Department of Physics,
University of Toronto, 60 St. George St., Toronto, Ontario, Canada M5S 1A7.
Icicles that have grown from slightly impure water develop ripples around
their circumference. The ripples have a near-universal wavelength and are
thought to be the result of a morphological instability. Using
laboratory-grown icicles and various species of impurities, including
fluorescent dye, we show that a certain fraction of the impurities remain
trapped inside the icicle, forming inclusions within the ice. The
inclusions are organized into chevron patterns aligned with the peaks of the
ripples. Within the chevrons, a substructure of crescent-shaped structures
is observed. We also examine the crystal grain structure of laboratory
icicles, with and without impurities. We present the first detailed study
of these growth patterns in the interior of icicles, and discuss their
implications for the mechanism of the ripple-forming instability.
The Experimental Nonlinear Physics Group / Dept. of Physics / University of Toronto / 60 St. George St. Toronto, Ontario, Canada, M5S 1A7. Phone (416) 978 - 6810