My friend Jill (from college days) and I do at least one trip together each year. Often the trip is coordinated by Elderhostel, which now calls itself Road Scholar. This year Yellowstone National Park migrated to the top of the list, so Labor Day weekend found us on our way there.
It was a very good trip. The group was congenial, the weather crisp but nice, and the viewing was nothing short of spectacular. Our wildlife list included bison, pronghorn, elk, bighorn sheep, mountain goats, mule deer, and wolves. The wolves were exciting, because I hadn't expected to be able to see them. We missed bears of any kind, moose, and coyote, but I've seen those before so it wasn't too disappointing. This bison didn't seem to care that we were there and gawking at him (from the safety of the bus). The sheep were higher up and more aloof. The wolves were seen with binoculars at dusk and at a distance--not a subject for photography under those conditions--but there were four young ones and adult. A nice find, thanks to our leader.
The geothermal features were, of course, the big draw, and we saw all four varieties. You expect to see geysers because of Old Faithful, but Clepsydra put on a bit of a show for us, too.
Mudpots were interesting. They reminded me of similar features in New Zealand. The mud appears to be boiling briskly as if it were on the eye of a stove turned on high. In a way, I suppose that's fairly apt.
Fumaroles just spout steam. You wouldn't want to stand too close!
Then there are hot springs, and the water from it can be very beautiful--but don't dare put your hand in it or you'll draw back a nub. The only easily accessible place for hot spring bathing is not too far from the northern entrance, and the water, while hot, is not so hot you can't bath in it. This pool is NOT one of the bathe-in types! I believe it is called Turquoise Pool.
As the water spills over the edges from the hot springs, it can leave a coating of various kinds in varying colors according to composition. One area has a series of terraces formed this way. To get the terraced effect you may have to click on the photo.
It was a great trip. To see other pictures, go to https://picasaweb.google.com/ejoyce2 and click on the Yellowstone album.