I tend to wear long pants, regardless of weather, when I know I'm going going to be around sharp rock. It's not a hard rule (and in fact I think I was in shorts this day, too), but it can make a big difference in encounters with nasties like the above vesicular obsidian.
Nearing the top of the stairway in yesterday's photo, this is the view off to the east. I don't think this is a blocked stream or anything, just a low area whose drainage was obstructed by the advancing wall of obsidian. I suspect that the water input is mostly from percolation through and out of the flow itself. As far as outflow, I think there must be a lip somewhere down there at the far end; there definitely seems to be an upper end to the water level in this pond- this is about it. However, when it's particularly dry, I think this can get pretty low. 2011, though, was a very cool and late summer.
The stairway up to the loop trail on top of the Big Obsidian Flow provides a rare sense of scale in this setting. The blocks of obsidian range from inches to many feet in linear dimension. The pines are stunted, like bonsai, so the landscape can seem oddly "big," visually. At over a square mile (~2.9 sq. km.), it is big, course, but the lack of visual references tends to make most fresh lava flows I've visited somewhat disorienting.
Standing at the toe of the Big Obsidian Flow in Newberry Caldera, looking ~NW to what I described on Sunday as "a smaller, unnamed, as far as I know, cinder cone between the road and the Central Cone." I also mentioned earlier that obsidian in its molten state would likely not really seem to be a fluid to our perceptions, if we could get at it in that form. So, like aa-aa, which is basaltic, it can slowly flow under confining pressure, but at surface conditions, most deformation is accommodated brittley- that is, it fractures. So most of what you see on the surface, and here at the toe, is loose rubble. In fact, though I wasn't looking for it specifically, I don't recall seeing *any* obsidian that looked like it was part of the unitary interior.
It's like standing on an enormous pile of broken glass. Indeed, remove, "it's like." Standing on an enormous pile of broken glass is quite literally what a visitor is doing.
Dana stands above the benchmark on Paulina Peak (not visible in photo), with Paulina Lake below and to the right, and Three Sisters and Mount Bachelor on the horizon to the left. After we'd each finished posing with the horizon, we headed down to the Big Obsidian Flow. You can see my moment on the stage (AND the benchmark!) in the sixth photo down in this post, and the full-size photo here.
And I just got distracted for a good half hour. Flicker, where I've started hosting some of these larger photos, has changed its layout and policies, apparently. You can now see these photos in full resolution. Follow that link, left-click on a photo of interest to bring it up in a "lightbox," then right-click on that image and select "original." You're welcome! Many of those images are ones I've not yet written about, some of them I have. Feel free to ask if you want to know whether there's more info available. Also, Flicker does not provide an option (so far as I've seen) to label things as Creative Commons Copyright. Feel free to use these for non-profit and educational uses, with attribution.
The above photo was stitched in HugIn, then opened in Paint.net. The blank areas were paint bucket filled with sampled nearby colors, then the whole thing run through the autolevel adjustment routine. This often ends up making a photo garishly, unnaturally vivid, and I think the above verges on that problem. However, in this case, it's not too bad, and more importantly, it's closer to what I recall than the hazy, washed-out colors of the original photo.
This is not so much funny as amazing, awesome, and kick-ass: Hope Johnson sings all the named moons in the solar system, in the manner and tune of Tom Lehrer's "The Elements." Found at The Planetary Society's Blogs, where you can also see the lyrics.