About the two Bogus flows... I thought I remembered discussing that topic when we sat on the plateau below the nipple and gazed through binocs at the tractor tread. We definitely discussed the unit to the right (in our view - toward the bend in the river) because it looked lower at the time. Glad the topography agrees.
Your question about the grinning gorilla is a good one - when we were looking at the photos at your house last week I was wondering the same thing - I hadn't remembered that there was more than one hyaloclastite, although I do remember that we found various pillow/hyaloclastite outcrops on our way down the ridge. It's a bit puzzling if it's really a hyaloclastite on a lower Bogus flow unless there was water in the local drainage from that side (otherwise, I don't see how a canyon-filling flow could form a lake). Also, the exposure just upstream from the grinning gorilla (across the gully) seems to show only a single thick Bogus flow (see photo).
Finally, the two thin upper flows with hyaloclastite look quite similar and different (at least in the photo) from the lower flow. Guess my vote is Greeley though I'm certainly not wedded to it!
A likely case of delayed revelation with regards to the Nipple and Tank Tread. I recall wondering about the weird contact, but believe I wrongly committed to a single flow interp. The concept of the nipple being surrounded by a flow is new...I think...our working hypoth was that the surrounding lava was stripped. Not sure which is the case now.
ReplyDeleteInteresting - I remember at the time thinking that it was worth walking up to the tank tread. And you're right, the concept that the nipple was surrounded rather than stripped is definitely new - time to go back!
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