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Posts Tagged ‘Mount Tufts’

Last Sunday I decided to climb Tuft’s Mountain in Ashuelot, NH. Tuft’s mountain is in Pisgah (pronounced piz-gee) State Park, which is over 13,000 acres of very rough terrain in old growth forest. It was one of the coldest days of the year, with temperatures in the mid-20s and a biting wind that made it feel more like zero. It was sunny though, so when the wind wasn’t blowing it was bearable. What was unbearable was the ice on the trail.

It was easy to see that this was a wet area even though the wide trail was frozen gravel. On one side of the trail a small stream tumbled downhill and every now and then there was an angled cut across the trail to divert runoff into the stream. The problem was that the runoff had frozen so quickly over night that there were large sheets of very slick ice across the trail. This forced me into the forest to avoid it several times and after a half hour of this, I decided it was too dangerous to climb in such a steep, icy place.

On the way down I saw something I hadn’t noticed going up; the sun was glinting off what at first looked like quartz crystals along the side of the trail. When I got closer I could see that they weren’t quartz but ice crystals. Or, to be more accurate, ice needles. 

Ice needles are special things that aren’t seen too often because several things have to happen before they can form. First there has to be groundwater. Next, the air temperature has to fall below 32 degrees F right at the soil surface while the soil and groundwater remain thawed. Hydrostatic pressure forces the groundwater, sometimes super cooled, out of the soil where it freezes instantly into a “needle.” As more water is forced out of the soil the process is repeated over and over, and each needle grows in length because of more water freezing at its base. I’ve read that each thin needle is hexagonal in shape, and that needles have been found that were 16 inches long. The needles in these photos were 1-3 inches long I’d guess. 

Just down from the top of this photo you can see small pebbles on top of some of the ice needle bundles. This is because the needles start growing slightly below the soil surface and lift the soil as they lengthen. I’ve seen pictures where they have lifted quite large areas of soil, mosses and stones.

 The upper left corner of this photo shows ice needle bundles joined into larger flat, wide bundles and curled like ribbon, while the center of the photo shows the same curling with smaller ice columns that haven’t joined. The sun, which is the enemy of ice needles, can be seen slowly creeping into view.

I was wishing for a real camera with a macro lens and tripod rather than the cell phone camera I was trying to hold steady as I shivered.

 Ice needles are so fragile that just the slight touch of a fingertip destroys them, yet they have the power to lift large areas of soil and stones. You can see sand and gravel that have been lifted by some of the needles in this photo. You can also see that they are now almost in full sun which means they are near the end of their very short lives.

 When the sun shines brightly melting happens quickly, and that is why ice needles are so rarely seen; you have to be at the right place at the right time. If you are ever walking on a cold morning and the soil crunches underfoot, stop and look down-you are probably walking on ice needles.

To learn more about ice needles and other unusual ice forms click here.

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