Category: Pacific Northwest geology

2024-06-21 Discovery Bay Tsunami Evidence Field Trip

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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, Dr. Carrie Garrison-Leavy (geologist) and Dr. Alexandra Peck (anthropologist), are active researchers in their respective fields, which are specific to this topic. They lead us through an examination of the possible link between tidal marsh tsunami sedimentation and indigenous oral histories as contrasting evidential methods of recording tsunami history.

About the Speakers

Dr. Carrie Garrison-Laney is a Coastal Hazards Specialist at Washington Sea Grant and a liaison to the NOAA Center for Tsunami Research. A focus of Carrie’s research has been the age and distribution of paleo-tsunami deposits with lessons learned from historical events. She earned her PhD from the University of Washington.

Dr. Alexandra Peck is professor and Audain Chair in Historical Indigenous Art at the University of British Columbia. Trained in archaeology, her research explores pre-colonial Native life, cultural change, and social interactions on the Olympic Peninsula. With extensive academic publications, she is also co-editor of Archaeology in Washington.

Carrie suggests for the wetland portion of the trip:

Wetland participants must come equipped with at least knee-high boots since the tsunami sediments are exposed in a tidal marsh. This will be messy but fun!!!!

 

2024-03-23 Brian Sherrod — New Findings on Earthquakes of Salish Lowland with Tree Analysis

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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

See Sept. 2023 Science Advances article: https://www.science.org/doi/10.1126/sciadv.adh4973

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 his points. Brian is a master story-teller, and his lecture will explain how this important event was detected.

For a complete version of the research paper:  Black, Pearl, et al., 2023, A mulitfault earthquake threat for the Seattle metropolitan region revealed by mass tree mortality:  Science Advances 9, Sept. 2023

THE SPEAKER:

Dr. Brian Sherrod is a Research Geologist and Pacific Northwest Regional Coordinator for the USGS Earthquake Hazards Program, based in the Department of Earth and Space Sciences at the University of Washington.

He received his BS in Geology from James Madison University in Virginia, his MS in Geology from the University of Pittsburg, Pennsylvania, and his PhD in Geological Sciences from the University of Washington. His main area of research is paleo-seismology:  finding evidence of past earthquakes in the Pacific Northwest using geological records. Much of his work uses lidar. His recent projects include looking for evidence of surface rupture along faults in central and western Washington, coastal uplift, and subsidence along faults in the northern Salish Lowland.

 

 

2024-04-20 Ralph Haugerud – Glacial Landscape of Puget Sound

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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 rapidly melted back. Later Sumas ice readvance in the Fraser Lowland may reflect stabilization of the remnant ice sheet by grounding as local sea level fell, followed by climate-driven retreat.

For a more detailed abstract, please see Ralph Haugerud’s detailed abstract Jan2024.

The Speaker 

Ralph Haugerud is an exceptional geologist. Many describe him as a structural geologist and geologic mapper interested in the evolution of the Pacific Northwest, and many know about his popularity from being featured on Nick Zentner’s programs.

Ralph is a Seattle native, with BS and MS degrees from Western Washington University and a PhD from the University of Washington. He began his career looking deep in the Earth’s crust at gneiss and tonalite in the North Cascades, moved on to study turbidites, then glacial till, and now spends much of his time looking at lidar topography. He is employed by the USGS and lives in Wenatchee, Washington.