Hello From Texas Hill Country

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Hello From Texas Hill Country

Postby lairdpg » Jul 31, 2018 11:05 pm

Howdy all. I am a newbie here. I live in the Texas Hill Country. I have been in an out of caves for at least 40 years. As recently as last year, my wife and I bought a property and built a home on it. Before the home was finished, I discovered cold air pushing out from a crevice under a large Cedar Elm Tree about 50 years old approximate. It took me 4 months to find some cavers (not spelunkers) that wanted to come out an explore. I had already dropped a Go-Pro camera on a long pole with a light into the crevice and saw a cavern ceiling about what I thought was 30-40 feet down. On the left side of the tree, we found a place to bust through and get into the cave entrance. The cavers were great and came out a couple of times when the had time available.

They were mesmerized (as I have been) at the amount of air pushing from the cavern entrance when the barometric pressure drops. Equally interesting is watching the cavern pull air when the barometric pressure is high on the surface. I have recorded these occurrences for about a year now. It appears the cavern is about 54-58 degrees in the winter here in Texas about 18 feet below the surface. In the summer. the air that is pushed from the cave is about 68 degrees. I have noticed that about every 10-15 days, we have cave crickets at night on the surface near the cavern entrance.

Now for the mysterious part. Our cave has a chamber about 25 feet below the surface and ( have so me pics taken by the cavers) but they were not able to find out the source of the air on their two visits. I have no idea whether they will come back out in the future and the caver that led the group has dropped from the radar. I sure would like to see where this cave leads to, but safety is a top priority. I will not list the location of the cave per forum rules.

I have always been interested in caverns, especially wet/solution caves. We found some stalactites in our cavern that are still growing and from the size of them some National Park Rangers at Mammoth Cave in Kentucky estimated the stalactites to be over 3,000 years old from pics. I am hoping to create dialogue here on the forums to learn as much as I can about our cave and if anyone has any advice on how to source the cold air pushing out, I would be much obliged.

I am not sure yet whether I can post a link to my cavern find, If its permissible per the rules, I will share. I am in hope that I can find a group of seasoned professional cavers that might find my cave interesting as well. I am an IT Exec here in Texas for an out of state company with interests in project management, Information Security, Photography and Geology.

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Re: Hello From Texas Hill Country

Postby GroundquestMSA » Aug 3, 2018 9:09 am

Is the chamber in the photo accessible? Is it the limit of exploration so far? There are lots of ways to trace airflow, but one of the easiest and most effective is to use smoke. I often bring a stick of incense when digging. I wish I was closer to your area, though I have traveled across the country to check leads in the past.

The Park Rangers may have given you an estimate based on an "inch per ---- years" formula, but the truth is that there is no such formula. Speleothems grow at dramatically varied and completely undredictable rates based on bedrock type and orientation, amount of rainfall, soil content and more.
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Re: Hello From Texas Hill Country

Postby lairdpg » Aug 3, 2018 10:28 pm

Re: Hello From Texas Hill Country

Unread postby GroundquestMSA » Aug 3, 2018 9:09 am
Is the chamber in the photo accessible? Is it the limit of exploration so far? There are lots of ways to trace airflow, but one of the easiest and most effective is to use smoke. I often bring a stick of incense when digging. I wish I was closer to your area, though I have traveled across the country to check leads in the past.

The Park Rangers may have given you an estimate based on an "inch per ---- years" formula, but the truth is that there is no such formula. Speleothems grow at dramatically varied and completely undredictable rates based on bedrock type and orientation, amount of rainfall, soil content and more.
====================

Yes, the chamber is accessible. You can walk down most of the way into the chamber, towards the opening, you have to squat or sit to get under a low hanging ceiling but the lead is a good one with a very accessible chamber. the chamber is the limit so far. The cavers that came out and worked with me were very knowledgeable. They used flagging to discover the air flow. What the cavers were interested in was the amount of air flow. They were a group of cavers who had worked professionally for over 20 years and they told me they had never seen so much air from a cave in Texas. We have a few show caves in our area and of course the Balcones Fault Line hosts a dry show cave in San Marcos, Texas. The cavers from the Texas Speleological Association Grotto also said it appears our lead is case by a "break down". Since we had to open a tunnel big enough to access the chamber below, we believe its the first time anyone has been in the cavern unless there is another access point we are unaware of. A check of unpublished cave locations revealed no caves in our area although Karst is a major feature in the area.

One interesting thing is that a group of 5 or 6 Raccoons lives somewhere in the cavern but as of yet, we have not found where. I did watch them one day at dusk and saw where they were exiting. It was a crevice in the rocks that led down to the chamber. I plan on looking into the as I do not have to go down into the chamber. However, the air flow is coming from down below in the chamber somewhere. I suspect it might be more accurate to catch the cave when it pulling air to see where the smoke ends up getting sucked into. Does that sound right? I have been in quite a few caves, but by no means a professional caver. Beyond that I do not plan to work in the lead without professional cavers for safety reasons. Maybe the Raccoons can lead me further in if I can locate the opening they go in at?

I do have more photos of the lead into the chamber. There are a lot of rim dams in the chamber from water/carbonic acid eating into the rock below. On the surface, I discovered four hand tools, identified as Paleo-aged. Well I will post another pic or two. Thank you for your response and interest.


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Re: Hello From Texas Hill Country

Postby trogman » Aug 4, 2018 5:47 am

Very nice! I wish I lived a bit closer, as I would gladly come and take a look. Sometimes these blowing leads take a bit of persuasion to get into, but they are usually well worth the effort. Have any of the Texas cavers done any drilling and "micro-shaving" to penetrate further?

I am also curious about the airflow, as you said it is relative to the barometric pressure. I get the impression that from the temps you measured that the cave may be drawing air in the winter (which would explain the cooler temps), and blowing air in the summer. I know in my experience that this generally indicates that there is another entrance at a higher elevation. Sometimes that other entrance is not humanly passable, but is enough to allow airflow to create what we refer to as "chimney effect." If, on the other hand, your entrance was doing the opposite (that is, blowing in the winter and drawing in the summer), that would indicate that the other entrance is lower.

Cavers have a saying that "if it blows it goes." A friend and I worked a blowing lead here in AL off and on for several years, but it was only a 4-6 inch wide crack as far as the eye could see. We even halted the project for a year or two, because it was so discouraging. Yet we measured winds of 15 mph at the entrance, so I was convinced there was a sizable cave in there. Eventually we got in, and sure enough, it goes!

You are very fortunate to have something like this right on your property. :drool: I must admit I am rather envious!

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Re: Hello From Texas Hill Country

Postby GroundquestMSA » Aug 5, 2018 12:34 pm

Very interesting. It is not uncommon to lose airflow once through a narrow restriction. Even a small volume of air movement is magnified in intensity when it passes through a small place. Imagine holding a dribbling water hose, then covering all but a pinhole with your thumb: the volume stays the same but the pressure is dramatically increased. So once you passed or removed the narrowest part of the cave passage it is natural that the air became more vague.

The chimney effect that trogman describes is temperature driven, not barometrically driven. If the air changes really do correspond to barometric changes, there is no reason to believe another entrance may exist. However, it takes a large amount of underground space to produce barometric wind, and very very tiny caves can produce a chimney effect. Make careful barometric observations within the same temperature range.

You are correct, it will easier to spot the airflow when it is sucking, especially if into a breakdown pile. Smoke is excellent in this setting.

Note that the number of actual "professional" cavers is very near to zero. A few people have found a job that involves or allows caving, but for a majority of cavers, including most of the world's foremost cave experts, caving is a passion or a hobby, not a profession. Texas Speleological Association for example is a non-profit hobby club, not a professional group. You are of course free to wait for experienced help, but I would encourage you to do what you can on your own. Caving is not highly dangerous and a few basic steps combined with common sense are all that anyone has or needs to work with.

Rimstone is one of my favorite speleothems. It comes in many forms and sizes. Since it is on the floor, it is sadly one of the first formations to be demolished after the discovery of a new passage. It is not formed by water/acid eating the floor, but by the deposition of dissolved minerals carried from elsewhere.

I hope you keep working at the lead as long as is reasonable. Finding a new cave is exciting but also involves the responsibility of treating a fragile and ancient place with the respect it deserves. I hope you get to experience all of that.
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Re: Hello From Texas Hill Country

Postby lairdpg » Aug 5, 2018 9:08 pm

Like GroundquestMSA stated, our cave is a barometric pressure cave. I have taken hundreds of measurements of barometric pressure rising and falling. The cave activity coincides with changes in barometric pressure and not so much with temperature although if a storm comes through, the cavern will become active for several hours, but again, related to pressure changes. I also take videos as historical data to show what is happening at the time/date coinciding with the barometric pressure and air flow. I can state without hesitation that when the barometric pressure is falling/dropping on the surface, the cavern is pushing air out in an attempt to stabilize the pressure of the cave with the surface. When the barometric pressure on the surface rises, the cavern reverses air flow and starts pulling air into the cave to stabilize the cavern pressure with the surface pressure. Each time, the air flow lasts for several hours and tapers off as the pressure maximizes or minimizes and reverses course. This is any day of the year. Since the property is only about 20 feet from the peak of the highest hill/elevation in the area, I doubt there is another opening nearby.

A couple of the cavers that came out were actually employed in the field 20 plus years. The others with them were as your described, experienced hobbyists. I also collaborated with the Director of Karst Biology at one of Texas's public universities. I have all the safety gear and know the risks but never take stupid chances. My one concern since the Balcones Fault Line runs through our area and shows up on Geological Survey maps is that our cave might be part of that fault line and although has enough volume to be barometric in nature, may not be worthy of much more exploration. We have several show caves in the area to boot, all except one are wet caves. Its interesting what you said of the Rim Dams. We have left them in place, videoed them and have taken photos but if we can save them, we will. We are reasonably sure with all the air flow and barometric pressure measurements that our cavern is not air driven. Now for a twist, we have caught pics of Mountain Lions on our property but none go in and out of the cavern and we did not find bones, cat hairs or other evidence that cats have used the cavern so far. Only Raccoons at this points, plus some Cave and Camel Crickets. No bats have been spotted so far either. We sure hope we can prove where the cavern goes at some point. In reply to Trogman, to my knowledge, no micro shaving or drilling has taken place although we did use hammer drills to break big rocks off in areas of interest. I had to pull all those big rocks up the lead to the surface on a rope and dump them for the guys/gals below. I sure thank both of you for your advice. It means the world to me.
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Re: Hello From Texas Hill Country

Postby Phil Winkler » Aug 10, 2018 3:55 pm

Geary Schindel at Edwards Aquifer may assist: geary Schindel <gschindel@edwardsaquifer.org>
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