This was called to my attention by reader Douglas Swartzenruber, who put it on his website, “A View from Planet Boulder”. (Do not click the link yet).
First, there are these “moguls” made by skiers; Douglas explains:
For any non-skiers out there, moguls are formed on steeper slopes when numerous skiers follow the same route down and push snow to the side on each turn. The snow begins to stack up and as more skiers follow the same line, the moguls grow, sometimes reaching heights of over 6 feet. I have never been a fan of skiing moguls [not enough talent], but if you want to be impressed with mogul skiing, watch these incredible folks ski the bumps.
But then there are these moguls—on a fence. Who made them? Now you can click the link to see the answer:
Oh, to be young and ski again!
My knees won’t let me keep up with the skiers or squirrels.
Has anyone every verified this with time-lapse photography? I have a hunch that its not necessary for skiers to follow each others paths, any random downward movement is enough. Once a slight packed bump is formed positive reinforcement enlarged it and others form around it in a pattern like standing waves.
http://www.pbs.org/newshour/rundown/how-skiers-move-moguls-uphill/
AH HA!! I was right!(sort of) Thanks for the link Douglas
That would be easy enough to do what with timelapse available on most smartphones.
I tend to believe that the followed line hypothesis is correct after skiing in Utah for a long time.
Mark – I agree. It seems clear to me that at the beginning of the day a slope can be groomed; soon turns make the small bumps and as the day goes on, most people are like me and use the bumps to make the next turn, adding to the pile. It also makes sense that this would cause the moguls to move uphill because folks would skim snow off the upper bump and add it to the lower bump.
But the fact that there are moguls all over the slope testifies to the fact that skiers don’t all follow the route downhill. Skiers can follow unique routes, while still turning in the same places as other skiers following different routes, just as pedestrians on city streets can choose different routes within the constraints of the grid.
“don’t all follow the same route”, obviously.
I don’t think that I implied the same route – just that many folks will use the same bump for a turn, choosing from among the many available.
Sorry if I misunderstood, but was that not you who Jerry quoted as saying “numerous skiers follow the same route down”?
Sorry – yes, from the original post about moguls. Too brief of a description; should have been more explicit in saying turning at the common point, not following the same route.
Never having even seen live moguls in either visit to the ski slopes, I don’t know how they form, but the photos of them always remind me of “anti-dune” fields in “applied sedimentology” (or “beach mud pies”, depending on how bad the professor’s hangover was and how horizontal the snow on that field trip).
I would not want to walk on that, let alone ski. Snow blade please.
Squirrels!?
Love snow skiing. Haven’t been able to do any for years though. Holy cow. Thinking about it has actually been more like decades. Somebody slow this thing down please.
Moguls can be lots of fun, though painful sometimes. But I favor runs with more variation. Mogul runs are, by necessity, relatively short, intense bursts of all out effort. Somewhat like an intense wrestling match compared to playing soccer.
Run faster. (1-v^2/c^2)^(-1/2)
Moguls on the fence: made by black or grey squirrels. I see it all the time on the deck railing behind my house.
🙂
So they hop along the fence rails, carving out the moguls?
I was going to suggest that its from snow on the tree branches above, dumping snow onto the rails. But I like your explanation better.
Yup – Garry got it right!
NORDIC skiing rules!! More fun skiing up the hill than taking a lift. Looks like Gus is back at it. But instead of jumping from boot hole to boot hole, he is practicing his cat-leaping skills along the fence.
Quite a few years ago we switched to snow shoes. No lift tickets, no lines, usually no one else to be seen, and one can go virtually anywhere there is snow.