Wednesday, May 29, 2013

Geo 365: May 29, Day 149: Toe and Talus

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.

Photo unmodified. August 21, 2011. FlashEarth location.

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