Thursday, December 23, 2010

A Few Hours Of Geologic Time

The ground-saturating weather system with its thick, gray cloud cover that has stretched across southern Utah for the past week is finally breaking up.  Patchy blueness peeking between the unraveling edges of thinning clouds gives hope that the worst of this storm is past.  For the first time in seven days, it isn’t raining.  I’ll be delighted when the sunshine returns. 

It often surprises visitors to the desert southwest that the dramatic scenery which leaves them (and me, for that matter) breathless is often primarily the result of the action of water.  Certainly, wind is involved — if strong enough it lifts into the air those particles of sand or clay light enough to be winnowed by the wind; it sweeps along those particles whose mass is small enough to be supported by some particular draft of air.  

But it is the water, really — H2O in its various frozen, liquid, and gaseous states.  We search for it on the Earth, Moon and Mars.  Lack of it has caused empires to crumble and civilizations to vanish without a trace. Wars are won and lost over its accessibility.  It is our sustenance.  Without it, life as we live it would be unattainable.  Its powers of weathering and erosion relentlessly alter our landscape, drop by drop, grain by grain.  

As I stood along the banks of the Virgin and Santa Clara Rivers yesterday these thoughts crossed my mind.  I watched as the turbulent water carried its murky load of silt and logs rapidly downstream.   Some of the upended detritus of river life had beached itself on the muddy bank as the peak flow slowed; other flotsam and jetsam had wedged itself upriver against bridge pilings and gravel bars.  I thought to myself “So this is how it all happens.”   Unremittingly, storm or no storm, the Virgin River and its tributaries eat into the western edge of a small portion of the Colorado Plateau in a classic example of headward erosion:  the erosion occurs in the direction from which the river originates.  The grandeur that is Zion Canyon was being sculpted grain by grain even as I stood there.  Geologic time was passing right before my eyes. 

1 comment:

  1. The power of water to erode can be witnessed in a patient enough amount of geologic time.