Geo 1095: March 23, Day 812: Baffling Bedrock

There is talus raveling down the small gullies to the left and upper right, and the base of a larger talus cone in the lower right. Note that most of the plants are rooted in that talus, which can hold small amounts of moisture later into the dry season. In the lower middle of the photo, there are some angular, larger cobbles of rock, which I suspect have fallen from the overlying lahar deposits. The remainder of what is seen here is a fairly light rock, overall, but with many much darker small pebbles. Internally, it's very poorly sorted, but within a narrowly restricted size range, from sand to pebbles in grain size. What this rock represents should have been much more obvious to me than it was, but here's the thing: I'd never seen anything quite like it, and I couldn't get my mind around those darker, more mafic, bits. It looked like a tuff- a solidified ash deposit- but what the heck was going on with the completely different rock types?

Photo unmodified. October 9, 2012. FlashEarth Location.