Needle Ice on Mt. Osceola

July 10, 2005

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Provided and copyright by: Dennis Isbell
Summary authors & editors: Dennis Isbell; Ray Murphy

While hiking Mount Osceola in the White Mountains of New Hampshire on November 14, 2004, I noticed an excellent example of needle ice and stopped to take close-ups of this outcropping. Needle ice crystals typically form over night when groundwater is seeping out of the ground. The extruded water freezes when it comes in contact with the below-freezing air, while the hydrostatic pressure of the groundwater below the surface forces the newly-frozen "cap" above the surface. The soil temperature must be above freezing for this to occur. These ice needles are typically 1-3 cm in length, but can be up to 40 cm in length. For scale, note the brown leaves. Alternate names for needle ice are kammeis, piprake and shimobashira.

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