minimum surface-area criteria applied to aspiring glaciers

[Chip Down]

I have an interest in glaciers. Can't claim to be an expert, but I have a fairly well-rounded knowledge based on years of reading from various sources, augmented by a significant amount of field research. So it's not often that I read something surprising on the subject.

A couple days ago, I read in a newspaper story that glaciers are, by definition, larger than 25 acres. Wondered what the source of this claim was. Found this: "The USGS Climate Change in Mountain Ecosystems Program minimum size criterion for a glacier is 0 .1 km² (100,000 m²), or about 25 acres." Hmm. To my knowledge, glaciologists/geologists haven't agreed on any surface-area criteria. Have I been out of the loop? Shouldn't The USGS Climate Change in Mountain Ecosystems Program use prevailing scientific standards for defining a glacier?

If I was part of the tinfoil-hat brigade, I might suggest that The USGS Climate Change in Mountain Ecosystems Program has an agenda at stake.

source: https://www.nps.gov/glac/learn/nature/glaciers.htm

[Aimless]

My first thought would be that there must be a difference between a perpetual snowfield and a glacier. My guess would be that no ice field smaller than 25 acres would have much chance to develop all the dynamic characteristics that typify glaciers, such as moraine building. At best, it seems like such a small ice field could be defined as a glacial remnant, left over as a true glacier shrank, or as a perpetual snow field that might be growing itself into a glacier.

But then, my expertise in glaciers is tiny enough it would take a while to find it if I dropped it in dim light.

[drm]

Why is it a problem for them to add a minimum size requirement? I think that research projects often modify traditional definitions if they do not conform to what they are trying to study. And I think that once glaciers get small enough, they do not have the mass to slide, so they become remnant snowfields anyway. I suppose they could say something like, 'for the purposes of our study, we are only considering glaciers that cover at least 25 acres".

[BigBear]

There is a difference between a snowfield and a glacier. A glacier is a "river of ice." A glacier moves down the mountain at several inches or several feet per day, depending on the glacier. Crevasses are formed when the ice block has to negotiate its way over uneven bedrock. The reason you don't see it moving when you are standing at the base is that it is also melting at a similar pace. However, we do know its moving because it "spits" things out, like climbing gear, or in the case of Mt. Baker (5-10 years ago) a WWII-era plane.

If global warming is true, you won't have to worry about size criteria, just stories around the campfire that begin, "Back when my pappy was young, they had these things called glaciers, way up there where the bare rock cliffs are today..."