Re: Can you tell me more about blowholes like at Wupatki Nat'l Mnmt in AZ?

Hello....Joann!

I found rather little available on the blowholes in Wupatki National 
Monument.

The blowholes are a result of the rising of the Colorado plateau. Limestone 
layers that are part of the plateau were rather well fractured during this 
event (which occured over several million years) and thus water seeped in 
and created fissures, caves, etc, that are connected and of a large total 
volume (one web site said something like 7 billion cubic feet, but did not
say, nor could I find a reference, on how this number was derived).  
Basically the water finds easy entry along the fractures, dissolves some of 
the limestone (calcium carbonate) into itself and carries it off leaving 
behind void space. 

When the atmosphere above the blowhole changes pressure (due to a passing
weather front, or even the normal heating/cooling of a day/night cycle),
the air inside responds.  If the pressure is falling outside (say in the
afternoon of a hot day), then air comes out of the hole; rising pressure
(night cooling) causes air to flow back into the blowhole.

I found nothing to suggest that the fissure complex related to the blowhole
has been explored. Given the predilictions of amateur spelunkers to explore
any accessible cave, I suspect that this lack of comment means that the
fissures are in general too small to enter. If they are being explored, no
one seems to be writing anything down about it. The USGS website does not
even mention the blowholes at Wupatki NM, for example.

I suspect that the blowholes in Wupatki have analogs wherever limestone
caverns can be found. Many entrances to caves in the Appalachians have been
noted to "moan" as air goes in and out of them. This is similar but not 
quite the same. The Colorado Plateau (on which Wupatki sits) is a fairly 
rare geological area. Large high plateaus really only exist in the
western USA and in Tibet. I have no idea if similar limestone fissure 
phenomena exist in the Asian area or other parts of the western US--haven't 
heard of any, and a web search came up empty. Searching for "blowholes" did 
come up with some other kinds of them. The most common was related to lava 
tubes in Hawaii...here the sea waves acts as a piston of sorts, causing air 
(and sometimes water, too) to shoot in and out of holes in the roof of some 
of the lava tubes where they near the ocean.

Your best bet for further information is to contact either the geology 
departments as the two major Arizona state universities and/or the rangers 
at the Wupatki NM and ask them for leads to more detailed geological studies 
of the area. I'm sure they've been done...probably a number of theses have 
been done on the area...but the references are obscure enough that I (my end 
of earth sciences is mineralogy) am not able to find them.