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Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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The Calculus of Caves
18 January 2005 (All day)
Deep within a limestone cavern, a fairy tale landscape glistens. Soda straws, draperies, popcorn, and flowstone mimic the everyday objects they're named for, while stalagmites grow upwards from the cave floor and stalactites hang from the ceiling like the fangs of some troglodytic monster. Now, a group of spelunking researchers has come up with a mathematical equation that explains how stalagmites grow.
Cave formations materialize in limestone caverns over thousands of years as water oozes out of the rock and deposits solid calcium carbonate in its path. The diverse shapes of these objects depend on the geometry of the rock and the amount of flowing water. Until recently, no one had been able to quantitatively explain why the deposited calcium carbonate forms graceful shapes instead of big globs of white stuff.
In the 14 January Physical Review Letters, a team of physicists takes the first step. According to graduate student Martin Short and colleagues at the University of Arizona and Kartchner Caverns State Park, the speed of stalagmite growth depends on the thickness of the water flowing over it. The water layer tends to be thickest at the tip of the stalagmite, where the drop of water initially lands, and thins as the droplet spreads down to the wide base. The thicker the water layer, the more calcium carbonate deposited, and the faster the stalagmite grows in that direction. Curiously, the math the physicists came up with predicts stalagmites and stalactites should have an "ideal form", a cone shape that varies only in size, never in the angle of the cone's slope. To verify this, the researchers went to Arizona's Kartchner Caverns, photographed stalagmites, and compared them to virtual stalagmites generated from the equation. The results matched beautifully.
The group "elegantly" explains a phenomenon familiar to many but poorly understood, says Howard Stone, a physicist at Harvard University. Meanwhile, the Arizona group is pushing on to explain other, more complex cave shapes.