Quimper Geological Society

We enjoyed hearing in-person USGS geologist, Dr. Brian Sherrod, on February 24, 2024 and by Zoom March 23. THE LECTURE:  High-resolution dating of a multi-fault earthquake and earthquake recurrence in the Salish Lowland Dr. Brian Sherrod discusses new evidence for a multi-fault rupture. This rupture occurred along the Seattle (SFZ) and Saddle Mountain (SM) faults in the winter of 923-924 CE. He presents new evidence for a proto-historic earthquake on the Seattle fault (in the 1830s), and he talks about recurrence of large earthquakes in the Salish Lowland. He employs photographs, USGS mapping, lidar measurements, charts, and graphs to elaborate… Read more2024-03-23 Brian Sherrod — New Findings on Earthquakes of Salish Lowland with Tree Analysis

The Lecture: Post-mortem of the southern Cordilleran Ice Sheet Death of an ice sheet can have many causes, as shown by retreat of the southern Cordilleran Ice Sheet about 15,000 years ago. East of the Cascades, the margin of active south-flowing ice retreated north as less snow fell and more melted. West of the Cascades, the Juan de Fuca lobe of the ice sheet appears to have floated away in response to rising sea level, perhaps without a proximal climatic cause. Collapse of the Juan de Fuca lobe diverted ice from the Puget lobe, which consequently stagnated at its margin and… Read more2024-04-20 Ralph Haugerud – Glacial Landscape of Puget Sound

Examine Discovery Bay’s Past Tsunami Record Using Two Contrasting Evidential Methods There are at least two salient features of Pacific Northwest history:  an extremely active geologic past, coupled with a region inhabited by indigenous peoples since “time immemorial”. These two features share common ground at Discovery Bay on the Quimper Peninsula of Washington State. Many tsunamis have occurred at this bay over at least the past 3000 years, during which time the area was concurrently inhabited by indigenous peoples. This field trip examines the geologic and anthropological evidence of the occurrence of multiple tsunamis in Discovery Bay. Our field trip leaders,… Read more2024-06-21 Discovery Bay Tsunami Evidence Field Trip

Baranof Island, Alaska, and Vancouver Island were neighbors 50 million years ago Darrel Cowan discussed the evolution of hypotheses about the large-scale coastwise displacements of tectonic elements or terranes along the western margin of North America. He presented the geologic evidence he published in 1982, which links Vancouver Island with southeast Alaska. The still-contentious Baja British Columbia hypothesis, developed in the early 1980s, was based entirely on paleomagnetic data. This IN-PERSON ONLY lecture was free and open to the public. The lecture was recorded and posted shortly after the presentation, as are all our events since 2020.  About the Speaker… Read more2024-09-14 Darrel Cowan – North to Alaska: Transport of Exotic Terranes

Uncovering ancient subduction mega-faults in the Olympic Mountains On October 5, 2024 the Quimper Geological Society hosted a lecture by Harold Tobin, professor of Seismology and Geohazards at the University of Washington and Director of the Pacific Northwest Seismic Network. Harold’s research employed field mapping and geophysical techniques to investigate processes that operate in fault zones, particularly those associated with subduction zones. One of his study areas is the Olympic Mountains, where recently (2023 and 2024) he and his graduate students have been studying a remote area west of Mount Olympus, last visited by geologists when Rowland Tabor and Bill… Read more2024-10-05 Harold Tobin – Cascadia Megathrust Lessons from Olympic Mountains

The Lecture: What Happens When You Crash Iceland into North America? A view of Washington 50 million years ago… The Puget Lowland of Washington State contains several potentially dangerous seismic faults, including the Seattle fault, which runs south of downtown Seattle. To accurately assess the earthquake hazard in this region, we need to understand the architecture and geologic history of the rocks that host these faults, deep below the Puget Lowland. Geologists do this by using small changes in Earth’s gravity and magnetic fields to create images of the Earth’s subsurface. These rocks formed in a subduction zone 50 million years… Read more2024-11-16 Megan Anderson – Siletzia’s influence on the Seattle Fault

EVENT: “Meet Your Local Geologists” The Quimper Geological Society (QGS) hosts lectures on Saturdays. Many of us enjoy (and rely on) the social aspect of the get-togethers at Port Townsend’s First Baptist Church and conversations before and after the lectures. The day of the lecture is filled with a flurry of activities and it is difficult to get to our members’ more “personal geologic” questions. So, QGS is extending our geologic events to provide more opportunities for our Quimper community to socialize and ask questions. QGS is happy to help you identify a particular rock. We ask that you bring… Read more2024-11-17 Meet Your Local Geologists