Most Of Yellowstone Lake Is Frozen This Time Of Year

But along the north shore, lots of hot springs and steam vents, both in the lake and just onshore, help defrost it:

And here's a use for the video feature of the Canon, recording both motion and the very loud sound of the steam vents:

UPDATE:

Yes, those steam vents are loud. And they smell very strongly as well, of hydrogen sulfide. (The Canon doesn't have Smell-O-Vision.)