Formation of Helictites?

[alastairgott]

Just a thought do you think that temperature differences in cold periods (ice ages) could help with the formation of helictites?
Does anyone know if they grow in normal conditions?

 

[gus horsley]

I don't know about temperature differences but I believe most helictites grow from either variations in draught ("bending" a water droplet), water squeezed under hydrostatic pressure through tiny pore or tubular spaces, or a mineral such as aragonite interfering with the formation of micro calcite crystals.  Or of course a combination of all these.

 

[cap n chris]

Maltsev has made reference to supercooled meltwater. Sounds reasonable enough.

 

[graham]

They most certainly do grow in normal conditions - if by that you mean a bit like now. There are show caves around the place where helictites have grown on fixtures that have been emplaced within the last century.

If you want all sorts of heavy stuff about the background science read this.

 

[Amy]

From Virtual Cave:
The twisted shapes are due to many factors, including:
(1) impurities in the deposited calcite
(2) wedge-shaped crystals causing uneven deposition
(3) plugging of the central channel may occur in dry periods, and when flow resumes, the pressure may force a new channel out the side of the original one
(4) air currents may favor growth in a particular direction. Sometimes helictites are found facing the same direction down a passage (see upper left photo in thumbnail table below).

 

[graham]

(3) plugging of the central channel may occur in dry periods, and when flow resumes, the pressure may force a new channel out the side of the original one

According to Vladimir Maltsev the central channel feeding thing is a bit of a myth, anyway.

 

[mrodoc]

From direct obs I would say draught is a significant factor.

 

[Jon]

From direct observations I would have thought that draughts had little to do with their formation

 

[graham]

There are certainly cases where draught is a significant factor, as there are places where large numbers of helictites are arrayed in broad parallel and it is difficult to think of a directional force, apart from gravity of course, which would otherwise be capable of producing this effect. However, it is clearly not always the dominant force and the fact remains that the one identifying feature of helictites (and heligmites of course) is that their growth pattern is affected mainly by a force other than gravity.

Two further points about the wind, the term anemolite can be used to describe stal that has been directionally affected by draughts and secondly, if the affect is due to asymmetric evaporation then it seems likely that the helictites will point into the wind rather than away from it.

In certain Aussie caves (especially) you can find large stalagmites whose growth is oriented by the light falling upon them. I suspect that most people would find these a bit too massive to be described as heligmites, though.

 

[4bags]

I don't know about temperature differences but I believe most helictites grow from either variations in draught ("bending" a water droplet), water squeezed under hydrostatic pressure through tiny pore or tubular spaces, or a mineral such as aragonite interfering with the formation of micro calcite crystals.  Or of course a combination of all these.

Aragonite crystals and helictites - Napps Cave, North Devon:

 

[alastairgott]

Could magnetism be another possible explanation? 4bags' your picture looks amazing but i can't help but think it looks a little like this

 

[alastairgott]

Thanks for the link graham, as you said, Heavy.

anyone able to pull a journal off for me?
Zeitschrift fur Geomorphologie/Applications of Paleomagnetism to Sedimentary Geology, 1993, p. 149-155
The paleomagnetism and rock magnetism of cave and karst deposits
Latham A. G. , Ford D. C.
maybe at http://sp.sepmonline.org/content/sepspapp/1/SEC11.body.pdf+html

 

[manrabbit]

Has anyone considered negative ions caused by falling water, could negative ions cause aerosolised minerals to be attracted to something on the cave wall such as quarts? I never read anything about negative ions and cave formations, just throwing a theory out there..

 

[graham]

alastairgott

I suspect that's more a case of convergent evolution, so to speak.

Sorry cannot pull that journal off for you. I cannot affords to get behind that sort of paywall. (Note that all the papers that I've linked to in this thread are open access.)

manrabbit

Not so much a theory, more a wild speculation.

 

[Brains]

Haha, I would say its a hypothesis that could be investigated, a wild speculation would the gods got bored and started doodling 

 

[Fulk]

I don't know how this delicate little thing formed, but I don't suppose a draught had much to do with it:

 

[TheBitterEnd]

Since we are speculating, has anyone considered aerosols as a mechanism for Helictite development?

 

[graham]

Since we are speculating, has anyone considered aerosols as a mechanism for Helictite development?

In what way?

 

[TheBitterEnd]

Very small water droplets, as in an aerosol, could respond to forces other than gravity, such as Brownian motion, convection, etc.  Crystal growing at school seems to indicate that there will be preferential deposition on existing seed crystals. So I wonder if an aerosol (or vapor) of water saturated with CaCO3 could contribute to Helictitites such as the one in Fulk's picture?

 

[graham]

Very small water droplets, as in an aerosol, could respond to forces other than gravity, such as Brownian motion, convection, etc.  Crystal growing at school seems to indicate that there will be preferential deposition on existing seed crystals. So I wonder if an aerosol (or vapor) of water saturated with CaCO3 could contribute to Helictitites such as the one in Fulk's picture?

I would doubt it. Given that calcite growth depends on degassing of CO2 from water when it hits the cave atmosphere, it is difficult to see how saturated water droplets would be moving about in that same atmosphere, without having already reached equilibrium with the cave atmosphere.