Glaciers form in areas where there’s more snow accumulating in each year than there is snow melting. The lucky snow flakes fortunate enough to survive into their second year are collectively called firn. Like fresh snow, firn is fluffier than ice, with open air spaces where gases can move freely about. Below the layer of firn lies a layer of dense, compressed glacier ice, which – like Swiss cheese – is interspersed with small pockets of air (these air pockets hold the key to understanding changes in earth’s atmosphere over hundreds to thousands of years: see, for example: link). In thinner glaciers (<150′ deep), the glacier is like the inside of a Butterfinger bar: when you bend it, the brittle layers snap apart.
On a tour of Seward Glacier in Alaska, I was told that 10″ of snow will yield about 1″ of glacial ice. A good estimate, though not entirely true. Dry (or really cold snow) is fluffier than wet (or warm snow), so it takes about 10″ of wet (around 32oF) snow to make 1″ of ice, and 50″ of really cold (-10oF) snow to make 1″ of ice. Regardless of what type of snow we get, Burlington is just too warm (average temps around 44oF) and too dry (~80″ of snow per year) to ever get glaciers. Except our good friend Buspy Brown.