Surreal Scenes in Yellowstone

I've spent the past two days in Yellowstone NP, my first visit there since 1971. Yellowstone is diverse; it features canyons, waterfalls, wilderness, beautiful mountain lakes, and lots of large wildlife including bear, moose, elk, wolf, and bison. But Yellowstone is probably known most for its vast concentration of thermal areas; geysers, hot springs, boiling mud pots. There are more thermal sites here than anywhere else in the world. Most of the park sits in a vast caldera, the remnant of a massive volcanic eruption about 650, 000 years ago. There is still a lot of subterranean heat here, and water from rainfall and snowmelt that percolates downward taps that heat and reemerges in a variety of forms. The result is very artistic; the landscape takes on a unique blend of colors, shapes, and textures.

The hot pools and geysers here are dynamic. They emerge, disappear, strengthen, weaken on a regular basis. This is also a major earthquake zone and each quake rearranges the thermal structure of the region.

The colors of the water depend on its temperature and chemical composition. They can change from season to season. This pool and the one in the picture above are near Old Faithful. I didn't see the famous geyser erupt, but the surrounding area was fascinating.

This is Castle Geyser, near Old Faithful. This geyser also erupts on a regular basis, about every 13 hours. Unlike many other geysers, Castle has been in operation for thousands of years, thus its large cone that has built up from mineral deposits. Blow the pic up and you can see bison in the background. Though thermal areas are roped off as unsafe for humans, the critters like it here, especially in winter; areas around geysers and hot springs are warmer and more snowfree than other parts of the park, so elk and bison have an easier time foraging for grass and other goodies on the perimeter of the thermal fields.

Here's a juxtaposition of a thermal pool, the Firehole River, and in the background (blow up the pic) more bison. The Firehole has extensive thermal input so I'm sure it has warm spots along its course. Look closely in the pool and you can see some logs. The pool probably grew in size over the years and swallowed up a bit of forest.