Unofficially Colorado’s most popular “glacier,” it likely comes as a shock to some that Saint Mary’s Glacier, near Idaho Springs, isn’t actually a glacier at all. It’s a semi-permanent snowfield. This might not seem like a big deal, but there’s a big difference between these two distinct designations.
According to Google Dictionary, a glacier is “a slowly moving mass or river of ice formed by the accumulation and compaction of snow on mountains.” Capable of amassing a huge amount of weight, glaciers are responsible for carving out much of the Colorado landscape. This is where a glacier differs from a snowfield – a snowfield doesn’t really move, which means it’s not altering the landscape in a big way.
One reason why semi-permanent snowfields are sometimes mistaken for glaciers is due to the fact that they do stick around for quite some time – just like a glacier. Semi-permanent snowfields also tend to vary in size or shape overtime, something that can create the illusion of movement.
It is worth mentioning that some sources compare a snowfield to a “young glacier,” indicating that if enough snow sticks around for enough time, that snow can be compacted into ice, at which point it may move with potential to change the landscape. Other sources indicate that a “snowfield” is often created when a glacier stops moving, often due to loss of mass.
So there you have it – because there’s no ice in motion on Saint Mary’s Glacier, it’s actually considered a snowfield, which means it won’t be making any new mountains or valleys anytime soon.
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