Central Oregon Geoscience Society upcoming events

Greater Siletzia and the Making of the Columbia Embayment, Northwest USA (24 Nov 2026)

Wed, 25 Nov 2026 01:30:00 GMT

Greater Siletzia and the Making of the Columbia Embayment, Northwest USA

Ray Wells

Research Geologist Emeritus, U.S. Geological Survey, Portland, OR

Ray Wells has 50 years of field experience documenting the geologic structure and earthquake hazards of the Cascadia convergent margin in Oregon and Washington.

We will look at the history of the Columbia Embayment (CE); the area of anomalous low topography that lies inboard of the Cascadia subduction zone and is enclosed by the oroclinal bend in the Mesozoic arc. We think that the accreted coastal basalt terrane of Siletzia extends eastward beneath the Columbia Basin, and that the timing of its emplacement overlaps with northward transport of far-travelled British Columbia terranes (“Baja BC”) and Laramide deformation of the US Cordillera. We propose a model that links the origin of the Kula Plate to the Laramide orogeny, its subsequent role in rifting of BC terranes out of the CE, about 400 km south of its present location, and contemporaneous emplacement of Siletzia. The model may help reduce the misfit between large paleomagnetic and smaller geologic estimates of BC terrane displacements.

Please join us at:

Worthy Brewing (eastside location)

495 NE Bellevue Drive, Bend

In the Hop Mahal Room

5:30 pm social hour

7:00 pm presentation

COGS talk are free and open to the public -- all are welcome! Please join us for the social hour before the presentation.

All presentations are also live-streamed through Zoom. There will be a registration link at the top of this page as we get closer to the date of this presentation.

To Go Boldly Where Few Have Gone Before: Exploring the Seafloor of Planet Earth (26 Jan 2027)

Wed, 27 Jan 2027 01:30:00 GMT

To Go Boldly Where Few Have Gone Before: Exploring the Seafloor of Planet Earth

Michael J. Cheadle

A Brit; BS & PhD from the UK, MS from the USA- Taught 10 years at University of Liverpool, UK and 24 years at the University of Wyoming.

More than 70% of the Earth's seafloor remains unexplored and unmeasured by direct, bathymetric surveys; in fact we know more about the topography of the far side of the Moon and Mars than we do about~ 50% of the Earth’s surface. Consequently, seafloor exploration has led to spectacular geologic discoveries in recent times, with likely more exciting finds still to come. During this talk we’ll re-visit some of those discoveries: the largest offset (normal) faults in the world; hydrothermal vents and their exotic chemosynthetic lifeforms (analogs of the origin of life?); the competition between tectonics and magmatism at mid-ocean ridges and the nature of ocean crust itself-especially the poorly explored lower oceanic crust that lies below the ubiquitous basalt carapace in the Pacific. The talk will also cover the basic principles that govern how mid-ocean ridges work, including the exhumation of vast tracts of the Earth’s mantle.

Please join us at:

Worthy Brewing (eastside location)

495 NE Bellevue Drive, Bend

In the Hop Mahal Room

5:30 pm social hour

7:00 pm presentation

COGS Monthly Presentation - Topic TBA (23 Feb 2027)

Wed, 24 Feb 2027 01:30:00 GMT

Jen McLeod

Assistant Professor, Oregon State University, Eugene OR

Please join us at:

Worthy Brewing (eastside location)

495 NE Bellevue Drive, Bend

In the Hop Mahal Room

5:30 pm social hour

7:00 pm presentation

Drama Llamas and Mantle Mystery (23 Mar 2027)

Wed, 24 Mar 2027 00:30:00 GMT

Drama Llamas and Mantle Mystery

John Boyd

Instilled with wanderlust and thirst for adventure from a young age, John was born and raised in one of the flattest places on the planet with the highest relief in the county being only about 10 m difference from its lowest point. From as early as the age of 6, he dreamed of expeditions to the Andes and some 20 odd years later, while working on his Masters of Geology at the University of Wyoming, that dream finally became a reality. Graduating in 2010, he moved to Alaska to work in the petroleum fields where he worked for a handful of years before moving on to other endeavors such as using geophysical surveys to investigate long-lived plutonic systems, teaching continuing education courses of the geology underfoot in the Bitterroot valley and surrounding areas of Montana, and most recently LiDAR processing for a mapping company that primarily produces high-definition 3D maps for the autonomous and semi-autonomous vehicle industry. In his free time, he continues to tell stories and look at interesting rocks and geologic features, while planning adventures with his wife and teenage daughter in the playground that is the Pacific Northwest.

Mysteries teach us that if one wants to understand what has happened, one needs to find a record of it. Just as in those mysteries, the record one finds is often a series of clues one must use to reconstruct the event rather than a complete record of it. In geology, if one wishes to understand what occurred during a particular orogen, one needs to go to the associated basins where those records or clues are stored. The sedimentary basins of the Altiplano-Puna Plateau in South America contain the record of retro-arc foreland basin evolution during the Cenozoic. The deformation of these basins is characterized by high angle reverse faults and thrusts deforming crystalline basement and sedimentary covers. While the mechanisms responsible for deformation within the region are not fully understood in detail, the relative abundance of intercalated tuffs within these basins and those within the bounding Eastern Cordillera enables the timing and pattern of deformation across the orogen to be constrained. As one of the largest intermontane basins within the Altiplano-Puna plateau, the Arizaro Basin is well suited to investigations of basin deformation in response to lithospheric processes. Here we present some of the data gathered to test a few of the models that have been used to explain the patterns of deformation, such as the taper of the orogenic wedge and lithospheric foundering or drips, as well as some of the adventures encountered in the pursuit of these clues. Finally, a brief overview of some of the recent work that has been published since the initial thesis that provides a bit of vindication and a current understanding of the processes responsible for the clues left behind.

Please join us at:

Worthy Brewing (eastside location)

495 NE Bellevue Drive, Bend

In the Hop Mahal Room

5:30 pm social hour

7:00 pm presentation

COGS Monthly Presentation - Topic TBA (27 Apr 2027)

Wed, 28 Apr 2027 00:30:00 GMT

Please join us at:

Worthy Brewing (eastside location)

495 NE Bellevue Drive, Bend

In the Hop Mahal Room

5:30 pm social hour

7:00 pm presentation

COGS Monthly Presentation - Topic TBA (25 May 2027)

Wed, 26 May 2027 00:30:00 GMT

Please join us at:

Worthy Brewing (eastside location)

495 NE Bellevue Drive, Bend

In the Hop Mahal Room

5:30 pm social hour

7:00 pm presentation