Ice spike
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2008-06-12T13:05:47Z
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[[Image:Ice spike.jpg|thumb|right|250px|An ice spike grown in an [[ice cube tray]]]]
[[Image:Ice spike02.jpg|thumb|right|250px|Another ice spike grown in an ice cube tray]]
An '''ice spike''' is an upward-facing [[icicle]] that forms as a body of [[water]] [[freezing|freezes]]. Ice spikes can form in natural environments or can be made artificially by freezing [[distilled water]] in plastic [[ice cube tray]]s.
Water expands when it freezes. If there already is a thin sheet of surface ice over the body of water, further freezing can force water out and upwards through a crack or weak point in the sheet. This can produce a tube-like structure where water emerges at the tip, progressively lengthening the tube.<ref>{{citation|last = Dorsey|first = H E|year = 1921|title = Peculiar Ice Formations|journal = Physics Review|volume = 18|issue = 162}}</ref> Tube formation stops when the tip freezes and seals.
Ice spikes rarely form when freezing "normal" non-distilled water because impurities in the water act as an [[ice nucleus]] so the water freezes before an ice spike can form.
The formation of ice spikes is related to the shape of the water body, the concentration of dissolved impurities, air temperature and air circulation above the water.<ref>{{citation|last1 = Libbrecht|first1 = K G|last2 = Lui|first2 = K|year = 2003|url = http://www.its.caltech.edu/~atomic/snowcrystals/icespikes/icespikes.pdf|title = An Investigation of Laboratory-Grown Ice Spikes}}</ref>
==References==
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[[Category:water ice]]
[[Category:Snow or ice weather phenomena]]