Tuesday, May 20, 2008
Accretionary Wedge, Spring Run Off
My favorite time of the year is spring. My wife and I go on countless "signs of spring" hikes at different elevations and have seemingly months and months of spring. (It is still winter above 10,000') Along with the various plants making their way towards the sun and blooms of different flowers showing their colors, one part of spring I look forward to every year is the spring run off. Small mountain streams slowly build throughout the day. Clear waters becoming more turbid as the discharge climbs with water that was snow just this morning.
The most significant geologic event to me is the spring run off in the Rockies. Every year this rush of water cleans out rivers, moves a boat load of sediment and provides great thrills for those of us who enjoy being particles ourselves and move down stream. Some years we get some big water, and this will be a big water year. You can stand above smaller streams and actually hear the movement of boulders along the stream bed. Rivers will overflow their banks in the "what was a flood plain before the housing development was built" and deposit smaller sized sediment that would enable great riparian health if we hadn't cut the trees down and built our houses there. The Animas Valley near Durango or the Yampa Valley near Steamboat Springs comes to mind. During the big snow years in the late 70's the whole valley would be flooded...now there are really expensive houses there.
I have been studying the changes in sedimentation in the canyons on the Colorado Plateau as a result of the drought. We see larger particles sitting still for a number of years until there comes an event with enough energy to move them. These big snow years can be the energy event that an get this sediment transported a little closer to the ocean... And, its also great fun just to watch the power of big water.