What's with Blue Hole????

[DandyDon]

From my observations and discussions with a city guy. The chamber that collapsed down deep may have started a chain reaction worry. I think they are trying to get some of the weight off the bottom to keep the main floor from going down. When I was doing a night dive last year, you could see cracks forming 20-30' back in under the floor. If you hung upside down and shined an HID light under the walls, you could see some chambers that had opened up way back in. If they pull out 5-6' of the floor sediment, there will be at least two rooms to swim back into. We also noticed that the depth by the grate had deepened by 2' in a years time. If the schematic drawing of the old magma chamber complex is correct, the roof of the 320' deep lower chamber may have been the one that collapsed. The hole could actually become deeper than Rock Lake...... I never heard if anyone found a bottom to the lower magma chamber.
If anyone has a phone number for the Corps of Engineers I would love to talk to one of their Geologists.
asta
Greg

Damn, now I'm getting excited.

I disagree. I used to think this, but observations over the years have led me to believe that it's the diver's that are diving the periphery at the bottom that cause the majority of the problem. This is because BH is wider at the bottom than at the top, so their bubbles roll up the sides and dislodge all the silt along the ledges all the way up, especially the organic stuff right at the top which rains down into the hole.

I don't see much "chocolate milk" silt (like I see in caves) in the hole that would be caused by the bottom muck being stirred up as much as I see tiny organic particles floating about.

Given, lots of bottom stuff is stirred up which shouldn't be, but unless it's right next to the grate, it has a tendency to stay near the bottom rather than rise through the water column.

Which of course means there's no solution to the problem, because once a diver has advanced beyond the "what's my pressure, what's my depth, where's my buddy" stage of awareness, the fun of the hole is to poke around the nooks and crannies of its sides, which causes the bubbles to be a problem.

Oh well.

Oh, and a story on why I suddenly changed my mind as to the bubbles around the sides being the problem:

Years ago a couple friends and I were experimenting with a "deco dome" (fancy name for an upside down cattle trough ) near the bottom of the hole -- it was put upside down under a ledge and filled with air from an AL80. We were seeing how hard it would be to eat and talk in it (turned out to be too small for two divers to talk without considerable effort, which means we learned something ).

We put the dome in Saturday morning and left it there until late Sunday morning. To remove it, I unscrewed the drain plug and the air roared out -- up the side of the 'hole.

In less than 5 minutes the visibility, which wasn't great to begin with being Sunday, was cut in half.

People were surfacing and commenting to their buddies. "geez, what happened? The viz just became horrible!"

We sheepishly pulled the dome out, threw it in the truck and boogied out of there, swearing that if we ever brought it back, we'd wait until Sunday evening to pull it, or find a way to divert the air further out into the water column so it wouldn't touch the sides on its ascent.

Guilty as charged

Roak

Yeah, I guess so. Never thought of that. Thanks.

 

[ddavies]

I disagree. I used to think this, but observations over the years have led me to believe that it's the diver's that are diving the periphery at the bottom that cause the majority of the problem. This is because BH is wider at the bottom than at the top, so their bubbles roll up the sides and dislodge all the silt along the ledges all the way up, especially the organic stuff right at the top which rains down into the hole.

Roak

I think you are correct. It would also explain why the viz is better at the bottom then at about 45 ft. The other thing I noticed was the organic stuff floating around. I commented after Sunday's dive it looked like all the divers were blowing their nose in the water. :redface:

 

[DandyDon]

Organic stuff = polite term for fish doodoo...!

 

[ABQdiver]

I disagree. I used to think this, but observations over the years have led me to believe that it's the diver's that are diving the periphery at the bottom that cause the majority of the problem. This is because BH is wider at the bottom than at the top, so their bubbles roll up the sides and dislodge all the silt along the ledges all the way up, especially the organic stuff right at the top which rains down into the hole. <snip>
Guilty as charged

Roak

I've noticed that problem as well! The more divers circling around, the more reduced the viz becomes.


Funny story about the dome!!

 

[Capnsnott]

I think Don has a fetish with fish doodoo...... LOL
I needed a good laugh, Thanks Don.

As for the flow. I agree with the 1/2 thing. Although, there is an increase because the grate is getting winnowed out. Look down into it, there is a lot more space now.
I think there is also some inflow coming from the other side. There is a crevace that is going off at about a 45* angle. If you get your light just right angle, you can see for a long ways. There appears to be some flow coming up it, my brother and I noticed particulates coming up it.
If you want an addrenaline rush diving the hole again, do it at night with an HID or big daddy Halogen light. Just go very slow and look into all of the cracks. I missed them for at least a year until another friend pointed them out. PS on that note, I have a 50w Halogen can light that I made for pretty cheap. If you go to the home built area on the SB do a search for "dive light" or can light. I used mine down to 97'. Now it's a spare.

asta
Greg

PS, I know what 500 cudas look like from the bottom.....

 

[DandyDon]

I've noticed what seems like new cracks and inflow, but forgot. So maybe the old volcano vent is lossening up, caving in below? Makes sense, with that much water flowing thru a vent as old as it is. Wonder if the room under the parking lot is stable?

And with the Army Corps of Engineers record, do we trust them?

 

[ABQdiver]

I think Don has a fetish with fish doodoo...... LOL
I needed a good laugh, Thanks Don.

As for the flow. I agree with the 1/2 thing. Although, there is an increase because the grate is getting winnowed out. Look down into it, there is a lot more space now.
I think there is also some inflow coming from the other side. There is a crevace that is going off at about a 45* angle. If you get your light just right angle, you can see for a long ways. There appears to be some flow coming up it, my brother and I noticed particulates coming up it.
If you want an addrenaline rush diving the hole again, do it at night with an HID or big daddy Halogen light. Just go very slow and look into all of the cracks. I missed them for at least a year until another friend pointed them out. PS on that note, I have a 50w Halogen can light that I made for pretty cheap. If you go to the home built area on the SB do a search for "dive light" or can light. I used mine down to 97'. Now it's a spare.

asta
Greg

PS, I know what 500 cudas look like from the bottom.....

Ahhh !! A mission!! You got it!!

 

[DandyDon]

Can I go? When?

 

[amascuba]

I may be there this weekend .. I should know by tomorrow.

 

[Divedoggie]

It sounds like things could change significantly at BH.
Will it be in a short time geologically? (which is a long time!) or
Will it be in the next few years?

It makes the possiblilty of something happening while diving a bit scary. Perhaps the drought has caused the water levels in the aquafers to drop, creating more airspace in the caverns, and decreasing the amount of support that the water itself gives to the rock above it.
The drought, population growth, and agriculture, all add together to change the dynamics which have kept the BH stable.
In addition to an increased depth(floor sinking), the water temp is fluctuating as well. When we were there in December, we had temps as low as 53 degrees.

When the city of Santa Rosa starts their construction project, I fear that it make cause a catastrofic sink/collapse, which will significantly change the entire area.