About the Talk

The Hazel/Oso Landslide of March 22, 2014: Geologic Background, Other Landslides, and Landslide Policy Implications for Washington

On March 22, 2014, at 10:37 a.m, a massive landslide struck a rural area of the Stillaguamish River Valley, killing 43 persons and displacing many more. News of this catastrophe spread through the surrounding communities, some of which were cut off from outside help. However surprising this may seem, the geology history of the area shows that is has a long history of hazardous behavior.

About 20,000 years ago, the advance of the Puget ice lobe into the Puget Sound area blocked the outlets of several rivers flowing out of the Cascade Range. Glacial-related sediments deposited within the Stillaguamish River Valley were later incised, initially by the combined flow of the Stillaguamish and Sauk Rivers and then by continued erosion of the North Fork Stillaguamish River. The erosion has left steep, high terraces of unconsolidated sediments along the valley walls, which have led to multiple deep-seated large landslides that have covered the North Fork Stillaguamish River Valley floor on multiple occasions. The catastrophic Hazel/Oso Landside is simply the latest valley-covering landslide in this long post-glacial history.

There are some unique geologic aspects of the Oso Landslide that will likely offer some valuable lessons regarding landslide risks and help inform policy regarding landslides. This talk will attempt to put the Hazel/Oso landslide in perspective with other landslide hazards in Washington State. While the Hazel/Oso Landslide may hold some technical and policy lessons, information on other landslide sites in Washington State will be presented, including some landslides in Jefferson County. Part of the presentation will discuss how landslide risks and public policy meet and various approaches to landslide hazard risk reduction.

About the Speaker

Dan McShane has a B.Sc. and M.Sc. in Geology from WWU in Bellingham. He has worked as a geologist and engineering geologist in Washington State since 1989. He is currently employed by the Stratum Group as an Engineering Geologist in Bellingham, WA. Dan writes a geology blog (http://washingtonlandscape.blogspot.com) that provided some early information about the Oso Landslide to the general public as well as geologists not familiar with the specific area.

About the Talk

Geology beneath the Salish Sea and how it controls its ecology

 On Saturday, Nov. 15^th, you’ll have a chance to see how the geology beneath the Salish Sea controls its ecology. The complex geology beneath the Salish Sea results from a series of long geologic processes including, but not limited to, plate collision and subduction, glaciation, and sea level changes. The sculptured landscapes and seascapes created by these processes provide unique benthic habitats for a variety of organisms critical to keeping the inland sea of the Salish both viable and healthy.

Many of the habitats are ephemeral, constantly being altered through oceanographic and tectonic activities. For example, dynamic bedforms created by strong tidal currents provide habitats for foraging fish, such as the Pacific sand lance, whereas rock rubble shaken from the flanks of islands by earthquakes forms habitat for rockfish and lingcod. Deep-sea sponge reefs trap sediment and provide relief on an otherwise flat seafloor that in turn provide shelter for fish and other organisms from strong seafloor currents and refuge from predation. Seafloor exposures of bedrock and basement rocks provide hard substrate for encrusting and sessile organisms that provide food and shelter to epifauna and fish, while organic and fine-grain clastic sediments fill bays and sounds, creating a substrate for eelgrass and other shallow water vegetation that provide recruitment habitats for a multitude of organisms. All of these geologic processes have been studied in detail with the use of up-to-date seafloor imaging technology that reveals the seafloor in great detail. These images and the conclusions derived from them will be presented in an illustrated hour-long talk sponsored by the Jefferson Land Trust’s Geology Group.

About the Speaker

Gary Greene is currently the Director of the SeaDoc Tombolo Mapping Lab on Orcas Island, WA.  He also holds positions at the Friday Harbor Marine Laboratories (UW) and the Moss Landing Marine Laboratories (SJSU).  Dr. Greene obtained his Ph.D. in Marine Geology from Stanford University in 1977, an M.Sc. in Geophysics from San Jose State University, and a B.Sc. in Paleontology from Long Beach State University.  Since then has had a long and varied career as a professor, research scientist, and manager.