Many of the lakes on Alaska’s North Slope are actually somewhat rectangular. It’s a noticable phenomenon when you fly over. The reason is that as they beging to thaw along their edge in the Spring, high winds from the north push them against the far bank causing them to pound and gouge out a bit of a trough. Over time they elongate in that direction, all parallell to the other elongated lakes. I assume this probably happens around the rest of the Arctic Circle as well.
Well, that’s the point, isn’t it? The round ice “boulder” melts to make the round kettle lake. What wasn’t clear to me was why it was round, not how the glacier got out of the way.
Wow, that explains all the cranberry bogs in Plymouth County, MA which has over 350 of those kettle ponds.
Even if the calved glacier starts with an irregular shape, it’ll become round as it melts – any corners are more exposed and melt faster. Plus melt water will pool and drain at the bottom of the glacier, which can create a sinkhole.
Interesting thread!
Most lakes here in Southern California are not round. They’re actually kind of snakey, since they’re damned up in between two mountains. Head up the 395 to Mammoth, however, and you’ll see some rounder (although, not perfectly round) lakes. Maybe it’s because of the volcanic activity or snow and ice, like previously mentioned in this thread.
That’s not at all obvious – I’ve seen bergs calving off glaciers that are extremely far from round. Even granted that the thinner parts melt first, you wouldn’t get a circle – you could get an ellipse, but more likely you’d get an irregular shape. And a very irregular mass depressing the earth would, I would think, create an irregular depression.
While several of the kettles in the Wiki picture appear roundish, I don’t see any literature either there, in a brief online search or in my Dictionary of Geological Terms that lists roundness as a defining feature of kettles. These kettles for example most certainly are anything but. So the long and short of it appears to be that some are and some aren’t.
Same here in the Cascades of Washington. On a recent drive up highway 97, I had a hard time telling when we were next to a lake and when we were next to a river. From my perspective, they were all long and narrow.
Randon slab of Central Ontario. Note the non-round lakes.
Not a chance. Pull up Google maps and zip around any part of Minnesota (15,000 lakes) or NW Wisconsin or up into Canada north of Minnesota.
If you wanna get picky, then nothing is really perfectly round.
That’s the one I had in mind but I couldn’t remember its name!
Thanks!