[BR-Crater] Columnar jointed rocks State of the Research-January 2009

[Rick Maschek]

>From a post by Ian:

"An interesting point is that we see these columnar jointed rocks at Black Rock at an elevation of around 4450 feet. Since they are all nearly the same elevation across the east and west sides of the playa (25 miles apart), it's an indicator of the possible impact melt pool in the suspected crater. It seems an extremely unlikely coincidence for a volcano to make a lava pool so big or to line up the elevations of similar but unrelated formations so closely. It also gives us an estimate of what elevation the crater floor might have been. That's about 500 feet above the current Black Rock playa. It goes to show how much of the suspected crater has been eroded away."

I graduated in geology though I've spent the last 7 years teaching chemistry before retiring. Since I haven't looked at any geological maps of the area and only read Ian's "State of the Research - January 2009" and have only been to Black Rock for BALLS events, I can't really say much about this. In reading this I would like to ask (and I might be wrong) if the columnar jointed rocks on both sides of the playa match up and are thought to have been the melt pool at the bottom of this crater that made Black Rock Playa, where is a lower area that this 500' of material eroded to if the playa is the bottom of the crater? Also, it would be very easy to take a sample of this columnar jointed rock and have some geology student at some university take a good look at (thin section, mass spec, etc) very cheaply or for free. And getting an age date would be easy and inexpensive as well.

Just a thought,

Rick Maschek
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