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Air movement in caves

PostPosted: Jul 30, 2019 11:17 am
by Yog-Sothoth42
Hi! I have done some reading on caves. I read Blind Descent and I am currently reading a cave geology book. I have tried to find information on air flow in caves for some writing I want to do and did a quick search here and other places online, but couldn't find want I wanted.

I understand in there can be a lot of heavy wind in large cave systems and large caves, but nothing really says where in the system. The only experience I have in caves is Wind Cave and Jewel Cave in South Dakota and there was no air movement, I could detect, on the tours even when the cave was breathing. Is the large air flow talked about with heavy winds basically in the large central through passages of caves? Near the entrances and massive chambers/shafts or where? I assume smaller passages, especially ones that end would have little to none unless they are connecting to something larger?

If someone could help with this I would appreciate it or point me to a website or reading with the answers I seek. Thanks for your assistance in advance.

Re: Air movement in caves

PostPosted: Jul 31, 2019 5:26 pm
by Squirrel Girl
The late Fred Wefer published information on airflow in caves. I don't know how to find those papers. It might have been something local to Virginia caving groups. I don't recall.

I can report that in Lechuguilla Cave (New Mexico), the air movement was at least in part, due to barometric pressure. When there was a low pressure weather system going past, all the air from that enormous cave system would have to pass through a body-sized opening to exit from the higher pressure in the cave. Geez, that was a strong wind. Wish I knew how much but extremely strong.

Re: Air movement in caves

PostPosted: Aug 1, 2019 4:13 am
by trogman
Us cavers have a saying: "if it blows, it goes." This is not an ironclad rule, but it has certainly proven to be true quite often in my experience.

As to your question regarding where this airflow is manifested, the most intense manifestation is usually in tight passages where the cave constricts down to very small proportions, thus funneling all the air through a smaller opening. In larger passages the airflow is often virtually undetectable.

As Squirrel Girl suggested, airflow is often present due to changes in barometric pressure, especially in extremely large cave systems such as Lechuguilla and Wind Cave. In most of the smaller and shorter caves that I am familiar with airflow is more often due to what is called "the chimney effect." Simply put, since most caves in this area are ~56° F, the air flows moves in or out depending on the relative outside air temp. In the winter, on a cold day, caves with upper entrances often blow mist plumes, sometimes visible several hundred feet away. Because the cave air is warmer than the outside air, the air rises out of the upper entrance. Any lower entrance to the same cave on the same day would be sucking in air. On warm or hot days, the airflow is reversed.

Several years ago I was walking with some friends at the base of a mountain on a rather hot late summer day. There was a small hole just above a spring that was blowing like crazy, and we made a note to come back later to work on it. Although the tiny crack was only ~6" wide for as far as we could see, the airflow told us that it was worth digging on. Later we measured the wind at 15 mph. Eventually we dug our way into a nice cave that has ~1/2 mile of passage.

From what I recall the wind speed in the entrance to Lechuguilla has been clocked at over 50 mph, and the cave is over 138 miles long.

Trogman :helmet:

Re: Air movement in caves

PostPosted: Aug 23, 2019 11:46 am
by Bodie the Dog
Well, I had a clever reply about flying polyps, based upon your user name, but I guess it wasn't serious enough for the mod's, lol, because they wouldn't approve it. Or maybe they thought I really am a cult member.

Cavers are about as funny as archaeologists, lulz. Oh well.

Good day to all, I'm off to the summit!

BTD

Re: Air movement in caves

PostPosted: Sep 10, 2019 9:48 pm
by Bumbalawski
In the past several years, we have been finding a lot blowers. Every one produced a cave. One blower was at the base of a dead tree stump. It has yielded 7000 feet of cave thus far. Not to bad for Maryland.

Re: Air movement in caves

PostPosted: Sep 13, 2019 10:38 am
by ohiocaver
You were in Wind Cave and there was no wind??? A basic part of the tour is the Ranger\Guide holding a light jacket by the entrance and showing the cave either drawing in air or blowing it out. Sometimes, the air current is so strong the jacket is horizontal.