Crennulations, as seen above the trail in the Grand Palace of Lehman Caves

NPS PHOTO Scott Babinowich

Crennulations: Those Ridges on the Stalactites
The horizontal ridges that developed on some formations in the cave, such as the stalactites over the path in the Grand Palace, are called crennulations. Crennulations tend to have a wavelength of about 1 cm, no matter what material they develop in. They are common on icicles as well. One theory says that they begin when water flows over a slight bump in the surface. The water film thins as it passes the bump, which increases evaporation and/or carbon dioxide loss. More calcite is deposited on the bump. Just below the bump the water pools up again, and below this small pool the water thins again due to surface tension, depositing more calcite to form another ridge. The whole cycle starts over again. Crennulations seem to be self-perpetuating below the initial bump. Microgours in flowstone and the saw-tooth edge of some draperies may also be self-perpetuating in the same way.

Last updated: February 28, 2015

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