When I said I was bored by Old Faithful the other day, I didn’t mean to imply that I found Yellowstone National Park a snooze. In fact, what I learned at Yellowstone is that geysers are among the least visually interesting geothermal features going.

You keep your semi-regular eruptions of steam and water, what I like are bacterial mats. It’s heat-loving bacteria, called thermophiles, that create the colors in the Grand Prismatic Spring, pictured above. These bacteria produce different colors depending on the time of year and the amount of sunlight they recieve, which in turn influences the ratio of chlorophyll, which produces a green color,  to carotenoids, which produce a reddish color. Lots of carotenoids on this day.

And by the way: what is this impulse to write our names on every surface? I purposefully did not photograph the defacement, but several visitors have taken it upon themselves to kneel upon the boardwalks constructed to give close access to this astonishing sight, and to use some implement to carve a message, usually their name, into the bacterial mats.  (I guess that implement would be a long-ish stick or a branch, because if you dip a finger into 160 degree water, you’re not getting it back in quite the same shape.)

What an astonishing ego you’d have to have to think that millions of visitors would want to see your name here.