Wednesday, September 25, 2013
Somewhere in one of our old hymnals is the line: “The valleys shall be exalted, the lofty hills made low …”
For years I sang it because it was there, not because it meant anything to me. And then one day in a geology text, came the explanation: Erosion!
Some of geology’s processes require explanation. They can be unbelievably slow, as is most erosion, or they can be devastatingly quick, as in earthquake or volcanic eruption, and even that last one often gives warning. But the process of cutting down mountains and building up valleys usually is slow.
I stood beside a creek up the Entiat Valley one day and watched the water slide without a ripple over the rounded surface of a large rock in the stream bed.
There was no mark on the water, but one knows that fine bits of rock in the water were acting like sandpaper and slowly wearing down the surface of that rock.
It won’t change perceptibly in my lifetime, but change it will.
On the other hand, there was the Lake Bonneville flood recounted by Alt and Hyndman (“Northwest Exposures”) — the greatest flood known of geological record.
A huge lake had formed during ice age runoff, and ultimately it eroded down through the hard rock that lined its outlet. When it hit softer rock beneath, water poured out in volume, draining off the
top 300 feet of the enormous lake.
In the huge outpouring it cut some marvelous features in its course. Since Hell’s Canyon was in it route, it left its mark there, too.
All lakes are ephemeral, they tell us. Those that do not have an outlet show the mark of standing water. And they come and go.
But the rising valleys and declining mountains?
Erosion does it, and I once read of it in connection with Mount Rainier. These are some of the slower earth activities.
On the mountain, certain hills had been worn down to where they were lower than those around them, perhaps of harder rock. Thus what had been highest was cut down to be lower than what had been higher.
In time, of course. But geology is accustomed to dealing with time, lots of it.
Elizabeth Widel is a columnist for
The Chronicle. This is the 2,854th column in a series. She may be reached at 509-826-1110.
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Short clip of a helicopter dropping water on the Tunk Block Fire today along Omak-Riverside Eastside Road. Enlarge