From the entrance the road follows the Gardner river for ~5miles before it comes to Mammoth Hot Springs. About halfway there was a traffic jam. This annoyed me, until I realized that everyone was staring at the barren cliffs above. There were some animals high up above us. Once I got through the jam, I pulled over and walked back to take some pictures. I tried to remind myself that traffic jams were an indication of something interesting to see and I should take them as a hint to look rather than rudeness on the part of the drivers. Still… why didn’t they pull over instead of stopping in the middle of the road?
It was late afternoon when I got to the hotel, too late to go anywhere else, but Mammoth has its own sights, so I went and looked at the traverine terraces just down the road. Hot acidic water from underground dissolves rock, and when the water reaches the surface and cools, the rock precipitates out of solution and leaves rocky terraces. Various bacteria which like hot water live on/in this rocky surface and color it. The color of the bacteria depends on the water temperature.
The rock will coat anything, and bits of tree that fall into the hot springs end up covered in rock (there used to be a business here where people would leave stuff in the pools for a week and go home with a unique, rocky, souvenir. This is no longer allowed, but I see it happens naturally on twigs).