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Cottonwood Canyon - OU0971
This is a beautiful place to take in the history and scenery and relax. You can really see nature at work here.
Owner:
Dulce-Joy
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Altitude: m. ASL.
Region:
United States > Oregon
Cache type: Virtual
Size: No container
Status:
Ready for Search
Date hidden: 2014-04-23
Date created: 2016-03-08
Date published: 2016-03-08
Last modification: 2016-03-09 
566 visitors 
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Rated as: n/a
Cache attributes
Description
EN
Geology is the foundation of the landscape, and it provides the template for ecosystems both today and through time. By understanding the origin of landforms, we first begin to grasp the meaning of the Cottonwood Canyon State Park Region. The John Day River mainstem, branches and tributaries travel 281 miles, exposing more than 300 million years of Oregon’s geologic history. This geologic richness results from the river’s persistence through a long history of uplift. Today, the John Day River slices through the core of the Blue Mountain anticline, a major up-fold in Oregon’s crust, to reveal the early history of the Blue Mountains and more recent history along its flanks. The river’s headwaters rise from the 120-million-year old granite rocks of the Elkhorn Mountains near Anthony Lake. The canyons of North Fork and South Fork cut through the remnants of volcanic islands and the sea floor that was Oregon’s first land. Farther downstream, in the John Day Valley, the river follows the trace of the John Day Fault and exhumes the broad valley from its entombment in vast volumes of ash. Known as the Rattlesnake Tuff, this ash erupted catastrophically from a vent near Burns, and filled the nascent valley to overflowing within hours. Known as the Columbia Plateau Ecoregion, the study area geology consists of basalt flows overlain by an accumulation of loess deposited during previous Ice Age events. The faulting, fracturing, and incising of the basalt plateau has resulted in the formation of many canyons and steep V-shaped valleys. The largest and most striking canyons occur along major fault lines, and contain some of the areas significant rivers such as the John Day River. Throughout the area, bedrock basalt lies on or near the ground surface, wherever the loess soil deposits have been eroded. In its last forty miles, the John Day River has carved spectacular meanders into its deep canyon. These entrenched meanders indicate that the river is still following its ancient channel across what was once, 14 million years ago, a relatively flat plain. The power to both widen its upper valleys and cut its way through a thousand feet of basalt along the lower river has been proved by gradual uplift of its headwaters region.
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