Yellowstone Thermal

Picture of old_faithful Okay, here's the Old Faithful picture we'll get it out of the way first. It's not quite the first thing we saw in Yellowstone but it was close. In fact, approaching the Old Faithful/Biscuit Basin area from the south affords an incredible view from the road (especially if geysers are erupting at the time). The so-called upper geyser basin that this area is part of has the largest concentration of geysers in the world. In fact, only Iceland, Siberia and New Zealand have active geysers besides the Yellowstone area (at least according to the Yellowstone rangers). Old Faithful is impressive, but notice the horde of people standing around it, plus it is on a hill so you can't see all the activity in the pool. It's not a bad place to get your intial geyser fix out of the way though, the rest of 'em are not quite as predictable.
Picture of hot_spring Besides all the geysers, Yellowstone showcases the other three types of geothermal features as well; fumaroles, mudpots, and hot springs like the one shown here. Yellowstone really has an incredible number of all of these. We visited at least one geyser basin each of our three days in the park. There are also smaller geyser areas in the backcountry that must be hiked to.
Picture of oblong_geyser Oblong geyser is not one of the featured geysers in the area but it erupted as we approached it (with so many geysers, you're bound to come across something erupting), crossing the Firehole River. Oblong's eruption lasted about 5 minutes and was rather violent, with lots of hissing and spasmodic water jets in various directions.
Picture of grotto_geyser Speaking of spasms, this is Grotto Geyser which has to be our favorite in the Old Faithful basin. Grotto erupts for 2-10 hours at a time so you can spend quite a while watching this one. The platforms that geysers sit on are called sinters and form from the mineral deposits (Silicon Dioxide mostly) in the geyser's water. The strange sinter cone on Grotto Geyser is speculated to be from the remains of one or more tree stumps in the vicinity when it first erupted. This process is still happening, one parking lot we stopped at had a section roped off because a geyser had erupted underneath it a few weeks earlier.
Picture of grand_geyser Grand Geyser is the focal point of the Old Faithful basin (once you get past Old Faithful anyway). It's the tallest geyser in the area reaching heights of 200 ft (60 m) and it is predictable within about a 2 hour range.
Picture of morning_glory_pool Popular since the 1880s, this is Morning Glory Pool. There are two basic rules to visiting Yellowstone (see the wilderness page for the other one). The geothermal golden rule is simply Don't throw things into geysers . That goes for hot springs as well. Eventually the debris (coins, rocks, you name it) blocks geysers and the vents for hot springs. This seems like a simple thing but we saw quite a few people doing it. Why? We have no idea what the attraction is. The blue and green bacteria that color the center of this pool thrive in hotter water, the orange and yellow live in cooler water near the edge. More than a century of vandalism has cooled this spring down enough that the yellow-orange spreads towards the center now.
Picture of grand_prismatic In the Midway Geyser Basin there are only two features but they're both impressive. Excelsior Crater is an enormous geyser crater that has been inactive for years although like all geysers, it could start up again without warning. Also located there is Grand Prismatic Spring (shown here), the largest hot spring in the park. The brown areas are the coolest water.
Picture of steamboat_geyser Norris Geyser Basin features the world's tallest active geyser, Steamboat Geyser. When it really erupts it reaches a height of 300 ft (90m) although these eruptions are completely unpredictable and seem to happen less than once a year on average. This is a more common eruption of Steamboat here. The sinter cone which can't be seen from this angle has multiple vents so the water shoots out in multiple directions.
Picture of pearl_geyser This is the rather vocal Pearl Geyser, also in the Norris Basin. The eruptions are particularly high but the entire surface of the pool seems to contract like a trampoline and throw water off while gurgling continuously. This area, Norris Basin, was a highlight of early tours to Yellowstone Park. In fact Minute Geyser nearby was the original featured geyser of a stagecoach tour of the park. It erupted nearly every minute at the time. Years of visitors throwing objects into the geyser have ruined its plumbing though.
Picture of echinus_geyser Echnius Geyser is one of the semi-predictable geysers in Norris Basin (as in, every one to four hours). We spent an hour and a half on a bench waiting for this one to erupt. (Okay we were tired from hiking and needed a rest anyway) Since nearly every geyser must have its one impressive stat, Echinus is the largest acid-water geyser known (pH = 3.5). The sulphurous fumes from the various geysers can do some damage as well, mostly to glasses and camera lenses. This is (finally) the beginning of its eruption.
Picture of echinus_eruption Once it finally gets going, Echinus puts on a good show. Several parts of the pool erupt and the water sprays out at various heights for about 5 minutes. If you look closely at these pictures you'll see the elevated wooden viewing platform wrapping around behind the geyser (Echinus has seating on three sides).
Picture of green_dragon The Dragon's Cave, elsewhere in Yellowstone Park (near Hayden Valley) is a fumarole. Fumaroles are too hot to erupt, as water never builds up inside them, it boils into steam immediately. They're great to listen to though, there are all sorts of strange noises coming out of this one and indeed all the fumaroles we visited. The fourth type of geothermal feature is the boiling mudpot.
Picture of melanie_terrace And of course there is Mammoth Hot Springs, the original Yellowstone visitor center located near a series of travertine terraces likes this one (Jupiter Terrace) behind Melanie. Often this is a highlight of a visit to Yellowstone although during our visit there was very little water coming out of the springs that form these terraces so while these would normally be multi-colored and overrun with hundreds of tiny waterfalls, they were nearly dry and chalk-white.
Picture of cleopatra_terrace There's a bit of steam coming off of Cleopatra Terrace and the reddish-brown color is indicative of the fact that it is still active although it's a bit off the main path so it cannot be seen any closer than this. Of course we should probably mention that all of these geysers and springs and such exist because Yellowstone park lies largely in a not-so-dormant volcanic caldera.
Picture of palette_springs Palette Springs was the most active terrace during our visit. The terraces exist here because the underlying rock is limestone as compared to rhyolite in all the other geyser basins. Travertine terraces like these are apparently extremely rare as a geothermal feature worldwide. The spring itself is atop the highest ridge in this picture and the water runs down in a network of interlaced streams. Mammoth Hot Springs was also the most crowded area of the park that we visited. Old Faithful had more people at Old Faithful itself but the rest of its geyser basin was fairly unpopulated.

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