What happened when the earth moved on a quiet Saturday morning in the Stillaguamish Valley was foretold, in some ways, by the relationship that people have with that sylvan slice of the Pacific Northwest.

Almost 25 years ago, I went into one of the headwater streams of the Stillaguamish with Pat Stevenson, a biologist with the American Indian tribe that bears the same name as the river and claims an ancient link to that land. The rain was Noah-level that day — just as it’s been for most of this March.

We drove upriver, winding along the drainage of Deer Creek, one of the main tributaries of the Stillaguamish. We couldn’t see Whitehorse Mountain, the dreamy peak that towers over the valley, that day. We could barely see beyond our windshield wipers. At last, we arrived at an open wound near road’s end. I’d never witnessed anything like it: an active slide, sloughing mud and clay down into the formerly pristine creek. We watched huge sections of land peel and puddle — an ugly and terrifying new landscape under creation before our eyes.

Stevenson pointed uphill, to bare, saturated earth that was melting, like candle wax, into the main mudslide. Not long ago, this had been a thick forest of old growth timber. But after it was excessively logged, every standing tree removed, there was nothing to hold the land in place during heavy rains. A federal survey determined that nearly 50 percent of the entire basin above Deer Creek had been logged over a 30-year period. It didn’t take a degree in forestry to see how one event led to the other.

The Stilly, as locals call the river, is well known to those who chase fish with a fly rod, and to native people who have been living off its bounty for centuries. Zane Grey, the Western novelist, called it the finest fishing river in the world for steelhead, the big seagoing trout that can grow to 40 pounds. What Stevenson showed me that day in a November storm was how one human activity, logging, was destroying the source of joy and sustenance for others. When the crack and groan of an entire hillside in collapse happened a week ago Saturday, I thought instantly of Stevenson and that gloomy day at Deer Creek.