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When I walk on Sundays with my faithful mutt along the bottom of the Snake River Canyon, I usually hear only the wind in my ears.
It’s surprising how loud a breeze can be in a human ear, and try as I might I’ve not found anything about breeze-sounds to be particularly interesting. Still, just to keep me awake, perhaps, Mother Nature punctuates the breeze sometimes with a snake’s rattle in the warmth of summer — and, of course, I do listen carefully for them.
But springs are actually my favorite for listening in the canyon. Some Sunday afternoons the air is absolutely still. When that’s the case, I get a special treat: I literally hear the Earth falling apart.
The sound comes from the rocks above my head. It starts as a little tink-tink murmur that is followed up by a tap-tap sound. Finally, the rock — usually no bigger than a piece of gravel — gets down near my level and I hear the swishing sound of it passing through the air as it reaches the ground.
Occasionally the high tink-tink murmur sets off a small cascade of sounds. One tink-tink leads to two tap-taps which lead to a miniature rolling thunder of gravel coming down toward me and the railroad tracks on which I walk.
Tink, tap, whoosh, smack. The rocks from above show me energy-of-motion, a kind of energy they briefly display in exchange for the energy-of-place they had when they were clinging higher onto the canyon wall.
Once the new gravel is at our feet, everything grows quiet again. The dog looks at me, and I look at the dog. We continue on our walk because we like long walks — and perhaps because we are both a little dim, too, and don’t quite believe we could be smashed by a boulder following the same path as the gravel.
One reason a lot of rocks are falling this time of year is what geologists call the freeze-thaw cycle. During the day, with the current mild winter here in the Northwest, temperatures along the Snake River are well above freezing. Moisture melts and penetrates into the cracks of the rocks and canyon walls. At night, the temperature can drop below freezing.
Water expands as it freezes (most liquid substances don’t do that, but water is an exception). The water in the rock cracks expands as it becomes ice, and that expansion is a powerful force. The ice helps pop bits of rock out of the canyon wall, or at least loosen them so they are ready to fall.
Little by little, a number of rocks are launched on their journey to tumble and fall below.
The rocks and their different forms of energy are something scientists learned to understand in previous centuries. The energy-of-motion of the falling rocks and the energy-of-place of the rocks high on the canyon wall were the first part of the analysis.
Next came the idea that to get the rock back to where it had once been, a lot of work would have to be done. (I’ll say it would be a lot of work — think of the dog and me having to scramble up the canyon wall to replace the gravel where it once had sat!)
Detailed measurements of all kinds of energy work in the 1800s, plus analysis on chalkboards, made it clear that — no matter how careful and smart we are — we cannot replace the rocks to their prior positions in the canyon without putting in a little more energy than we can get out by their fall.
That’s the bad news of what’s called the second law of thermodynamics of this sad and sorry world. In the words of t-shirts that undergraduate geeks like to wear on college campuses, “You can’t even break even.”
Those are heavy thoughts, to be sure, to harbor on a spring’s Sunday afternoon walk. But they take my mind off fears of being beaned by boulders from above as I listen to the Earth change around me.
Dr. E. Kirsten Peters, a native of the rural Northwest, was trained as a geologist at Princeton and Harvard. Follow her on the Web at rockdoc.wsu.edu and on Twitter @RockDocWSU. This column is a service of the College of Sciences at Washington State University.