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Deep Time All Around

Posted by | April 25, 2009

It’s eighteen miles from the front door of my house to the Snake River. The road between my home and the river is rural and empty. Even my 1987 truck gets good gas mileage going toward the river because the Snake is at the bottom of a big canyon. I coast along at an idle, looking at all the rock outcrops and some of the wildlife. (I have my priorities straight.)

When my knees were in better shape, my dog and I would walk from the bank of the river to the top of the canyon. It’s a vertical trip of about 2300 feet each way. The canyon is made of many layers of lava rock. I would pick my way upward, avoiding the very steepest parts by hugging the gullies.

As an old lady, I limp along the railroad tracks by the river, covering the steep ground above me only with my eyes. I amble by the river in summer and winter, spring and fall, looking down into the water at the steelhead and carp in their season, at the occasional beaver eyeing my dog with great suspicion, and at the rock outcrops that continue to amaze me even after all these years. My walks may sound repetitious, I know, but I’ve got a simple mind, and the long ambles suit me (as well as the dog).

The rock layers of the Snake River Canyon are horizontal, just as they formed millions of years ago when molten rock belched out of large fissures and covered thousands of square miles. It was only after all the rock layers were solidified that the Snake River Canyon started to fully form. It was created as the river eroded the rock, bit by bit, over vast stretches of geologic time. In a similar way, the Colorado River eroded the rocks of the Southwest, ultimately creating the Grand Canyon.

You’ve heard about canyons and erosion in countless nature programs or merit badge lessons. But gradual erosion can create huge canyons only if there is lots and lots of time available for rivers to wear down and erode solid rock.

In the 1700s most educated people believed the Earth was only a few thousands of years old. Sometimes modern geologists speak of those people with scorn, as if such a belief was nonsensical. But there’s no disrespect in me when I note that, back in 1776, educated people assumed Earth history went back only as far as Old Testament times.

But in Scotland a gentleman farmer and naturalist named James Hutton came to a different viewpoint. Hutton noted that if you pick up a piece of granite – the common salt-and-pepper rock you see in many mountains or in the stones used in bank buildings – the clear and jagged minerals in the rock are quartz.

Looking at the streams of Scotland, Hutton saw quartz sand being eroded out of rock and moved downstream, getting rounder, mile after mile, in its journey to the sea. The quartz ends up in sandy layers on the beach. Those layers are sometimes made into solid rock, namely sandstone. If the rocky sandstone later gets lifted up onto land, we can see it. It all makes sense, once you accept the notion that Earth history is very deep, indeed.

Hutton wrote about the day he clearly realized that the history of the planet must be millions and millions of years old. I imagine he felt a leap of joy when he first clearly saw the evidence for “deep time” around Scotland and his ideas fell into place.

James Hutton wasn’t a well-traveled man, and he wasn’t a highly-trained geologist by modern standards. But he correctly deduced that the Earth is incredibly ancient from the simple evidence we can all see around us on Sunday strolls.

It’s the habit of clear-headed observation that gives science its backbone. And although the mindset to see the world in new ways can be encouraged by a good education, it doesn’t depend on having any diploma or degree.

Here’s wishing you long springtime walks and the good fortune to see Mother Nature afresh.