Question Blue Hole at Santa Rosa NM

[boulderjohn]

Depth at BH doesn't matter, as the flow is so high there's effectively no variation in temperature.

The Blue Hole and nearby Rock Lake are both sinkholes, with the water entering from a cave system far below them. With the Blue Hole, we were able to explore that system down to a depth of 200 feet. Rock Lake is about 280 feet deep, but it has no openings big enough to allow entry. The water seeps in through small openings in the rubble left by the collapse of the roof.

That means the water temperature in both lakes is largely determined by the temperature of that deep ground water. The Blue Hole does indeed have a lot of flow because the cave feeding it is relatively large, and the flow goes all the way to the surface. With Rock Lake, the upward flow exits instead through a pipe at about 37 feet, taking the water to the nearby trout hatchery. As a result, there is a layer of water that sits on top and warms up considerably during the summer. When doing a decompression stop at 40 feet, it can be psychologically difficult to be so chilly knowing how much warmer the water is 3 feet above you.

The ground water is actually slightly warmer than the water in the lakes, so some old maps refer to the vents in Rock lake as "warm water vents," leading some people to think there is thermal activity involved, but it is really just the temperature of the ground water.

 

[bryankwatts]

The Blue Hole and nearby Rock Lake are both sinkholes, with the water entering from a cave system far below them. With the Blue Hole, we were able to explore that system down to a depth of 200 feet. Rock Lake is about 280 feet deep, but it has no openings big enough to allow entry. The water seeps in through small openings in the rubble left by the collapse of the roof.

That means the water temperature in both lakes is largely determined by the temperature of that deep ground water. The Blue Hole does indeed have a lot of flow because the cave feeding it is relatively large, and the flow goes all the way to the surface. With Rock Lake, the upward flow exits instead through a pipe at about 37 feet, taking the water to the nearby trout hatchery. As a result, there is a layer of water that sits on top and warms up considerably during the summer. When doing a decompression stop at 40 feet, it can be psychologically difficult to be so chilly knowing how much warmer the water is 3 feet above you.

The ground water is actually slightly warmer than the water in the lakes, so some old maps refer to the vents in Rock lake as "warm water vents," leading some people to think there is thermal activity involved, but it is really just the temperature of the ground water.

John, thank you for the reply. I always enjoy reading your posts as they are very informative.

 

[VikingDives]

The Blue Hole and nearby Rock Lake are both sinkholes, with the water entering from a cave system far below them. With the Blue Hole, we were able to explore that system down to a depth of 200 feet. Rock Lake is about 280 feet deep, but it has no openings big enough to allow entry. The water seeps in through small openings in the rubble left by the collapse of the roof.

Technically, I believe they are considered artesian wells, since sinkholes have no external flow.

Speaking of the exploration though, why doesn't the website about the exploration mention or picture you? Were you a late addition to the team?

 

[boulderjohn]

Technically, I believe they are considered artesian wells, since sinkholes have no external flow.

Speaking of the exploration though, why doesn't the website about the exploration mention or picture you? Were you a late addition to the team?

There were two explorations. That website is for the first one, and I was not on it. That is the one that first opened the top enough to let divers in.

I was on the second a year later, and it was almost an entirely different team. We had the goal of expanding that opening, making the deeper levels accessible by opening a restriction, and further exploring the deepest levels. I did not have (and never will have) the credentials of the top divers on the team. Only two could get past the first restriction to explore, and two others worked on that restriction. I (and others) confined my activity to expanding the opening and clearing out the area from that opening (85 feet) to about 130 feet.

 

[VikingDives]

There were two explorations. That website is for the first one, and I was not on it. That is the one that first opened the top enough to let divers in.

I was on the second a year later, and it was almost an entirely different team. We had the goal of expanding that opening, making the deeper levels accessible by opening a restriction, and further exploring the deepest levels. I did not have (and never will have) the credentials of the top divers on the team. Only two could get past the first restriction to explore, and two others worked on that restriction. I (and others) confined my activity to expanding the opening and clearing out the area from that opening (85 feet) to about 130 feet.

Ah, that makes sense.

 

[Marvinshirley2]

After the fatality of a cave team member a few years ago, I had heard that the city has permanently closed the vent to exploration. Is that true? (Though I do not have the Skills to do that kind of diving, nor am I interested in trying to gain them…)

 

[VikingDives]

After the fatality of a cave team member a few years ago, I had heard that the city has permanently closed the vent to exploration. Is that true? (Though I do not have the Skills to do that kind of diving, nor am I interested in trying to gain them…)

The snorkel (the pipe blocking the entrance) is back in place and no one should be going down into the cave.

That being said, when the last expedition was conducted, they placed a grate under the snorkel, which appeared to increase the rate at which the opening to the cave expanded.

2019'ish, the grate was removed and I believe the opening has continued to expand. I just took some measurements of the opening last weekend, and I'm planning to continue to document the rate at which the opening is growing. The bottom line for me is, I could probably squeeze through there today.

I'm also pretty sure that there are some people who have, and it is only a matter of time until someone dies in there. I was down there this year and saw a silt cloud that made me think that someone had entered, freaked/gotten stuck, and was awaiting a body recovery. Fortunately, that wasn't true, but given the quality of divers that most shops are turning out, I fear it is just a matter of time until my fears come to pass.

 

[boulderjohn]

After the fatality of a cave team member a few years ago, I had heard that the city has permanently closed the vent to exploration. Is that true? (Though I do not have the Skills to do that kind of diving, nor am I interested in trying to gain them…)

After the fatality, we had to recover the body. The site was deserted except for our team. It was not a happy day, and we wanted to get it over with. There were two pieces of grating that had been there previous to the exploration, and we put them into place as well as we could, put the snorkel in place, and left town. It was not the best piece of work we ever did.

The obvious problem was that one of our goals was to improve the initial access to the cave, and that meant expanding the entrance. On my first dive there, I could barely fit through, and it was an uncomfortable initial plunge straight down. When we were done, it was a much easier swim. That meant those two pieces of grating, which fit over the opening easily before we got there, barely covered it when we left.

When the army corps of engineers closed the site nearly a half century ago, they dumped two truckloads of loose rock into the cave. That was what was blocking entrance. Some of those rocks were pretty big, and they weren't easy to get out, but that was all it entailed--pulling out rocks and moving them. That explains why the hole is enlarging--they just have to fall into the cave below. (I haven't been paying attention to myself because I usually dive at Rock Lake.)

The afternoon before the fatal dive, I did the last dive of the day as a solo dive. The exploration team (Mike and Shane) would go first in the morning, and they talked about the problem of dislodging loose rocks upon entry. The plan was for me to do something about that. I was solo because bringing anyone else would be dangerous. The entry widens considerable at about 100 feet, and that is where I started my work. I focused on clearing out the opening as much as I could, creating a load of silt. In the last minutes of my dive (which was timed so that people would know whether to come in after me), I started at about 100 feet and headed slowly toward the surface, digging my arms into the rocky silt and throwing it all behind me as I ascended. We counted on the flow from the cave to clear it out, and I imagine it was all clear within a half hour.