Simple enough question, right? Well, not really; at least I was not so sure about my “euh…no?”. And when the next question was “why?”, I understood I needed to do some research on the topic. Hence this morning back-to-work post on glacier formation.
First of all, what is a glacier? Basically, a glacier is only a pile of snow that has accumulated over the years. Because of the weight of the snow above them, the “old” layers get compressed and expel their air, turning into ice. So, to form a glacier, we need only two things:
– snow must fall
– snow must not melt totally
Where does that happen?
This image came a bit as a shock when I saw it earlier. Polar regions (Alaska, Canada, Greenland, Iceland, Scandinavia, Russia and Antarctica), it makes sense. Very high mountains (Andes, Alps and Himalaya), it makes sense as well. Both cases are cold year-long. But glaciers in California and New Zealand, why? Or rather, why there and not in Scotland, which is much closer to the pole? And that, dear reader, is when I understood that I am bad at geography.
There is a common feature to all the non-polar glaciers: they form at relatively high levels. New Zealand, California and Nevada glaciers are around 3000 m altitude (I did not know that). The Alps peak at 4000 m, while the Andes and Himalaya reach 6000 m and 8000 m respectively. Ben Nevis, highest point in Scotland, is only 1344 m. And that is key, for the average air temperature on Earth decreases with altitude by about 6.5°C per kilometer. So with an average surface temperature of 14 or 15°C depending on the reference, you need to be above 2150 or 2300 m respectively before temperatures are below 0°C on average. Ben Nevis is not high enough, so he is too warm.
But here comes the twist: I have only mentioned average temperatures so far. Anyone who occasionally walks outside on a sunny day knows that the temperature is anything but average, and that there can be a large difference between the sunny side and the shade. This is why the north face of mountains is often the hardest to tackle: the sun never shines on it, so it is colder, with more snow and ice. And according to the news, it turns out that the north face of Ben Nevis, Scotland, mere 1300 m high, might well be forming a glacier! Surprised, aren’t you?
Note that I am not a glacier expert. This blogpost only arose because my curiosity was tickled by a friend’s question. If you want to learn more about glaciers, you should read the excellent blog Antarctic Glaciers. I purposely did not mention the wind because it has a complex dual effect: cooling the surface, but drying it and blowing the snow away, but I’d agree with anyone who argues that it is a key element in glacier formation.