I have to say, Yellowstone provided us *all* an unsurpassed education in geology. There is nothing quite like witnessing the evolvement of the earth first hand.
To begin with, Yellowstone, in case you didn't know, is basically a *huge* volcano.
On our way up to the park we listened to 'A Short History of Nearly Everything' by Bill Bryson, specifically, the part about Yellowstone. We learned, that Yellowstone was always assumed to be volcanic and situated on a hotspot (a place on the earth that has experienced frequent volcanic activity for a long period of time), but early on no one could figure out where the volcano actually was, a very puzzling matter! Then, by chance, NASA flew a satellite over the area taking pictures and gave them to the park. Suddenly, the volcano was revealed! There was no regular volcano cone anywhere in the park, like everyone was looking for. It was a supervolcano, the most extreme and catastrophic kind there is. That supervolcano, then collapses in on itself creating was is known as a caldera. A huge bowl, or crater, in the ground. When seeing from above, it was clear as day apparently. Almost the entire the lower half of the park IS the caldera, approximately 34x44 miles by some estimations.
The earth's crust at the park is so volotile and so thin that stepping off the boardwalks anywhere can be deadly. In one parking lot a corner was closed off since the asphalt started crumbling inward, in other words, the crust was falling apart giving way to hot boiling water and maybe acid! It is said that Yellowstone is late in its eruption cycle. I forget the exact numbers, but the area has erupted every so often historically and it's running a little late now.....it's pretty humbling walking around a place you know can, quite literally, explode any minute! And it looks like it too, what with all that steam and water bubbling out of the earth and all.....
There are four main geological hydrothermal features in the park: Hot springs, fumaroles, geysers (of course) and mudpots.
Here we are, encountering our first geological demonstration of the fragility of the earth (we won't count Old Faithful quite yet): A hot spring, the most common hydrothermal feature in the park. Seems innocent enough yes? Well, no, not really. The water collects just under the crust of the earth in a large space and bubbles up without any constriction. It's hot since its been heated to tremendous temperatures by the magma.
"The superheated water cools as it reaches the surface, sinks, and is replaced by hotter water from below. This circulation, called convection, prevents water from reaching the temperature needed to set off an eruption."
It's hard to tell here, but that pool is very very deep and one can see the interesting rock formations as it gets deeper and deeper.
And BTW, if you think nothing can live in and around these phenomenon you'd be wrong. In the 60's it was discovered that indeed tiny little organisms, called thermophils, thrive exactly here! In fact, there are all sorts of bacterias living here. But more on those a little later.
Moving on on down the trail, literally, we came across what's known as a mudpot. Our second geological find.
I apologize for the photo, it really doesn't do it justice. If you look closely you'll see what basically amounts to mud boiling and bubbling. Those circular indentations you see are exactly that. Colors vary by modpot, this one happens to be a bland one. Below you'll find the explanation as to what's happening:
On to fumerals! Number three.
Basically a lot of steam rising up out of holes in the ground. Basically. Behind the scenes this is what's happening: There's so little water collected below and the heat is so intense that the water turns into steam before it reaches the surface.
Number four of course would be the geysers! We saw MANY! Some erupting and some not, but that's ok. So what IS a geyser anyway?? Going in I knew of course that it was water and lots of pressure, but how and why were beyond me. Geysers are, simply put, a hot spring with a narrow plumbing system! Thanks to these constrictions the water, and therefore the heat, cannot circulate and escape freely at the surface and KABOOM! You've got a geyser! A pretty simplified explanation, there's obviously a lot more to the process that I won't go into here.
Later we took a 2 hour guided tour with a park ranger. I think they were some of the best few hours we spent in the park! We learned so much from the ranger and had a good time in the process.
Inventor is taking the temperature of the water, from a safe distance. This little doodad was in the science backpack we checked out from the visitor center.
Another hot spring with amazing colors!
Look at all that bacteria! Didn't think that would ever be a good thing did you? :-) (aside from your intestines maybe!) Well, aside from the blue, all the colors represent different types of hydrothermal life! All require slightly different temps to live and thrive. Obviously the further out you go the cooler it gets.
And finally, at the end of our day, we were treated to this fellow....
..in all it's glory!
Why is Old Faithful so titled? Quite simply it erupts at predictable intervals. About every 60 to 90 minutes. The intervals have grown over the years, thanks to nearby earthquakes. It's not the most frequent nor is it the largest, but it is the most famous. BTW, it was also the the first geyser in the park to receive a name. Names were chosen by the first government expedition into the park. The same expedition that convinced Congress to declare the area a national park, the very first one at that!
All quotes are taken from the park newspaper, Autumn 2010 addition.