I had absolutely no idea of what to expect in Jellystone.  Perhaps smarter-than-average bears, along with the standard rock-tree-water backdrop.  I was pleased that I did not research the park in advance, because this meant I was taken by surprise all day long.
The first surprise was not a pleasant one:  YNP is so busy it's like being on the public highway, with its full complement of jams and terrible signposting.  I even had to queue to enter the park, a first.

I quickly discovered that the bear-jams were far less common than bison-jams.  The wild bison in YNP simply stroll around without a care for the motorists, even walking along the road as if they were a vehicle. Everyone wants a photo, not knowing when they would have the chance to rubberneck again, so I am sure that I am not the only visitor with dozens of identical bison photos.

Upon finally reaching the visitor centre I enjoyed the video, in which I learned how the park formed:  just like Crater Lake it was an explosion that left a caldera (cauldron-shaped valley).  Unlike CLNP, though, YNP is still active.  The visible surface sits on a fast-moving plate that slides over a relatively static plate, in which a huge ball of magma sits.  As the upper plate slides, the surface above becomes volcanically active, before it moves on.  There is apparently a long chain of extinct volcanoes that were all once over the ball.


After looking at the torrential waterfalls I then got my first taste of YNP's dozens, perhaps hundreds of geysers, mudpots, fumaroles, hot springs and mud volcanoes.  There are several areas in the park, called basins, where many geothermal features seem to congregate.  In the space of about an acre there may have been 50 features, some as
small as a mouse hole and some as large as a front room.  Each had its own noise, ranging from gurgling to hissing to booming.  Even the mouse-sized holes, with no apparent water, made noise.
The most beautiful features were the deep pools, azure blue and seemingly bottomless. Around their fractal edges were colonies of bacteria that stain the rocks yellow and orange.  With the exception of a blanket of steam over each, these pools looked exactly like a slice through one of those pretty agate lodestones that you see in gem shops.
One of my favourite sights of the day was that of a bison through the steam of a boiling pool. 

Then came the geysers. These come in two types, cone (like a jet from a fireman's hose) and fountains (like an upside down waterfall).  Old Faithful is a cone geyser which erupts faithfully every 90 minutes.  I caught the end of one show and then waited for the next, which sadly was not so spectacular.  I was amazed at how many so-called sight-seers turned and left halfway through Faithful's performance, as if 30 seconds was all they needed to see.

After seeing several dozen features I started to get geysered-out and headed back into town for a dinner of....

bison steak. 

Tomorrow I will upload some videos once I have compiled the best.  Only in video can you appreciate the movement and sounds of the features. I wish that I could convey the sulfur smell via Smell-o-vision too.