I walked out the front door of my little cabin/house this morning and was faced with a problem. All winter the plow has been driving by and creating a big pile of snow next to the sidewalk. I have dutifully shoveled a pathway through it after each storm (more on the pride of shoveling my own walk another time). Now, however, the air has a different quality and the snow is beginning to melt. What I am left with is a shrinking pile of snow and a growing pile of loose gravel. Each time the plow pushes the snow aside it also scrapes loose rocks and moves them with the snow. As the snow melts the rocks are left behind. But what do I do with the sediment? As I pondered the problem on my commute to work (a seven minute walk), I had a moment of brilliance akin to the apple falling on Sir Isaac Newton's head. "Eureka!" my inside voice exclaimed (I've learned not to talk to myself while walking around Gardiner--it's a small town and people might start to talk). My inside voice continued, "I have my very own terminal moraine."
Glaciers carve and landscape much as a plow scrapes snow off a road surface. As a glacier slowly moves it also pick up rocks from the landscape and carries them embedded in the snow and ice. When a glacier retreats, or melts, all the sediment that it has picked up along the way is left behind in a pile of loose soil and rocks--this is called a terminal moraine. They mark the maximum advance of the glacier and can be quite big. One of the largest moraine's is in Norway. It is so big that local legends tell of how giants built it to keep invaders out of Norway. My own terminal moraine is quite small. I am proud to report that the glaciers in Gardiner, Montana are retreating until the next ice age (which should begin around Thanksgiving). Now, if you'll excuse me, I'd better go skiing before this changing climate catches up with me.