascinating. The only glaciers that I have knowingly walked on are the Franz Josef and the Fox glaciers on the south island of New Zealand. They are both unfortunately retreating fast. For what has happened on Franz Josef in the last decade, see the time-lapse video here

I also enjoyed the reference to Johann Jakob Scheuchzer and the belief that dragons resided in the Alps. More images can be seen here.
Francis Gribble, in his 1899 book The Early Mountaineers (p.81), wrote this:

‘For Scheuchzer fills many pages with these proces verbaux of credible witnesses who have met dragons face to face among the mountains. His belief in the beasts is as firm as the belief of his great forerunner, Gesner, in the essential beneficence of Nature. But we do not grudge it him; for his credulity in this regard is the final touch of human nature which still keeps him alive for us in spite of the long intervening years. Panting up the hillside in pursuit of knowledge, jesting genially at his own infirmities, keenly observing all the facts of natural history that invited observation, and seeking out some ingenious scientific explanation for any fable that any guide or peasant told him to beguile the tedium of his journey, he is no shadow of a name, but a real man whom we can know and like - can like all the better, perhaps, because he so often allows us the privilege of a smile at his expense.’

To be fair to Scheuchzer, he did state that the dragon stories were probably myths, writing ‘At last I must mention, that furious rivers from the mountains are called by the locals … also dragons. If a river flows down from the mountains, and carries large stones, trees and other things with it, so they say: The dragon was unchained… and that many false stories about dragons have their origin in this explanation.’


Ah, this is also the first thing I wrote down while watching this lesson! :grinning_face_with_smiling_eyes: Zac explains: … most located in the polar regions, in Antarctica, in Greenland, or the Canadian Arctic.

Some of my favorite bits:

  • Antarctica Ice Sheets: Learning what ice sheets are and that Antarctica is made up of two huge ones.
  • Glacier types — I particularly enjoyed learning about tidewater glaciers, flowing straight into the ocean, and hanging glaciers (when I was watching the video, I thought to myself “oh, this is a sort of hanging glacier”. I was pleased to learn that that’s actually their name. :grinning_face_with_smiling_eyes: )
  • Misc participants: In this lesson, several experts were interviewed. Reminded me that a lot of effort was put into creating this course!
  • Crevice vs crevasse: Never realized these were different.
  • Effects of glacier erosion: Moraines, aretes, valley shapes. I’d seen the Matterhorn before, but now I understand how it got its unique shape.


This helped with some of my confusion about glaciers. My main remaining confusion is: how do you tell the difference between snow and glaciers? I’m still a little hazy on that. Maybe, if it goes away in the summer, it’s snow, and if it stays, it’s probably a glacier? This is partly because I’ve paid so little attention to mountains. The ones that are snow-capped year round, those are glaciers?

@hamish, thanks so much for your wonderful literary references and quotes - I am enjoying them tremendously!


Hi @sloopie72 - According to the USGS a glacier is a large, perennial accumulation of crystalline ice, snow, rock, sediment, and often liquid water that originates on land and moves down slope under the influence of its own weight and gravity. So it is not all just ice! As well, glaciers persist over multiple years without entirely melting.

Snow is precipitation in the form of ice crystals. and it undergoes further physical changes when it accumulates on the ground. We generally refer to the seasonal (or annual) snowpack - the snow that falls onto the ground and does not melt until temperatures warm up in the spring. If snow accumulates above the thermal equilibrium line of a glacier, then the seasonal snowpack may also contribute to the positive mass balance of the glaciers (the accumulation zone).

Of course this implies that there is snow on the surface of a glacier sometimes (above the melt line or ELA) and sometimes a glacier is just bare ice (ablation zone). Glaciers tend to move (creep) slowly down a slope, while snow can either melt in situ, or will move rapidly downslope as an avalanche, or undergoes scintillation to form new ice layers on the surface of the glacier.

Here is a nice explanation to reinforce some of the processes that Zac describes in the Lesson.


Thank you - very helpful!