Man-made cave formations

Joe Duxbury

Joe Duxbury

Active member
What are the rounded lumps that get created by the passage of people on the dry mud floors of cave passages? If they were on ski slopes they'd be 'moguls'. If they were on dirt roads they'd be described as 'washboarded'. The formation process must be similar.
I'm sure I've seen a term for them somewhere.
 
My guess, Joe, is that the mud floors originally had cracks in and the cracks denude preferentially to form "valleys" so the "islands" end up raised by comparison, think along the lines of pingos or similar. The cracks obviously become obliterated by the passage of people and hence the resulting landscape is lumpen.
 
I too have wondered what causes the ripples to form. They appear to be very close to the amplitude and pitch of a sandy beach or stream bed as water flows over, but obviously the mechanism is different.

With regard  washboarding on loose surface roads - we used to experience this a lot in 4x4 motor racing. The cause in this case was the bouncing of vehicles on their suspension. Every time the vehicle went over a slight bump, the vehicle would lift, suspension would extend and the pressure on the ground reduced. As the vehicle came back down, the suspension would compress and the ground pressure increased and the rotation of the wheels would dig out a trough. The vehicle would rebound back up and so the process went on. Since each subsequent vehicle would lift at the same point it just made the washboarding worse. The washboarding effect was a lot more pronounced on up hill climbs as the vehicles would be driving slower but with more wheel spin as they struggled for grip and hence digging and throwing more of the surface material backwards. 

In a cave environment I've noticed that the peaks of the ripples are almost polished with a harder crust than the troughs. So perhaps it's the peaks that get compacted and are less easily worn away by foot fall, where as the troughs get less compaction and as a booted foot rolls forward with each step the toe being the last point of contact gouges out a little each time which gets pushed backwards. Any loose mud/sand on top of the peak will get compressed into the surface the next time someone steps on it.

Maj. 

 
Maj said:
I too have wondered what causes the ripples to form. They appear to be very close to the amplitude and pitch of a sandy beach or stream bed as water flows over, but obviously the mechanism is different.

With regard  washboarding on loose surface roads - we used to experience this a lot in 4x4 motor racing. The cause in this case was the bouncing of vehicles on their suspension. Every time the vehicle went over a slight bump, the vehicle would lift, suspension would extend and the pressure on the ground reduced. As the vehicle came back down, the suspension would compress and the ground pressure increased and the rotation of the wheels would dig out a trough. The vehicle would rebound back up and so the process went on. Since each subsequent vehicle would lift at the same point it just made the washboarding worse. The washboarding effect was a lot more pronounced on up hill climbs as the vehicles would be driving slower but with more wheel spin as they struggled for grip and hence digging and throwing more of the surface material backwards. 

In a cave environment I've noticed that the peaks of the ripples are almost polished with a harder crust than the troughs. So perhaps it's the peaks that get compacted and are less easily worn away by foot fall, where as the troughs get less compaction and as a booted foot rolls forward with each step the toe being the last point of contact gouges out a little each time which gets pushed backwards. Any loose mud/sand on top of the peak will get compressed into the surface the next time someone steps on it.

Maj.
Click to expand...

I believe there's a similar washboarding affect on regularly ridden horse trails, and successively it becomes easier for each horse to step into the gullies rather than alternate in out and so they become more pronounced. Somehow I doubt cavers feet have been there long/frequently enough for the same affect to occur.
 
Bernie Woodley (SWCC) investigated this in the sandy passages of Ogof Ffynnon Ddu top entrance. The names that come to me are "tonkarren" and "Bouma" patterns. I can find no reference to this first on the web, so I may have misremembered slightly...
 
I just found the reference in an SWCC newssheet/E-Bulletin: 22nd January 2005

"CONSERVATION TAPE REMOVED FROM OFD Bernie Woodley
The taping, from four areas inside Top Entrance, on the way to Gnome Passage has been removed. These areas
were protected whilst investigations were undertaken to establish the veracity of a reported new type of
sedimentary formation, variously named, Schweinkarren, Tonkarren and Bouma Patterns.
I have discovered that these phenomena have been discussed at a previous BCRA cave science symposium and the
consensus was that they are caused by cavers. Where they do appear, they will only be found in heavily used
passages, created by the pounding of size ten wellies. There is, apparently, a fine example of these patterns to be
found on the main path in Wookey Chamber 3.
I would like to thank Peter Collings-Wells and Dr. A.R. Farrant for their invaluable help in sorting this out."
 
Owen Clarke brought them up in 2OO6:
http://bcra.org.uk/pub/search/aut_abs.htm

Although Bouma sequences are a series of mud deposits, so could cause confusion.
 
I recall now that Owen Clarke was involved. I found this too.

SWCC Newssheet: No. 1 / February 2004

"Taping in Ogof Ffynnon Ddu Top Entrance Bernie Woodley
There are some new areas that I have recently taped off, on the main route into OFD from the Top
Entrance. This has been done to protect a possible newly identified sediment feature whilst more
information is gathered. These formations resemble sand ripples but apparently are formed by an
as yet undefined process and warrant further study. There is a paper in preparation on these
formations, which will be presented at the next BCRA conference by Owen Clarke and will, no
doubt, provoke enough scientific debate to decide on the merit of the taping.
Although these formations have been walked over by many cavers for many years, please respect
the taped off areas and walk around. There is a clear and easy path to use.
If there are any sedimentologists out there interested in this, I would be glad to hear your opinions."
 
Rhys said:
The taping, from four areas inside [OFD] Top Entrance, on the way to Gnome Passage has been removed. These areas were protected whilst investigations were undertaken to establish the veracity of a reported new type of sedimentary formation, variously named, Schweinkarren, Tonkarren and Bouma Patterns.
I have discovered that these phenomena have been discussed at a previous BCRA cave science symposium and the consensus was that they are caused by cavers. Where they do appear, they will only be found in heavily used passages, created by the pounding of size ten wellies
Click to expand...

Thanks, Rhys. The areas mentioned in this quote are exactly the ones I had in mind.
"Schweinkarren" eh? That must make us cavers the "Schwein".
 
That must make us cavers the "Schwein".

No, I got that wrong. The 'formations' aren't caused by schwein, but look like the rounded backs of piggy-wiggies.
 
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