Saturday, October 20, 2012

Cheshire Cat! A Sketch of the Quarry Area

It's crude, but if you could strip off all the distractions, like vegetation and soil, this is approximately what you would see in the neighborhood of the Cheshire Cat quarry. I'm thinking I may have the rubble a bit too low- that is, there's less of the hackly jointing visible under the columnar jointing than I've depicted, but that's okay: it doesn't really affect the interpretation here. I realized that the first photo in Dana's post fortuitously catches a bit of the contact between the basalt and the older, underlying altered rock- here's a direct link to that picture.

Also, you might want to check out the comments and my responses on Dana's post. In particular, this: "Yes, the flow *is* thicker in the middle. You’re getting awfully close, but I have no reason to think this was affected/influenced by ice at the time of eruption, and I’ve not seen any pillow basalt in this area. However, I think you’re on the right track. There is a key place name I’ve avoided mentioning in the clues so far, but it’s related to why I brought up Boulder Creek for clue 7."

And for the sake of completeness, I'll add the age of the volcanics and volcaniclastics in the area is perhaps 30 +/-5 Ma, the age of alteration is about 18 Ma, and the age of this volcanic cone and flow is >2 Ma, but I don't know an absolute age.

So once again, what will we see when we cross the road and look down toward Canal Creek?

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