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a block of frozen soil

What is “needle ice?”

February 17, 2020  |  Topics: Stories

By Ed Makowski

Have you ever heard of “needle ice?” Believe it or not this picture contains water with a little bit of soil mixed in.

a block of frozen soil with needle ice crystals

At Riveredge Nature Center, the land manager Matt Smith was working off-trail in an area with extensive leaf cover near Riveredge Creek. He kept stepping in holes and finally cleared the leaves away to discover he’d been crunching down on elongated ice crystals, known as “needle ice.” 

Needle ice is formed when the ground temperature is above freezing but the air temperature is below freezing. Through capillary action, water is drawn up through the soil and then freezes upon contact with the colder air. The leaves had both obscured and insulated the phenomena that Matt had been unexpectedly crunching upon. 

If, in winter, the trails crunch beneath your boots, chances are needle ice is below!

Text and images by Ed Makowski, Marketing and Communications Manager at Riveredge Nature Center, which is a project partner of A Wealth of Nature.