Small blowing holes?

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Small blowing holes?

Postby GroundquestMSA » Jun 2, 2013 4:56 pm

I noticed something new to me during the survey of a small cave yesterday. On the right wall of a high narrow passage, were a series of 5 small holes. These were found about 12' from the floor and scattered over a 20' area. They ranged in size from 3" to 8". Some of these were blowing cold air, one very prominently. These holes were very shallow and seemed to lead only to narrow cracks parrallel to the cave passage. Water and flowstone issued from several of these. How would you interpret this? Since the cave is developed along a big joint, I theorized that these holes lead to a very narrow parrallel passage that communicates with deeper sections of the cave that we cannot reach. That's what I'll write in the description unless I get some better ideas from you folks. I know this is a vauge inquiry, but I'm trying hard to learn more about cave geology and formation and will likely be asking some bad questions for a while.

I tried to load a photo...postimage says it's loaded, but it won't show.
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Re: Small blowing holes?

Postby GroundquestMSA » Jun 2, 2013 5:29 pm

Here's a photo

The left nostril blows really hard.
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Re: Small blowing holes?

Postby Scott McCrea » Jun 2, 2013 7:37 pm

"If it blows, it goes."

There is something on the other side. Could be miles of cave. Could be a higher or lower entrance. But there is something. They don't just blow for no reason.

The trick is determining if it is worth the effort to find out.
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Re: Small blowing holes?

Postby rlboyce » Jun 2, 2013 8:39 pm

Scott is 100% correct.

Also, the best any of us will ever be able to do is guess. You can support a theory as much as you want, but at the end of the day it's still a guess. If it's deemed as not worth going through the physical effort to find out, a best guess has always been sufficient for me. : ) In addition, I think having an occasional unsolved mystery adds to the mystique of caves... caving would seem much less interesting to me if everything was known, and everything was completely predictable.

As for my rough guess, I'd actually say the water and flowstone suggests a higher passage developed in this parallel joint. I'd have to see the passage in person to have any degree of confidence in a guess.
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Re: Small blowing holes?

Postby GroundquestMSA » Jun 3, 2013 4:56 pm

It's all guesswork sometimes, but since my descriptions are going to be published I'd prefer that they don't include ridiculous speculation. I like your rough guess pretty well. It makes good sense and would explain everything, I think.
Which of these possibilities makes most sense to you?
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Re: Small blowing holes?

Postby rlboyce » Jun 4, 2013 5:39 pm

Oh, I did not realize the passage was this close to the surface (assuming everything is more or less to scale). A close look at the surface above this passage may yield more insight, especially if there is snow on the ground and if airflow is predominantly temperature driven. You may have been over the surface before, but if you were not looking specifically for air last time, you may be surprised at what you find the second time around... happens to me all the time. If you find a melt spot or blowhole (or a sucking hole in summer), then it would be reasonable to conclude that possibility #1 is true. Else, possibility #2.

If the surface is farther than indicated in the sketch, and it is not reasonable to immediately assume a surface connection, you may have to gather more facts (In which direction does the main passage itself dip? What are the joint sets, and does this mystery crack follow one of them? Have you been overlooking a common speleogenesitic pattern in other parts of the cave that may help predict what this crack does? How does the geology influence the cave in general? Is there fluting? Scallops? Have you determined what the air really doing... descending, or moving laterally? Sooo many other little things you can investigate to help make a good guess) and reanalyze.

If you dwell on speculation for any significant amount of time in your write-up, don't forget that readers may find speculation on where this cave may be going in general to be just as interesting. Focus not just on the bridge, but what is on the other side as well. : )

Good luck, and keep us informed if you learn more!
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Re: Small blowing holes?

Postby trogman » Jun 5, 2013 6:27 am

Another factor to take into consideration is the outside air temp- at this time of the year, most caves airflow will move from high to low, with the lower entrances blowing, and the upper entrances drawing air. This is due to the chimney effect; warm air rises, and cool air sinks. Of course in the winter, the relatively warm cave air will usually rise out of the upper entrances, oftentimes causing the steamy plumes that we all love to see on a mountainside.
Since you indicated that the holes in question are blowing air, it stands to reason that they are likely connected either to the surface above, or to a higher cave passage. This is assuming, of course, that you observed this phenomena during warm weather.


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Re: Small blowing holes?

Postby Leclused » Jun 7, 2013 6:24 am

Hi,

There is a good reference work about airflows in caves. Called “Vent des Ténèbres” from Baudouin Lismonde.

It can be downloaded here : http://cds38.org/climatologie-du-monde-souterrain/

There is only one potential problem, it is written in French.

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Re: Small blowing holes?

Postby arizonaowl » Sep 15, 2014 5:18 pm

It should be possible to measure the cross sectional area of the blowholes, measure the air velocity, and then to calculate the volume of air needed to keep up the flow or air. I have never heard of this being done, but it does seem plausible to me.Regards, Al Coplely 20845
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Re: Small blowing holes?

Postby charles80 » Sep 25, 2014 8:38 pm

I'm posting this question here since I didn't feel like opening a new topic and the forum guidelines support using related existing threads.

If at the bottom of a cave there is a wall of probably collapsed rocks and a gentle/moderate stream of air can be perceived there, does it mean that said cave has another opening or expands further? Would that same opening be about at the same level of the blowing wall or could it be higher too, like the known cave opening?

Also I'm curious if by looking at a moderately-sized hole in a known karst-collapsed area one could guess if it develops into a cave or it's just a very shallow opening (without having to explore inside).


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Re: Small blowing holes?

Postby GroundquestMSA » Sep 25, 2014 9:17 pm

charles80 wrote:If at the bottom of a cave there is a wall of probably collapsed rocks and a gentle/moderate stream of air can be perceived there, does it mean that said cave has another opening or expands further?

Yes, even though the rest of the void may not be accessible.
charles80 wrote:Would that same opening be about at the same level of the blowing wall or could it be higher too, like the known cave opening?

Here's a simplified version of cave airflow rules, as I understand them. Airflow is caused by the barometric equalization of the cave to the outside world, only easily discernable in caves with large volume, or by the "chimney effect" in which air enters the cave and is either cooled or heated by the stable ground temperature. In the wintertime, when this air is heated, it will then rise, eventually exiting through discernable or indiscernible openings/cave entrances. In the summer the opposite is true. Thus if air is blowing from a cave in the summer, the indication is that another entrance or a large volume of cave passage is present at a higher elevation. If the cave is blowing in the winter, expect a lower entrance, or a lot of passage at a lower elevation. In very large caves, barometrically driven winds can be very complex and unpredictable.
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Re: Small blowing holes?

Postby rlboyce » Sep 26, 2014 6:18 pm

Sometimes, "local circulation" can also be to blame, where air is entering one hole, and exiting through another (or collapsed rocks covering an opening) nearby. Did you happen to notice if there was any airflow in the known cave opening? If so, what direction was the flow? Airflow at the known opening, if it exists, may be a little more difficult to discern with a larger aperture (Q=v*A).
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Re: Small blowing holes?

Postby GroundquestMSA » Sep 26, 2014 7:27 pm

rlboyce wrote:Sometimes, "local circulation" can also be to blame, where air is entering one hole, and exiting through another (or collapsed rocks covering an opening) nearby.


Yep, I forgot to mention this. This kind of airflow is often influenced by wind outside. A little cave near me "scoops" up air since the main entrance opens toward the west, where most of our wind comes from. This makes a blowhole of a tiny second entrance about 70' away and creates a loud howling inside the cave on windy days.
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