Tuesday, February 17, 2015

A Little Mystery to Accompany the Moving Stones of the Basin and Range

I'm back from an intense journey through Death Valley National Park and surrounding regions. Much photography and commentary can be expected in the next few weeks, but for today, I'll just lay out a bit of a mystery.
The sliding stones of Racetrack Playa in Death Valley are justly famous, and the mystery of their mode of movement has recently been made clear. But the Racetrack isn't the only place where the stones slide. Bonnie Claire Playa, close to the California-Nevada border, also shows the phenomena. We headed up there on our field studies class. The stones are fascinating, but something else caught my eye while exploring the playa surface.
I don't know what this circle is. It was there by itself, and had no obvious tracks leading to it. Because of its singular nature, I strongly suspect human intervention (SBCC, did you have anything to do with this??). But who knows? If some folks dragged something in a circle, how did they not leave tracks around the edge? Did someone leave a large tire for awhile and retrieve it later?
I even found the circle on Google Earth (below). Again it seems to be all by itself, with no tracks leading to and from.

What do you think is going on here?


Scott Madsen said...

A water escape feature partially stripped and in cross section, probably created when this part of the muddy lake floor was last saturated with any migrating water. That would be my guess.

jrepka said...

Back in the days before artificial rocks implanted with GPS devices, we were brainstorming about rocks with accelerometers, connected by radio with cameras set up on the edge of the playa. We never got beyond these discussions, assuming that if anything interesting happened it would naturally only occur in the dark of night (we also assumed, it turns out wrongly, that the conditions under which the stones could move would involve near-zero visibility).

Anyway, one suggestion involved isolating a small area and flooding it, to determining the force needed to move a stone under different conditions of saturation and varying water depths.

At first glance this looks like someone fenced off a small area for a saturation experiment

AnJaCo said...

I'm inclined to think human caused too, as jrepka above suggests.
My hypothesis: a couple of(perhaps drunk) geology grad students are out there, they empty a water jug in a circle. They sit, have a beer or three, waiting for the water to soak the circle thoroughly. Then the lighter of the two sits in the mud and the heavier person stands in the center, grasps the ankles of the other and spins the person about several times. They depart carefully so as not to step in the wet parts (only the circle), chuckling all the way about how funny it will be when some geologist comes along and thinks that the feature is worth writing a paper or blog post about it. Sure its a 'long game', but hey, when one drinks in the desert, the mind has plenty of time to think shit up. At least that has been my experience.

Well, that's what I'd do anyway.
And no, I haven't been there.