Friday Rock Blogging: Mud

Picture courtesy reader Martin. Or maybe Martin doesn't actually read this blog, and it's just Wren. Anyway, thanks, Wren and Martin!

Today's rock is a geopuzzle: What's up with these ridges? How did they get there, and what determines their size?

I don't actually know the answer, so this is the best hint you're going to get out of me.

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Based on your clue, this is clearly a strange phenomenon that exists only along the border of Wales and England, possibly due to a secret EM fence between them :)

Could it be that a tidal bore moves up this waterway and when the tide drops, these ridges of sediment result from erosion?

Just guessing here, but looking at the raised edges and their shadows, I'm wondering if this is mud that has run over a tilted slate bed, or some such similar structure.

Overbank flood deposit? Control: duration and size of flood


A semi careened off the m48 and into the water and created a big wave. Control: Size of semi.

Well geez, let's bring the entire aviary in on this! I think these waveforms are actually mimicking the wingbeats of an unladen swallow. The real question is... African or European?

I wonder if the pylons of the bridge there play some role in the formation.

Ooo! The M48! The road that takes me home. This picture is making me homesick for the Severn, there's some great fossil hunting to be done along there... *sigh*

Anyway. Before I saw the larger picture I was going to say that they were current formed ripples as there is definite bifurcation on some of those crests. first glance, the features have an erosional rather than depositional look to them ... I might have to agree with cope above...something along those lines.