Geyser Row

Yellowstone houses some 10,000 thermal features, and more than 500 of these are geysers. Here are some of our favorites. Here's Opal Pool:

And Grand Prismatic Springs, the largest hot springs in the U.S. and the third largest in the world. The colors are the result of the pigmented bacteria in the microbial mats that grow around the edges of mineral-rich water:

Excelsior Geyser, the tallest active geyser in the world, active for 10 years ending in 1888, with one major eruption in 1985:

Great Fountain Geyser, our favorite, which we happened upon its eruption by pure luck:

And, of course, Old Faithful: