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Post by amy on Aug 10, 2006 11:23:41 GMT -5
I just heard about the ice caves in the Bandera volcano tube in New Mexico and I was wondering if any one can explain why the ice doesn't melt. The ice is supposedly several meters thick and milennia old, but the cave is in the middle of a desert - how can the ground temperature not melt it? I've looked for answers on the Internet and all I could find were more examples of ice caves (some in more "logical" places, like Austria). Any insight from your experts here would be appreciated. Thanks!
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L Roebuck
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Post by L Roebuck on Aug 10, 2006 13:41:05 GMT -5
Hi Amy, Welcome to the forum! I looked it up for you. Here is the information that I found as well as the link. The Ice Cave Located in part of a collapsed lava tube, the Ics Caves temperature never rises above 31 F. The natural layers of perpetual ice glisten blue-green in the reflected rays of sunlight. The temperature in this cave never gets above 31 degrees Fahrenheit. As rain water and snow melt seep into the cave, the ice floor thickens. The floor of the ice is approximately 20 feet thick. The deepest ice is the oldest and dates back to 1100 BP. The green tint is caused by an Arctic algae. The back wall was formed in the early days when ancient Indians and early settlers mined the ice. In 1946, ice removal was stopped at which time the ice wall was nearly 12 feet high. Since then, the ice floor has risen relative to the back wall. The rate of ice accumulation varies with annual precipitation. The cause of original formation of ice back in 170 AD is uncertain. However, its perpetuation is due to a combination of existing conditions that make a natural ice box: 20 feet of ice in a well insulated cave shaped to trap frigid air. www.icecaves.com/cavetrail.html
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Post by amy on Aug 11, 2006 1:28:18 GMT -5
Hm. That's a start, but I was hoping for more detail. How does the old ice stay and not melt when the hot wind blows into the opening? There has to be an evaporative process going on that cools the ice 30 meters below. Can someone describe how that works? Is there some kind of gas coming from the volcano tube that keeps the atmosphere and ground temp supercooled? I read the reply, but it doen't answer how the ice could remain intact for over 1000 years. Thanks!
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Brian Roebuck
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Caving - the one activity that really brings you to your knees!
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Post by Brian Roebuck on Aug 11, 2006 6:12:40 GMT -5
Hm. That's a start, but I was hoping for more detail. How does the old ice stay and not melt when the hot wind blows into the opening? There has to be an evaporative process going on that cools the ice 30 meters below. Can someone describe how that works? Is there some kind of gas coming from the volcano tube that keeps the atmosphere and ground temp supercooled? I read the reply, but it doen't answer how the ice could remain intact for over 1000 years. Thanks! Amy, It's all about airflow in the cave or in this case lack of it. Cold air is more dense than hot air and thus is sinks down to the lower levels of the cave during winter and just stays there. Hotter air coming into the cave in summer lies in a layer on top of the cold air if there is no airflow to make the layers mix. There is some small amount of convection air flow due to temperature differences at the boundary of hot and cold air but in that cave it doesn't do much to mix the layers so the overall temperatures don't change much. The next winter the process is reversed and over long time periods it has sought equilibrium with the low areas staying cold all the time. Since it's below freezing in the deeper areas water entering the cave freezes as it is driven deeper by the force of gravity. Thus the ice stays there in the deep "cold trap" areas and will continue to do so unless the average temperature of the outside air is raised considerably (climate changes etc) or another way for air to flow out of the bottom of the cave is opened up (another entrance perhaps) where air flows through the cave like a chimney (out the top in winter and out the bottom in summer). I hope that answers your question.
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Post by amy on Aug 11, 2006 11:11:39 GMT -5
Excellent - yes. Thank you!
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Post by madratdan on Aug 11, 2006 11:32:26 GMT -5
Excellent discription Dr. Beaner I could even understand what you were saying and I'm as far from a scientist as you can get.
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L Roebuck
Technical Support
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^V^ Just a caver
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Post by L Roebuck on Aug 11, 2006 13:10:26 GMT -5
Thanks Dr. Beaner I didn't have to type details and so it saved me a few brain cells. Isn't cave airflow so amazing!
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Kelly
Beginner
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Post by Kelly on Aug 12, 2006 15:17:37 GMT -5
I don't know anything about this cave, but caves in general are usually around the average temperature of the area. This cave is in New Mexico a state with a general average temp well above the freezing. The only places in NM that may have an average lower than freezing are in the mountains. Rather than in the desert, is this cave is on a mountain where temps are cooler?
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Brian Roebuck
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Caving - the one activity that really brings you to your knees!
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Post by Brian Roebuck on Aug 12, 2006 20:53:13 GMT -5
I don't know anything about this cave, but caves in general are usually around the average temperature of the area. This cave is in New Mexico a state with a general average temp well above the freezing. The only places in NM that may have an average lower than freezing are in the mountains. Rather than in the desert, is this cave is on a mountain where temps are cooler? Kelly, Just to make things clear, the average temp of TAG caves is about 56 degrees F but there are many caves in TAG that stay colder than this in the deep areas that have no airflow to speak of. One in particular comes to mind that I am actively surveying. The deeper parts of the cave will definitely make you chill down to about 50 degrees. It is one of the only dry TAG caves I actually need to wear more than a tee shirt in while surveying. It gets chilly if you are moving slow! The average ground temps will influence how cold such caves get though. Caves in higher altitudes should stay colder than those at lower elevations etc. I hope that helps a bit.
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Post by Azurerana on Aug 13, 2006 0:28:51 GMT -5
This may sound odd, but it is true. Earth is an insulator. For much of the 19th century, people would cut ice off the Mississippi at St. Louis, store it in straw in caves only about 20 ft below street level, and the ice would keep until July or August, with no artificial refrigeration other than the other ice against the rock. Like TAG, our average mean temp is about 56-57 F, however there are springs which have a thermocline and passage configuration which holds spring water about 47 F. on a consistent basis. Gray bats and Indianas rely on cold trap passage to help maintain their chilled temperature during hibernation. There are also warm trap caves (always significantly higher than ambient) which are used to keep baby bats warm in the summer when Momma leaves to feed at night. Nature is often stranger than fiction...
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