While I'm posting this series- more for my convenience than anything else- as discrete segments, I do want to note that I hope readers realize that these different bits were designed to dovetail seamlessly together. Yes, I organized the presentation around a few topics that I wanted to highlight, but it was delivered as one continuous talk, over a period of about an hour and twenty minutes. Moving along from rocks and their human uses to the different kinds of rocks one might find in the Willamette Valley and surrounding areas is a natural transition. I imagine most of the audience didn't even really notice we'd changed topics.
There's a very nice photo of this texture here, (scroll down to "Onion-skin weathering") though the explanation given is no longer accepted as the predominant mechanism by which this texture is created.
A Bright Moon Impact
1 day ago