Welcome to the Magnuson Geyser Basin!
Took the dog for a walk on this most sunny of December afternoons and came upon this scene.
Apparently, this is what happens when you "drain" a water fountain line (or something) for the winter.
Sounded like a real geyser too, great whooshes of air.
If you haven't been to the Park in a while you really should take a look at the "new" wetlands constructed on the former site of "Mud Lake".