 |
| Eel River area with close-up view of site of ancient lake (uoregon.edu) |
Scientists from West Coast universities have been using remote sensing technology and a number of handheld GPS units proved the late Pleistocene, landslide dammed lakes along the river, about 60 miles southeast of Eureka. Evidence that blocked the river with 400-foot wall of loose rock and debris. Now this river length is about 200 miles carved into the land of high mountains on the California Coast to the mouth in the Pacific Ocean in Humboldt County.
This helps to explain the evidence emerging from other studies that showed a dramatic reduction in the number of river sediments deposited in the sea off the coast just about the same time period, say the authors H. Benjamin Mackey, who began the research while pursuing doctorates earned in 2009 from the University of Oregon. He is now a postdoctoral researcher at the California Institute of Technology.
"Perhaps of most interest, the presence of this landslide dam also provides an explanation for the results of previous research on the genetics of steelhead trout in the Eel River," Mackey said, referring to a 1999 study by U.S. Forest Service researchers J.L. Nielson and M.C. Fountain. In their study, published in the journal Ecology of Freshwater Fish, they found a striking relationship in two types of ocean-going steelhead in the river -- a genetic similarity not seen among summer-run and winter-run steelhead in other nearby rivers.
An interbreeding of the two fish, in a process known as genetic introgression, may have occurred among the fish brought together while the river was dammed, Mackey said. "The dam likely would have been impassable to the fish migrating upstream, meaning both ecotypes would have been forced to spawn and inadvertently breed downstream of the dam. This period of gene flow between the two types of steelhead can explain the genetic similarity observed today."
LIDAR (Light detection and ranging) remote sensing technology as a tool, evidence of this ancient lake could not be obtained. Therefore, landslides and erosion in the past have removed evidence of the existence of this lake.
The area affected by the landslide-caused dam accounts for about 58 percent of the modern Eel River watershed. Based on today's general erosion rates, researchers theorize the lake could have been filled in with sediment within about 600 years.
Source: http://uonews.uoregon.edu/archive/news-release/2011/11/evidence-ancient-lake-californias-eel-river-emerges
Post a Comment