Wauna Viewpoint, November 11, 2016

Reynolds, now with the U.S. Forest Service, said his study indicates the landslide probably happened between 1670 and 1760. "These results demonstrate that the Bonneville Landslide may have occurred more recently than previously believed," Reynolds said in a recent article in Washington Geology. The dates "provocatively bracket" the powerful offshore Cascadia Subduction Zone earthquake of 1700, he said, but he cautioned that the study doesn't prove that the quake caused the landslide

And that 1699 date, almost the same as the 1700 earthquake date, just stopped me cold."

Despite the finding, however, the mystery of the landslide date remains unsolved. Although the tree-ring and lichen studies point to a slide date around 1700, the radiocarbon dates O'Connor obtained from the tree samples found at the World Forestry Center indicate that the trees died about 1500. "So now we have conflicting evidence," Pringle said. "We have our work cut out for us in trying to resolve these ambiguities from the different dating techniques.".

http://columbiariverimages.com/Regions/Places/bonneville_landslide.html

Millions of years agor, mudflows poured off volcanoes, covering the land with hundreds of feet of ash, boulders, and cobbles, creating the Eagle Creek Formation. You can see this beige formation on cliffs north of Bonneville Dam and along I-84 near exit 41. Beacon Rock, just downstream from the dam, is the ancient core of one of these volcanoes. Landslides broke away from Table Mt. and Greenleaf Peak and pushed the river course south, with debris forming a land bridge maybe in 1500 or 1700.

 

 

Salmon in Eagle Creek