Winter

The Magic of Ice

Winter’s chill has surely arrived, but I enjoy these few weeks of bitter cold as much as the few weeks of stifling summer heat. Neither lasts long, and both extremes are parts of the weather continuum here in western North Carolina.

Having grown up in eastern South Carolina, ice was uncommon to see, except in a glass of tea. Here, in western North Carolina, winter ice seems full of magic. After winter storms, whole forests that are backlit by the brilliant sun sparkle like diamonds, tiny trickles from rock ledges become ice palaces with fantastic, yard-long icicle columns, shaded rock faces transform into massive walls of ice like glaciers meeting the sea, and ponds glaze over to tempt the intrepid to venture forth. It’s that time in the yearly cycle when the chaotic motion of water transforms into a crystalline rest.

From a scientific perspective, the transition between liquid and solid water is equally magical. Water is the only substance on Earth that expands as it freezes. Other chemicals become denser and heavier as they change from a liquid to a solid, shrinking down to occupy less space as they contract. This unusual, expansive property of water results in several significant aspects of ice. One, it creates great erosive power, for liquid water can seep into small spaces between rocks, but as it freezes it expands and creates an impressive force (400 psi and 9% increase in volume for those who like numbers). What seems to be insignificant, a constant little drip of water, can dislodge enormous rocks and crack pipes, as anyone who has seen a Parkway rockslide or replaced burst pipes can attest.

Additionally, expanding ice is often forced up out of the soil when groundwater freezes. As it forms, the ice takes the path of least resistance and squeezes out onto the surface of the porous ground. Soils heavy in clay create hairlike fibers of ice that curl as they emerge from the soil. Together, the ice hairs merge into wider ribbons that resemble shaved ice. Damp areas along road cuts where the clay is exposed are good places to look for these strange ice sculptures. On rare occasions, after an early hard freeze that hits before the sap has been resorbed by herbaceous plants, these ice ribbons burst from the soggy stems like bizarre ice flowers.

Yet another magical property of ice is that it floats on water because it is less dense. There is no other chemical in which the solid form floats on the liquid. The fact that ice cubes float in the top of the tea pitcher should surprise you, for it is a little bit of magic right there in front of you! Since ice floats on water, as a pond’s surface freezes, the surface ice remains there to insulate the underlying water. Any other chemical would freeze and then sink, leaving the exposed liquid to freeze and sink again. Soon the entire pond would be frozen solid. Not only would it therefore be extremely slow to thaw, if it ever did (remember that the ice would stay on the bottom of the pond but would thaw from the top as the air warmed), but all the plants, fish, and other animals that live in ponds would be frozen and crushed by the solid, sinking ice. Happily, none of this happens because ponds freeze at the surface and the ice floats there, insulating the deeper layers of water from the cold air temperatures.

Next time you drop an ice cube in your drink, remember that you are holding one of the most magical aspects of the natural world right there in your hand. Not bad for a glass of water!

PHOTOS: Frozen groundwater as it emerges from soil (left) and ice on Blue Ridge Parkway with climber (right)

Text and photos may not be used without permission of the author