Channeled scablands
From Biocrawler, the free encyclopedia.
The Channeled Scablands are unique geological erosion features in the U.S. state of Washington. They were created by cataclysmic flooding of the Columbia River Plateau during the Pleistocene epoch. Geologist J. Harlan Bretz coined the term in a series of papers in the 1920's. Debate over the origin of the Scablands raged for forty years and is one of the great battles in the history of geologists.
Geology
River valleys formed by erosion normally have a 'V' cross section, and Glaciers leave a 'U' cross section. The Channeled Scablands have a rectangular cross section and are spread over immense areas of eastern Washington State. They exhibit a unique drainage pattern that appears to have an entrance in the northeast and an exit in the southwest. The eroded channels also show an anastomosing, or braided appearance. When first studied, no known theories could explain the origin of these features.
Bretz conducted meticulous research and published many papers during the 1920's describing the Channeled Scablands. His theories of how they were formed required short but immense water flows, for which Bretz had no explanation (the source of the water was never the focus of his research). Bretz's theories met with vehement opposition from geologists of the day, who tried to explain the features with uniformitarianism theories.
J.T. Pardee first suggested in 1925 to Bretz that the draining of a glacial lake could account for flows of the magnitude needed. Pardee continued his research over the next 30 years, collecting and analyzing evidence that eventually identified Lake Missoula as the source of the Spokane Floods and creator of the Channeled Scablands.
Research on open channel hydraulics in the 1970's put Bretz's theories on solid scientific ground.
Pardee's and Bretz's theories were accepted only after decades of painstaking work and fierce scientific debate. It is worth noting that many of the most vocal critics of Bretz and Pardee never studied the Channeled Scablands with their own eyes.
External links
- Historical Discussion (http://www.geo.ucalgary.ca/~macrae/t_origins/bretz_re.html)
- 3D relief map (left eye-red lens, right eye-blue lens) (http://www.ndsu.nodak.edu/instruct/schwert/geosci/g496_columbia_plateau/ana_scablands_2.gif)
