Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: air blowing out of an old mine


Herbert H Gottlieb says:

In which part of the earth's interior is the temperature 58 F?

A few meters below the surface.

Every time I have toured a cave (admittedly not extremely often, and only
within a narrow range of latitudes), a big deal is made about how the
temperature in the cave is a constant temperature, not varying with the
seasons. The temperature always seems to be in the 50's (F), although I
don't remember any specific numbers. Bring a sweater, but not a down
jacket.

This depends ot least partially, under some circumstances, insert legal
dislaimer here, on the cave. Here in AZ I have been caving twice (shamefully
neglectful of a great hobby I guess) -- one in the cave of the bells outside
Tuscon, where the about 58F rule worked as it always did back in caves
in IN and KY. HOWEVER, just outside of Flagstaff here is a large lava tube
collapsed at one end, about a mile in length and not very deep underground.
It contains ice year round. Another lava tube near sunset crater is also
called an ice cave although it has been closed to the public for 2-3 years
now. In these caves you need the down jacket (and gloves -- especially
gloves) if you stop exercising.

I KNOW this is not typical for caves, but they are clearly more complex
than simple rules like the 58F rule.

I have always assumed that this was mainly due to the earth acting as a
very large thermal resevoir, averaging the daily and seasonal temperature
variations. Now, I'm not so sure. Are caves in the tropics cool, or near
the average air temperature? How far down does the permafrost extend in
Antarctica?

In any case, the expected effect on air is clear. In a mine with multiple
openings at different heights, it should blow down in the summer and up in
the winter. Now whether that matches the observed behavior is another
question!!!

We have a breathing cave in Northern AZ near Wupatki that was used for
summer air conditioning by Native Americans in their village about 1000AD.


--
--James McLean
jmclean@chem.ucsd.edu
post doc
UC San Diego, Chemistry

Where the temperature doesn't vary much seasonally, even the air
temperature.

Dan MacIsaac, Assistant Professor of Physics and Astronomy, Northern AZ Univ
danmac@nau.edu http://www.phy.nau.edu/~danmac