Ice needles in Sierra: A delicate winter occurrence with a crunch

A handful of ice needles.
A handful of ice needles. Michael C. Brelle

Winter is here, and so are ice needles in the Sierra Nevada, a frozen phenomenon.

Michael C. Brelle, a chemistry professor at Sierra College, discovered them on his property in Alta, Placer County, elevation 3,700 feet, in 2014, his first winter in the rural community.

“Walking on them is very strange as it collapses under foot with an odd crunching noise,” Brelle wrote in an e-mail. “My dogs seem to love it though.”

Each year around the winter solstice, Brelle observes ice needles all over his 9-acre property. The pushing-up of the ice needles from the ground this year followed, as it usually does, a good rain and then cold temperatures.

Since Oct. 1, the weather station on Brelle’s roof has recorded 37.6 inches of rain. Then came the frigid nights of the past week – and several days of ice needles

While he has a doctorate in chemistry, Brelle was quick to point out that he is no expert in ice needles. However, the professor applied what he does know about chemistry and physics, plus some quick research, to provide this explanation for the delicate icy formations: “Ice needle formation starts with very moist soil that is above freezing and then a quick drop in the air temperature to below freezing. So the water in the soil is still liquid and has not frozen yet but the water at the surface will freeze.

“As the water freezes more water is drawn up from the soil through capillary action, which then freezes and draws up more water, which freezes and the process continues, thus building up ice needles.

“When it warms up the process stops but will continue when the temperature drops again.”

Brelle, who loves to share science and nature with others, provided photographs of the ice needles on his property.

In some of the pictured ice needles, he said, “interfaces” between the growing needles can be seen, which basically shows how many nights the formation process occurred – and how many nights it got very cold.

Bill Lindelof: 916-321-1079, @Lindelofnews

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