|
|
|
|
A Cave Climate
12/16/2002
Listen in RealAudio 
When you think about alterations in the landscape that occur when climate changes, it's often
about icecaps, forests, prairies, things like that. But do changes in our climate also lead to
changes in the landscape underground? Hi, I'm Bryan Yeaton, and this is The Weather Notebook.
The geological features which form subterranean, or cave, landscapes -- stalactites,
stalagmites, columns, draperies, and the like -- are mostly created by the dripping of
mineral-laden water from the roofs of caves. The water evaporates, leaving the minerals
behind, in fantastic shapes. The minerals come from the rocks forming the ground above the
caves - but where does the water in the ground come from?
It comes from rain and snow. In times of significant precipitation, more water percolates
through the ground, dissolving minerals as it seeps or drips into the caves. Thus, more
precipitation means more rapid creation of cave features.
You might think, then, that climate changes, particularly changes in precipitation, would be
reflected in cave formations. But, the geological time scale and the human time scale are very
different. Radioactive dating and paleomagnetic data show that most growth spurts for cave
formations in America's southwest, for example, correspond with the increased storminess of
the ice ages; the last such period ended about 10,000 years ago. Since that time, shorter-term
climate fluctuations are NOT preserved in the cave record.
Major and long-term changes in climate do have an impact on cave formations, but shorter-term
variations, on the scale of decades or even centuries, are as yet indiscernible in the
landscape underground.
Special thanks today to Paul Burger, hydrologist at Carlsbad Caverns National Park. The
Weather Notebook is underwritten by Subaru, with major support from the National Science
Foundation. Thanks today to Assistant Producer Doug Sanborn.
|
|
